Another PP GU50 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 30th April 2013, 04:15 PM   #1
diyAudio Member
 
Join Date: Mar 2008
Default Another PP GU50

This is schematic for my new PP with GU50. Max power more than 100W, THD at 80W 0.55%. I plan to build that amp in next few mounths. All voltages other than 700V will be regulated.
Ask for comments.
Attached Images
File Type: png GU50 C3G PP.png (31.5 KB, 395 views)
  Reply With Quote
Old 30th April 2013, 09:15 PM   #2
diyAudio Member
 
Join Date: Mar 2003
Location: Zürich
Hi, I think it would be good to leave some more headroom for the source followers. With headroom I mean a bit more than the +20V (maybe +100V) and possibly more negative voltage as well (more than -100V, and larger resistor). The reason is that the capacitances of mosfets are not very linear when VDS becomes small, so it is better to have at least 30V VDS under all circumstances.

I think your definitive amplifier will have independent voltage sources (pots) for bias adjustments, to compensate for differences between GU50's?

have you looked into the 'bestpentode' connection for the input stage? I do not know if it works together with the local feedback arrangement, but I think it will. It could give a bit more gain, less noise, and possibly better balance in the LTP.
__________________
my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!
  Reply With Quote
Old 1st May 2013, 01:07 AM   #3
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Good luck! :-)

Please come back when you get some results, and I will share my Pyramid experiences. And probably PCBs. :-)
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 1st May 2013, 09:37 AM   #4
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
IRFP240 as followers at 90 mA? Surely not - there are far better suited MOSFETs, IRFP240 has WAY too much capacitance, and this will be extremely nonlinear as Vgd approaches 8-10V. Even at 100mA per follower (which seems a bit excessive but I am guessing you are trying to make the change in current lower as the G1 of the GU50 goes positive) there are better (smaller) MOSFETs to use, also a bit more voltage on the current 20V supply...

Last edited by ilimzn; 1st May 2013 at 09:41 AM.
  Reply With Quote
Old 1st May 2013, 09:39 AM   #5
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally Posted by ilimzn View Post
IRFP240 as followers at a few mA? Surely not - there are far better suited MOSFETs, IRFP240 has WAY too much capacitance.
Yes I know that. This is testing schematic in LTSpice. I am still looking for better MOSFET. Which one do you prefer?
  Reply With Quote
Old 1st May 2013, 09:45 AM   #6
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally Posted by ErikdeBest View Post
Hi, I think it would be good to leave some more headroom for the source followers. With headroom I mean a bit more than the +20V (maybe +100V) and possibly more negative voltage as well (more than -100V, and larger resistor). The reason is that the capacitances of mosfets are not very linear when VDS becomes small, so it is better to have at least 30V VDS under all circumstances.

I think your definitive amplifier will have independent voltage sources (pots) for bias adjustments, to compensate for differences between GU50's?

have you looked into the 'bestpentode' connection for the input stage? I do not know if it works together with the local feedback arrangement, but I think it will. It could give a bit more gain, less noise, and possibly better balance in the LTP.
Very good idea for bestpentode, I must find the Linear Audio publicitation where is that described. I belive that is in volume 1?
  Reply With Quote
Old 1st May 2013, 10:34 AM   #7
diyAudio Member
 
Join Date: Oct 2011
Location: Tauberbischofsheim, Germany
I think your design lacks the possibility of adjusting the GU50's bias, doesn't it?

Best regards!
  Reply With Quote
Old 1st May 2013, 12:11 PM   #8
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally Posted by Kay Pirinha View Post
I think your design lacks the possibility of adjusting the GU50's bias, doesn't it?

Best regards!
As I wrote before - this is working schematic for LTSpice. I always do bias like this:
Attached Images
File Type: gif gu50pp bias.gif (4.5 KB, 304 views)
  Reply With Quote
Old 1st May 2013, 05:46 PM   #9
Funker is offline Funker  Germany
diyAudio Member
 
Join Date: Feb 2009
Location: Hamburg, Germany
Quote:
Originally Posted by matejsirk View Post
As I wrote before - this is working schematic for LTSpice. I always do bias like this:
Hi,
it will be more comfortable to use two potmeters , one for the bias balance and another to set the idle current, like this example:


73
Wolfgang
Attached Images
File Type: jpg idle-current-1.JPG (73.9 KB, 280 views)
__________________
Ground your devices before they ground you
  Reply With Quote
Old 2nd May 2013, 07:14 AM   #10
FLT is offline FLT
diyAudio Member
 
Join Date: Nov 2009
Default bias circuit

Hi,

I prefer this circuit:

http://www.diyaudio.com/forums/attac...s-kt88_amp.png

No matter which trimpot fails the bias voltage will go full negative and
switch-off the tubes.

No, I am not kruesi...but i use the same bias circuit for my amps.

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Chinese GU50 PP wazza220951 Tubes / Valves 47 18th October 2012 08:01 PM
Help~ GU50 ? maxxtro Tubes / Valves 3 2nd October 2012 07:01 PM
PP GU50 triode strapped project FrançoisL. Tubes / Valves 63 27th July 2012 10:33 AM
OPT PP for GU50 Triode ? pwan Tubes / Valves 0 12th March 2011 11:30 PM
Gu50 cristelu2006 Tubes / Valves 13 18th November 2009 10:29 PM


New To Site? Need Help?

All times are GMT. The time now is 10:47 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