Marantz 2325 - Intermittent Channel and Some Additional Testing

[@jimomertz]

I’m thankful I have a Marantz 2275 that survived my youth dragging it to college and through several long distance moves. It’s still in perfect condition and I still use it occasionally today. I always lusted after the big boy 2325, but couldn’t afford it. It’s such a beast. These things are nearly 50 years old. Such amazing build quality.

[@jeffberwick]

I had a very interesting experience debugging my Marantz 2325 recently. I heard a rapid-fire "bad-a-bad-a-bad-a" noise in the background, especially on the right channel. It was independent of the volume control, I traced it to the tone board, specifically to the BA312 IC (which is really just 3 transistors). I saw a little square wave (sort of a dip and tone burst) every 100ms on the scope. After doing all sorts of experiments (shorting input cap, adding extra output cap, putting a 30pF cap across the feedback resistor), completely disconnecting the signal at the input and AC shorting it to its own ground, nothing worked, although some things reduced the noise a bit. I figured it was some kind of RF interference but did not know what. I gradually started turning off stuff in my garage and VOILA! It was the Google Mesh wifi puck! Once I plugged that into a different outlet across the room and moved it away, the Marantz was back to normal with an inaudible noise floor. Another noise generator (for a different AM radio project) was the computer monitor. Again plugging into a different outlet made the noise go away. Lesson learned! The noisy new digital world is not kind to analog vintage electronics.

[@richardkelsch3640]

Phase inversion uses the actual design of speakers to do its trickery. Typically, in a bass note, the first impact is positive going, causing the cone of the woofer to push out. This causes the pressure to be solely initially built in the air. However, if the cone moves backwards, it gets further damped by the enclosure and sounds tighter. The difference is subtle as some damping occurs in both directions, but there still is a differences. Once again, the damping is distortion masquerading as pleasing, just like tube damping also is perceived as pleasing. I find "audiophiles" that think they are purists actually tend to be the biggest fans of distortion. Tube amplifiers warm the sound because of their spongy power supplies and high impedance nature. This "warm" sound is distortion, but it pleases many audiophiles. Phase reversal sounds pleasant because of the bass dampening that occurs. In reality it introduces distortion. It distorts the signal 180 degrees out of phase and dampens the bass which makes it sound tighter. It's not a pure reproduction of the original. Nevertheless, it pleases the ear of "purists". Is the average human being going to notice the difference? No. Are they going to care? No. Most can't tell the difference between a 128K MP3 file and an original CD (I can), but most won't. Maybe there was a method to the Marantz madness in the inverter. Who really knows? If you like it, then you obey the speaker terminal labels, if you don't like the inversion, then flip the speaker polarity and problem solved.

[@ligius3]

I wanted to write a comment but yours basically sums it up. In my younger years I could hear the difference whether both speakers were running in one polarity vs the other. Maybe now also, but there are so many factors at play (such as room layout) that I just randomly wire them up and make sure they are in phase.

[@thomaskitz1185]

I ran an authorized service center for Marantz and other brands at the time that the 2325 was new. There was a service bulletin on some diodes in the main amp units. They were a small round diode with leads no numbers. We were to change them regardless of the complaint. Symptoms were crack snapple pop and clicking out of the protection relay.

[@thjbird]

I repaired hundreds of those back in the day. Intermittent channels in that vintage of Marantz receiver were most often corroded contacts on front panel switches. Cold solder joints were another possibility. Memories.

[@savagedick1462]

Were those 2325 built to last and easy to service?

[@mbf9690]

Great video as usual. More proof that vintage is really superior to what is sold now. Your video of this and the Sansui 9090 confirm my thesis. I’ve owned both and wish I still had them. Needed the money at the time : ( . One thing we have to keep in mind is that both receivers cost about $950 in 1976 which is ~ $4400 today.

[@jubemarsh2202]

Excellent as usual Tony 💯💕🇺🇸🤙 I brought a 4430 back to life Love it!

