Hi,
I have a Denon PMA-1080R (1990s) stereo amplifier that i have thought to give recap of all smaller caps and upgrade some components.
I would like to have your advice on is this amp worth the effort and what aspects to look into?
So far i have thought to add clipping indicator circuit and drill 2 holes for clipping leds to front panel.
Also to add ~20-30mF extra capacitance if it is going to improve signal quality and maybe help to extract maximum power from the transformer with less quality loss.
Are the rectifier-bridges also worth replacement?
Are there any parts that i could change/remove/bypass to give better sound in midrange without losing bass precision and high freq quality?
Amp is used with Jamo concert 7 speakers and small Fostex fe108ez widerange speakers that should be capable of good midrange.
It seems to drive 8" push pull woofer of concert 7 well and bass is precise and highs are great already but is there any hope to extract better midrange from this amplifier?
For DAC using USB Sounblaster xfi , May it be the weakest link on midrange instead of the amp?
Schematic:
https://www.hifiengine.com/manual_library/denon/pma-1080r.shtml
Inside:
I have a Denon PMA-1080R (1990s) stereo amplifier that i have thought to give recap of all smaller caps and upgrade some components.
I would like to have your advice on is this amp worth the effort and what aspects to look into?
So far i have thought to add clipping indicator circuit and drill 2 holes for clipping leds to front panel.
Also to add ~20-30mF extra capacitance if it is going to improve signal quality and maybe help to extract maximum power from the transformer with less quality loss.
Are the rectifier-bridges also worth replacement?
Are there any parts that i could change/remove/bypass to give better sound in midrange without losing bass precision and high freq quality?
Amp is used with Jamo concert 7 speakers and small Fostex fe108ez widerange speakers that should be capable of good midrange.
It seems to drive 8" push pull woofer of concert 7 well and bass is precise and highs are great already but is there any hope to extract better midrange from this amplifier?
For DAC using USB Sounblaster xfi , May it be the weakest link on midrange instead of the amp?
Schematic:
https://www.hifiengine.com/manual_library/denon/pma-1080r.shtml
Inside:
An externally hosted image should be here but it was not working when we last tested it.
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I upgraded and recapped my PMA-680R and there has been a major improvement.
to be safer don't exceed few 1000μF on powersupply caps. I changed my 6800μF caps to 12000μF caps. Added some bypass caps(pp). Then changed the opamps to BurrBrown OPA2134PA after socketing them.
Changed all the electrolytics. And changed all the caps on signal path to panasonic polypropylene.
Oh yeah, changed all the ceramics too...
to be safer don't exceed few 1000μF on powersupply caps. I changed my 6800μF caps to 12000μF caps. Added some bypass caps(pp). Then changed the opamps to BurrBrown OPA2134PA after socketing them.
Changed all the electrolytics. And changed all the caps on signal path to panasonic polypropylene.
Oh yeah, changed all the ceramics too...
Nice work.
How long it took? , How was the caps condition before and did it give big sound quality difference?
There also are opamps used for the "Optical class A" bias triggering.
I tested the bias system and opamps wont trigger higher bias with low signal at all , only at medium volume and at high volume it cut off.
Is the "optical class a" supposed to work at very narrow volume range or some cap, optron or other component may be out of spec more likely?
I am thinking to upgrade 1 channel and compare the sound before doing other.
What would be good choice for the signal path and rest of caps to make it better quality and last long.
Would adding 22000uF and moding soft start circuit be ovekill or may it help with quality and extracting extra power from transformer?
Tested rectifier bridges and they dont heat much , would there be any other reasons to upgrade those?
How long it took? , How was the caps condition before and did it give big sound quality difference?
There also are opamps used for the "Optical class A" bias triggering.
I tested the bias system and opamps wont trigger higher bias with low signal at all , only at medium volume and at high volume it cut off.
Is the "optical class a" supposed to work at very narrow volume range or some cap, optron or other component may be out of spec more likely?
I am thinking to upgrade 1 channel and compare the sound before doing other.
What would be good choice for the signal path and rest of caps to make it better quality and last long.
Would adding 22000uF and moding soft start circuit be ovekill or may it help with quality and extracting extra power from transformer?
Tested rectifier bridges and they dont heat much , would there be any other reasons to upgrade those?
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1. You cannot upgrade this. It is a very high quality amplifier and Denon certainly knows their stuff. You do not, with no offense intended. If you want better sound, get rid of those speakers. Jamo is junk.
