Nakamichi PA200 upgrades - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th March 2014, 07:14 AM   #1
ishiru is offline ishiru  Indonesia
diyAudio Member
 
ishiru's Avatar
 
Join Date: Oct 2013
Location: Jakarta, ID - Nagasaki, JP
Default Nakamichi PA200 upgrades

hello all..

i have Nakamichi PA-200.

previously, i changed all of the electrolytic w/ the better one (i suspected all of them was dried out).

they actually sounds pretty good but kinda dried from my thought.

so changed the pre-driver w/ a mosfet. (i previously changed the original w/ ISC A968/C2238)

the mosfet i used was IRFP240/9240 (i only have them in my shelf)

i was pleased w/ the vocal.they sounds better.but strange!.i heard some distortion on the highs.

i couldn't write how they sounds like but they're pretty audible.no.not pretty audible.but very audible!

is it caused by the mosfet?.does the mosfet was too big?..

oh.i forgot to mention this.originally this amp's bias was very low (i couldn't measure them).and then i re-biased them to 10mV (don't say "that's low!".this amp runs freakin hot after re-bias).

but now after i changed the driver to mosfet the bias back to unmeasured.is this causing the amp has distortion?.this amp before re-bias has no distortion even runs cold.


thanks!

-add-

before i perform this change, i simulated this to LTSpice and got no problem w/ the sinewave

i recorded the video but don't know how to upload it here
__________________
HDD - Tube DAC - XV-2 xover - Krell Clone 50 + 4W class A mosfet amp - Technics SB-2470 (modded)

Last edited by ishiru; 5th March 2014 at 08:12 AM.
  Reply With Quote
Old 5th March 2014, 08:33 PM   #2
ishiru is offline ishiru  Indonesia
diyAudio Member
 
ishiru's Avatar
 
Join Date: Oct 2013
Location: Jakarta, ID - Nagasaki, JP
i figured it out..
i simulated the amp to LTSpice and i figured that when i use mosfet w/ the same bias resistor, the bias goes lower (2.1kOhm bjt was around 3W while mosfet was only 20nW).

i'll try to set the bias pots to around 500Ohm and let's see the bias (yes.when i simulated this amp using mosfet, 495Ohm gave closest result on 2.1kOhm on bjt)

idiot me being idiot
__________________
HDD - Tube DAC - XV-2 xover - Krell Clone 50 + 4W class A mosfet amp - Technics SB-2470 (modded)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Nakamichi PA-5 upgrades kotofei Pass Labs 33 2nd October 2014 04:32 AM
Upgrades for D1 sixty9 Pass Labs 13 2nd July 2012 10:18 AM
Hickok Upgrades Zero Cool Tubes / Valves 0 23rd June 2008 12:36 AM
Lm3886 Pa200 mrquality Chip Amps 0 26th June 2007 05:36 PM
PA200 and 8ohm load? CJ900RR Chip Amps 9 7th March 2007 05:44 PM


New To Site? Need Help?

All times are GMT. The time now is 05:07 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2