[@warrenmacdonald1372]

Thanks Tony for your attention to detail. My 2325 ( from 1976 ) has, in the last 35 years, taken about 20 minutes to "settle-in" before it exhibits its' classic subjective adjectives that most Marantz owners talk about. That's fine with me; while it's doing that, I get to look at the classic 2325 panel, and smile. BTW, it's was restored about 15 years ago, and it's due for some more TLC, so thanks again for allowing me to see what goes on, on the desk of a top-notch surgeon like you.

[@bobgauthier1569]

Just got my 2325 back from my tech. And it is sounding great 👍

[@R3TR0R4V3]

I really hope to see a Marantz 2230 serviced (hopefully recap, etc) on your channel someday.. Surprisingly, there are literally zero videos about this on YT, other than bulb changes and simple stuff like that. Anyways, love all your videos either way, whether I own the particular receiver in the video or not. Happy Thanksgiving! 🍻

[@craigm.9070]

Happy Thanksgiving Tony & family! Thank you for posting this; Marantz receivers always seemed well organized in the internal layout and this one looked fairly straight forward to work on. The owner I'm sure will be ecstatic with his revived hi-fi gem, this one tested in the Brute category!

[@BobWilson84]

Happy Turkey Day Tony!!! I was laughing when you finally saw that failure for the 2nd time, what a relief to catch it with enough time to test the point on the transistors. Thanks as always for the videos. I'm interested to learn more about the THD multimeter. I don't currently have one on my bench, and I'm on the hunt! You clearly have the heart of a teacher sir, in the spirit of Thanksgiving, Thanks again sir!

[@VaughanGuitars]

Lol Back in the day I remember Bang and Olufson pardon the spelling, used design of their speakers with the Bass driver farther out towards the face their cabinets, midrange speaker set a little farther in and the tweeter was set back the farthest. I asked a B&O sales person why this was done. He explained low frequencies move thru air slower than high frequencies, so in a room situation the hope was to have all frequencies hit at as close to exactly the same time. This may be another example as you explained about inverting voltage so you miss the half step or however you explained it to us. Thanks 2 years later for the video.

[@greengrayradio1394]

I watch your videos with great interest, Tony! You caught the intermittent transistor! That circuit glue decomposing into acid and causing corrosion and leaking current we see often in Eastern stuff from this age. Interesting info about the phase inversion built into these, like you I wonder why..

[@johnbeckham1483]

From my observations it seems that the Marantz stereos are quite reliable as stereo receivers from the 1970s for the most part! From what I have seen it's usually a leaking transistor, a dried out capacitor or a zener diode as the culprit!

[@TY-ob7fz]

Happy Thanksgiving Tony. Best to you and family 😊. BTW I always have a phase switching slide switch on either ( not both) the right or left channel to get optimal sound. Been using the set up for longer than my hair turning white. “I believe” how the phases hits your ears is relative to placement of the speakers also and there’s a comfort zone or sweet spot that the slide switch allows vs swapping leads on the speaker.

[@Godzilla941]

The only thing I had energy to do when I was off work for this Thanksgiving holiday was sleep for two days straight. :( I have a few BGW amps here (150, 250D, 750C) that all send the output feedback to the non-inverting input of the front end op amp--meaning they invert the input signal. Right now I'm driving the 150 and 250 from an active crossover that has phase inversion switches, so with a tone generator at the crossover frequencies you can play around to get the speakers (internal cost-optimized crossovers yanked) to sound right. I guess in the pro audio world that's more of a thing since someone at some point is guaranteed to have wired one or more somethings backwards and it's better to fix it by pushing a button on a piece of gear than crawling around or hanging upside down someplace inconceivably awkward and dangerous with a butane soldering iron. Remember that 50/50/90 rule... You can take the recording in question, say an LP, and run the phono preamp output into a DSO and look at the attack signatures of something obvious like a kick drum or tympani, and set up your speakers to create the same positive or negative pressure spike. It would also depend on what they did in the studio and at the mixing table, with no guarantees if the vocalist is in phase with the kick drum to begin with, because...well...someone at some point is guaranteed to have gotten something backwards. :)

[@jrumiano]

I have a Marantz 4400 receiver that had an very intermittent problem that turned out to be a grounding issue with the power supply. Good luck with the troubleshooting.

