Why you need a mono amp in your system - Fosi Audio ZA3 review

I review and test the Fosi Audio ZA3 power amplifier, which works in stereo or bridge-mode mono. Don't you really need a pair of monoblocs in your system?
PURCHASE LINKS
Amazon US amzn.to/3RmV5sI
Amazon UK amzn.to/3RHUcwd
Aliexpress s.click.aliexpress.com/e/_oCb...
Fosi Audio Official bit.ly/za3influtrack
15% off promo code：FAZA3MKT15
(This code will expire on 27th December)
OTHER EQUIPMENT USED IN THIS VIDEO
Function generator amzn.to/48rXRUp
Oscilloscope amzn.to/3thvV6X
Fosi Audio V3 amzn.to/3v9UQtB
OnOdio Monitor 60 headphones amzn.to/3v9UQtB
Sit-stand desk amzn.to/4arKbKO
LINKS
Marantz manuals.marantz.com/AMP10/NA/...
Wikipedia on BTL and PBTL en.wikipedia.org/wiki/Bridged...
CHAPTERS
0:00 Introduction
1:12 Unboxing
2:35 Chat
3:14 Bridge mode
4:21 Why do audiophiles like monoblocs?
5:56 ZA3 features
8:55 Tests
10:19 Frequency response
11:05 Power output
12:45 In use
13:31 Summary
14:36 Beauty pics
David Mellor on Spotify open.spotify.com/artist/6OkaD...
EQUIPMENT USED TO MAKE AUDIO MASTERCLASS VIDEOS
CAMERA - Sony Alpha A6600 amzn.to/3uj7Dtq
COMPUTER - Apple Mac Mini M2 Pro amzn.to/47tW6Wg
MICROPHONE - Sennheiser MKH 416 amzn.to/3QWWvuO
ALTERNATIVE MICROPHONE - AKG C414 amzn.to/3SLqCad
BUDGET MICROPHONE CHOICE - Rode shotgun amzn.to/3G0ni36
MICROPHONE PREAMPLIFIER - Comica LinkFlex AD2 amzn.to/40SMHFT
TELEPROMPTER - Padcaster Parrot alternatives amzn.to/40A55TJ
TELEPROMPTER SOFTWARE - PromptSmart Pro promptsmart.com/
AUDIO INTERFACE - Behringer UMC202HD amzn.to/3ugj6db
HEADPHONES - Sony wired amzn.to/3sEjlht
SPEAKER CABLE - KabelDirekt amzn.to/3ucgQ6T
POWER AMPLIFIER - Fosi V3 amzn.to/3vRumNH
KEYLIGHT- Amaran 100d amzn.to/40A5Gor
FILL LIGHTS - Switti RGB amzn.to/3ufhOPu
SOFTBOX Phot-R alternatives amzn.to/3QGoTjJ
LIGHTING STANDS Phot-R alternatives amzn.to/3QWXOKe
MONITOR - Samsung UJ59 amzn.to/3MEoBsk
MONITOR ARM - Invision alternatives amzn.to/40SLqi5
MIC ARM - Neewer amzn.to/49Ob0sD
TRIPOD - Velbon alternatives amzn.to/46gu2oa
GREEN SCREEN - Elgato alternatives amzn.to/3SG2F3L
DESK - FlexiSpot E7 Pro amzn.to/3QVIWvS
VIDEO EDITING - Apple Final Cut Pro www.apple.com/final-cut-pro/
IMAGE EDITING - Adobe Photoshop amzn.to/3FZ7Ww0
AUDIO EDITING - Avid Pro Tools amzn.to/3QA5Wz7
NOTEBOOK - Leuchturm 1917 hardback amzn.to/47zonKX
PEN - Sakura Pigma archival pen Sakura Pigma archival pen amzn.to/47zz3cP
OSCILLOSCOPE - Hameg HM 203 alternatives amzn.to/47tWN1O
GROOMING - Philips 3000 nose hair trimmer amzn.to/40BdLJo
GROOMING - Betty tells Debbie and Audio Phil a joke for the New Year. But will they get it?
EQUIPMENT USED TO MAKE AUDIO MASTERCLASS VIDEOS
CAMERA - Sony Alpha A6600 amzn.to/3uj7Dtq
COMPUTER - Apple Mac Mini M2 Pro amzn.to/47tW6Wg
MICROPHONE - Sennheiser MKH 416 amzn.to/3QWWvuO
ALTERNATIVE MICROPHONE - AKG C414 amzn.to/3SLqCad
BUDGET MICROPHONE CHOICE - Rode shotgun amzn.to/3G0ni36
MICROPHONE PREAMPLIFIER - Comica LinkFlex AD2 amzn.to/40SMHFT
TELEPROMPTER - Padcaster Parrot alternatives amzn.to/40A55TJ
TELEPROMPTER SOFTWARE - PromptSmart Pro promptsmart.com/
AUDIO INTERFACE - Behringer UMC202HD amzn.to/3ugj6db
HEADPHONES - Sony wired amzn.to/3sEjlht
KEYLIGHT- Amaran 100d amzn.to/40A5Gor
FILL LIGHTS - Switti RGB amzn.to/3ufhOPu
SOFTBOX Phot-R alternatives amzn.to/3QGoTjJ
LIGHTING STANDS Phot-R alternatives amzn.to/3QWXOKe
MONITOR - Samsung UJ59 amzn.to/3MEoBsk
MONITOR ARM - Invision alternatives amzn.to/40SLqi5
MIC ARM - Neewer amzn.to/49Ob0sD
TRIPOD - Velbon alternatives amzn.to/46gu2oa
GREEN SCREEN - Elgato alternatives amzn.to/3SG2F3L
DESK - FlexiSpot E7 Pro amzn.to/3QVIWvS
VIDEO EDITING - Apple Final Cut Pro www.apple.com/final-cut-pro/
IMAGE EDITING - Adobe Photoshop amzn.to/3FZ7Ww0
AUDIO EDITING - Avid Pro Tools amzn.to/3QA5Wz7
NOTEBOOK - Leuchturm 1917 hardback amzn.to/47zonKX
PEN - Sakura Pigma archival pen Sakura Pigma archival pen amzn.to/47zz3cP
OSCILLOSCOPE - Hameg HM 203 alternatives amzn.to/47tWN1O
GROOMING - Philips 3000 nose hair trimmer amzn.to/40BdLJo
GROOMING - Nose plier amzn.to/41IOZaR
Disclaimer: Videos on this channel may include affiliate links and may feature software that has been received free of charge with an NFR (not for resale) licence, equipment that has been loaned or donated by a manufacturer or distributer, or equipment that has been bought for less than full retail price.

[@Douglas_Blake_579]

From the Williston Labs channel, we now have confirmation that flipping the stereo/mono switch while the ZA3 is powered up is *not safe* . It puts the chip into protection immediately and we can't be sure it will always come back on after a power cycle. That switch has no business being on the front of the amp, right in the middle of "Daddy what does this do?" land.

[@mergru6371]

Chinese kids don't do things like that. They raise kids different. Not judging btw, I think Western society has a much bigger problem raising the youth

[@deareeMusic]

Your sarcasm has reached levels where I have no idea when u are for real and when u arent and I want to keep it that way

[@jerryBearBennett]

Sarcasm level 9,000 , music enjoyment level, 10,000 !

[@jz6373]

You really need enough power, processing, and separation in the mid-range to parse the dimensionality of his sarcasm. With the right atmos/ Dirac setup you can literally hear it coming.

[@samlee2562]

Welcome to England 🤝

[@deareeMusic]

@@samlee2562 haha best response

[@DiscipleRay]

You just have to understand British humo(u)r!

[@theman-pc2ej]

Got one of these yesterday and it's great . Volume all the way up and speakers are silent!.. cranked it up and it sounds amazing.. definitely a keeper for my home studio!

[@matrixplace]

I recently found your channel and felt in love with your sense of humor, cant believe there are people who are triggered :D Keep the great work!

[@paulfriedman4767]

You Sir, are informative and entertaining. Bravo

[@Exgol2005]

as always with unique insights or trivia plus wit/humour

[@garyd2698]

Wow that was different. Your witty and somewhat entertaining. Keep it up.

[@richh650]

Your "unboxing" portions are hilarious. I am glad you pointed out how speaker loads can vary greatly with frequency. I dare say most YT reviewers don't comprehend that fact. Thank you!

[@Douglas_Blake_579]

1.5 and 2 db at 25khz is not "greatly" ... it's "slightly" at worst.

[@gurratell7326]

They can vary if they are badly designed or just cheap. But as already said the difference is just a few dB and can fixed by adjusting your DSP.

[@Douglas_Blake_579]

@@gurratell7326 Yeah about 1.5db at 25khz ... a frequency nobody can hear to begin with.

[@gurratell7326]

@@Douglas_Blake_579 Yup exactly. Though 1.5dB at 25khz could also mean 0.5dB at 17khz which someone miight every so slightly notice if they really tried. So yeah I wouldn't worry about it no :)

[@marklawrence17]

I'm an EE. I've had superlative stereos since '79. Bridged amps, which this is not, deliver twice the voltage and therefore four times the power. The price is each side of the amp sees half the speaker impedance. So, for example, if you bridge into 4ohm magnepans each side of the amp sees a 2ohm load. Few moderately priced amps can reliably handle a 2ohm load. So bridging is for high impedance speakers that don't drop much below 8 ohms. Few modern speakers fit that description. I've never been a fan of bridging. You're all too likely to have stability and overheating and current clipping problems. Paralleling, as this amp does, results in each side seeing double the speaker impedance. For example, when driving our 4ohm magnepans, each side of the amp sees an 8ohm load. This is much easier for most amps to handle. You would run this amp in mono mode to handle very low impedance speakers. I've seen some speakers drop below 1ohm in the audio band, dropping below 2 ohms is not uncommon, dropping to 3 ohms is rather common. This amp in mono mode would be a good choice for such speakers, and a lot cheaper than an ampzilla 500 or a mark Levinson. On the other hand this amp in mono mode would be wasted on a high impedance high sensitivity speaker like any Klipsch. There would be twice the cost and no benefit. All these considerations really only count if you play your speakers loud. I have a small stereo in my bedroom which averages about 50db never gets over about 80db. Power considerations are just silly. This amp in mono mode would be a decent choice to drive the magnepans in my living room, which sometimes get quite loud. However, in mono mode each side of each amp sees an 8ohm load and that results in the minor high frequency rise of a couple db. Personally, at age 68 I can't hear anything over about 11khz and I've never measured anyone my age who can. Few over 25 can hear above 16khz, and few under 30 can afford a stereo that works well over 16khz. I've measured several dozen people. No one over 15 in this country can hear 20khz. You may have ribbons that go to 50khz or plasmatronics that go to 200khz, but you can't hear it. I have trouble imagining someone with $20k speakers using this amp in mono mode. But for my bedroom stereo, elac ubr62 playing soft music, this amp in stereo would be a good choice. For a budget stereo with ss-cs5 or bs22-lr or elac debut 5.2 or emotiva b1+ or Klipsch r41m or rp600m, this amp in stereo would be a very appropriate choice, IMHO.

[@daleboylen6427]

It's NOT bridged according to the lit. They run the amp in a parallel type mode.

[@daleboylen6427]

I'm VERY familiar with bridged amps. I sold high end audio for years. THIS is NOT bridgeable, sorry.

[@robertbox5399]

I'm an EE. What is current clipping? Shouldn't high current cause the feedback loop to increase the drive, ending up with voltage clipping?

[@marklawrence17]

@@robertbox5399 you're correct if the power supply can keep up. If not you get clipping at a lower voltage than you expect. Which some of us call current clipping, as the solution is a power supply with more current capacity.

[@Douglas_Blake_579]

You need to look up the TPA3255 spec sheets ... The chip itself natively supports ... 4xSE -- 4 single ended outputs 2xSE+1xBTL -- 2 single ended and one bridged output (2,1 stereo) 2xBTL -- 2 bridged outputs (stereo) 1xPBTL -- 1 Parallel bridged output (mono) The base mode for stereo in these chinese amplifiers is 2xBTL ... that is each channel is already bridged. For the mono mode they reconfigure the chip for 1xPBTL or Parallel Bridge Tied Load as a means to increase output current capacity.

[@Jan-ic9iq]

I have the Fosi V3 with 48v powersupply , hooked it up to JBL L90's 😁. To my amazement it is capable of handling them. It does get warm, the powersupply stays cool. Two ZA3's would be nice to let those drive the L90's. Unfortunately you can not do bi-amping as far as I know.

[@neilw4569]

I like the Grant Wood painting in the background!

[@4ujase]

Oh my goodness, I upgraded my Fosi V3 to the 'C'est magnifique Atoll IN100SE! What a sublime amazing sounding beast of an AB amp but not cheap. Two ZA3 in mono I would have considered in a heatbeat, if only it had come out sooner.

[@fosiaudio]

Fosi audio's fault!

[@jbrc1322]

One feature missing here that would take this amp to the next level is a high-pass filter for the speaker outs when using a subwoofer. This would take a huge load off the amp if the high demand from the passive woofers was reduced. Distortion would drop substantially at high listening levels and there would be much more headroom for harder to drive speakers. But.... a little birdie told me I just might get my wish in the not so distant future.

