Pioneer A400 Power supply Caps

[James189]

Hello all, previously been a lurker finally joined now I actually have something to ask - I've a-level physics knowledge so, I can take a reasonable amount of technicality in answers but my dad's decided to replace the four 15,000µF slit foils in his original cyrus PSX, they're not damaged/ non-functional to the best of our knowledge, and as although they're 5 pinned caps, only two pins are connected in the circuit, could two of these replace the two 10,000µF electrolytic's in my Pioneer by means of an experiment [both are rated at 50V] for a possible improvement or will the greater inrush current likely fry the rectifier?

Thanks, James

 

[ticknpop]

It's probably fine

 

[James189]

I was in a rush when i posted this last night, apologies. Just checked the datasheet on the rectifier [d5sb20] 6A rating with heatsink, 2.8A without, seems like it should be fine, currently running without a heatsink but, i guess if it does blow i'll be forced to upgrade to something a little fancier, so long as nothing else pops in the process, Thanks ticknpop!

 

[James189]

Incidentally could anyone recommend any shottky diodes which could suitably replace a d5sb20? [ http://www.datasheetcatalog.org/datasheet/Shindengen/mXxsyus.pdf ] I'm looking but current matched diodes I've come across so far don't seem to have the required voltage characteristics to be suitable.

 

[AndrewT]

Keep the existing rectifier/s.
Try the replacement capacitors.
Try to allow for returning to near original, if the experiment fails.

 

[James189]

One thing at a time, good idea, Thanks! I'll post [subjective] results after i get hold of the new caps, and see where I stand.

 

[James189]

After 7 hours of fiddly labour I've just finished, fitted two 15,000µF 50V slit-foil cyrus psx capacitor in place of the two 10,000µF Pioneer ELNA electrolytic PSU caps, and i've disconnected one of the input on the back from the selector switch and wired it straight the the volume pot with 5A [i think, its all i had available] solid core copper wire. The difference really is night and day, bass is stronger and more 'full' sounding, I think a slight bit deeper, there seems to be less noise at the speakers with no source playing and the sound as a whole feels to have opened up, sound more airy, and at the same time taken on a sense of 'effortlessness' which wasnt previously there, so thanks for the heads up gentlemen, first major Hifi mod a success! Incidentally i also replaced the 4 caps inside the cyrus PSX with ELNA electrolytics, so replacement of those is perfectly possible for anyone reading this in future, 3 of the capacitors 5 terminals are for mechanical support.

 

[sgrossklass]

Looking at the A-400 schematic, I'd say your imagination is helping out with the sonic improvements - expectation bias in full swing. With these two mods, something like a lower noise floor is close to impossible (at least if the volume pot is still active, which I assume it is). Anything else would require a selector switch in need of a good cleaning (which isn't even unrealistic but should have shown as intermittency) or the original caps to be pretty much flat with dreadful ESR (not all that common with these big ones, which usually are of decent quality and in many cases don't have an overly hard life in home hi-fi amps; anyway, I would have expected noticeable hum under any kind of loading then).

 

[James189]

Is this to say any changes I've noticed following work on the amp are primarily psychological? I find it interesting that characteristics of the low frequencies following the change remind me of the same differences noticed when a PSX [which the caps are salvaged from] is added to a cyrus two. Still, a psychological change is as big as any measurable difference [or so I believe].

 

[sbrads]

The big test is to put the old caps back into the Pioneer to see if the sound quality goes back down to what you remember. Somehow, I don't think we'll be seeing a post from you saying you've tried this

 

[analog_sa]

Is this to say any changes I've noticed following work on the amp are primarily psychological?

Absolutely not. Apart from the lowered noise floor of course. Getting the old caps back in order to confirm your impressions is certainly a good idea. Watch out you don't lift any tracks.

 

[James189]

I would actually like to 'retract' the lower noise floor comment, I think I little excited at having not destroyed the amp, and possibly the 'effortlessness', though it may not be a completely consistent test, a close friend also has an A400, I might need to see if we could arrange a comparison sometime, his is completely unmodded so although the condition of the components may vary, what's actually inside is exactly the same. Still, I feel very very pleased with the results, if only I weren't poor and in need of a job I'd get to work on the coupling caps, volume pot, input RCA's, adding an IEC socket and I'd love to find more of what tom evans actually did in his GTE mods, the addition of a DC servo sounds interesting.

 

[MykhailoM]

Hi,
Could you please help me to find the right capacitor replacement which are THE BEST possible for natural sound reproduction.
This is for Pioneer A400 Integrated Amplifier

The original capacitors (2 of them) are:
10,000uf each - ELNA 50V ACH1152 CEW 85deg

I heard that going for HIGHER uf. something like 20.000 or 30.000 is even better for its performance.

Can you please recommend the right one desirably from trusted Brands.
Amplifier Picture: http://www.avforum.hu/uploads/post-6-1253471757.jpg

Would you recommend these:
1). 2 pcs Japan Nichicon KW 10000Uf/50V Audio Capacitor for audio cap | eBay
Nichicon KG type electrolytic capacitors

Nichicon 10000uF / 50V, KG Series
Nichicon 10000uF / 63V, KG Series
Or

Nichicon KW 10000Uf/50V
Nichicon KG type electrolytic capacitors homepage
Thanks