Hello guys, i have an old Denon PMA-980R amplifier who needs some re-caps and i have decided to make un upgrade to opamps. I'm not an engineer, i have looked into service manual and i not understand too good if IC701 has a voltage +/-16.5v or just +16.5v.
For +/-16.5v, i was searching opamps with +/-18v and in this days is verry hard too find what you want! Amplifier has 4 opamps and i'm thinking to put Ad8599/ad8066, opa1612 (but i can't find it) lt1469/lt1358 or dual lt1028/ada4627!
I need some help for choosing the right opamp voltage!
Thank you!
For +/-16.5v, i was searching opamps with +/-18v and in this days is verry hard too find what you want! Amplifier has 4 opamps and i'm thinking to put Ad8599/ad8066, opa1612 (but i can't find it) lt1469/lt1358 or dual lt1028/ada4627!
I need some help for choosing the right opamp voltage!
Thank you!
As you state, you are not an engineer.
The op amps were selected for a specific reason; stability, reliability and performance.
The op amps you list were available when this amplifier was in production, the design engineer would have requested them if they were better than the ones selected. I don't think you will improve anything by fitting other types, you may end up with odd results that cannot be resolved without circuit changes.
The op amps were selected for a specific reason; stability, reliability and performance.
The op amps you list were available when this amplifier was in production, the design engineer would have requested them if they were better than the ones selected. I don't think you will improve anything by fitting other types, you may end up with odd results that cannot be resolved without circuit changes.
Denon sets are like highly tuned cars, you change one setting, the whole thing goes out of kilter.
Leave it alone.
Change the caps only if damage is evident.
Same goes for Onkyo and Yamaha sets as well.
And there are many people who advertise their knowledge, and try to sell op amp upgrade kits and so on.
Just bear in mind that a slew rate of more than 15 (at most 20) V/us is enough for audio, anything more than 40 will cause the system to oscillate.
That is within the capability of TL072, 5532, 6556 and other similar parts.
Any op amp must faithfully reproduce and amplify the signal without distortion, so I would not get into that op amp rolling circus.
Many threads here about that, and bear in mind, once again, Denon are good pieces of equipment, and difficult to repair, not worth the risk of experimenting.
You can always make an external pre amplifier, and progress to a complete unit.
Leave it alone.
Change the caps only if damage is evident.
Same goes for Onkyo and Yamaha sets as well.
And there are many people who advertise their knowledge, and try to sell op amp upgrade kits and so on.
Just bear in mind that a slew rate of more than 15 (at most 20) V/us is enough for audio, anything more than 40 will cause the system to oscillate.
That is within the capability of TL072, 5532, 6556 and other similar parts.
Any op amp must faithfully reproduce and amplify the signal without distortion, so I would not get into that op amp rolling circus.
Many threads here about that, and bear in mind, once again, Denon are good pieces of equipment, and difficult to repair, not worth the risk of experimenting.
You can always make an external pre amplifier, and progress to a complete unit.
Op amps mentioned above, all of them are rated at 30v/+-15v.
Denon have mentioned in this manual, 16.5v but i have put a multimeter and i have +-17.5/35v.
It is normal to have distortion and oscillentions at that voltage!
Denon have mentioned in this manual, 16.5v but i have put a multimeter and i have +-17.5/35v.
It is normal to have distortion and oscillentions at that voltage!
Please tell us the specific type used, check with the data sheet.
1 or 2 volts high should not be a problem, I think.
How good is your meter, are its batteries fresh?
A slightly used lithium coin cell will read
2.96V.
1 or 2 volts high should not be a problem, I think.
How good is your meter, are its batteries fresh?
A slightly used lithium coin cell will read
2.96V.
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I don't know how good is, but i can check/replace battery.
I found a way to change voltage to 26v/+-13v
I found a way to change voltage to 26v/+-13v
Imagine the amp's slew rate is more likely +-15...20v/us and has to slew +-30...35V on an inductive load while the op amp may be 6...13v/us on a resistive load which is waaay easier to do and has to slew only 2...6V.Thus the frontend is faster and 10...100 times lower distortion than the power amp already .You won't get higher speed by changing a car's tires until you change the motor and the chassis...
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