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Denon PMA-520

Stereo Integrated Amplifier (1989)

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Denon PMA-520


Power output: 70 watts per channel into 8Ω (stereo)

Frequency response: 20Hz to 20kHz

Total harmonic distortion: 0.015%

Input sensitivity: 0.2mV (MC), 2.5mV (MM), 150mV (line)

Signal to noise ratio: 68dB (MC), 88dB (MM), 105dB (line)

Output: 150mV (line)

Dimensions: 434 x 140 x 343mm

Weight: 7.4kg


schematic   English -

service manual   Deutsch -

A instruction/owners manual   English Francais - denko

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Reviewed Apr 14th, 2015 by ivanmasss

Great cristal sound. versatille



re: PMA-520

Hi, I have a pma 520 denon and my problem its than i can turn on but it doesnt work, the equipment start but i cant hear nothing, can you help me?, thanks

output from my pma520

my problem is when I switch it on the loudspeaker has a very loud click noise. I think it probably due to the delay switching of the relay to connect the loudspeaker to the output. Can anyone help please. If it is the relay or softswitch problem where to get the component for replacement please. I am in hong kong.

loud noise transient - protection relay ckt problem?

Hello Cobra,

Sounds like the relay is stuck CLOSED. It's unusal for a relay to fail in a closed state (MUCH more likely that the contacts become mildly-to-severely corroded, this causing sometimes awful distortion as the corroded contacts act like low-breakdown diodes!).

Looking @ the schematic posted here on HiFi Engine (which you may want to download also); the speaker/ amp protection relay (R401) is controlled by a multi-factor sensing ckt, mainly consisting of TR601-607 (also 609 & 610 in the output stages). Somewhere in all that there's probably an R-C delay circuit (could be R606 & C605?) which is supposed to hold the relay OFF, until enough time has elapsed after applying power, for the rest of the cirucuitry to stabilize (usually set for ~3-5 sec). If any part of that relay control/ delay ckt has failed, it could result in relay being energized from moment power is applied.

Long & short is, you've got to figure out WHICH part is mis-operating, 'cause you only need to replace THAT one (& replacing any other of course won't fix it!).

The click noise may have enough power to damage your speakers - & could be cumulative - so do be careful w/ it! You could switch the speakers OFF, before you turn amp off each time, then switch them back on, after a suitable delay (say >~5sec) each time you turn it back on. A 'manual' relay, if you will. Of course, any other amp failure will be un-protected, & could damage/ ruin the speakers if something like that happens...


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