Douk Audio A100 amplifier test & review

[@doukaudio]

Thanks John, thank you for your review and pointing out its problems may exist. It is with honest reviewers like you who keep giving us feedback that we can make faster progress. As for the two problems of without cooling paste and volume knob, I consulted our engineers. 1. We use thermal grease between the TPA3255 chip and the cooling block, but not between the cooling block and the case. The A100 uses a solid aluminum block with a size of 85*65*8.5mm inside. Under normal use conditions, the internal radiator is sufficient to support the working temperature and heat dissipation of A100. In order to ensure the more stable performance, we make the internal radiator and the shell directly and seamlessly connected. The thermal conductivity of aluminum alloy is fast enough to dissipate heat through the case under extreme power output. We have done many temperature tests, the A100 won't be obviouly warm even at continuous high power output. 2. A100 uses a type B linear potentiometer but not type A. SInce we think that the A100 is mainly used as a high power desktop amplifier , type B will make the volume adjustment step in the first half will be more uniform. While the type B potentiometer we used in the A100 is 50K, which is relatively higher so that the volume adjustment is not obvious at the first half. We are very happy to see our A100 is discussed, even if some are critical, which is also very valuable to us. We will continue to collect customer opinions and make corresponding improvements in the future. Thank you again! ❤

[@isoguy.]

Every time you review one of these amps I find myself looking for my flexible friend because I want to hear those sounds for myself, currently have three Douk amps you have reviewed. You are one of the very few youtubers I trust to give an honest review because I know you tell it as it is. Great review and thanks for sharing and taking the time to make these vids

[@JohnAudioTech]

If you want, I can send you this amp if you're within the US. I have a bunch of reviewed products sitting around that needs a home. I do hang on to products for a month or so after the review in case I need to address something.

[@isoguy.]

@@JohnAudioTech That's such a generous offer, and I can't thank you enough. However, I'm in the EU so postage would probably cost more than the price of the amp which I guess you probably already know if you have ever purchased anything from the EU to be shipped to the US or vice-versa. During the pandemic I ordered some replacement parts from the US that cost $45.75 postage was $138 (the company would only ship via UPS) + import duty + handling charge in the US + European handling charge + currency exchange charge) then 20% value added tax in the EU charged on the total of previous service costs; deliverd cost in the EU close to $275. (Crazy) Once again, I can't thank you enough for your generous offer. I really enjoy both the educational content and honest reviews you present in your vids and because of that you have one very loyal subscriber.

[@1pcfred]

Rubycon? Judging by the poor printing on the sleeves I'm kinda doubting the authenticity there. The 4 caps in a line in the middle of the board look like black gates. Yeah I don't think so. But hey at least that shows they know what the good stuff is. Imitation is the sincerest form of flattery there is too.

[@bobisyouruncle1]

Designing amplification myself, I've never been convinced about the '1 chip does it all' concept. Thank you for the in depth review John👍

[@Mr_Meowingtons]

the controls confuse me what is this amp for lol it just need Bass, Treble, bal and volume

[@jeffk204]

Can you comment on the build quality? I know it is somewhat subjective, but do the pots feel like they are good quality or do they have that cheap feeling? When you looked at the board, was it well made? I couldn't really get a close up look on my screen. The last amp I build online was pretty poorly made and I had to replace the banana jack connectors since they just didn't work. Even though that was also inspected by QC1. I wonder if QC1 works at all the same factories. Sorry about all the build quality questions, I'm on the fence about picking one of these up. Thanks for all the great videos. I love both the build videos and the review videos.

[@strangersound]

Was not expecting something from Stay Hungry. That was my fav album when I was a young one. SMF! :)

[@yo3429]

It's a normal behavior for TPA3**** and other D-chips to rise distortion with frequency. Normally it starts around 5k, some do a little better. This is still the last hurdle for this type of amp. If they manage to keep distortion low in high frequencies ... well.

