Pioneer A400 coupling caps

[mudan]

Hi,

I have recently replaced the coupling caps on my A400 with Audyn MKP QS, which were quite a large component to fit on the amp but luckily there was space at their location. (C201/C202).

Replacing them brought about a warmer sound with a fuller bass, but I'm now wondering whether they were the best choice within a reasonable size and price. I later replaced many of the other caps with Black Gates and was wondering whether replacing the Audyn with high quality black gates i.e. N or NX range, would be a better choice as I am suspecting that these Audyns may be slowing the sound down.

Any ideas ?

[mudan]

I'm surprised that no one has replied.

Anyway I've decided to order some more black gates to replace the MKP, which I believe (and hope!) will resolve the problem.

[lucpes]

I guess that you're talking about the input capacitors You should've shown a schematic part. You can leave those in, I'd also go for quality electrolytics (Panasonic FC series will do in the large values needed) in the feedback loop unless you haven't done so.

To get an idea of how the caps sound leave them for a couple of days, make a 'test' track list from your cds, listen, then change the caps and listen to the same music through the new caps. Also leave them in for a couple of days so you can have a good idea on the performance.

[Bill Fitzpatrick]

Originally posted by mudan
. . . . . . as I am suspecting that these Audyns may be slowing the sound down.

What do you mean by "slowing the sound down?"

[mudan]

In my opinion, the Audyn MKP QS caps added greater bass depth and warmth but also blurred details, resulting in a less sharp sound.

Well I've gone ahead and replaced them with Black Gate Type C.
The sound already is more detailed and transparent with greater attack. Obviously the parts are still running in, so will have to wait and see how they improve.

[Fin]

After 2 1/2 years how does it sound now? That is probably long enough to let the caps settle down.

[mudan]

Compared to how it sounded before the modifications, the amp now sounds more dynamic and detailed with less of the cold 'colourless' sound it was sometimes accused of. Though to be honest most of this 'colourless' sound was removed when I replaced the original main 2 Elna PSU caps with Panasonics, which due to the age of the amp probably weren't doing their job well anyway.

Included the coupling caps, I have replaced 9 of the caps per channel with Black Gates (18 in total), added some internal copper shielding, RF clamps and a new mains cable, all contributing to a much better sound.

So anyone who is wondering whether to replace theirs with Black Gates, the answer is a clear 'yes'!

P.S. Before this amp I owned a NAD C370 which amazingly the Pioneer walked all over.

[ImSparticus]

Mudan, any chance of some serious details of the mods so i can follow for the A400, values locations etc ?

Do you have a circuit diagram or manual etc ??

[mudan]

Hi,

There are some threads on here that list where you can get the schematics from. Unfortunately as you can't attach files here, I can't provide them, however naturally the corresponding part positions below are marked on the PCB.

Revealed for the first time are my modifications below ! :

C201/C202 (coupling cap) : Rubycon Black Gate Type C 2.2uF 50v
C212/C212 : Rubycon Black Gate Standard 220 16v
C301/C302 : Rubycon Black Gate Type C 2.2uF 50v
C220/C225 (check!): Rubycon Black Gate Standard 330uF 16v (Original was 10v)
C237/C238 : Rubycon Black Gate Standard 100uF 50v
C235/C236 : Rubycon Black Gate Standard 10uF 50v
C217/C218 : Rubycon Black Gate Standard 100uF 16v (Original was 10v)
C219/C220 : Rubycon Black Gate Standard 3.3uF 250v (Original was 100v)
C221/C222 : Rubycon Black Gate Standard 3.3uF 250v (Original was 100v)
C233/C234 : Rubycon Black Gate Standard 10uF 50v

All replacements correspond to ratings (excluding dimensions) of original parts unless otherwise stated

Other changes – Increase of bias current to approx 180 mA (60mV?) - (similar to an A400GTE mod done by by Tom Evans)
Mains cable addition – Audusa CSA with silver plated MK ToughPlug
RF clamps to internal mains cables where possible
Elna PSU Smoothing caps (10,000 uF 50v) replaced with Panasonic TSUP.
C306 (next to PSU smoothing caps) also replaced with Jelmax Black Gate NX HiQ 0.47 uF 50v.
Blue power LED !
BluTak damping
Internal copper shielding round PSU and certain other places with copper shielding tape.

Hope all A400 'modders' find this helpful

Dav

[Leolabs]

Originally posted by mudan
In my opinion, the Audyn MKP QS caps added greater bass depth and warmth but also blurred details, resulting in a less sharp sound.

Well I've gone ahead and replaced them with Black Gate Type C.
The sound already is more detailed and transparent with greater attack. Obviously the parts are still running in, so will have to wait and see how they improve.

Have you bypass them with a smaller value caps???