Hi dear DIY colleagues!
I bought me a great vintage denon poa 2400 power amp and pra-1500 preamp.
Sounds nice but when i change the preamp by a newer denon that I still have (pma1055). Well, then i prefer the sound of the latter.
When listening to the pra1500 I experience listening fatigue and it’s like I’m really missing dynamics and the highs are really overly bright...
I didnt’t notice anything physically wrong with capacitors. So I bought me a cheap capacitor tester and started disassembling some capacitors (randomly). I measured the two biggest capacitors (right after the transformer), then some in the tonal circuit. But they all measure fine.
I could measure all, but first I would appreciate some feedback from you people.
Do older capacitors affect dynamics and tones?
Even if they measure fine, should i replace them? Consider their age: + 30 yrs old.
Could i be measuring wrong?
Maybe its just the sound of the preamp? Find this hard to believe though, cause the preamp Im using now is really low end. But sounds better.
One more thing: the transformer does have a hum. But still outputs a nice 23,6 volt.
Thanks for your thoughts on this one!
Ps: i attached the manual (part of) of the pra 1500
Gr
Willem
I bought me a great vintage denon poa 2400 power amp and pra-1500 preamp.
Sounds nice but when i change the preamp by a newer denon that I still have (pma1055). Well, then i prefer the sound of the latter.
When listening to the pra1500 I experience listening fatigue and it’s like I’m really missing dynamics and the highs are really overly bright...
I didnt’t notice anything physically wrong with capacitors. So I bought me a cheap capacitor tester and started disassembling some capacitors (randomly). I measured the two biggest capacitors (right after the transformer), then some in the tonal circuit. But they all measure fine.
I could measure all, but first I would appreciate some feedback from you people.
Do older capacitors affect dynamics and tones?
Even if they measure fine, should i replace them? Consider their age: + 30 yrs old.
Could i be measuring wrong?
Maybe its just the sound of the preamp? Find this hard to believe though, cause the preamp Im using now is really low end. But sounds better.
One more thing: the transformer does have a hum. But still outputs a nice 23,6 volt.
Thanks for your thoughts on this one!
Ps: i attached the manual (part of) of the pra 1500
Gr
Willem
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I would power it continuously for a couple of weeks, and then see if the sound improves, which is likely.
If it does improve, run it another couple of weeks, and then it should be about as good as it's going to get.
If it does not improve enough for you by that time, consider replacing the electrolytic capacitors that are
in the power supply, and in the parts of the circuitry that you actually use. If you don't use the phono stage,
for example, then there's no reason the replace the electrolytic capacitors in the phono stage.
In any case, don't replace any film capacitors, since they don't normally degrade.
If it does improve, run it another couple of weeks, and then it should be about as good as it's going to get.
If it does not improve enough for you by that time, consider replacing the electrolytic capacitors that are
in the power supply, and in the parts of the circuitry that you actually use. If you don't use the phono stage,
for example, then there's no reason the replace the electrolytic capacitors in the phono stage.
In any case, don't replace any film capacitors, since they don't normally degrade.
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Hello Rayma
Thank you for your reply. The preamp has been playing for a few weeks, sometimes the whole weekend. To leave it switched on for a few weeks (also at night) doesn't make me feel safe though... Is there some logic behind your suggestion? Is it to fully charge the capacitors? Don't they charge in a few ms?
I took the liberty to filter the relevant pdf pages for my model and make a new pdf. Please find it with the attachments.
I think the capacitors you're talking about are?...
Power Supply
- C401
- C402
- C301 (near rectifier?)
- any else?
Circuitry I use...
CD:
- C312
- C307
- C306
... And so on...
Thank you for your reply. The preamp has been playing for a few weeks, sometimes the whole weekend. To leave it switched on for a few weeks (also at night) doesn't make me feel safe though... Is there some logic behind your suggestion? Is it to fully charge the capacitors? Don't they charge in a few ms?
I took the liberty to filter the relevant pdf pages for my model and make a new pdf. Please find it with the attachments.
I think the capacitors you're talking about are?...
Power Supply
- C401
- C402
- C301 (near rectifier?)
- any else?
Circuitry I use...
CD:
- C312
- C307
- C306
... And so on...
Update: I started reading about ESR values...
So a good read on a capacitor doesn't necesarily mean the capacitor is still good, ESR readings can be bad?
Maybe i should have bought a capacitor tester WITH esr reading also...?
Gr
W
So a good read on a capacitor doesn't necesarily mean the capacitor is still good, ESR readings can be bad?
Maybe i should have bought a capacitor tester WITH esr reading also...?
Gr
W
Many Denon integrated have pre-out made just with voltage divider from speakers output, probably your pma 1055 too, so it is not real preamp.
But of course, subjective that can sound better to you.
But of course, subjective that can sound better to you.
Hi Nironiro. Yeah, you’re right. It’s an integrated amp with pre out connection. That’s what’s making me wonder why it sounds better than the much more hifi pra 1500.
Only explanation for me is that the pma1055 is younger and has still good elco’s and capacitors. But I wonder if ‘recapping’ would do the trick.