[@fosiaudio]

Cant agree more.

[@ThaVoodoo1]

I will be sticking with my Class AB power amp thanks.

[@fosiaudio]

Haha, in which case you may turn to class amps?

[@gomiwomi]

No one cares.

[@denis4072]

Every video outro always put a smile on my face. 🤣🤣🤣

[@stevenewtube]

Please do the impedance verses frequency video 👍

[@IAmThankfulToday]

I quickly realized that I had no interest in the product but stayed for the sarcasm...reminds me of a more verbose version of Granny Crowley, The Dowager Countess on Downtown Abbey. The script was quite funny and so promising that I subbed. Will be more than worth it when he gets his timing down

[@improbablehandle]

Thanks for that handy nose hair trimmer link.

[@geevee1045]

Enjoyed your interesting review. Thanks. Just wanted to add that the Fosi Za3 is the first cheap class D amp I've heard that reproduces male voices with body (elevated lower mids perhaps?). It actually sounds rich on my Kef LS50 Metas and manages to inject some warmth into my Maggie LRS+ speakers. So, this is a great relief compared to stereotypical class D leaness, in which hollow body guitars for example, sound like solid body guitars. Just received it today, but so far it's a very pleasant sounding amp. Well worth the cheap investment, for what you get in return. And the sub-out is a nice bonus too.

[@JukeboxAlley]

What preamp are you using?

[@geevee1045]

I'm not using a preamp with it. I'm running a Dragonfly DAC from my laptop into the stereo Fosi Za3 (48v supply), then into my speakers. I've also tried setting the Fosi volume to full and also to 3 o'clock, while controlling the volume with a Nobsound ALPS27 (50k) volume control but didn't like the results. Having lived with the Fosi Za3 for awhile now, I'm recognizing that it's not as powerful, hard-hitting and spacious as my cheap class A/B SoundArtist SA-200IA, which I prefer with my Maggie LRS+. Both amps were connected to a subwoofer. The Za3 is on the softish side and I'm beginning to wonder whether the warmth might possibly be a result of intentional 2nd harmonic distortion. Need to do further testing against my Aiyima A07.@@JukeboxAlley

[@JukeboxAlley]

@@geevee1045 I would definitely recommend running a preamp on the za3, that would make a tremendous difference in gain and impact, always does, as it's still basically separates, the za3 by itself just isn't going to cut it, all of those need a decent preamp behind them.

[@geevee1045]

I ran a passive preamp with it, but I believe you're talking about an active preamp with gain. What preamp are you using with the Za3? I assume you're objecting to the NE5532 preamp and volume control quality in the Za3. Well, my Dynaco Pas3x tube preamp is presently out of commission, but I'll try the preamp section of my original NAD 3020, or the pre-out of one of my vintage integrateds when I get the chance, thx. @@JukeboxAlley

[@geevee1045]

I ran a passive preamp with it, but I believe you're talking about an active preamp with gain. What preamp are you using with the Za3? I assume you're objecting to the NE5532 preamp and volume control quality in the Za3. Well, my Dynaco Pas3x tube preamp is presently out of commission, but I'll try the preamp section of my original NAD 3020, or the pre-out of one of my vintage integrateds when I get the chance, thx. @@JukeboxAlley

[@DiscipleRay]

What do you think about this amp running main stereo LR channels from the pre-outs of a 7+ channel AVR? Would it help much in taking the power demands off the AVR? Would running two as mono blocks improve things even more?

[@RomiPetrut]

Hi, it's a very good review. I have a question: if I use two za3 as monoblocks with a tube preamp is it a good idea? ...and how is recommended to set the volume controls, at max on za3 using as main volume the preamp? My respect

[@AudioMasterclass]

Set the preamp volume to minimum then set the power amp volumes to max. Play some audio and advance the preamp volume slowly. It's almost certain this will be OK and you can continue to use your system like this, controlling volume with the preamp. Caution is always good though.

[@Douglas_Blake_579]

David is correct. But there is a plan B that works too... Start with the pre-amp at 3 o'clock volume and the amps at 0. Advance the amplifiers until you get the maximum level you are likely ever to use. (for me this ends up around 11 o'clock on the dial). From there use the pre-amp to adjust from zero to your limited maximum. This has the advantage that the kids won't be able to get you in trouble with the noise police.

[@thelowprofile9767]

The knob will match the Klipsch speakers.

[@sabrowenie]

Best unboxing ever!

[@AudioMasterclass]

Until my next one.

[@petertys]

Do you have an issues when you slow down the volume the left channel is unbalance audio compare with right. Please comment..thanks

[@wric01]

It rocks 90% vs my latest and greatest gan amp. It's a multi do all play amp, once you tinker opamps mono xlr, then duo with mono or biamping without needing thousands to entry. It powers my magnepan lrs+ via single amp It's a winner. Duo Mono immediately adds realism faster impactful more fullness to everything.

[@chuckmaddison2924]

My old Dansette had a " mono block. " and it was tube single end class A. So, I guess it made me an audiophile.

[@AudioMasterclass]

Self-certified audiophiles apply their own criteria.

[@JC-xf5jc]

Love thus GUY👍🏼

[@davelistenstohifi]

Thanks for the review. How does it sound though?

[@AudioMasterclass]

Not bad.

[@stu-po]

These sold out really quick! I'm blaming your very informative review 😄

[@fosiaudio]

They are on pre-order on our website.

[@earthoid]

Decades ago I had two NAD 3040 integrated stereo amps that NAD made easy to bridge for mono so I did. Note: the 3040s already had twice the power of the beloved 3020s. Unfortunately the bridged sound was terrible and was only suitable for maybe a PA system. So I left that mess behind but still can't shake the nasty taste that bridging left behind. Therapy might be needed before I can bridge to mono again.

[@Douglas_Blake_579]

I think you'll find things have moved on considerably since "decades ago".

[@holycowmanheck]

@10:56 The 20kHz sine wave seems to have a negative bias. The Vmax and Vmin don't seem to line up with what's shown. It looks more like 32V and 41V.

[@Douglas_Blake_579]

What do you expect from a $65.00 portable scope? The display is not centered on 0 volts.

[@carlsitler9071]

Very well sir. I shall sub (not subwoofer, subscribe). Although I am mounting the 2 opposed 10" subwoofer drivers into the box I built for them (4' x 13" x 17"). I was truly shocked at the quality of the Parts Express $44 driver.

[@ShazeemKhan]

Is it a GRS driver?

