which amp would be better... - 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 9th December 2014, 10:41 PM   #1
diyAudio Member
 
Join Date: Jan 2009
Default which amp would be better...

Hi everyone , I wonder which of these two designs would be better for a high power yet simple amplifier that actualy sounds decent (i'm afraid to use the word HI-FI) even though i have used similar schematics before and with the right speakers and good signal source they do sound much better than some say.

Ok so here are the two contestants. One is a modified version of Rod Elliot's project 3a , which i have built in the oriignal form and I'm happy with it , this modified version I found on the internet.

The other one is from long time forum member Apex.
Attached Images
File Type: png 100nieks upgrade.png (22.8 KB, 562 views)
File Type: jpg APEX BA1200 SCH.jpg (576.9 KB, 562 views)
  Reply With Quote
Old 9th December 2014, 11:16 PM   #2
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
They are quite different topologies.
I would guess they both sound very similar.
The second one does have the advantage of some protection.
I have built similar amps to both and they both sounded good.
__________________
PCBCAD51 pcb design software. http://murtonpikesystems.azurewebsites.net/
  Reply With Quote
Old 10th December 2014, 12:05 AM   #3
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Smoky Mountains , Tennessee
Why do you choose those ? because they have simple inputs stages , or because
they have lot of outputs ?

There are many , many different designs.

OS
__________________
Mongrel website , always current and updated :
http://www.fidelityforce.com/ostripper
  Reply With Quote
Old 10th December 2014, 02:02 AM   #4
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour
The question will not be about the best design- there is no such thing as a generalised "best" design. Any professionally designed power amplifier built to a tested standard layout with appropriate commercial standard components and wiring will sound "decent".

The person who doodled the P3a mod should do some homework and consider how MJE340/350 are going to drive 5 pairs or even more than 2 pairs of any kind of power transistor in a CFP topology output stage. That one is a certain disaster!

I think a 1,200W PA might shred your speakers and your party friends, though. That might not sound decent at all.
__________________
Ian
  Reply With Quote
Old 10th December 2014, 02:43 AM   #5
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour
Sorry guys, the second paragraph should simply read "....should consider how to drive 5 pairs or even more than 2 pairs...." etc.
__________________
Ian
  Reply With Quote
Old 10th December 2014, 05:23 AM   #6
JMFahey is online now JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Quote:
Originally Posted by Ian Finch View Post
The person who doodled the P3a mod should do some homework and consider how MJE340/350 are going to drive 5 pairs or even more than 2 pairs of any kind of power transistor in a CFP topology output stage. That one is a certain disaster!
Dear Ian, I think you missed counting one current gain stage.

On the top side, for example, the MJE340 is not straight driving 5 x 2SC5200 but through an 2SA1943 which, just out of the top of my head must have at least Hfe>20 , and probably higher.

Which will reduce its workload by the same factor.

If anything, I am somewhat worried about optimistic Apex's design.

Not sure that the meager current provided by the Vas stage is enough to drive that bucketful of power transistors boosted just by a pair of power transistors used as drivers.

If enough, it will probably be just so, with no extra margin, with the certain possibility that on some transistor batches of not being enough at all, simply because of Hfe spread.

No doubt they will be a pair of robust drivers though
  Reply With Quote
Old 10th December 2014, 05:46 AM   #7
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour
Quote:
Originally Posted by JMFahey View Post
Dear Ian, I think you missed counting one current gain stage....
You were briefly right but that was the purpose of the following post. More apologies if it doesn't appear to correct the statement.

My point was not about enough drive current, but instability and current sharing in a CFP output stage where some builders find it necessary to fit individual drivers to each output device and this becomes counterproductive.

EF designs don't have this problem, as perhaps millions of working amps prove.
__________________
Ian
  Reply With Quote
Old 10th December 2014, 05:56 AM   #8
diyAudio Member
 
Join Date: Apr 2013
I think the P3A derivative is the most interesting of the two, but very much doubt it will be stable as presented. Personally I would convert the output stage to an EF3, insert base stoppers in all the drivers and outputs and liberally decouple the driver/output collectors.

The emitter resistors should be brought up to 0R22 - 0R33 to improve current sharing with that number of outputs. R6 is superfluous. If you are going to the trouble of building such a high power design, it would be worthwhile improving the input stage, starting with emitter degeneration to the LTP and then bring up the tail current to improve slew. 2mA per device and Re = 100 ohm would be a reasonable start. A degenerated current mirror would improve slew even further, which might be beneficial for an amp with high voltage swing. All standard D. Self fare.

With the radially different output stage, I doubt it will retain the P3A character anyhow.
  Reply With Quote
Old 10th December 2014, 01:49 PM   #9
diyAudio Member
 
Join Date: Jan 2009
Well , thanks for the opinions , since english is not my first language maybe if someone is willing could you please make some quick corrections to the p3a project schematic or just explain a little more naming where the change needs to be made.

like what is an ef3 or base stoppers etc ?

thank you.
  Reply With Quote
Old 10th December 2014, 02:01 PM   #10
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
Either amp should be converted to EF3, if you want to build either of them and have the minimum fuss getting it working. There's no way you can use EF2 on +/-110V - there just isn't enough gain. The thermal stability problems with EF3 (bias wandering around) can be dealt with by splitting up the bias stack and compensating driver and output devices individually. You can even get away with splitting up the + and - output banks if they are compensatied individually. To do that you use Leach's bias stack and sprinkle the diodes around. One on an NPN output, one on a PNP, one on each driver. And then dare the bias to move.
  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
Modify & build out (2) Western Electric 300B / 2A3 Hammond monoblock amps & UTC LS-5 quality sound Tubes / Valves 0 9th May 2009 03:59 PM
Krell KSA 80 bias & dc offset check & adjust procedure Clouseaupte Solid State 3 9th August 2007 09:39 AM
DIY-AMP <ZAS> Low THD & IM high bandwith murphy Solid State 18 30th December 2005 10:28 AM


New To Site? Need Help?

All times are GMT. The time now is 01:20 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2