After my Denon PMA-560 output relay tripping thread, diyaudio user Karl vd Berg asked for a scan of the service manual.
I thought I'd do that and put it on a "PMA-560 fan site": Denon PMA-560 fan site 🙂
Karl did a major overhaul of his PMA-560, which is documented here: Denon PMA-560 Restoration / Refurb / Recap / Rejuvenation / Overhaul
Feedback/comments welcome
I thought I'd do that and put it on a "PMA-560 fan site": Denon PMA-560 fan site 🙂
Karl did a major overhaul of his PMA-560, which is documented here: Denon PMA-560 Restoration / Refurb / Recap / Rejuvenation / Overhaul
Feedback/comments welcome
The latest news is that Karl actually sold the refurbished amp to me 🙂
It sounds much "tighter" than my "stock" PMA-560, much more detail,
less woolly, much better placement, etc. (how do you describe these things..).
However, the highs (high singing voices, "S" sounds, hihats, etc.) sound too bright.
From looking at what was done in the overhaul (see the link in the previous post),
is there an obvious candidate for what's causing this?
Thanks 👍🤔
It sounds much "tighter" than my "stock" PMA-560, much more detail,
less woolly, much better placement, etc. (how do you describe these things..).
However, the highs (high singing voices, "S" sounds, hihats, etc.) sound too bright.
From looking at what was done in the overhaul (see the link in the previous post),
is there an obvious candidate for what's causing this?
Thanks 👍🤔
(.. from my other thread about using an iphone to get a calibration signal, copied here because it's more relevant to this topic)
I now replaced the stock power cord with the one that was on my old amp: a 3-wire cable, grounded to the chassis, and with a ferrite core around it where the cable enters the amp (see picture).
This seems to improve things (still some more listening to do) 🙂
I now replaced the stock power cord with the one that was on my old amp: a 3-wire cable, grounded to the chassis, and with a ferrite core around it where the cable enters the amp (see picture).
This seems to improve things (still some more listening to do) 🙂
I now bought some heavy-duty shielded installation cable, and tried a meter of that
(this cable: https://www.allekabels.nl/grondkabel/7118/1299326/vd-draad-3-aderig.html).
The problem with the highs is gone. But it was already much better with the plain cable + ferrite core shown above.
And I'm thinking that the shielded cable sounds just a little bit duller, and with less depth in the sound.
I think I'll swap back to the first cable after a while.
(this cable: https://www.allekabels.nl/grondkabel/7118/1299326/vd-draad-3-aderig.html).
The problem with the highs is gone. But it was already much better with the plain cable + ferrite core shown above.
And I'm thinking that the shielded cable sounds just a little bit duller, and with less depth in the sound.
I think I'll swap back to the first cable after a while.
In general, it is driving me up the wall that the mains cable has such an influence on the sound. 😡
Why would this shielded cable sound "duller" ?
Reading around on the forum a bit: should the mains wires be twisted maybe?
Why would this shielded cable sound "duller" ?
Reading around on the forum a bit: should the mains wires be twisted maybe?
It doesn't.
Also, generally not a good idea to add a mains ground cable, when the amp isn't designed for it. All you will get is possible ground loop noise.
Looks like the driver transistors and an Opamp was changed to different types. This could well have changed how it sounds - could be better, could be worse. If the modified amp hasn't been tested for stability and performance with oscilloscope etc., you can't know for sure.
I quite like the old Denon amps (80-90's), they are decent quality and last a long time. But it's still "just" an old standard amplifier, so I wouldn't expect miracles 🙂
Couldn't it be because one cable is more susceptible to picking up noise than the other?
Or the other way around, if the mains cable is (too) close to signal cables?
(what is a good minimum distance anyway)
The mains power cable is not likely to pick up any noise - more the ther way around: It radiates noise.
So don't run your signal cables close along side the power cable. Then you might get noise pickup in the signal cables.
Regarding minimum distance, I would say about 20cm (8") is good, but perhaps even 10cm is enough.
Usually it's ok if the power cable crosses the signal cables at a right angle - it's the parallel run that should be avoided.
But you can just test it: Try doing it "the wrong way", and listen for noise in the speakers with no music playing (but with the volume turned up).
Edit>> Just noticed that the original DEC speaker relays are still in there! Those could easily have bad contacts. I would change them.
So don't run your signal cables close along side the power cable. Then you might get noise pickup in the signal cables.
Regarding minimum distance, I would say about 20cm (8") is good, but perhaps even 10cm is enough.
Usually it's ok if the power cable crosses the signal cables at a right angle - it's the parallel run that should be avoided.
But you can just test it: Try doing it "the wrong way", and listen for noise in the speakers with no music playing (but with the volume turned up).
Edit>> Just noticed that the original DEC speaker relays are still in there! Those could easily have bad contacts. I would change them.
Thanks a lot for these tips. Going through my wiring I also found that the power cable to the DAC was (1) too long, and (2) pretty close to the speaker cables, so I shortened and rerouted it.
With some more listening I also went with:
- not attaching the ground lead to the chassis
- leaving a ferrite bead (core/ring) around the power cable where it enters the amp
- connecting the amp to a grounded socket
In between the socket and the amp is a Tacima CS929 "mains conditioner". I'm reading mixed
reviews about that one at the moment. I'll test without the CS929 as well.
Yes, maybe. I'll ask Karl why he didn't change them (since he changed so much 🙂 )
I'm thinking that in my old "stock" amp the relays should be fine (the amp has been in storage
for 15+ years, and I've always been careful about setting the volume to zero before switching on/off)