[@jked7463]

Great video. It perplexes me why 4 people (at time of this writing) would vote thumbs down. And we give thanks for you and your videos. Happy belated Thanksgiving.

[@jamiestarr1022]

Some people just can't feel good about themselves or their reality, unless they are putting others down. Great video and instruction Tony!!!!!!!

[@harrycallahan686]

I have that receiver 2325. Lost power in 1997. Power restored in 2021, bought some Klipsch 5.5's and haven't even tested it yet.

[@jf-3945]

Interesting... Always wondered WHY on some old Tube Amplifiers there IS a REVERSE setting to reverse speaker polarity. Shall have investigate further.

[@tubeDude48]

When an Amp. has a Loudness control, I always turn it ON, otherwise you loose a lot of Bass, and some Treble.

[@MichaelBeeny]

When you look at the speaker cone of a bass unit, playing a deep, say drum beat. It seams that if the first beat pushes the cone outwards, it appears to have a more extended bass. I'm not sure how or why this should be, as you pointed out it is AC after all. Try it yourself. Don't ask me how or why!

[@rodwilliams1381]

Hi Tony. Another great video. I don't understand much of the tech but I find your vids mesmerizing. Wish you were related to me as I have my Sansui AU9500 which is playing up. I'll need to do some research and hopefully find an Australian version of you. Cheers

[@jimharmon3404]

There is a lot of focus on the audio sections which is always interesting and useful. Since this is a AM/FM receiver and we have all seen lots of AM alignments, so guess what I am going to ask for. Yes you got it, Can you make a video or two demonstrating what equipment we need to align FM and what the process is? It is far more complex with side-bands and sub carriers and demodulators. Does anyone else have a hankering for some FM fun? ThanX Tony!

[@xraytonyb]

I've done so many FM and MPX alignments in previous videos that i didn't think i needed to do it in this video. Look at some of my past videos. Lots and lots of FM stuff. Thanks for the comment!

[@universalhead]

That was amazing, and sounded great streaming from the telephone pole.

[@Nickbazukaho3nt]

Excelent 😎👌👍

[@harryshector]

Could it be that the inversion is meant to attenuate feed back through components such as turntables, which can couple audio signals back into an amplifier if speakers are driven at high enough levels? If the signal was inverted, then the feedback would be degenerative?

[@ralphralph8832]

Hi Tony, thanks for the video. When I measured my 2240 1 year ago, (1kHz input and output side by side on the scope) I first thought I did a mistake. Yes, 2240 also inverts. I'm also interested in affortable THD measurements (below 1%) and 2015 is a bit out of my budget. So if you have an alternative recommendation, it would be nice. Greetings from snowy Austria.

[@billmcdonald2436]

Gorgeous receiver

[@abelabner]

Nice vid, I got the warm sound on my system Denon and Sherbourn, not sure if that's just my equipment or not but definitely "bassy" if that's a word, lol.

[@erikdenhouter]

Inverted signal: how about feedback like to a turntable ? Think about when you reverse ONE speaker lead, the air pressure won't build, the pressure only 'flows' from one cone (the one going out) to the other cone ( the one going in), with as a result the deep base is GONE, a well known connection error. Likewise you can imagine that inverting has a good effect on unwanted feedback to a turntable, or even a mike maybe ?

[@jamesmdeluca]

Greetings: When you get it to act up; STOP IMMEDIATELY and let it sit with the symptom showing. Resist the temptation to play with the knobs. Go right to the record outputs and divide the problem as to before or after that point. Ignore the dirt for now. If you stop right away, you have a chance to see if the problem cares about the signal level when the problem appears. Trigger on the good channel, please.

[@alanarmstrong2323]

Some older 80s realistic receivers had a turnover button for both bass and treble. Happy Thanxgiving!

[@mackfisher4487]

The scourge of a technician is an intermittent problem, I'm a little superstitious. Return it to your relative but wait in the driveway until he fires it up as it'll probably act up again, and of course when you have it back on the bench it'll work fine. Good luck happy Thanksgiving to your family and workmates.

