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 22nd October 2009, 08:30 PM   #11
diyAudio Member
 
Join Date: Apr 2002
Location: Cayman Islands
While I don't think this is what Sy was suggesting it may be of some help nevertheless.

Williamson amplifier

An Ultra-Linear amplifier by David Hafler & Herbert I Keroes

see also

Audio amplifier with improved stability - Patent 4066975
__________________
None of us are leaving this world alive. Enjoy it responsibly as you may.
  Reply With Quote
Old 22nd October 2009, 08:32 PM   #12
diyAudio Member
 
Herr Grau's Avatar
 
Join Date: Nov 2008
Location: North-Western Germany
Send a message via ICQ to Herr Grau
Quote:
There are literally cazillions of circuits out there for KT88 PP (don't use Google Image search, you have been warned) but if you suffer from procrastination as I do, I would suggest only looking at perhaps half a dozen and then decide otherwise you will be forever comparing them against one another.
I know and after about ten or twenty hours of research in the last few days I feel like I've seen all of em. I basicaly excluded everything that used tubes too rare, everything that used only one split tube in the pre-stage, everything that I spontaniously disliked of some other reason...

Quote:
The article I had in mind appeared about a year later. I think it's in Audio Anthology- I'll check when I get home.
Thanks.

(Regarding the Quad, I just read that the design only plays out its great cards if hooked up to a very specificaly designed OPT.. So screw that too. :-P )
  Reply With Quote
Old 22nd October 2009, 08:43 PM   #13
diyAudio Member
 
Join Date: Apr 2002
Location: Cayman Islands
I believe it is Sowter in the U.K that made a duplicate or perhaps Woodside, in any case I remember a reproduction transformer being manufactured for the Quad II and also an anniversary and or a reissue amp. Sorry I cannot be more specific as this is all from memory. The only thing I remember is the primary was 10K and it was quite a special wind.

If I can find any further info I will let you know.
__________________
None of us are leaving this world alive. Enjoy it responsibly as you may.
  Reply With Quote
Old 22nd October 2009, 08:58 PM   #14
diyAudio Member
 
Join Date: Apr 2002
Location: Cayman Islands
Both of these do Quad II replacement OPT's.



Woodside Electronics
Telephone/Fax: +44 (0) 1758 741026

Email: m.davis@virgin.net


Sowter Audio Transformers
E. A. Sowter Ltd, PO BOX 36, Ipswitch. IP1 2EL, England, UK.

Telephone: +44 (0) 1962 620135

Fax: +44 (0) 1962 870299

Email: techsupport@sowter.co.uk

Web: SOWTER AUDIO TRANSFORMERS

Quad output is model 8778
__________________
None of us are leaving this world alive. Enjoy it responsibly as you may.
  Reply With Quote
Old 22nd October 2009, 09:43 PM   #15
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Franz-Wichlas-Red-Hot-PP-UL/Red-Hot-PP-UL.htm

Absolute minimum bits & spec, as per German schrift (great lingo). Amp is a reasonable start but later can be massively improved apon....Comment 4 on the handworking: < my woman is quite helpful with tasks around the bench> Rather fun and comical for a matched pair:-(More than mine is...)

I'm ingrained with Williamson, lock-stop-and-barrel. No change.
richy
  Reply With Quote
Old 23rd October 2009, 01:46 AM   #16
diyAudio Member
 
Herr Grau's Avatar
 
Join Date: Nov 2008
Location: North-Western Germany
Send a message via ICQ to Herr Grau
Well, if there are no rudimental objections against Williamson...
Then the new favourite design is the so called 'Ultimate' Amp.

Let's wait for SY's article before deciding anything about changes.

Is there any problems with transfering the PSU of a Dynaco Mk III (schematic) into this one?
(I found most KT88-PP-Amps working with less plate voltage then this one, the MK III too. Since I do not know what that changes exactly, I ask before I do something (most likely stupid).)
If so, a choke of which specs would you recommend?

Second question is if I can replace the OPT (Pliton 4142) with a Sowter U070 since it has 4,5kOhm instead of 4k. Or would you have to adjust some things?

