Esp P3a - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

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
Reply
 
Thread Tools Search this Thread
Old 22nd July 2004, 06:20 PM   #1
audioPT is offline audioPT  Portugal
diyAudio Member
 
Join Date: Aug 2002
Location: Right here
Question Esp P3a

Guys,

I'm working two ESP's P3A in bridge mode with a load of 4Ohm.

Rod wrote that this must not be done.

My question is:
There is any problem with my amp, since the PSU is made with a 18x0x18V 380VA xformer?
  Reply With Quote
Old 22nd July 2004, 06:44 PM   #2
paulb is offline paulb  Canada
diyAudio Member
 
Join Date: Jun 2001
Location: Calgary
You're effectively driving a 2-ohm load from each amplifier. This will be very efficient and you may find the output transistors get really hot with only moderate power going to the speaker. You may want to double up all the output transistors; see the original P3 article (I think) for details.
  Reply With Quote
Old 22nd July 2004, 10:00 PM   #3
audioPT is offline audioPT  Portugal
diyAudio Member
 
Join Date: Aug 2002
Location: Right here
Yep, I know that I'm driving 2 Ohm...

I also forgot to write that I'm using 2 pairs of MJL in each amp.
Also read Rod's text about bridging the amps and if I'm using 25-0-25V, I think the amps are working in class A (as explained in P3Ab project).

But now I have a doubt:
If this amps are working in class A, why they don't get hot?

They are driving an isobaric subwoofer, and after "The day after tomorrow" movie, the heatsink still cold... I mean, not very hot.

My LM12 'gainclone' gets more hot...

I've measured the output and got this at 100Hz / 4Ohm (bridge):
Umax=19,7V
Imax=4,9A

Does it mean a power of 96,53W?
  Reply With Quote
Old 22nd July 2004, 10:09 PM   #4
Mark25 is offline Mark25  United Kingdom
diyAudio Member
 
Mark25's Avatar
 
Join Date: Feb 2002
Location: The Netherlands (Friesland)
the p3a is not class A, IIRC p3b is. some poeple increase the quiecent current of the p3a to 300ma, etc to get part of the output in class A.

what quiecent current are you running? you can go quite low if you are only driving a sub.
__________________
We will pay the price, but we will not count the cost...
  Reply With Quote
Old 22nd July 2004, 10:21 PM   #5
audioPT is offline audioPT  Portugal
diyAudio Member
 
Join Date: Aug 2002
Location: Right here
I can't get more than 230mA...

Only know that my neighbours are not happy

I've said Class A because I've a 18x0x18V xformer
  Reply With Quote
Old 25th July 2004, 07:16 AM   #6
Mark25 is offline Mark25  United Kingdom
diyAudio Member
 
Mark25's Avatar
 
Join Date: Feb 2002
Location: The Netherlands (Friesland)
The fundamental difference between Rod's Class A (P3B) and his class B (P3A) is the quiecent current. The P3A runs at 40 - 100mA, the P3B runs at 1.5 amps, nessesitating a BIG heatsink and different power supply topology.

If i were using a p3a for a sub, i'd start with the quiecent current at 10 mA, increasing it to max 40mA, ONLY if it made an audable difference, i suspect it wouldn't.

when measuring the quiecent current, it can be useful to measure the actual emmiter resistance value. The actual value of those high power 0.33 ohm resistors can vary from 0.33 quite a bit in my experience.
__________________
We will pay the price, but we will not count the cost...
  Reply With Quote
Old 26th July 2004, 09:58 AM   #7
audioPT is offline audioPT  Portugal
diyAudio Member
 
Join Date: Aug 2002
Location: Right here
Wanna know something?

I've changed some things in both amps (of course, they are bridged and must be equal):

Output resistors -> from 1 x (0,33 Ohm 5% 5W) to 3 x (1Ohm 2% 2W);
Q9 (bias) from BC546 to BD139 and attached at the heatsink;

The surprise:
Iq down to 28mA. And after one hour of true "earkilling", visceral shaking and other tremours with "Chemical Brothers" at full power, the Iq just stop at 41mA.

By the way, the heatsink was not very warm...

This word is for Rod Elliott: Very nice amp, apart from being undestructable!

obs: if any word wasn't well written, I'm just sorry


Regards!
  Reply With Quote
Old 26th July 2004, 11:54 AM   #8
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
You should not attach Q9 to the heatsink because the CFP output stage configuration requires you to sense the temperature of the driver transistors.
  Reply With Quote
Old 26th July 2004, 12:06 PM   #9
Mark25 is offline Mark25  United Kingdom
diyAudio Member
 
Mark25's Avatar
 
Join Date: Feb 2002
Location: The Netherlands (Friesland)
Quote:
Originally posted by audioPT
The surprise:
Iq down to 28mA. And after one hour of true "earkilling", visceral shaking and other tremours with "Chemical Brothers" at full power, the Iq just stop at 41mA.
out of interest, how low could you go before it made an audible difference?
__________________
We will pay the price, but we will not count the cost...
  Reply With Quote
Old 26th July 2004, 12:36 PM   #10
audioPT is offline audioPT  Portugal
diyAudio Member
 
Join Date: Aug 2002
Location: Right here
It's only for low consuption in idle.
In low frequencies, I think nobody can hear the difference.

You can call me anything you want, but in these frequencies, Class A or Class B or Class D sound the same at the same power output, and the power consumming is very different, right?

regards
  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



New To Site? Need Help?

All times are GMT. The time now is 05:14 PM.


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