[@jerryBearBennett]

Would you PLEASE test the SMSL AO200 mark 2 ??? Uses the German infeneon chip and supposed to be “better “ than the amazing Texas 3255 chip, and the integrated amp Ao200 mk2 is only 200$ US dollars right now. I have the aiyima a08 pro it’s amazing for 92$ used , but I am eyeing the fosi zv3 or smsl ao200 mk2. I have Sony cs5 speakers 6 ohm

[@schemkesa]

Ow what a great amp. I need one for my extra Atmos channels. This would be great! Let's waait your review first 😂

[@billsmith5166]

Getting complicated here, but since Fosi seems to be listening, how about an HDMI in and out along with an internal equalizer so that we could adjust via a TV interface Now that you've agreed to that, how about a mic input so that we can balance the room via a contained frequency response display also shown on the TV, or.. even an app. Now that you've also agreed to that, how about creating a DSP contained in the chassis with your wonderful amps? It would be just the thing to eliminate crossovers in DIY speaker design. There, that completes my list for now.

[@graememorrison333]

Shhh. Put myself on the waiting list for two ZA3s, and then had second thoughts so cancelled. Suggested to Fosi though that if they brought out dedicated power monoblocs with XLR inputs then I'd buy a pair. Fosi quickly and kindly replied they're releasing that exact thing in a couple of months.

[@AudioMasterclass]

Yes it does seem that Fosi listens to their customers.

[@RomiPetrut]

Thank you very much.

[@AudioMasterclass]

You're welcome.

[@SubTroppo]

The outro music didn't make me want to do anything nasty; which is nice. How hot does the power supply run?

[@richardgrumbine4867]

Looks like a great little amp... I would have liked to have seen a more standard on off switch... and perhaps no need for volume... and put the mono stereo switch on the back as I would think you would need to be touching very often if at all once you have it set up... but doing so inadvertently like have bad results!

[@timwoodward3381]

Yep...power amp only. no knobs, RCA/XLR, mono/stereo on the back 👍

[@theman-pc2ej]

Power button is just fine..long push on volume knob and walah

[@werner.x]

I like your approach 😁

[@BatteryAz1z]

These type of class D amps have an impedance dependent frequency response, increasing the upper treble with higher impedance, so the frequency response will be different depending on the speaker's impedance curve. It's an issue that is solved by more sophisticated class D designs such as ncore and purifi.

[@scottlowell493]

All of the "budget" class D amps that I have tried do that. Not to mention, they modulate noise and the treble is vague and rolled off. Good class D amps are a few thousand, not a few hundred.

[@werner.x]

I bet, that's exactly designed that way to sound more lively just out of the box without any sound controls added. And rightly so from the sellers point, because trebles get lost anyway for many reasons.

[@niklasschmidt]

They are roughly 500 euros. Which would be the entry point hypex. Or 300 if you go for a SMSL.

[@niklasschmidt]

They are based on ti chips.

[@david1rosenthal]

Exactly right. This amp is based on the TI TPA3255 chip. We are just on the cusp of seeing implementations of this TI chip with an extra "post filter feedback" circuit that cures this issue, but this doesn't have it. Those more advanced class D amps from Purifi have the extra circuit.

[@sjors01]

Hi Audio Masterclass, the back is much more interesting you said, than the front, but the inside is even more beautiful and educational. Could you include this in the next reviews?

[@aljosamlinaric8705]

I think you should use termination on osciloskop or at least switch probe from 1x to 10x. That's probably why that voltage difference on oscilloscope.

[@werner.x]

Then he would have seen that same voltage response, when he did check the generator with the same setup, wouldn't he?

[@Douglas_Blake_579]

FWIW ... that peak in output power is due to the output filters being underdamped at 8 ohms. It's only about 1.5db and it's at 25khz where nobody's going to hear it.

[@billsmith5166]

So if I provide 48V at 10A would I pretty much avoid the need?

[@davidcorner1174]

thank you.

[@sguttag]

In the fun fact department...the XLR connector (which gets its name from Cannon where that was its connector type)...It was not developed as an audio connector, persay. Have you ever checked the specifications for the 3-pin version? 15A...a bit excessive for mere mic or line level audio! Even its voltage rating is up to 133V on the 3-pin.

[@chinmeysway]

three pin version? all xlr is that

[@sguttag]

@@chinmeysway Not at all. There are 3, 4, 5, 7...etc. 5-pin is popular with DMX lighting systems, for example. However, 3 pin XLRs have notably larger pins than their higher pin count version.

[@PlatinumMastering]

It’s true some amps have very big crosstalk … and yes 2 mono blocks are better

[@TheRockerxx69]

I love mono!!! I Need 6.

[@rhwinner]

I once caught mono at sleep away camp.

[@jimhines5145]

Listen to the best Toy Matinee release you can find through this amp. It's a true test!

[@MarkThomas-hm3ju]

This is probably wrong but just in case it's right I read where there are two TI 3225 chips one for each channel If that is the case what is the point of using the ZA3s as mono blocks. I know two power sources are often advantageous, one for each mono block but the Class D is very efficient. There probably is only one TI chip surely for each ZA3.

[@chinmeysway]

audioperves are just never satisfied

[@Projacked1]

How does it work with impedance dips at certain frequencies? Still struggling with that one. 🤔

[@Douglas_Blake_579]

First ... way too much import is applied to speaker impedance variations. For the most part, amplifiers are voltage sources. As long as they can produce the required current, impedance is largely unimportant. I have a pair of towers that dip to about 3 ohms in the upper bass region. Far as I can tell my TB10D, which is also a TPA3255 based amplifier, is unaffected by it.

[@jameswarren1831]

The Quant Asylum Q304 is $600 and does a great job testing audio gear and by the look of your T-shirt I think you can afford it.

[@AudioMasterclass]

Don't worry! eBay has kindly provided me with a Ferrograph RTS2. It will be making its debut soon. Oh yes, and a new batch of t-shirts.

[@jameswarren1831]

No excuses! You have to sell your soul to the audio gods! I’m tall so my t-shirts are 3x the price and it’s limiting my ability to buy nice gear.

[@CreateListenCreate]

The oscilliscope link is for the fn generator.

[@deanodley]

Yes noticed this too…

[@AudioMasterclass]

Fixed it!

[@Off2Witness]

Started my addiction with a pair of AR 3a, powered by a pair of MAC 60's. Yummy

[@Douglas_Blake_579]

For the frequency response test ... the rise in output at 20khz is an artefact of poor output filter design. Fosi is designing for 6 ohm loads as a compromise between 4 and 8. If David tested at 4 ohms he would find that 20khz was down slightly. For most uses this is pretty harmless, especially since almost nobody would ever hear it.