[@marka1986]

Yeah been there and done that with intermittents. Then customer saying you didn't do anything on it. Lol

[@herbward5240]

Did you tighten the collector screws on the output driver transistors ? Make sure you tap the speaker relay while looking at the distortion waveform on a null type distortion analyzer.

[@Columba_Kos]

The mind boggles! Why would Marantz invert the phase? Generally, so much effort is made to ensure that proper phase is maintained in the signal chain. On the off chance that you uncover some reason for why Marantz did this inversion ploy, it would make for a very interesting follow-up.

[@bradfordaudio]

Happy Thanksgiving Tony!

[@markanderson350]

I don't think phase is an issue. I do know if speakers are out of phase, it is an issue but phase relative to the source is not and now with digital sources delayed several seconds, that is the least of your worries. It's just how many stages you go through, even or odd. When you bridge, you need a phase shift on one channel too.

[@Asriazh]

The only time I saw phase inversion switches or phase inversion being used in general is with subwoofers. I guess it's to make sure that they don't cancel out the same frequencies that may come through other, main right and left speakers. I did a phase inversion too when designing a crossover, cause i send the same low freuencies to two different bass chassis who were pretty much canceling each other out. Switching the polarity on one of them brought the bass back to how it was supposed to sound. They used to get different lower portions of the frequency spectrum, but i decided to give them both the same frequency range for added surface. I wonder if Marantz did the inversion on purpose. It couldn't have been by mistake?

[@jwl9286]

Great video! I learned so much. I was knocked off my chair when you pointed out the phase inversion. I've always thought the amplifier should represent the events in the recording studio. This is puzzling. It's also puzzling that it occurs at 700. Do you think it would be permissible to reverse the speaker leads? Man, I'm going to mess with some other amplifiers and see if any do the same thing. Gosh, you may have unleashed some Ancient Chinese Secret.

[@Homer19521]

👍 Awesome channel. I quoted you on a Ham IO group about fader dexoit & the cleaner type. Looks like Caig has decided to call everything "deoxit" unfortunately. I liked it better when they called it Fader Lube. -73

[@aminbjt5843]

Hi dear friend Nice to meet you And I learned a lot from you Thank you very much for your great videos

[@johnwilliamson467]

Both one I have and a friend have had the same problem with the volume pot.

[@pablosaenz6541]

Hi Tony! Thanks for your videos. I have learned a lot. What about using acetone ( nail polish remover) for remove that obnoxius glue under the capacitors?? I have tried it and worked!

[@jdmccorful]

Learning, learning. Appreciate your work tremendously. Thanks for the look! Happy Thankgiving.

[@johnnytoobad7785]

So are you going to use colored dim-bulbs for Christmas time ?😄

[@xraytonyb]

I hadn't thought of it until you mentioned it, but now........... ☺

[@robertmceuen3630]

Beautiful reciever. I love Marantz. I have a 1200b integrated amp that has an intermittent channel problem also. Can't find anyone who wants to fix it...😬

[@DAVIDGREGORYKERR]

Seen a single inline chip used as an power amplifier used in the DIGI-GAKKEN Electronics Kit.

[@queenssmith9438]

Perhaps the inverting design is to save component counts or increase SN ratio. As long as you invert both channels the same amount (180 degrees or any amount), there will be no phase cancellation between the left and the right channel. And one should not hear any different. I may be wrong because I am no expert on anything.

[@gearheadted9210]

Happy thanksgiving Tony!

[@Asian_Connection]

Watching this on Thanksgiving a year later.😅

[@NovaluxStereophonic]

A lot of the Conrad Johnson stuff has inverted output and absolute phase is actually explained in the manual which is kind of cool. They must have come up with the gain they needed with a lower tube count and did not want to add another stage to maintain absolute phase. I bet the invert switch on high end sources and preamps is to account for power amplifiers that invert by design.

[@BobWilson84]

I have a CJ solid state preamp… it also inverts the phase. The manual claims it’s important to reverse the speaker polarity to account for this. But, in reality, I don’t see how reverse polarity would affect anything as long as the speakers are in phase with each other

[@davids4610]

Cool, X-Ray Tony and a tummy full o'turkey!

