about the Denon PMA-700 amp

[ring]

oops

I finally discovered how to make downloads work over at elektrotanya, so I am covered.

thanks all!

 

[tiefbassuebertr]

Hi, You are pretty much off base here.

The Biasing is not done by the IC's, it uses a normal VBE multiplier (TR501/502). The power stage is unity gain.

The Op-Amp's appear to form some kind of crazy error correction for high frequencies only (IC7 and IC 8 respectively) plus feedback loop for AC only (IC5) that encloses the power stage. It seems unable to work correctly at high levels if there is a significant difference between the channels as well, as the available voltage swing will be way exceeded, due to using a dual op-amp with bootstrapped supplies shared between channels.
I am not sure I would hold this circuit up as paragon of good design next to (say) a Hitatchi lateral Mosfet Amp or the improved versions. I am equally unsure all this shebang is really better than just putting the output stage into the line stage feedback loop (good reasons for that), or letting it run open loop with some slightly less convoluted error correction (good reasons for that).

The power stage is preceded by a very high gain and output voltage line-stage with a tone control in the feedback loop. The line-stage has the kind of circuit you described (triple differential - good for tons of NFB and many zeros after the THD decimal point, less so possible for transient response and TIM/PIM and others like them), however it is a fully stand alone discrete Op-Amp including emitter follower output stage and not really part of the power amp.

Ciao T

I don't understand exactly the theory of operation of this power amp circuit from DENON - especially those of the OP-Amps.
In order to the front-end there is a certain similarity to Electrocompaniet's Ampliwire AW-100 go to post #3 (first PDF file) under
Electrocompaniet Ampliwire 100 (AW 100 AW100) different Versions
But what are the aim of the operational amplifiers IC511 and both halves of IC711 in detail ? - go to the attachment in post 12 and also to the attachment in post #2 under
Denon PMA-900V lowering gain/opamp swap
for PMA900V.
Are this an invention from DENON or is there a well-known naming for this topology ?
Thank you very much for some advices.

 

[tiefbassuebertr]

check out post 4080 on page 408 under
Bob Cordell Interview: Error Correction

 

[tiefbassuebertr]

I am looking for test reviews and brochures of this model and the PMA-900V.

In German magazine "Stereoplay" was a review in the issues 10/1986 and for PMA-900V in 10/1987

Maybe here was to find DENON's circuit description to this version of error correction

Thank you for upload of brochures and reviews.

P.S.: some URLs:
denon pma-900v no bias/idling voltage — Polk Audio Forum
Denon PMA-900V Short review - 2 Channel - HiFi WigWam