hifi engine

Please Help with Denon PMA-1080R info opinions or owners manual

Hi Hoping someone can tell me what the Denon PMA-1080R Intergrated amplifier is like, Ive spent hours trying to find some reviews, A user manual basically any info on this amp, Apparently it won amplifier of the year twice in a row. In Australia
I have the chance to buy this amp and dont know if or what the optical class A is. Does this mean its an A class amp, or the optical out is class A.
Any help or user manual would be welcome please.
1000 thankyous
Mr Lester Wilson

Service Manual for PMA-1080

Also has owner info towards the front of the manual.
hope it helps.

optical class A

I hope that will help.

The Class A concept is well known for the purity of the sound.
However ,several technical must :-) do put the amplifiers in real class A in a special place, due to costs and ease of use due to heat dissipation.But IMHO,they remain the best....

Different constructors use specials technics to improve the classic output class A stage.But not all due use a class A output circuit..sometimes the class A on the front panel reffers to something else that the power output circuit !

One of the biggest amp designer is Nelson Pass,who made history on that field.

His concepts were used by Denon to make some wonderfull amps.

Class A here does not mean that the output stage is functioning in class A, but that a special circuit is use to mainain the bias of the output transistor constant and the feedback under control.One of the best ,stable way is to use optocouplers to do this,they are not stressed by external interferences,hence the taransistors will be very well current controlled ,so the output stage will function within stable parameteres.
Final result : wonderfull sonic performance .

Some details with copy/paste from the net :

Opto-isolated bias circuit for operating push-pull amplifiers in class A and class AB modes
A high fidelity audio amplifier of the push-pull complementary symmetry type, featuring a feedback circuit with a bias sensing element connected to the output terminals of the output transistors. The feedback circuit includes a photoemitting element in optical communication with a photoconductive element which determines the relative voltage difference of the input terminals of the complementary symmetry output transistors.

Inventors: Pass; Nelson S. (Auburn, CA)
Assignee: Threshold Corporation (Auburn, CA)
Appl. No.: 086932
Filed: August 18, 1987

(regular bias circuits)are non-linear and can introduce distortion into the amplified signal.

It is an object of the present invention to devise an amplifier using a bias circuit incorporating a feedback connection to the output nodes of subsequent gain transistors for the purpose of controlling the bias of these transistors, but with an isolation mechanism to eliminate the distortion found in prior art.


The above object has been achieved in an audio amplifier having emitter follower, complementary symmetry output transistors utilizing feedback from the output stage. It has been found that use of optical coupling in a feedback loop for biasing the output transistors reduces distortion by isolating the bias circuit from the output nodes and preventing saturation in transistors forming the bias circuit. Sufficient feedback is provided to maintain Class A or Class AB operation, yet input current is not drawn off to the output node through the feedback circuit, thereby preventing distortion.

Best wishes !

Thankyou Soundcheck for the

Thankyou Soundcheck for the excellent information, The Denon PMA-1080R is the clearest amp Ive owned, very nice for blues, And quite mellow music Also it is loud enough if you need to hear it while visiting down the road ;) the subsonic bass reduction is a good feature if its cranked up. I listen to it around 4 which is about 7 oclock, I'm running 2 sets of JBL-L112 that are easy to drive, and a fine match between speakers and amp, also using Marantz CD-80 for CD player. Nice combination all round.
I'm a bit of a simpleton on the ins and outs of what was written, but sort of get the idea of the curcuit feeding off the transisters surplus energy going to the speakers, its recycled and turned into more energy. making for a clearer sound. Would that be sort of on the right track.
I appreciate your reply soundcheck
1000 Thankyou's
Mr Wilson