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Please Help with capacitor replacement
Please Help with capacitor replacement
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Old 1st December 2009, 06:47 PM   #1
hearingisbelieving is offline hearingisbelieving  United Kingdom
diyAudio Member
Join Date: Aug 2009
Location: West Midlands
Default Please Help with capacitor replacement

Hi, I have an ageing Pioneer A400 which I am looking to replace/upgrade the caps on. (schematics available for d/l here:Download hfe_pioneer_a400_a400x_schem.pdf for free on uploading.com )
I have already replaced the two PSU caps with some high quality Mundorfs with great results. I am now looking to replace the rest of the caps with Black Gates where possible.
The problem is I dont know much about the different types of caps so when ordering replacements I dont know whether i should be getting coupling caps, polarised, non polarised, std caps etc.
I have read a very helpful thread on this forum by Mudan (Pioneer A400 coupling caps replacing the caps in his A400 but i dont know why he chose to replace only the caps he did - should i replace all of them?
I have emailed the extremely helpful member Sakis but unfortunately im not smart enough to understand what he has said to me:

"well ...there is not much to say
this is relativelly simply
where ever you have psu caps ( means caps that used for local stabilization of power on board of the amplifier you can go to any quality you think its better and the higer possible capacitance if the size will allow you to ..... adding bypass of 100nf will also make some diference it can be done down under )
in signal capacitors will take some more expirience to do and also will require instruments
the miller caps if are ceramics ...will need to be replaced if a miller cap of 120 pf is placed by mom you may replace it with silver mika or styroflex .... with this quality you may lower the capacitance till almost 68 pf which will alter the quality of your amp and sonics dramatically .... but will also alter the safety margins )
a lot of work needs to be done to stude the behavior of this amp and why the designer choosed to stabilize the amp with capacitirs in the drivers and not in the vas .... this is a strategy that many designers do and many dont .... carefull listening and choise of components or strategy will bring amazing sonic results
input caps can be upgraded from cheap electrolytics to film types and some of them may removed totally ... types and capacitance will measure almost the same but will sound diferent ... you may choose what you like

playing around with things like that will cause results to better quality sonics and sound but the evaluation versus stability can only be done with instruments ....
there is another thing that you will also take in mind .... if your amp is made to ha ve a specific distortion doing upgrade as discribed above you may lower the distortion to a maximoum of 5%
there is other things beyond the capacitors that will make biger and more audible diference...
please notice that this type of designs als have been made with correct calculations between quality safety and cost playing arround can be also risky since altrering of quality will also alter the safety margins
you are welcome to make a new thread in diy regardind this issue and also place my comments so we can start talking there which others will see and add their 2 cents

if anyone can offer any help at all it will be very much appreciated!!

Last edited by hearingisbelieving; 1st December 2009 at 06:50 PM.
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Old 3rd December 2009, 09:05 PM   #2
hearingisbelieving is offline hearingisbelieving  United Kingdom
diyAudio Member
Join Date: Aug 2009
Location: West Midlands
Just to clarify... I am only looking to replace the aged capacitors with new(and hopefully better quality) caps of the same values.
The Black Gate caps are available in following varieties:
C - Polarized, coupling applications, compact, great value for money
FK / K / VK - Highest technology polarized, rated up to 350V
N - Non-polar
NH - Non-polar, high voltage
NX - Highest technology non-polar
STD - Polarized, standard grade, excellent value for money

This note is added on a web page of a store that supplies the caps:
NOTE: Use N/NH/NX series in the most critical coupling and power supply applications

The problem i have is i dont know which caps on the amp are which...
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Old 3rd December 2009, 11:18 PM   #3
kirk57 is offline kirk57  United States
diyAudio Member
Join Date: Feb 2008
Default Are there little arrows?

Look at the capacitors on the amp, do they have little allows on them or plus/minus signs? If so they are stardard polarized electrolytics, which is what I would expect on that amp.
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Old 3rd December 2009, 11:36 PM   #4
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
Join Date: Nov 2005
Please Help with capacitor replacement
Be careful, BlackGates dont like other caps
No joke, they really do say that
And it might even be true
But that would make it completely impossible

Last edited by tinitus; 3rd December 2009 at 11:39 PM.
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