Ordered me an esr measurinf device though. ☺️
Gr
W
Only explanation for me is that the pma1055 is younger and has still good elco’s and capacitors. But I wonder if ‘recapping’ would do the trick.
Ordered me an esr measurinf device though. ☺️
Gr
W
Vldr yes, PMA 1055 is typical Denon integrated amp, with preamp-out from speakers output, via voltage divider (12k, 580ohm), so it is not a classic type of preamplifier output.
I don't say it is bad, just different.
With your PRA 1500 preamplifier, I would first deeply clean all switches and potentiometers, than it is time to check the capacitors.
I never see ESR as important specification in the service manuals, more important is Leakage in the coupling caps, and Leakage in the NFB caps.
I don't say it is bad, just different.
With your PRA 1500 preamplifier, I would first deeply clean all switches and potentiometers, than it is time to check the capacitors.
I never see ESR as important specification in the service manuals, more important is Leakage in the coupling caps, and Leakage in the NFB caps.
As you can use the PMA1055 only with mm carts i suspect that using mm carts is what your setup is all about.Now PRA1500 would beneffit some mods that you can do to improve the sound a little bit, but honestly i wouldn't touch that thing ...I'd sell it right away.
Believe it or not the little integrated amp, although much simpler ha smuch better quality components in the audio signal path than the control preamplifier.Besides the control preamplifier is a faded version of PRA1100 which again is a downgraded version of PRA1000 which in itself isn't really great either among other high end control preamplifiers.
Believe it or not the little integrated amp, although much simpler ha smuch better quality components in the audio signal path than the control preamplifier.Besides the control preamplifier is a faded version of PRA1100 which again is a downgraded version of PRA1000 which in itself isn't really great either among other high end control preamplifiers.
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I've got a pra-1500 paired with a Denon poa-2200 that has had the amp boards swapped out with honey badger boards. I am very pleased with the combo, and have done a b comparisons with a NAD 1155 preamp, and the NAD sounds a hair better, but the Denon still sounds great, especially in source direct mode. I am using it in my vinyl setup. I am happy with it. No fatiguing, just nice clean sound. If yours is definitely the source of your issues, then something is wrong. I have not recapped or done anything to mine other than deoxit the pots. Sorry, not many suggestions for you to work off of, but I did want to offer another data point. I am happy with mine.
Hi Summitp
Thanks for sharing your experience. Not sure what’s wrong with it but it’s really worse than using the pma1055.
As said before, stereo 3d image is terrible, little fatiguing in the higher tones znd very poor dynamics. It’s just too flat...
I already cleaned the pots because there were some issues with the source direct switch.
I will investigate if there’s something wrong with it and will update this thread with my findings. But dreamth made me starting to doubt about the quality of the pream though ☺️
Gr W
Thanks for sharing your experience. Not sure what’s wrong with it but it’s really worse than using the pma1055.
As said before, stereo 3d image is terrible, little fatiguing in the higher tones znd very poor dynamics. It’s just too flat...
I already cleaned the pots because there were some issues with the source direct switch.
I will investigate if there’s something wrong with it and will update this thread with my findings. But dreamth made me starting to doubt about the quality of the pream though ☺️
Gr W
It may probably sound better after recap and resoldering the whole circuit , maybe cleaning some switches, but what the pma1055 has is simplicity of the whole audio chain and that's usually better for longer periods of times while its components are really good quality.
Hi People
So I promised an update.
I did a whole extra checkup on the capacitors' soldering, I resoldered a whole bunch of them & I did an extra cleanup on all the pots. I did not replace any capacitors.
Then I have let it play for many days and stuff got better... Actually, more relaxed then the PMA1055r... Maybe the resoldering did the trick.. or maybe my ears popped 🙂
Things did get better though! So the PMA1055r has to go. There are too many amps in my office.. 🙂
Greetz
So I promised an update.
I did a whole extra checkup on the capacitors' soldering, I resoldered a whole bunch of them & I did an extra cleanup on all the pots. I did not replace any capacitors.
Then I have let it play for many days and stuff got better... Actually, more relaxed then the PMA1055r... Maybe the resoldering did the trick.. or maybe my ears popped 🙂
Things did get better though! So the PMA1055r has to go. There are too many amps in my office.. 🙂
Greetz
Extra update: I managed to get a DENON DAP5500 for a bargain.
But I have some work to do with it.. Will start a new thread about this. Please check up on that one.
Gr
Will
But I have some work to do with it.. Will start a new thread about this. Please check up on that one.
Gr
Will
thanks for the update,
i own denon pra-1100, and dap-5500, both recapped and cleaned adjusted completely.
plus i installed opamp sockets on both,
and keep the originals for the case i want back to stock sound.
,so easy to swap opamps.
and im happy with the results.
Eldad.
i own denon pra-1100, and dap-5500, both recapped and cleaned adjusted completely.
plus i installed opamp sockets on both,
and keep the originals for the case i want back to stock sound.
,so easy to swap opamps.
and im happy with the results.
Eldad.
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