a question of tube behaviour - 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 13th November 2005, 07:56 AM   #1
g-banjo is offline g-banjo  United Kingdom
diyAudio Member
 
Join Date: Nov 2005
Default a question of tube behaviour

As the owner of a Vox Tonelab amp modeler I've been experimenting with various valves as substitutes for the stock EH 12AX7.
The Tonelab uses the 12AX7 in it's "valve reactor circuit", I'll quote the Vox website:

" The Valve Reactor circuit uses a 12AX7/ECC83 dual triode vacuum tube, a virtual output transformer and a dummy speaker circuit that simulates impedance changes of a real speaker. In other words though the output power (level) is low, it has the same power amp circuit as an actual full-tube amp, and faithfully reproduces the response of the power amp circuits of the original amp that is being modeled. It reconfigures itself so that its characteristics are the same as the amps it's modeling (class A, class AB, negative feedback circuit, etc.) This means that all of the nuances of the original amp model including sound, feel, distortion and presence are reproduced."

I have been comparing various 12AX7s and 12AT7s both in this unit and in a DBX preamp. The differences between the valves seem to be greater in the Vox than in the DBX. My questions are;
why do the differences between individual valves seem more pronounced when run at lower power? Or am I just imagining this?
  Reply With Quote
Old 14th November 2005, 01:44 AM   #2
diyAudio Member
 
Tom Bavis's Avatar
 
Join Date: Jun 2002
Location: Macedon NY
I suspect that the Vox runs the tube at at the edge of linear operation - near saturation or cutoff to produce a particular tone - distortion, really. So different tubes may react quite differently. In a preamp (especially if negative feedback is used) there may be little difference if the tube stages remain in their linear region.
  Reply With Quote
Old 14th November 2005, 08:05 AM   #3
g-banjo is offline g-banjo  United Kingdom
diyAudio Member
 
Join Date: Nov 2005
But it's actually on clean sounds, with no distortion, that the differences in dynamic response is most obvious to me. Does that fit?
  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
PTC Behaviour jayam000 Solid State 11 4th May 2009 03:35 AM
bass reflex tube phase behaviour Helmuth Multi-Way 4 21st January 2009 03:02 PM
F3 - LED behaviour Nicola Pass Labs 2 22nd August 2007 08:02 AM
Question about PP EL34 power supply behaviour arnoldc Tubes / Valves 22 25th March 2004 04:39 PM


New To Site? Need Help?

All times are GMT. The time now is 03:39 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