2. The things Ronj did to his amp aren't upgrades and not worth bothering with. It won't improve anything and can potentially wreck the amp. Also a waste of time and money.
2. The things Ronj did to his amp aren't upgrades and not worth bothering with. It won't improve anything and can potentially wreck the amp. Also a waste of time and money.
I disagree with your blanket statement. To substantiate my claim I have to to tell you, I have worked more than 1.5decades for a European consumer electronics company in Systems, electronics and Software. And I have learned and seen all manufacturers, including the one I worked for, build systems to a price point.
Denon chose to use cheap op-amps, absolute minimum required power supply caps and electrolytics on Signal line because of that very reason. They also under design models so that their models don't eat into the profits of their higher models. Every manufacturer does that.
PMA 650R, 850R and 1050R all basically use similar topology. But bigger transformers , more filtering caps and slightly different power stages. Most of the input stages also are very close.
So upgrading op-amps, increasing reservoir caps by a bit more, using similar spec'd but better op-amps and finally replacing the signal path electrolytics with polypropylene caps after a judicious consideration always result in improvements. These are not blind changes.
And certainly did make a big difference in my case. By the way my amp was an early 90s amp so I decided on recapping first because electrolytics after 25years certainly would warrant that. So if was a recap endeavour to start with.
I stripped everything off and even repainted the chassis while I was at it.
Sent from my iPhone using Tapatalk
'have to go along with this, not only with the recapping but the whole re-furb thing that people look for in assessments of value, whether it results in audible improvements or not. Typical DIY opamp and film or ceramic cap changes don't do much but if it pleases them and they appreciate the impact of fitting less well suited types in the particular circuit, there should be no harm done apart perhaps, from damaging old copper foil tracks with poor technique/tools.
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DIY, kind of says it all, we do what we want...
The op put up a picture that has some odd rust colored areas around the mixed brand filter capacitors, might want to clean that up if it isn't part of the sacred design (glue) or anything. Any coupling capacitors are a good place to introduce upgraded parts, would hold off on the rest, that brand was good about getting nicer capacitors, not a common practice.
The op put up a picture that has some odd rust colored areas around the mixed brand filter capacitors, might want to clean that up if it isn't part of the sacred design (glue) or anything. Any coupling capacitors are a good place to introduce upgraded parts, would hold off on the rest, that brand was good about getting nicer capacitors, not a common practice.
Typical DIY opamp and film or ceramic cap changes don't do much but if it pleases them and they appreciate the impact of fitting less well suited types in the particular circuit, there should be no harm done apart perhaps, from damaging old copper foil tracks with poor technique/tools.
Ok in my case I did not try to fit in grenade size big high voltage polypropylene caps or out of PCB caps. And Op-Amp, well NJM4558DD that was on in the Tone control section and M5218AP on Phono section are quite mediocre spec wise. I don't remember whether I used both op-amps same, but if I remember correctly, tone control definitely was upgraded with a OPA2134PA. And Denon, won't design with an OPA2134PA because it costs at least 8 times more than teh JRC NJM4558DD. And I did do a proper specification comparison before I changed the op-amps. I also used 8PIN DIP socket for the Op-Amps.
I used Panasonic polypropylene caps on Singal line except one place where there was a 10uF cap was required but with not much space where I used a Vishay pp cap rated 64V. Even if they were slightly bigger nothing like too over sized. You can see the pics here
And I definitely did not damaged the tracks. Partially because, I think I have decent enough tools to do my work as I use a Hakko FR-300 for desoldering, A Weller WES51 as my soldering station and an old Hakko 850 hot air rework station which I use with SMDs also.
Here are some more pics...
Signal Path Caps
And you can see socketed op-amp for the PHONO section.
Oh yeah I also changed the mica insulator sheets and reapplied some new heatsink/thermal paste
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1. Surely Denon engineers knew how to do better with least cost and i have no doubt the capacitors are calculated to be optimal size.
Why would you conclude Jamo junk , There are loads of different models manufacured with different philosophy troughout different eras.
I also recapped the Jamos and it ended up worth it because i did side by side comparison before and after with one speaker recapped and other without.
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Made image diagrams from the multi page diagrams in pdf file.
Pasteboard — Uploaded Image
http://pasteboard.co/O0SgcZmfi.jpg
So far the plan is to replace caps, some electrolytics are surely out of spec if not most.
Pasteboard — Uploaded Image
http://pasteboard.co/O0SgcZmfi.jpg
So far the plan is to replace caps, some electrolytics are surely out of spec if not most.
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