Amp woes... Denon POA2400. - diyAudio
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Old 11th April 2013, 04:41 PM   #1
mortron is offline mortron  Canada
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Default Amp woes... Denon POA2400.

I have a Denon POA 2400 amp that has been loyal to me through thick and thin, even when I tried to trade her in and she sat in a shop for 6 months. Lately I have notice the output will occasionally drop and the amp sounds a bit anemic, if that makes sense. Now since it happens in what sounds to be both channels, is it safe to assume its a power supply issue? I am limited in my tools, and could only take a gander inside... is there a place go start?
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Old 11th April 2013, 05:25 PM   #2
wahab is offline wahab  Algeria
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Whatever the trouble , keep it , that is a fine amplifier , surely
a triple stage like the POA3200 , with exceptional linearity.
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Old 12th April 2013, 02:27 AM   #3
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Have you downloaded a sevice manual to follow the basic checks?
Denon POA-2400 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
This model has some fairly complex bias and management circuits so it may not be practical to troubleshoot the logic circuits remotely. Nevertheless, it could still be a simpler matter related to ageing of caps, for example. If you are limited in tools like even a DMM, you need to think of service by a Denon service technician if you are not able to DIY.

Do any warning lights show?
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Old 12th April 2013, 12:30 PM   #4
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if it's sounding "anemic", it's probably the DC correction caps. these will be on the inverting input of the diff amp, usually somewhere between 47uf and 470uf. if they are dried out, they will first affect the rolloff frequency of the amp, reducing the bass. as they get worse, they will reduce the overall gain of the amp.
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Old 12th April 2013, 01:17 PM   #5
mortron is offline mortron  Canada
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Quote:
Originally Posted by unclejed613 View Post
if it's sounding "anemic", it's probably the DC correction caps. these will be on the inverting input of the diff amp, usually somewhere between 47uf and 470uf. if they are dried out, they will first affect the rolloff frequency of the amp, reducing the bass. as they get worse, they will reduce the overall gain of the amp.
Used to live next door to a Jed... Wise man he was... Thought you may be him. This sounds most like my situation.

Problem is a tech wants $400 to recap
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Old 13th April 2013, 04:24 AM   #6
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i saw a copy of the schematic today.... the caps you are looking for are 10uf/50V bipolars, one for each channel.... now i've forgotten the ref-des.....
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Old 13th April 2013, 07:26 AM   #7
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I have had this problem before and would advise a total recap, if one capacitor has dried up it stands to reason the rest are not too far behind..
I used nichicon kz's as replacements in signal pathways and panasonic's in psu. It took me half a day but i am very happy with the results, i also changed resistors for vishay's, for me if a job is worth doing it is worth doing well and only cost a few bucks more, personally i used slightly larger replacement components than the stock ones.

Best of luck with your project
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Old 13th April 2013, 01:57 PM   #8
mortron is offline mortron  Canada
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Originally Posted by goodguys View Post
I have had this problem before and would advise a total recap, if one capacitor has dried up it stands to reason the rest are not too far behind..
I used nichicon kz's as replacements in signal pathways and panasonic's in psu. It took me half a day but i am very happy with the results, i also changed resistors for vishay's, for me if a job is worth doing it is worth doing well and only cost a few bucks more, personally i used slightly larger replacement components than the stock ones.

Best of luck with your project
My biggest concern is that I will change the sound of the amp by swapping resitors etc... caps I know need replacing but do the resistors really?
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Old 14th April 2013, 06:24 AM   #9
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The best thing to do in that case is decide the kind of sound you want the amp to produce then use components which will deliver that.

For resistors here is my opin: Carbon comp :
1) kiwame ( lush sounding - the best ( to my opinion ! )
2) rihken ( taut and three dimensional but very expensive )
3) kamaya ( very good but 5 to 10% tolerance )
4) Ohmite little devil ( see kamaya )
5) morganite ( pleasant sound - tend to drift !! )

Metal :

1) roederstein ( tight 'n' fast - a little thin )
2) Holco ( very fast - "metallic treble )
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Old 14th April 2013, 06:37 AM   #10
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Sorry, hit the wrong button and my post was cut short.

To continue: Google and find out from previous posts how different resistors and capacitors sound. You are right in that the sound may change if you shove any old resistor or capacitor in, but simply do some research and you can minimize or eliminate this. This may take a few days so it depends on how much time and patience you have

I think it would be a good idea to replace the old resistors as resistors last for about twenty years before they need changing so at least this is one less worry to think about.

For the bipolar caps i would recommend nichicon es

Personally i upped the psu caps by twenty percent so there is a little more juice for the components if they should need it..

Best of luck.:
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