[@InfinitygamingFtw]

What timing you have. I'm about to rebuild a Marantz 4240 with a dead channel and it's very similar inside. This is a great help! I noticed it has some of the 2sc1318's you mentioned and I think one of them let go or possibly a main output transistor.

[@tubeDude48]

That green-coated resistor lead looks nasty!

[@davewilliams5932]

Hi Tony, what do You use to clean the inside of the unit?.

[@frankporfidio9813]

Happy Thanksgiving Tony , I been fixing these things for 30 plus years and never noticed the polarity inversion . Usually , crumbled pre amps transistors and blown outputs , bad discriminator board etc , etc .......Never noticed it , what tipped you off to it ? nice video !

[@leeclinton2652]

Great, informative post. What's the model number of the GWINSTEK instrument?

[@geirendre]

MDO-2204 EX

[@lucaspatterson]

Hi tony, apologies for the pestering question but do you have an videos or useful information about the output transistors on the SX 80s series (880, 980, 1080)? I have a 980 and I’m slightly concerned about them being bad/going bad as they are hard to source. Any workarounds with other parts similar to the stk packs?

[@xraytonyb]

I did a video during the Sansui AU-X1 series called "The Big Crazy Transistor Video" (or something like that) where I talk more about these types of transistors. The higher-end 80 series Pioneers use ring emitter transistors. They were specifically designed and made for high-end audio amplifier applications. They are no longer in production and are getting harder to find. There is another type of transistor still made by Sanken called the LAPT (linear amplifier parallel transistor) transistor. They are a good substitute for the ring emitter transistors used in the Pioneers (same performance, just a slightly different internal design), but they have a different case type (TO-3P or MT100) instead of the MT-200 type. MT200's have two mounting holes and the MT100 has only one. You will need to modify the mounting to the heatsink to get them to fit, but it's not impossible.

[@lucaspatterson]

@@xraytonyb hey thanks for the quick reply! I’ll give those videos a watch! Have a great holiday

[@tommybewick]

@@xraytonyb Tony your knowledge of these things continues to amaze me. I know it's only because of your experience and you're very humble about it, but you know more about these things than the average person.. We have all learned a lot from you and we appreciate it very much!

[@seanobrien7169]

TONY!!! Man, you let Marantz's secret out of the bag...

[@terencekaye9948]

Hi Tony,, where did you find the incandescent lamps?

[@avro66]

A, lot of quality cd players from the 80,90s had a inversion button because some cds were recorded out of faze it was a useful feature and I could definitely hear a difference when a recording was out of faze,

[@hoobsgroove]

you should build a carlson's lab magic probe non-contact probe, for picking up interference produced by breaking down of components, would be very handy for you. would they have invited the phase for bridge amplification,? speakers are sensitive to phase displacement the lower down the frequency the more the phase flips a speaker is never constantly in phase in its frequency range that's why if you have a 3-way speaker you flip the midrange out of phase so it's in phase with woofer

[@dhpbear2]

8:23 - Did you clean the trim-pots?

[@xraytonyb]

NO. They seemed to be working fine, so I left them alone.

[@seanobrien7169]

One factor when a customer decides what work they want done is the simple fact that the equipment is in the hands of a tech getting attention now. If it is on your bench I want you to pull all the stops. Do everything you think needs done, your discretion. I would rather pay the piper at that point than have to live with future problems, find techs to work on it, get the equipment to them, wait on a waiting list for maybe years, and Lord knows some of these parts and components are drying up.

[@johncoops6897]

Another factor is that the customer's "value" of an old amp like that can vary. For many people, any extra tech time spent on it is completely non-viable. A brand new 7.1 amp with all the bells and whistles is under $200, and that will claim much higher power than only 120W/2ch. They don't care that it's a classic old Marantz, just like they don't care that an iPhone 3 was a ground breaking phone.

