The Right Tube For The Job - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps

Instruments and Amps Everything that makes music, Especially including instrument amps.

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 4th May 2013, 01:22 AM   #1
diyAudio Member
 
Join Date: May 2013
Default The Right Tube For The Job

Ok forgive me since I'm a newb to all this valve techy stuff but I just bought an ashton vp50 combo not the worlds best amp but I liked the sound in the shop and looks pretty rugged so for 200 I went for it. I noticed in the manual it claims to have 12ax7's in the preamp upon closer inspection it seems to have a 12at7 in the V2 position when I searched the net I noticed lots of other shops selling this amp said the same that it was 12ax7+12at7. I was just wondering why this might have been changed? Would I be able to just swap the at7 with an ax7 without biasing and would this have much of an impact on the sound quality/volumes?

any help would be great
  Reply With Quote
Old 4th May 2013, 02:54 AM   #2
diyAudio Member
 
FullRangeMan's Avatar
 
Join Date: Aug 2009
Location: Brazil
My 2 cents are:
12AX7 has gain of 100 times, 12AT7 has gain of 60/70 times, so sound certainly will change.
Maybe it was a price choice.
__________________
>Never go to a psychiatrist, adopt a cat or dog from the streets. On the streets pets live only two years average.
  Reply With Quote
Old 4th May 2013, 03:18 AM   #3
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
Quote:
Originally Posted by FullRangeMan View Post
My 2 cents are:
12AX7 has gain of 100 times, 12AT7 has gain of 60/70 times, so sound certainly will change.
Maybe it was a price choice.
depends on the circuit used........perhaps they had no real need for more gain....
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 4th May 2013, 06:24 AM   #4
diyAudio Member
 
Join Date: May 2013
that's what struck me as unusual it's meant to be an amp with 4 gain channels (technically 2 channels with 2 sub channels) clean, gain, distortion and more distortion (lead I guess) but clean and crunch seems to be louder than the second 2 channels I wondered if the 12at7 could cause that imbalance of volumes?
  Reply With Quote
Old 4th May 2013, 10:37 AM   #5
AJT is offline AJT  Philippines
diyAudio Moderator
 
AJT's Avatar
 
Join Date: May 2003
Location: Palatiw, Pasig City
a schematic can help....
__________________
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
  Reply With Quote
Old 4th May 2013, 03:43 PM   #6
diyAudio Member
 
Join Date: May 2013
I had a look at a schematic myself but being a beginner/novice at this it's not much more than a great big headache to me. I know someone else who had a look that said v1,2 and 4 are 12ax7's and v3 should be a 12at7 so I switched them over and the sound quality is much better however the clean/ crunch channel still seems to get much more volume with the level set to 12 o'clock where as when I switch to the distortion/more distortion channel I'll have the level set to 3 o'clock and it's only barely keeping up volume wise I'm wondering if that's just the impact of the 12at7 or perhaps a bad tube?
  Reply With Quote
Old 4th May 2013, 08:59 PM   #7
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Please post ALL musical instrument amp threads to the appropriate forum which is Instruments And Amps, Not Tubes / Valves. Please make note of the forum sub-headers which indicate where to post what. Thanks...
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 6th May 2013, 04:13 AM   #8
Banned
 
Join Date: Oct 2012
Not sure about that amp if V2 is gain hole/gain stage but 12AT7 wasn't relly designed as gain stage tube and by itself I don't think its that musical but it really shines and was designed for a driver position/PI lower Mu and waaay higher trans compared to a 12AX7 so it really pushes.
  Reply With Quote
Old 6th May 2013, 06:52 AM   #9
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
People tend to call ALL the small tubes preamp tubes, but the phase inverter tube is part of the power amp, and thus not a preamp tube. A 12AT7 there would leave all 12AX7s in the preamp.

If you bought the amp used, someone could have substituted the 12AT7 for one of the preamp tubes. Guys do that to tame overly gainy channels sometimes.


SOmething else to watch out for: The V numbers refer to the schematic, not the tube order on the chassis. IN many amps those are the same, but on many others the tube order on the amp is not 1,2,3,4,5 straight across. For example the Peavey 6505+ has small tubes in order V6-1-2-5-3-4. But many people assume the third tube from the end will be V3. I don;t know this amp at all, but if there is some confusion or disagreement as to which socket needs what tube, that could be a factor.


And another factor. The marketing description may state all 12AX7 but the amp may ship with one 12AT7. But that doesn't neccessarily mean something changed, it could simply be a mistake or oversight in the advertising copy. In any case, in guitar amp preamps you can usually just swap 12AX7s and 12AT7s as you like. There is no bias adjustment for a preamp tube.
  Reply With Quote
Old 6th May 2013, 11:18 AM   #10
Banned
 
Join Date: Oct 2012
Phase inverter is still part of the preamp it serves both functions in them coupling pre and power and I don't care what amp it is if its run wide open/overdrive and depending on what is stuck in there it will overdrive and clip and add some certain layer/color/distortion to the sound, and saying its not part of the preamp and not effecting tone is pretty ignorant in my opinion lol
  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
Looking for job JBishop The Lounge 2 1st January 2010 10:56 PM
First DIY job: Dual Tube Recording Preamp neoific Tubes / Valves 82 21st December 2007 04:54 PM


New To Site? Need Help?

All times are GMT. The time now is 10:03 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