[@niklasschmidt]

Which is my point. For the segment it is not flawed. And for 500 this problem has been solved. Like in my purifi amp. Fosi provides a path to more to what should matter for an audiophile noise and distortion free gear. Which is often not the case for audiophile brands. The question is when fosi will provide an amplifier that has addressed the problems of cheap class d

[@Douglas_Blake_579]

@@niklasschmidt First, lets understand that the TPA3255 is clearly not "cheap class D" ... The chip was developed by TI for pro-audio use. You will find it in studio monitors, sound reinforcement and public address roles and you will also find it in some high end home theatre gear. To my surprise a couple of the lower powered ICEPower modules are using it as well. The TB10D version of the TPA3255 tests favourably beside some of the best gear like Naim and Parasound and beats the pants off just about the entire "vintage" market. Don't mistake the small size and lower pricing for a lack of sound quality. These little guys will surprise you, if you give them the chance. What they won't do is make your friend's eyes bulge or win you status within a community of audio snobs. My current main system is a Windows HTPC, DAC, modified TB10D and a pair of Pioneer towers. Total outlay about $1500, including a 60 inch TV. All the electronics fit into a vacant drawer well on my TV stand, with room to spare. I will stack that up against just about any $10,000 system out there on all counts except raw power.

[@fosiaudio]

@@niklasschmidt Great news, we have a big improvement on that.

[@niklasschmidt]

@@fosiaudio. Great!

[@xlr82bgr8]

Big improvement? When? Can the improvement be implemented with software or do I have buy another Amp? Just curious .)@@fosiaudio

[@allanmoorhead9492]

It's surprising how small an audio power amp can actually be, if you take out the PSU and the radio and phono sections, and the input selection switches. Car audio amplifiers can be very small yet put out a very high level, far more than is needed for the small interior of a car for comfortable listening levels. It seems that many home audio power amps are made larger just to look more powerful.

[@Douglas_Blake_579]

These little guys are "chip amps" based around an amplifier IC chip. They are basically a chip in a box... don't need to be big.

[@dost328]

I thought I heard you said "McIntosh"😊

[@philrobinson4329]

I don't think your music is anoying at all. It's very well mixed and mastered and I can hear all the instruments all the time via my Naim DAC-V1 and Sennheiser HD650s. Nice review BTW.

[@AudioMasterclass]

Gosh, an audiophile listening to my music.

[@werner.x]

Let the mix be good or not - still annoying as a background music 🤣 I'd assume, by intention. Or what else? 😅

[@Roddy451]

2:35 🤣🤣🤣🤣🍿🍿👀👀 14:37 🤬🤬👈 After watching that display of a great, wry sense of humor, why the heck wouldn't I subscribe?

[@chinmeysway]

i like it other than that damn orange knob color!

[@stevengagnon4777]

What about an ear test as they are the ultimate testing instrument that maters in the end. Really I would have liked a test with a pair of low impedance speakers with a nasty dip in the base region. Yeah make that a pair with low sensitivity just as a torture test. Maybe you would have a better idea what's going on with that high octave . We could have gotten some words out of Audio Phil he's always entertaining. His highly resolving ears almost never miss anything....especially the stuff I cannot here myself.

[@Douglas_Blake_579]

A small change in frequency response in the top octave is not going to affect the bass response. I have multiple tpa3255 amplifiers here and I run them on Pioneer towers that dip to about 3 ohms in the upper bass regions ... no problem.

[@fotouhi]

I wonder if one could use this unit for individual mono channels of a surround system and will the audio improve because of separate power supplies?

[@AudioMasterclass]

No reason why not other than multiple volume controls. Separate power supplies are good in theory but the improvement would be a tiny fraction of what you could achieve with acoustic treatment in your listening room.

[@MrRocktuga]

Forget about it. This is a bad amplifier to start with, and if your AV receiver has the individual line-level outputs for all channels, it should have a better quality amplification than this piece of crap. 😉 If you want or need more power from your AV receiver, try instead: - buying good external amplifiers (they don't need to cost an arm and a leg); - Buy only one stereo amp for your main channels, and let the AV receiver handle the rest (the internal power supply won't be as taxed by the main channels).

[@jasontimothywells9895]

​@@MrRocktugaeggszackly. Turn off the mains and loosen up the a/v receiver handle only the soft loads .

[@ricksmith7659]

​@@MrRocktugabuying a good external amplifier (they don't need to cost an arm and a leg). Okay but you didn't mention any, because the amp you just described only comes out of China and is a Fosi. 😂😂😂

[@marca9955]

Long speaker cables are better than long amp input leads. Better to amplify less noise and distortion than more.

[@StrangeBrewReviews]

Not if your running pro shielded fully balanced XLR cables. Think DIY DJs and smaller mobile audio , small gig musicians...

[@Douglas_Blake_579]

That's why the balanced inputs. It allows for much longer runs than RCA does.

[@hennievangalen3789]

Actually it is the other way round. Long interconnects are no issue, since there is extremely low current. Speakercables have quite some current running through. Soundwise speakercables srs best at close to 2,5 meters.

[@Douglas_Blake_579]

@@hennievangalen3789 Interconnects do indeed run low current, in microamps, but that isn't the issue. That low current also makes for a relatively high impedance, often 10k or more, The concern is for EMI and specifically RFI picked up as they tend to act like antennas and will pick up noise and radio signals very easily. Speaker wire, of adequate size, is a very low impedance thing, it is not going to pick up noise and interference at all. In the trade off ... it is far better to run 100 feet of speaker cable than even 20 feet of shielded interconnect wire.

[@fredashay]

Actually, I have a retro hi-fi system with two mono amps (they're actually bridged stereo amps).

[@thelowprofile9767]

How do you set it up as monoblock considering that it has left and right rca inputs? Do you just use either the red or the white rca for input?

[@Douglas_Blake_579]

The back of the amp is marked ... you use only the right speaker terminals and only the right input channel. So a dual monoblock setup looks like this... Preamp out right -> za3 #1 input right->speaker output right->right speaker Preamp out left -> za3 #2 input right->speaker output right->left speaker

[@thelowprofile9767]

@@Douglas_Blake_579 thank you so much. Exactly what I wanted to know. I asked the same question to another vlogger but he can’t seem to understand the question. But you got it right away and answered it in a very clear and detailed way. You’re the best.

[@thelowprofile9767]

@@Douglas_Blake_579 Hi, was this documented anywhere? I was watching another review although it was for another brand which is Aiyima A07 MAX. The reviewer says that he uses the left input instead of the right input. I understand that they are different brands but just wanted to clarify. Ultimately, if I had to set up a monoblock configuration, I can try either left or right input.

[@Douglas_Blake_579]

@@thelowprofile9767 Input/output choice in mono mode is not a function of the chip itself, so different designers can implement this differently. Best advice: follow the manufacturer's instructions.