Well, that's that for today... Its 3:46am over here, propably bed time... :-)
  Reply With Quote
Old 23rd October 2009, 02:01 AM   #17
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
"Ultralinear Operation of the Williamson Amplifier," Hafler and Keroes, Audio Engineering, June 1952. It's reprinted in "Audio Anthology, Vol 2" from Old Colony. There's things that one might do differently these days (e.g, power supply regulation), but built as drawn, this is a classic circuit which will do well for you. The original used 6L6-type tubes, but with KT88, 4-5k plate-to-plate, and 450V on the output stage plates, you should be good for a solid 40 watts. The amp schematic you link to is taken from this article almost part for part, but for the output stage. It looks like a good direction to go in.

"The low frequency time constants of the original circuit's interstage coupling networks were the same for both networks. This is not particularly desirable in a feedback amplifier since a given frequency loss is accompanied by maximum phase shift. Separation of the time constants permits less phase shift for the same frequency loss. Increasing one pair of coupling capacitors from .05uF to .25uF gives a five-to-one ratio of time constant for the two pairs of networks and increases the low frequency stability margin at nominal increase in cost."
__________________
"The way to deal with superstition is not to be polite to it, but to tackle it with all arms, and so rout it, cripple it, and make it forever infamous and ridiculous."- H. L. Mencken
  Reply With Quote
Old 23rd October 2009, 02:22 AM   #18
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
Langford-Smith (...the guy behind the Radiotron Designers handbook...) colaborated on a redesign of the Williamson: http://www.mif.pg.gda.pl/homepages/j...iamson-807.pdf

(Note: the page / pdf file sometimes does not load, and you may have to 'refresh / F5' it in your internet browser to get it to load).

The amp is rated to 15W, but regard it as a 10W amp and it seems very clean. Their notes state very low and consistent distortion from 1 to 10W.
  Reply With Quote
Old 23rd October 2009, 03:37 AM   #19
88man is offline 88man  United States
diyAudio Member
 
Join Date: Aug 2009
Location: Boston
Sy, are you suggesting to change the low frequency time constant in the "Ultimate Amp or leave it the way it is?" The feedback in this circuit is accomplished with a 39k ohm resistor.

I posted a thread last week on this exact amp. It's the most appealing circuit I've seen for a DIY 6SN7/KT88 PP amp capable of producing >25W.
VTV Push-Pull 6SN7/KT88 Amp: DIY or China?

Eli D. pointed out that the Williamson circuit requires top notch transformers to prevent unstable phase shift oscillation. He says that the Mullard circuit is more stable in this regard. Unfortunately, I lost my Mullard Circuits book that I bought from Parts Express, so I can't access any schematics.

Furthermore, a set of Plitron transformers alone in the VTV Ultimate Amp is around $800. I was even considering buying an integrated amp from China and modifying it for less money than a DIY project, but then again, that wouldn't be the point. I've thought about using the Edcor CXPP60-8-4.2K for the OPT which has a 4.2k ohm primary (very close to 4k ohm). It's $62 vs $316!

Let us know how the build turns out...
  Reply With Quote
Old 23rd October 2009, 05:49 AM   #20
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Quote:
Originally Posted by Herr Grau View Post

Second question is if I can replace the OPT (Pliton 4142) with a Sowter U070 since it has 4,5kOhm instead of 4k. Or would you have to adjust some things?

Well, that's that for today... Its 3:46am over here, propably bed time... :-)
The Plitron is a gapless core: the Sowter is conventional E&I. Swapping to the Plitron in a Williamson can be done but one effectively alters the Bode map so the loop gains when global nfb is used have to be re-worked to avoid LF instability. Reminds me of the Eckland amp:may be worth examination.

richy
  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
SE KT88 Amp Cassiel Tubes / Valves 50 24th March 2011 08:33 PM
Would it be possible? OTL/OCL KT88? Layberinthius Tubes / Valves 4 24th January 2004 11:31 PM


New To Site? Need Help?

All times are GMT. The time now is 02:44 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