[@seanobrien7169]

@@johncoops6897 In that case, would it be in a tech's hands in the first place? It is getting extremely difficult to find anyone to work on this kind of thing, surely if someone owns something like this they understand what it is. Grandma Frank is not going to even try to seek anyone out to fix it, she will just put it up on ebay, or more likely at a garage sale.

[@jamesmdeluca]

Greetings: Have you determined whether the problem is before or after the record output?

[@JayH7745]

Hello. What do you recommend for cleaning out dirty potentiometers? And where's the best place to order it? I heard that some sprays will actually damage the carbon in potentiometers. Figured you would know what's best. I have a vintage Kenwood amplifier that has some dirty controls. Volume and balance mostly. Thank you for the information.

[@NiHaoMike64]

There's a special kind of Deoxit just for potentiometers.

[@JayH7745]

Thanks! Deoxit brand has a D5, F5 and G5 spray. I heard somewhere that the D5 or F5 is good for potentiometers but one of them will actually eat the carbon away. I definitely don't want to get the wrong type. The red can or the green can is the question I guess? 🤔

[@randyr.parker2698]

@@JayH7745 Green can for pots.

[@JayH7745]

@@randyr.parker2698 Thank you Randy. 😊

[@randyr.parker2698]

@@JayH7745 You're welcome. I ruined a carbon pot one day, that's when I learned there was special cleaner for pots. ;)

[@brianbloom1799]

If someone is interested, In buying my Marantz 2325, It sit and does not get used anymore, since I got sick,It works But needs to be cleaned, All controls need spraying, I bought this 20 or so years ago, Off a old couple, The out side wood cover was worked on buy him, But was find for me. I payed good money for this, I will be honest, I payed 650.00 for this, I know it Now sells for double that restored, Give me what I payed its yours.

[@deangale4496]

Where are you located?

[@harrycallahan686]

Did you sell your receiver?

[@brianbloom1799]

@@harrycallahan686 Hi sorry I only look at the computer , When there nothing else to do, Yes, I still Have it, I will Not ship ,Have bad legs and getting help is like pulling Teeth, You will have to come and pick up, In ct

[@harrycallahan686]

@@brianbloom1799 I'd like to see some pitcher's of the Marantz?

[@MrMac5150]

Question: I was taught to test a speaker with a 9 volt battery to see which terminal was the positive, but said that, what difference would there be if you switch the polarity. Will it damage anything, and can the average ear hear the difference. .

[@johncoops6897]

Both speakers must be in the SAME phase. If not, then the Bass sounds are somewhat cancelled out. That's because Bass is generally mono (hence one subwoofer sounds OK) and if the speakers are not in phase then one woofer cone is pushing the air, whilst the other is retracting from the air. You can definitely hear a difference by reversing one speaker's phase. You cannot hear any difference if ALL speaker's phase is reversed.

[@DAVIDGREGORYKERR]

can you not use BC182L and BC212L as well.

[@barryf5479]

In the 2200 Series Marantz receivers, the last two digits "generally" denote power output but with this 2325, that convention is broken. What's the real story about the product numbering? Also, what does the 23 prefix denote?

[@deanmorris9622]

I believe they went with the “23” prefix on receivers that had over 100 wpc. Hence “2325” = 125 wpc, “2330” = 130 wpc and so on…

[@pablosaenz6541]

Sorry if my english is not correct...

[@NovaluxStereophonic]

Tony, which oscillator do you use when measuring distortion with the Keithley?

[@xraytonyb]

You can either use the built-in one on the 2015, or an external source. I use the Rigol DG-4162. It seems to have very low distortion and works well with the 2015. Thanks for the comment!

[@NovaluxStereophonic]

@@xraytonyb I use a Siglent SDG 1032X and it has too high of a distortion spec to take accurate THD measurements with my Tektronix 5000 series analyzers. I use a Tektronix SG505 for this but not have precise digital control for levels and sweeps is a bit of a pain. The Siglent is .08% residual. I am going to look into the Rigol specs. Thanks!

[@zitoparreira7993]

Hi,,I have one too.