[@immanuelsuresh7739]

Will this be better or equivalent to Marantz PM 6007? In terms of power and sound quality.?

[@wadesouza6402]

At the risk of being attacked by the Class D lovers, I would go with the Class AB Marantz for the combined package of including a solid more built out preamp with tone controls, good solid power supply with headroom and proven longevity, remote, quality components plus the 3 year warranty. I have 2 of the larger PM series amps, the 8005 and 8006 and they are excellent integrated amps which delivers more power and current than rated. They are obviously larger and thus take more space but they are also more adjustable in tone which many audiophiles hate but can help with crappy early recordings on CD, poor live recordings, etc. The comparison is kind of apples vs oranges. I have used these little chip amps in a garage with cheap speakers as well as on a deck where its all background lower quality listening. To me that is kind of their reason to exist. I have not found listening to them side by side that Class D is to me as transparent and good quality sounding as the AB amp. The Marantz is a good entry level amp which will likely service you much longer than this Fosi. If all you want to do is turn it on and listen to music go with the Marantz.

[@immanuelsuresh7739]

@@wadesouza6402 somone selling used MZ PM7003 is it worth considering? Will be a better choice than PM6007? My speakers are q3050i.

[@ashneel]

For the price.. it's a lil gem

[@VicariousAdventurer]

Most reviewers screwed up the basics of power measurement. Refreshing to see someone actually correct. UK versus US education?

[@AudioMasterclass]

As I've only had UK education I can't comment on that. I'll stand by my preference for continuous average power measurements though. They many not reflect the listening experience perfectly but you know where you stand.

[@VicariousAdventurer]

Also, everybody mods the input opamps, but I've only seen one guy for not cheaping out on the output. Having looked at TI's app notes, I have a hard time believing that any audible change (as opposed to changing a THD digit) will occur with improved input opamps; however, inductance drops as a core heats on the output is a real thing and might explain another reviewers results (and give me just that bit of buyer remorse for getting an Aiyima over a Fosi)

[@VicariousAdventurer]

One guy praise Fosi for not cheaping out on the output stage

[@VicariousAdventurer]

RMS makes sense - audio signals are >20 Hz. I was not going to post more stuff, but as I looked at LC output stage design notes and DIY audio forums and NAD/Purify bragging, I realized that the output frequency curve at high frequencies is only flat for a particular impedance. If the impedance is higher or lower than the design of the LC output is for, the frequency response will vary. NAD claims they've fixed this with a feedback network. but Fosi and Aiyima don't have the time/money for that, so you should have easily driven 8 Ohm speakers for the best results.

[@saardean4481]

First of all. I love your content. Just a remark as i am listening. „two monoblocs two volume controls“ … not really. Unless i missed something over the years which is quite possible , a monobloc is most times a power amp with no volume control So you will have a single Volume control on your Pre-Amp driving both your monoblocs volume (just wanted to be a smart ass for a second )

[@AudioMasterclass]

My studio Quad 306 doesn't have a volume control but if I use it as it is then the output level control on my audio interface has to be ridiculously low, and stereo pots often don't track well at very low levels. A pair of 20 dB attenuators is my solution.

[@saardean4481]

@@AudioMasterclass i hear ya. Yes i know this issue. Then again even though its a very good amp its an old amp. I stopped my „audiophilia“ beginning of the 2000`s Now i have active studio monitors and since i spend most my music-sound relevant time in front of them i let my other stuff go. Feels refreshing having a more minimalistic setup. I stopped caring about silver cables and audio expert „fights“ as like Phil said „i don`t care anymore“ :-) I still enjoy watching your channel though

[@davidkclayton]

The Output filter has been optimized for 4 ohms not 8 this is why you get a bump and output at 20,000

[@Douglas_Blake_579]

Actually I did some testing on a couple of these amps using the 10uh coils and 1uf caps, per the development module. The flat response is at about 6 ohms. 8 ohms allows a bit of peaking in the filter. 4 ohms results in a slight roll off. 6 ohms is a good compromise for consumer gear. For pro gear replaceable coils makes more sense.

[@aesculetum]

I keep wondering if this channel has any common ground with a channel like Techmoan's.

[@CristiBaciu]

Imagine a version 2.0 with just HDMI input to connect to tv arc hdmi to control with tv remote

[@markovlasic1978]

2 mono fosi ZA3 for 2 speakers as mono blocks

[@ShanePleasance]

My experience with stereo and mono switchable power amps has been to have 2, but keep them stereo mode into biwirable speakers.

[@hallmufc]

How that set up work?

[@ShanePleasance]

Lets say you have 2 x 30 WPC stereo amps that can be switched to mono. Switching them to mono gets you a change to the total output power, and usually a change to the noise figures, not always an improvement. Power usually isn't the issue anyway. Take one stereo amp for each bi-wirable speaker. Y shaped RCA's from source, so one input RCA to 2 Output RCA's - one plug to left amp left channel which connects to the tweeter, other to the right channel of the same amp with connects to the Bass driver. Same with the other amp and speaker (right channel). Then you have - ostensibly - 2 x 60 WPC power amps - and can be done with any two of the same (or same gain) power amps, even if they are NOT mono compatible. Then of course you can have one stereo amp for tweeters, one for bass..... or consider dumping the speaker crossovers and exploring an active crossover twixt pre and power amps, but thats another video... 🙂

[@Douglas_Blake_579]

@@hallmufc Shane has it... Remove the speaker jumpers. Amps in stereo mode: Pre0ut left -> za3#1 L+R -> za3#1L -> left tweeter + za3#1R -> left woofer Pre0ut right -> za3#2 L+R -> za3#2L -> right tweeter + za3#2R -> right woofer I just want to add a small note of caution here... the outputs of these amplifiers are in BTL mode. That is they are already bridged. You cannot connect the two black binding posts together, that will cost you an amplifier... So get a meter or continuity buzzer and check your speakers before powering this up, to be sure the bass and treble sections are fully isolated.

[@MichaelBeeny]

You have just found one of the main issues with cheap class D amplifiers. They sound very different on different loudspeakers. All loudspeakers have a very variable impedance curve. These class D amplifiers give a different high frequency response to different speaker impedance. Because of this some speakers will sound extra bright, some over dull. That's the price you pay for cheap class D. Ok for the undemanding use but if you want real HiFi go class AB

[@niklasschmidt]

Or hypex or purifi

[@Douglas_Blake_579]

You do realise that "different frequency response" is about 2db that occurs well above 16khz where almost nobody could hear it.

[@jasontimothywells9895]

Even class b and h are awsome power amps , Mitsubishi receivers and amps in the 70s up till mid 80s was awsome , sounded solid and pushed a ton of current .

