Go Back   Home > Forums > >

Solid State Talk all about solid state amplification.

P3A based question ....
P3A based question ....
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
Old 13th January 2021, 10:18 AM   #1
east electronics is offline east electronics  Greece
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Default P3A based question ....

Now i need some advise ....

Current set up in my house is a P3A dual mono at 48+48 rails with 1302-3281 outputs @50 ma bias ....

Ok rails are a bit on the risky side Load also is low about 5ohms so i kept the bias low
Listening demands are very low i think that the average power needed should be no more than 20 W
Obviously i know i am out of SOA but since i operate the system and no one else will abuse it i might get away with it ....

Now my actual problem is bias meaning that amplifier plays superb when warm ,,,So given the conditions above if i crank up the bias @100 ma i think i am pushing my transistors way too much ...Often i power up my amp in the morning to go home in the night to listen ....or i keep it always on the weekends

remember i live in Greece so in my home as we speak temp is 18-22 degrees but in the summer time it could easily go 35 .....

One solution will be to go for 1216 combo .... 15 MHZ more faster( 40 instead of 25 ), 17A instead of 15, and generally better SOA , also LAPT technology ....

any ideas ? Lowering rails or adding more transistors is out of the picture ...
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 13th January 2021, 07:48 PM   #2
mjf is online now mjf  Austria
diyAudio Member
 
Join Date: Jan 2009
Location: Austria
.........afaik the p3a has a cfp output stage and i guess you have emitter res = 0,33 ohms.
d. self recommends for this combo an optimal bias of 8,54mA (with an 8 ohm load).
quoted from
d. self "audio power amplifier design handbook" fifth edition, page 183.........
  Reply With Quote
Old 13th January 2021, 10:12 PM   #3
adason is offline adason  United States
diyAudio Member
 
adason's Avatar
 
Join Date: Nov 2004
Location: Maryland
Quote:
Originally Posted by east electronics View Post
Now i need some advise ....

Current set up in my house is a P3A dual mono at 48+48 rails with 1302-3281 outputs @50 ma bias ....

Ok rails are a bit on the risky side Load also is low about 5ohms so i kept the bias low
Listening demands are very low i think that the average power needed should be no more than 20 W
Obviously i know i am out of SOA but since i operate the system and no one else will abuse it i might get away with it ....

Now my actual problem is bias meaning that amplifier plays superb when warm ,,,So given the conditions above if i crank up the bias @100 ma i think i am pushing my transistors way too much ...Often i power up my amp in the morning to go home in the night to listen ....or i keep it always on the weekends

remember i live in Greece so in my home as we speak temp is 18-22 degrees but in the summer time it could easily go 35 .....

One solution will be to go for 1216 combo .... 15 MHZ more faster( 40 instead of 25 ), 17A instead of 15, and generally better SOA , also LAPT technology ....

any ideas ? Lowering rails or adding more transistors is out of the picture ...
...use small computer fans
I use 12V fans with DC regulator, and set about half the voltage, so they rotate comfortably, start reliably, and produce no noise
have two dozens of classA amps, almost none without fans, I do not like things too hot
reliability is important to me
  Reply With Quote
Old 14th January 2021, 12:36 AM   #4
Ian Finch is offline Ian Finch  Australia
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour, NSW
P3A based question ....
Hi Sakis. It seems to me that since you have been operating your versions of P3A with a higher (up to 130Ma IIRC) bias current for some years, the only problem to deal with is heat dissipation, meaning bigger heatsinks and better airflow than in typical Japanese amplifiers up to about 1990. Assuming this is basically a modified commercial product, perhaps the original power transformer will be running warmer and the power supply components may be stretched a bit too.

Even if your load is only 4 ohms, you are still talking of 96V rail-to-rail at 50 or 100mA which is only 5W or 10W idling dissipation for each output stage. Surely that's not a problem for TO264 power transistors operating at low average output level.

I think we are aware of the bad effects of protection relay contacts so the only concession I would make, is to add a version (such as Bonsai's design) of a Mosfet output protection relay to eliminate further risks from accidental overloads, shorts, failures etc. but with no affect on the audio.
  Reply to this post

Reply


P3A based question ....Hide this!Advertise here!
Thread Tools

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
TGM8 - an amplifier based on Rod Elliot P3a Bigun Solid State 1155 19th October 2020 02:56 PM
P3A transformer question DIY_Peter Solid State 13 10th October 2003 09:10 AM
P3A question: high input impedance sobazz Solid State 1 14th July 2003 06:45 AM
Not quite P3a question Paulr Solid State 0 10th January 2003 10:44 AM
Elliot P3A question... JoeBob Solid State 17 2nd May 2002 04:59 PM


New To Site? Need Help?

All times are GMT. The time now is 09:56 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki