P3A transformer - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

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
Thread Tools Search this Thread
Old 13th January 2004, 06:26 PM   #1
Hitz is offline Hitz  Canada
diyAudio Member
Join Date: Jan 2004
Location: calgary
Send a message via MSN to Hitz
Question P3A transformer

I have a 300VA 32-0-32 transformer and I was wondering if this could be used for the P3A, or will the rails be too high, I'm guesing that this transformer is too large for the output trnasistors I have. They are the MJE3055/2955 pair. And if I can't use this transformer any recomendations would help thanks.
  Reply With Quote
Old 15th January 2004, 04:24 AM   #2
paulb is offline paulb  Canada
diyAudio Member
Join Date: Jun 2001
Location: Calgary
Maybe, mercator built a P3A with a 30-0-30 and he had to add a fan; he plans to move to a lower voltage and ditch the fan.
It sounds great, though.
  Reply With Quote
Old 15th January 2004, 04:50 AM   #3
diyAudio Member
Easyamp's Avatar
Join Date: Nov 2003
Location: United states
Well, If I had a 32-0-32 AC supply I'd would use a higher voltage output device such as mjl21193/94 pair or others in this range, then the mje2955/3055 pair. Although cheap and easy to get the mje2955/3055 pair being on a to-220 platform don't have the surface area or the vceo to make good use of your supply unless paralleled.

I have always like the 2sb688/2sd718 combo but I'm finding these hard to get lately. These trannies would work well with your supply.
  Reply With Quote
Old 15th January 2004, 05:18 AM   #4
Jean is offline Jean  United States
diyAudio Member
Jean's Avatar
Join Date: Mar 2002
Location: Sacramento, CA
Send a message via AIM to Jean
I would use it but change the output and maybe even driver transistors to something else. Also, you might want to think about what speakers you going to use, 4 ohm or 8 ohm.
left lane is for passing, slower traffic keep right please.
  Reply With Quote
Old 15th January 2004, 06:31 AM   #5
diyAudio Member
Join Date: Feb 2003
Location: Leuven
I think it's not a good idea to build the p3a with that transformer. I tried it with a 2x30V one, and the outputtransistors got really hot. Now I'm using a 2x25V and everything stays really cool.

You should try Rod's new Mosfet amp (P101) . You can use up to 2x70Vwith that design
  Reply With Quote
Old 15th January 2004, 10:50 AM   #6
diyAudio Member
bigparsnip's Avatar
Join Date: Apr 2003
Location: Cambridge
Hi, if you have a look through this thread I started a while ago you should be able to see the changes I made to the circuit (mainly to do with altering the driver/output transitor types and then adding a couple more output devices so that the amp should be able to drive up to about 250W into a four ohm load) as well as the board alyout I finaly came up with for it. Unfortunately I haven't gotten round to building this up yet, but hopefuly I might be able to do that soon.

With regards to the amp getting to hot, you could always just use larger heatsinks instead of adding a fan to keep things quiet.
  Reply With Quote
Old 15th January 2004, 11:19 AM   #7
diyAudio Member
Join Date: Feb 2003
Location: Leuven
I used a really large heatsink and it got pretty hot. about 45°C with no load on the amp...

Now (with 2x25V transf) it stays at room temp.

The p3a just isn't designed for high power. If you want to use that transformer, I suggest trying a different design.

Why push the p3a to it's limits, if you can build another amp that you don't have to push?
  Reply With Quote
Old 15th January 2004, 01:09 PM   #8
diyAudio Member
Easyamp's Avatar
Join Date: Nov 2003
Location: United states
If you were to use the components listed in Rod Elliot’s design then you are right this amp is not capable of much more then it's rated at.

You could parallel up 10 output devices if you really wanted to given the driver stage is adequate and achieve vary high output power. The design is solid and easy to alter for much higher power.
  Reply With Quote
Old 16th February 2004, 02:40 AM   #9
Rodrigo is offline Rodrigo  Brazil
diyAudio Member
Join Date: Feb 2004
Location: Sáo Paulo
Sorry i dont speak english

I You send for me, PCB Layout Amplifer P3A .. ???

Very Thanks

São Paulo - Brasil

  Reply With Quote


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
Using mains transformer as output transformer Elias Tubes / Valves 176 11th March 2013 09:35 PM
Modulation transformer for a driver transformer? ironradio Tubes / Valves 6 28th December 2008 05:05 PM
filament transformer vs plate transformer contaxchen Tubes / Valves 10 14th January 2005 10:43 AM
toroid Transformer as power Transformer for tube tone Tubes / Valves 7 11th February 2003 08:57 AM
toroid Transformer as output Transformer for tube preamp? tone Tubes / Valves 15 2nd February 2003 04:36 AM

New To Site? Need Help?

All times are GMT. The time now is 01:23 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2