[@clemmtec9506]

Dose the amp sound better than crown xls1502 ?

[@Douglas_Blake_579]

Less hiss ... but aside from that, when level matched, it's about a tie.

[@JukeboxAlley]

​@@Douglas_Blake_579no kidding? I had the 1502 and it's very good, so a set of these on a good preamp can most likely hang with the 1502 you think?

[@Douglas_Blake_579]

@@JukeboxAlley The Crown is more powerful ... but at reasonable listening levels, yes I do think the Fosi will compare favourably.

[@georgejohnson1498]

Or you could have a really mono only amp! Quad II Forty here. just the one. Fits nicely between my Leak Trough-line Mk 1 from November 1957], and my 1957 Quad ESL [two black inputs on the amplifier inputs as phase does not matter in Mono according to Peter Walker and I agree], so my daily radio set has more years on it than a human lifetime plus half another. As the great conductor, Otto Klemperer, observed, when requested to remake recordings in stereo, "Stereo is the invention of the fakers!" ... or, on another occasion, "it is a scandal!" Well balanced mono is far more like what you can hear when listening from a good seat in a real concert hall, unless you insist on sitting in the front six rows, than almost any over separated stereo styles recording! What I need is a competent way of converting stereo to mono for my very nice set! Best wishes from George

[@AudioMasterclass]

Stereo recordings often don’t collapse well into mono. But you can listen to one channel at a time, then you have a choice of two perspectives.

[@georgejohnson1498]

@@AudioMasterclass Yes you are quite right, though in the glory days stereo was mono compatible. Sometimes in multichannel mixes, there is the horrible comb filtering effect with phase incompatibility, that ruins stereo to mono! Fortunately few great artists have made recordings during this era of incompatibility, so I am not much concerned by that. And if all else fails, then listen to the left channel where the soloist in a concert is [usually], and the first violins. You get a skewed balance like sitting too far to the left in a real concert hall too close to the front. Been there, done that, and got the tea-shirt! Love your videos! Best wishes from George

[@jasontimothywells9895]

Eggszackly, I always have loved mono , and I still own a old black and white television.

[@robturner3065]

@georgejohnson1498 Want to give that Troughline 1 the shot in the arm it desperately needs? Swap the EF80s for EF184s (mine's December 1957!)

[@georgejohnson1498]

@@robturner3065 Dear Rob, My Trough-Line 1 was totally restored and recapped in 2018 and keeping as close as modern capacitors and resistors allow, to original specifications. The valves are either original fitment Mullards or in three [of the eight] cases NOS Mullards of thee original type. Thus it is working about as close to original as is possible. I rather like it. With the equally old ESL and a good Quad valve amp, it has a lovely sound. Very revealing of poor recordings, and fairly hopeless on pop music, but magic on a good live concert relay. I would not want a more modern sound quality. For that I have a solid state stereo set. Rotel radio, Denon integrated amp and Mission QX ! [mk 1] speaker's. That is s nice little set, but not nearly so nicely balanced as the veteran set. I use the solid state set for iTunes and LPs. It is stereo, but I have only a paper narrow air gap between the speakers, so it becomes effective mono. Thank you for you nice reply!🙂 Best wishes from George

[@adivarso8175]

Fosi markets this as PBTL on the spec sheet. Not a true mono then?

[@Douglas_Blake_579]

Yes it's true mono. PBTL is the TPA3255's mono mode,

[@thrdwrld3]

But what does Audio Phil think about the amp...?

[@AudioMasterclass]

I've a feeling he might be changing all his volume knobs for orange.

[@MichaelManningPA]

I know these little amps are all the rage right now. I have read a lot of these reviews, and I keep saying to myself, "why not just get a Crown XLi1500 Two-channel, Power Amplifier?" It's bridgeable, not "chifi," THD is

[@scottlowell493]

FWIW: I prefer the polymid tweeter of the B&W Dm100 (or older polyester) to the new diamond anything.

[@gteaz]

My centre just needs a mono.

[@ke5ufg]

In mono does the sub out output in mono also?

[@mattfranklin3622]

The Sub out is always mono, hence one output. 👍

[@ke5ufg]

@mattfranklin3622 Sorry for my confusion: If running one Amp in stereo mode, does the sub out combine base from both left and right channels into 1 out for the sub? If so, running amps in mono block, you'd only get base from whatever channel is feeding the Amp. You'd lose base intended for the other channel? Or is base not recorded in stereo?

[@ke5ufg]

@@mattfranklin3622 I appreciate that and I don't want to be a hassle. Is base recorded in stereo? is different base information being sent from the source to the left channel than the right? If so, I assumed a stereo amp would combine left and right channels into one mono out for the sub. Is this all wrong? is the base information identical on the right as the left channel coming from the source to the amp? Thanks

[@mattfranklin3622]

@@ke5ufg Yes, the left and right audio signals, including bass, coming from the source to amp are completely separate. The sub out however is mono. I can’t be 100% certain but logically speaking the mono signal comes from both channels combined. Why do you ask?

[@ke5ufg]

@@mattfranklin3622 Thanks. I have two running mono block. With my limited understanding, I am concerned that if I use the sub out from say the left side amp that is only receiving the left channel, I may be missing base detail from the right channel that would have, on a stereo amp, been combined for the mono sub out.

[@supercompooper]

Each driver needs its own amp with at least 10 Farads of capacitance. 😊😋

[@mariokrizan399]

👏👏👏👏👏👏👏👏👏

[@edmatzenik9858]

Mono is sadly lacking in many setups. I think you particularly need a mono switch in a car because not everyone can sit in the middle. And as for cross-talk, in some rooms I've longed for that. In some rooms you just have to put the speakers too far apart, so a bit of cross-talk could be a good thing if you could control it. Maybe.

[@crazyprayingmantis5596]

I'll wait until the Za3 pro mk2 plus special edition comes out next week im sure it will "blow the original ZA3 out of the water" 😂

[@Douglas_Blake_579]

For certain the paid reviewers will say it does.

[@AudioMasterclass]

Meanwhile the unpaid reviewers will say what they think.

[@Douglas_Blake_579]

@@AudioMasterclass Absolutely. Way too much gushage going on.

[@anahatamelodeon]

OK - I'll bite... First - on PBTL: simply paralleling the outputs is fine to be able to deliver more current and drive lower impedance loads, but you really can't call it "bridge-tied" - surely that means specifically connecting each side of the load to an amplifier output instead of one side to ground. Why not just call it something truthful like parallel mode? Next - Who invented balanced lines? Probably telephone engineers in the 19th century. Oh, and I agree about separate switch and volume control, but at least with this type you might be able to switch it on and off without turning the know if you're careful - even so I wouldn't want that arrangement; rocker switch for power is fine for me here.