[@carlose.martinez545]

The volume pot seems to be a linear one, if we consider John's comments of it increasing volume rapidly just in the last rotation third. A log pot should be better. Pity the PS is just 48v/5A instead of 48v/10A. What is the measurement system John is using?

[@ford1546]

It uses (TPA3255) you can buy a good TPA3255 amplifier board if you want to build your own amplifier The problem with almost aller is that they use far too small a heatsink.

[@carlose.martinez545]

The problem of going the DIY way and starting from a TPA3255 board is the metal box you will use and the heat sinking system to cool it. The Douk A100 attaches the metal box to a plate which is in contact with the chip. So there should be more grease over all that plate, and then more grease on the box surface in contact with the ribbed heatsink. Temps reached on the first point and then on the heatsink would give some idea on how effective the full chain is.

[@karllangeveld6449]

Hi John, Just an off-topic question, when will you go back to your own amplifier projects? I kind of appreciate those much more than you reviewing the Chinese products.

[@JohnAudioTech]

Explanation coming...

[@FaBianrecord]

Yeah, it comes with linear type pot for the volume... what happened? there's not LOG anymore?

[@Douglas_Blake_579]

Thanks John ... looks like another in a growing line of products from people who don't actually know what they are designing. Recent products from a lot of these Chi-Fi companies seems to indicate "feature loading" rather than functional design. Simple logic tells us that if you want a 2.1 setup you're going to need two amplifiers... a stereo one for the mains and a mono one for a passive sub. So wouldn't it make more sense to produce two amplifiers, each specialized for the job? That rise in distortion at higher frequencies is indicative of coil saturation in the output filters. I'm betting that if you fired it up, outside the case, you'd hear those tiny inductors singing like a good soprano! I'll take the older toroidal inductors with nice beefy wire, any time. The cooling solution is a full on case of "Missed it by THAT much" .... nice big fins on top (undoubtedly a cosmetic choice) so they bolt the heat spreader to the bottom of the case. One has to ask "What were they thinking???" And finally that volume control. That kind of behaviour is a marker for a volume pot that is way -- way too high in value. The last time I saw that was on an old Radio Shack amplifier with a 100k pot feeding 10k input resistors. Oh well ... thanks for the review... but I think this one is a "Pass". kzbin.info/www/bejne/pYHao6KarcybqNksi=O8eQanC_9BUfcXzE

[@isoguy.]

I just purchased this amp and at the price point offered I don't expect perfection or longevity but I believe it's fit for the intended purpose. (shell looks tough). I guess if money was no object then I would spend a few thousand on an amp but with kids and a dog in the house, it appears robust and is, as I say fit for my purpose. I need another amp for the den but under $400, any suggestions. Thanks for your comments and can't wait to peel off the top and hear those components sing, is there a fix for this, other than doorstep to bin?

[@JohnAudioTech]

@@isoguy. If your source has a volume control, use that. Set this amp's level and forget.

[@isoguy.]

@@JohnAudioTech thanks for the tip John

[@ford1546]

is the power switch a proper switch or is the standby connected to the ic.

[@JohnAudioTech]

I'd have to investigate. I think it is a soft power switch.

[@haraldh.9354]

John what is about JAT801 ;)))

[@JohnAudioTech]

Doing videos that are quick to make now. Hope to get back into the projects soon.

[@ebs6846]

18:12 VR2 to B50k. Do regulacji głośności należy stosować potencjometry o charakterystyce logarytmicznej "A", a tu jest potencjometr liniowy "B". Dlatego ta regulacja jest taka dziwna, błąd Chińczyków.

[@MichaelBeeny]

In sub mode you are bridging both channels, hence mono. NOT a good idea to use a 2-ohm load, 4 minimum. Good heatsinking, probably the best I've seen on this type of amplifier. Should really have heat compound between the case and the heat spreader. Should appeal to the valve people that love all that high THD.

[@JohnAudioTech]

Each channel is already a bridge configuration. I'm assuming the relay on the output is paralleling the two channels for better current handling.

[@Douglas_Blake_579]

@@JohnAudioTech Check the TPA3255 data sheet. It is paralleling channels in what TI calls PBTL mode.

[@garygranato9164]

lin pot volume control ??

[@JohnAudioTech]

A linear control gets very loud almost from the start. I think they got the log backwards.

[@andymouse]

@@JohnAudioTech Reverse Logarithmic Taper (C Taper): Resistance decreases logarithmically with rotation, used in specific applications where reverse response is needed or they wired up a normal one wrong ?!

[@christopherkise]

Oh new measure eqipment?

[@ford1546]

How can this metal plate transfer the heat to the case without cooling paste or cooling pad?

[@Douglas_Blake_579]

It is rather dumb to bolt the IC heat spreader to the bottom of the case with the fins on top ... and yes, thermal paste would improve the heat transfer.

[@ford1546]

@@Douglas_Blake_579 I think that would help a LOT!

[@Douglas_Blake_579]

@@ford1546 If you get two well mated surfaces with no gaps you can sometimes get better performance without the paste. But I seriously doubt that is the case here. I'm still chuckling about the beginner level mistake of bolting the chip to the bottom with the fins on the top.

[@MichaelBeeny]

@@Douglas_Blake_579 I don't know what the makers of these amplifier must be thinking. Heat transfer from one surface to another is basic school science stuff. Maybe they were off school that day!

[@Douglas_Blake_579]

@@MichaelBeeny Hello Mike ... Especially the rule about "heat rises", I've seen this hot spot down thing in a lot of Chinese stuff, ranging from these little amps to ham radio gear all the way to home appliances. Maybe physics works differently over there...

[@leeeagle5994]

8 Ohms both chnls. , " 100.09 " ? watts

[@Douglas_Blake_579]

Yep ... that's typical of the TPA3255 chip.

[@gamiwv]

Just 3300μF/63V ? What ripple current can handle ? 2,5 A or maybe less ? NO !! With 10000μF maybe 2 x 50W (rms at 8Ω) could be possible with LOW HARMONIC DISTORTION

[@JohnAudioTech]

There are two 3300uf caps plus the filtering in the power brick

[@Douglas_Blake_579]

You forget those caps are not being recharged 120 times a second like in a linear supply. This is SMPS bricks and they refresh the bulk caps thousands of times per second.

[@gamiwv]

I know what I measure. In a (very common in AliExpress) TDA7379 amp. board powered from a 19V brick, I add a 6800μF / 25V capacitor soldered directly to the "power terminals" and the "bass" improved dramatically

[@Douglas_Blake_579]

@@gamiwv So you expect a 20w/ch class AB amplifier powered by a laptop charger to behave the same way a 100w/ch class D amplifier powered by a 240 watt SMPS does? Y'all gots a lot to learn, son....

[@gamiwv]

@@Douglas_Blake_579 I'm NOT your "son". I'm a professional engineer in automation & power electronics and I am in my 70 y.o. So , behave better pls

[@antibrevity]

I reckon that Douk Audio doesn't know about the word d-o-o-k-i-e. This is like naming a company Poup Audio ;). We're entirely out of names available for trademark, however, so beggars can't be choosers.

[@bobisyouruncle1]

It's the same with headpone company 'oneodio'. The word odio means bad in italian. I read an article about it but by the time the manufacturer realized the meaning, all the marketing was already done, so they stuck with the name. I guess it's better than naming it 'schiit' i guess. That's a real bad one. 😂

[@ralphbesser1125]

I bought one of these from amazon based on these youtube reviews. Didnt work right out of the box. Garbage, don't waste your time.

[@supergwizzo]

All cheap junk all serious coments of crap and thankx Douk lol old lie seem like you work with them ! 😅😊