[@johnnytoobad7785]

I'm curious why the scope "flipped" the phase signal measurement EXACTLY at 700 hz ?🙃

[@johncoops6897]

He never explained it. I think what is happening is that there is a small phase shift throughout the whole frequency sweep, but the whole signal is fundamentally inverted. For my explanation below, let's say that it changes from *absolute* phase angle of 185° at 20Hz to *absolute* phase angle of 175° at 20KHz. ... Now we humans can understand that there are 360° in a circle, and that the change from 185° to 175° is a 10° shift centered around 180°, right? However, the measuring tool doesn't see it the same way... it is displaying phase *shift* (not angle) as "degrees away from zero", and it's zero point is the centre horizontal line of the display. ... Now, at 20Hz it needs to display (say) +185° out of phase, but it cannot plot that because it'd be past it's maximum of 180°. Hence, it flips around the other way and shows the +185° as -175° behind of zero instead. So the plot is down near the bottom, almost as far as it can get away from the zero centerline. ... As the audio sweeps towards 700Hz, the *absolute* phase angle is seemingly going forwards from 185° to 180°, yet the display shows it worsening from -175° and approaching -180°. When the audio sweep passes through 700Hz, the display passes through180 degrees, and the display cannot go any further. So at that point, it quickly flips from -180° (below the line) straight up to +180 (above the line) and continues plotting from the other side. ... In other words, it cannot display 185° to 175° as a -10° shift, because the centreline is set for zero (rather than 180). The display cannot plot off the bottom of the screen, so it must display it as a +350° shift instead. I hope that makes sense. ... It's similar to the situation with Power Factor, where the angles can be confusing either side of zero. You can have a Phase Angle of -10° (stated as "10 degrees lagging"), than increase that Power Factor by 20° and end up with the same Phase Angle of 10°, which seems to be the same value! However, the actual result is -10° plus 20° = +10° (because you passed through zero on the way). Gosh that is hard to explain LOL

[@johnnytoobad7785]

@@johncoops6897 OK. So 700 hz is where the freq. phase shift EXCEEDS 180. Makes sense.

[@johncoops6897]

@@johnnytoobad7785 - yeah, or maybe visa-versa. It all depends on whether you worked out the angle going backwards or forwards from zero. It's quite hard to explain phase shift in words, as it's hard for most people (including me) to visualise what is happening.

[@russellhltn1396]

He mentioned there's a delay going though the amplifier. A fixed delay will show up as changing phase as the frequency increases. Still, I'd expect a more gradual change rather than a sudden jump from -180 to 0.

[@xraytonyb]

This is correct. Most amplifiers will slightly shift the input/output phase with increase in frequency. In the case of this amp, after you pass a certain point, it flips because the signal is already inverted 180º. This is also due to the way the trigger works on the scope. Thanks for the comment :)

[@andybonneau9209]

Doesn't phase inversion drive the speaker cones in reverse?

[@johncoops6897]

Yes, and then at exactly half of the frequency later, it pushes it in reverse. But our ears don't only hear from the "forward", we hear from the WAVE (which is the change from back to forward to back to forwards, etc). So you need to remember that the sound is from the REPEATING of the wave, not just one half of one wave (which would just be an extremely short click).

[@frankgeeraerts6243]

A lot of amplifiers are inverting......

[@Wizardofgosz]

So no Marantz people here know the answer about why the choice was made to invert the phase out of the preamp?

[@jeffberwick]

I have amp design experience, but don't exactly know why Marantz chose this approach. My guess is that they changed one stage in the preamp and found it more convenient (or reduced component count) to keep it inverting in order to achieve some performance parameter like input impedance or noise floor. Generally this is a "don't care" from the design point of view. In fact, moving your head by just a fraction of an inch changes the phase dramatically in a listening room at high frequencies. Also, you can much more significantly alter the phase when using tone controls or loudness. Relative phase between speakers and correct room placement is much more important than absolute phase. However, it would probably have been best to stay consistent with a majority of other amp designs and keep phase non-inverting.