[@glenngundlach9907]

Do NOT try "parallel" mode. Nearly ALL amplifiers wil kill themselves in parallel.

[@naibafabdulkobor4301]

When running the channels of a stereo amp in parallel there is usually still an arrangement of resistors one could call a "bridge". Even with both channels' gainadjusted as precisely as possible, this is needed to compensate for tiny differences (so the amps do NOT kill each other).

[@anahatamelodeon]

@@naibafabdulkobor4301 that's true - I wondered how they balanced the output currents and it would need some sort of current sensing resistor network. I still think BTL is a bad name for that case, because the *load* is not part of a bridge.

[@Douglas_Blake_579]

The mode is PBTL ... Parallel Bridge Tied Load and it is one of several standard configurations the chip is designed to work in. Do a search for "TPA3255 spec sheet" and see for yourself.

[@sepg5084]

Where are the frequency response quantitative measurements tho? You already have a workable setup with that signal generator and oscilloscope, but only tested two frequencies somehow. 30 measurements from 20hz to 20khz and a spreadsheet graph could greatly help your content. What sounds good to one person might not sound good to another.

[@AudioMasterclass]

No thank you.

[@PhilipBallGarry]

XLR inputs can be especially useful with an amplifier powered by a switched mode power supply. If you've ever run your hand gently over the case of a device powered by a SMPSU you feel a tingle. That's because they're not fully isolated from the mains supply. It's not harmful of course, it's only a few milliamps but it does represent potential for noise to be imposed on any signal with a common ground. The three terminals of a balanced connector allow true isolation from the chassis of the equipment.

[@Douglas_Blake_579]

Horsepucky. There are regulatory bodies all over the world that would not let a product that posed a shock hazard onto the market.

[@idwalwilliams3713]

Fun

[@fredashay]

Wait! Why would banana plugs be illegal?

[@AudioMasterclass]

They are not, but there is legislation around them in Europe. Reason? You can plug them into a mains socket. Don't try it.

[@fredashay]

@@AudioMasterclass Oh! Thanks for the quick reply! I'm in America, and despite everyone complaining about our horrible outlet design, it's very difficult to plug anything into our narrow slits.

[@Cola.Cube.]

checkedy check blank book and pen

[@AudioMasterclass]

Puzzled comment readers may wish to know that this comment is a reference to TV game show Blankety Blank.

[@Cola.Cube.]

@@AudioMasterclass you have the best channel on the platform, Happy Christmas.

[@StrangeBrewReviews]

They just need to eliminate the vollume knob for a VU meter and make them true mono blocks for $199.

[@AudioMasterclass]

I have a feeling they'll read your comment and do just that.

[@StrangeBrewReviews]

@@AudioMasterclass replce the stereo/mono switch with on/off ....Keep RCA/XLR ....one set of speaker terminals....but now add in full sized bus out XLR and RCA connections for daisy chaining.

[@ENGLISHISBEST]

This is audiophile stuff . I enjoy music more than the inners of technology, thats why I buy hifi equipment of hifi quality off the shelf, they do all the technological thought processes & design as its their career. I open a magazine & go on internet to see what is the best rated for the money I have for a component with no real headache worrying about what makes it tick. I then sit back & enjoy my music rather than assessments of the machine. It's when you read comments like you need a machine that reads 10 farads you know it's O.T.T.

[@robertbox5399]

If you put 100W into those resistors without a heatsink, they most certainly will burn through that book!

[@AudioMasterclass]

Don't worry! I'm a quick worker.

[@robertbox5399]

Until you forget the thing's been left on... The green ones change colour when they get properly hot and you can smell the warmth! Proper audiophile comment that.

[@AudioMasterclass]

And then the magic smoke.

[@Douglas_Blake_579]

Sine wave testing is particularly brutal. Most amplifiers are not meant to sustain full on maximum power for more than a few seconds. So one takes their readings then lets things cool off. I have pairs of those resistors on rather large heatsinks and I've burned fin marks into a piece of scrap wood while working on amplifiers. So far they seem to handle it well enough.

[@robertbox5399]

@Douglas_Blake_579 Yes, the difference between PA amps, guitar amps, and home cinema stuff. PMPO rules!

[@ChiefExecutiveOrbiter]

Pual McCartney's ears are WORNG!!!

[@rf0022]

Balanced audio was first developed by the telephone industry, using transformers for common mode rejection.

[@NotSure723]

A KZbin 'play button' is not something you should be seeking to attain, or be proud of.

[@jimbanville]

So has anyone actually tested this amp’s ability to deliver more current to 4 ohms when in mono mode? All the tests I see, show a very minimal increase in watts in 4 ohms in mono mode vs 8 ohms.

[@Douglas_Blake_579]

That's right ... the mono mode is not like in AB amplifiers where bridging ups the power... it is a PARALLEL mono mode designed to give increased current capacity for speakers below 4 ohms impedance.

[@jimbanville]

@@Douglas_Blake_579 Great. I need more than a datasheet for a chip’s capabilities. I need an independent test to show *this* fosi amp has substantially increased current capacity into 4 ohm loads in mono mode.

[@Douglas_Blake_579]

@@jimbanville No sir ... what you need is a lesson in Ohm's law. The data sheet tells the whole story. It's not an advertising document. It is an engineering paper that describes the capabilities of the chip to other engineers so they can use it properly.

[@jimbanville]

@@Douglas_Blake_579 No sir. I understand ohms law. You are ASSuming this particular board and its power supplies are designed and equipped with all the necessary components to use this CHIP to its fullest capabilities. So you actually think no one should even have to measure the output to verify a board (and it’s PS), no matter how cheaply built, is fully capable of delivering the chip’s power specs. Gotcha👌🏼

[@Douglas_Blake_579]

@@jimbanville Oh my, now you're starting to sound like one of those "conversation is competition" trolls. I get it... you want proof. Unfortunately you appear to be expecting the ZA3 and it's cousins to behave like Class AB amplifiers where "mono mode" actually means Bridged Stereo. The TPA3255 amplifiers we're seeing on the market are *already bridged* in stereo mode. That's what BTL -- Bridge Tied Load -- is all about. You can't bridge an already bridged amplifier... the chip is already producing maximum wattage at 8 and 4 ohms. What you can do is parallel the power outputs in PBTL mode for more current delivery, leaving you with a mono output that can handle very low load impedances. Your mistake here is in expecting an already bridged amplifier to act like the old school bridged stereo amps, and I can tell you from a couple of years experience with this chip... that simply is not how this works. In BTL or PBTL modes the output power will remain the same for 8 and 4 ohm loads... but in PBTL it will deliver surprising power at 3 and 2 ohm loads. Things have changed ... try to keep up.