NEED HELP for Pioneer A400x mods

MTO audio · 31st July 2007, 09:24 AM

NEED HELP for Pioneer A400x mods
Hi every one, I am new to this forum, I am working on a A400x at the moment.
For the dc coupling I used WAMA 3.3uF MKS4 non-polar. On power supply, i used a high speed rectifier bridge and 0.1uF WAMA bypass on every filter caps. I also added few 100uF/50V Panasonic FC and WAMA MKF on V+/V- of each transistor.
After the mods, rectifier replacement improved the quality of the bass a bit, WAMA give very nice high end, however the whole image became too bright.

Is there anyone have experienced on mods A 400 or A 400x?
Q1: how can I avoid the sound become too bright?
Q2: how can I get better bass control?
Q3: if I increase the bias current, does the 2SA/2SK driving pair needs a heat sink?
Q5: A400 originally 20mA on each power transistors, I am going to boost up to 100mA. Would that give me a warmer sound and better bass control?

Thanks very much!!!!!!!!!!!!!!!!!!

rabbitz · 31st July 2007, 11:33 AM

Did a few small mods on my A400X.

Input caps changed to 4.7uF Nichicon ES and maybe Black Gate N or NX would work well here.

The main power supply caps were changed to 10000uF Nichicon Gold Tune.

Caps for op amp were changed to 100uF Nichicon Fine Gold. Tried a few different op amps such as OPA2134, 5532, AD826 but the original M5220 sounded the best. The other op amps may have needed some different power and by-pass caps but wasn't worth playing with.

The mods have seemed to give a bit more drive all round and more control in the bottom.... deeper may be?? ... a tad more clarity but no other noticeable changes. For the few dollars, was worth it.

zanash · 1st August 2007, 07:12 AM

I suspect your dc decoupling caps are the issue ....try doubling them up to get 6-10uf ...or try a different cap..

I don't have the schems so can't offer any more advice.

MTO audio · 1st August 2007, 01:58 PM

Hi, thanks for the replys. here is the link to A400 and A400x manual: http://www.hifiengine.com/manuals_ty...oneer&mod=A400

simplymortified · 21st January 2009, 03:57 AM

Hey Rabbitz, where did you source the Nichicon Gold Tune caps in Australia?
Many thanks, Richard.

rabbitz · 21st January 2009, 01:02 PM

Had to get them from Canada.

http://www.minisemi.com/Nichicon%20M...apacitors.html

simplymortified · 21st January 2009, 09:41 PM

Thanks for the info

Cheers,
Richard.

31st July 2007, 09:24 AM	#1
MTO audio diyAudio Member Join Date: Jul 2007	NEED HELP for Pioneer A400x mods NEED HELP for Pioneer A400x mods Hi every one, I am new to this forum, I am working on a A400x at the moment. For the dc coupling I used WAMA 3.3uF MKS4 non-polar. On power supply, i used a high speed rectifier bridge and 0.1uF WAMA bypass on every filter caps. I also added few 100uF/50V Panasonic FC and WAMA MKF on V+/V- of each transistor. After the mods, rectifier replacement improved the quality of the bass a bit, WAMA give very nice high end, however the whole image became too bright. Is there anyone have experienced on mods A 400 or A 400x? Q1: how can I avoid the sound become too bright? Q2: how can I get better bass control? Q3: if I increase the bias current, does the 2SA/2SK driving pair needs a heat sink? Q5: A400 originally 20mA on each power transistors, I am going to boost up to 100mA. Would that give me a warmer sound and better bass control? Thanks very much!!!!!!!!!!!!!!!!!!

1st August 2007, 01:58 PM	#4
MTO audio diyAudio Member Join Date: Jul 2007	thanks every one! Hi, thanks for the replys. here is the link to A400 and A400x manual: http://www.hifiengine.com/manuals_ty...oneer&mod=A400

21st January 2009, 01:02 PM	#6
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	Had to get them from Canada. http://www.minisemi.com/Nichicon%20M...apacitors.html __________________ No longer DIY active

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31st July 2007, 11:33 AM	#2
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	Did a few small mods on my A400X. Input caps changed to 4.7uF Nichicon ES and maybe Black Gate N or NX would work well here. The main power supply caps were changed to 10000uF Nichicon Gold Tune. Caps for op amp were changed to 100uF Nichicon Fine Gold. Tried a few different op amps such as OPA2134, 5532, AD826 but the original M5220 sounded the best. The other op amps may have needed some different power and by-pass caps but wasn't worth playing with. The mods have seemed to give a bit more drive all round and more control in the bottom.... deeper may be?? ... a tad more clarity but no other noticeable changes. For the few dollars, was worth it.

1st August 2007, 07:12 AM	#3
zanash diyAudio Member Join Date: Feb 2005 Location: Notts	I suspect your dc decoupling caps are the issue ....try doubling them up to get 6-10uf ...or try a different cap.. I don't have the schems so can't offer any more advice.

21st January 2009, 03:57 AM	#5
simplymortified diyAudio Member Join Date: Oct 2007 Location: Melbourne	Hey Rabbitz, where did you source the Nichicon Gold Tune caps in Australia? Many thanks, Richard.

21st January 2009, 09:41 PM	#7
simplymortified diyAudio Member Join Date: Oct 2007 Location: Melbourne	Thanks for the info Cheers, Richard.

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