[@StillCloser]

"... it doesn't need tone or loudness controls..." Typical audiofoolery statement - Our hearing system is made to be LESS sensitive to some frequencies when these are played at a low level... Of course audiofools will also say they can spot when a signal is out of phase... What concerns me in this case is that the amplifier only inverts the phase around 600Hz which can sound awkward if you feed a signal from a sweep generator from say, 50 Hz to 20KHz... I would like to see if there's a difference when the sound changes from inverted to non-inverted, that would give an interesting video... Happy Thanksgiving !!!

[@johncoops6897]

NO - the amplifier DOES NOT only inverts the phase around 600Hz. It inverts the WHOLE frequency spectrum, but with a very slight shift. It just happens to be exactly 180° at 600-700Hz. Let's call that frequency the "centre point", where it's exactly 180°... Below that centre point, it inverts slightly more, let's say 185¯ at 20Hz. Above that center point, it inverts slightly less, let's say 175° at 20KHz. All amplifiers shift the phase slightly, it's just that this one centers it's phase shift around 180° (inverted) whilst other amps center their shift around zero degrees (in phase). Audiofools don't realise that the SPEAKERS are where all the phase shifting occurs. Take a look at that plot for any speaker and you'll see why LOL

[@davidgriffin79]

"StillCloser" wrote: "Our hearing system is made to be LESS sensitive to some frequencies when these are played at a low level..." Which is the argument for the "loudness control". Tone controls have little meaning in themselves because they affect very specific set frequencies which will most likely not coincide with any room/headphone resonances. Also many amplifiers of this era had controls which cut/boosted treble and bass by up 10dB; and which would sound hideous through speakers or headphones if fully utilised. Even simple parametric controls which could shift frequency and and vary Q would have been far more effective and some prosumer DACs produced now (such as the RME ADI-2) have parametric equalisation which can work wonders for headphone users (such as myself).

[@99MikeHamilton]

Its ok, I found it... thx

[@TheGtownbaseball]

Hey Tony, I got a sansui model 2000 that I'd love for you to work on for me. I messaged you on patreon, please get back to me if interested!

[@drewbjorke9839]

Tony, love your show. I've learned so much. I made it through the crazy year recapping vintage Kenwood 4140 because of the confidence you gave me. Just a idea, could you restore a cheaper entry level receiver like a JCPenney or Sears piece of gear. I'd be interested in hearing your analysis.

[@robertdestefano1409]

DONT YOU LOVE WORKING FOR FAMILY they never pay

[@thulinp]

Unless you have a second amp on the same signal, it doesn't matter in any way that the signal is "upside down". It's absolutely not audible.

[@johncoops6897]

Don't be so silly. Of course it's audible to people who can hear the improvement in fidelity from a $2000 OFC quad-braided hand-laid platinum-shielded teflon-insulated triple-physically-isolated #2 AWG conductor mains power cord.

[@R.AudioElectronics]

@@johncoops6897 absolutely John

[@richardmarshall6751]

@@johncoops6897 Right!? So much of the newer generation of audiophiles are completely invested in the idea that cables (speaker, interconnect, power) are critical. I call BS. Look at the cable used inside the Marantz, going to the speaker terminals....or inside most speakers, including my LaScalas and now tell me I need to spend $$$ on the cable between these two? Lamp cord is fine. As for the "audio quality" power cords, have these folks never seen the Romex that carries the mains AC to the outlet? Oh, but those last 6 feet of cord are going to make the difference...... The nonsense around cables and cords is a perfect analogy for the woke nonsense that also consumes most young people these days.

[@johncoops6897]

@@richardmarshall6751 - You know the old saying, which seems to date back to the late 1500's... _An AudioFool and his money are soon parted_ .

[@xraytonyb]

#2 mains cord is for peasants! I only use 400mcm oxygen-free power cord. It is only good for 300B SE amps up to 3 watts. Above that, you have to double them up in twisted pairs. ;)

[@coldfinger459sub0]

I was told some sources of LPs and CDs that were recorded overseas and even possibly this country were recorded inverted. Some preamp and source output devices components put out inverted signal and the button 180° would correct that.

[@xraytonyb]

I've heard the same about this. It makes sense. Thanks for the comment!