GM-70 design approach - Page 7 - 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
Thread Tools Search this Thread
Old 29th December 2012, 06:45 PM   #61
diyAudio Member
Join Date: Oct 2010
Location: se england
i use some lundahl 1620 /120ma which can be set for 11k5 which is what i use, think at that impeadence they are only rated at 14w, i was testing yesterday and saw 16v into 8.8r so 29 w at some massive clipping.
still they were 200 delivered about 15 years ago

  Reply With Quote
Old 29th December 2012, 06:47 PM   #62
diyAudio Member
Join Date: Oct 2010
Location: se england
I thought they were more like 2k6?
  Reply With Quote
Old 31st December 2012, 09:24 PM   #63
diyAudio Member
Join Date: Feb 2010
Originally Posted by cotdt View Post
Of course distortion will get lower with higher impedance transformers, but that is not the goal for a SET amp. The GM70 has output impedance at 1.1k, so a 4.4k transformer makes more sense. I use a 5k but it sounds great even with 3.5k transformer.
True, but not the point I was trying to make. The GM-70 (in particular) is more sensitive to loading (in terms of IMD) than many tubes of its ilk (845, 572, 211, etc.) so I don't agree that "4.4K makes more sense" - (you can talk with Jack Elliano of Electra-Print if you need actual test results).
Also, I would say that lowering IMD is the goal of any amp as it's by far the most objectionable form of distortion.

That being said, much of this depends on operating bias (quiescent voltage/current) and you do get wider frequency response (less inductive roll-off) with a 5K winding than w/10K.

All designs are compromises of one sort or another.
  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
GM-70 All done MelB Tubes / Valves 33 10th January 2015 12:59 AM
GM 70 Schematic needed! rvrazvan Tubes / Valves 23 1st December 2012 03:28 AM
GM-70 Build Issues Pyre Tubes / Valves 95 28th July 2012 08:29 PM
FS: GM70 ( GM-70 ГМ-70 ) Russian audio triode radiostar Vendor's Bazaar 0 23rd February 2011 06:12 PM
6C33C and GM-70 Colt45 Tubes / Valves 21 20th November 2002 11:38 PM

New To Site? Need Help?

All times are GMT. The time now is 01:42 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