Using a Dynaco ST-70 audio transformer for a guitar amp - 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 19th July 2010, 11:53 PM   #1
diyAudio Member
 
Sal Brisindi's Avatar
 
Join Date: Nov 2006
Default Using a Dynaco ST-70 audio transformer for a guitar amp

I am in the planning stage to build a guitar tube amplifier with a spare A-470 audio transformer from a Dynaco ST-70. Does anyone have an opinion on this.

Any advantages or disadvantage using a "Hi-Fi" audio transformer in a guitar amp? The transformer is rated at 35 watts with push-pull EL34's.

Thanks,
Sal
  Reply With Quote
Old 20th July 2010, 12:02 AM   #2
diyAudio Member
 
Shamrock's Avatar
 
Join Date: Jul 2010
It depends on the sound you're going for. A lot of people (myself included) prefer the sound of the compression (or narrowing of the bandwidth) on a transformer for guitar use. It has a desirable sonic trait (to these ears). Wide bandwidth hi-fi type transformers can be used with no problem what-so-ever, and some amp companies did, but you may not find the sound to your liking.

VTL used Fender bassman transformers in the early days to good effect.

If you have an A470 laying around- try it!

Last edited by Shamrock; 20th July 2010 at 12:25 AM.
  Reply With Quote
Old 20th July 2010, 12:13 AM   #3
diyAudio Member
 
Join Date: Aug 2002
Location: Arlington, TX
Ampeg used Mark-III transformer sets for a long time.
__________________
Hey is for horses.
  Reply With Quote
Old 20th July 2010, 12:26 AM   #4
diyAudio Member
 
Shamrock's Avatar
 
Join Date: Jul 2010
Quote:
Originally Posted by CharleyW View Post
Ampeg used Mark-III transformer sets for a long time.

I didn't know that. Thanks!
  Reply With Quote
Old 20th July 2010, 12:28 AM   #5
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I think a lot of it is going to revolve around your sonic expectations, if you like a clean sound or something similar to the Standell then this might be an excellent choice for you. I would expect it to be a bit lacking on the crunch end of the spectrum, but you know what? - You can always replace it later if you are not totally happy with the sound..

Try both UL and pentode operation and see what you like best with this transformer.

Consider 6L6 and 807 output tubes as well as the EL34.. Making an amp that will work with both the 6L6 and the EL34 should not be much of an issue..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 20th July 2010, 12:34 AM   #6
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally Posted by CharleyW View Post
Ampeg used Mark-III transformer sets for a long time.
Requirements for bass guitar and Hi-Fi amps are the same, I mean output stage only.

The tranny you have may be used for 100W guitar amp, with twice higher plate voltage and a quad of EL34.
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 20th July 2010, 12:36 AM   #7
diyAudio Member
 
Join Date: Aug 2002
Location: Arlington, TX
Mike (MagneQuest) LaFevre has written that the A470 is good for an honest 60 watts at 30hz.
__________________
Hey is for horses.
  Reply With Quote
Old 20th July 2010, 12:49 AM   #8
diyAudio Member
 
Sal Brisindi's Avatar
 
Join Date: Nov 2006
This is all great information, Keep them coming.

Thanks,
Sal
  Reply With Quote
Old 20th July 2010, 12:56 AM   #9
diyAudio Member
 
Join Date: Aug 2002
Location: Arlington, TX
The low 'E' string on a guitar is (I think) 83hz (concert pitch). Tuning it to a 'D' (one step lower) is not uncommon (although somewhat rare in the rock world).
__________________
Hey is for horses.
  Reply With Quote
Old 20th July 2010, 01:01 AM   #10
diyAudio Member
 
Shamrock's Avatar
 
Join Date: Jul 2010
Quote:
Originally Posted by Sal Brisindi View Post
This is all great information, Keep them coming.

Thanks,
Sal

Wire that thing up and let it rip! Part of the fun in building a guitar amp is that it can be disarming and fun to experiment with what's laying around.
  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
preamp suitable for Dynaco st-70- OTHER than dynaco namatjira Tubes / Valves 3 22nd December 2011 01:21 AM
dynaco st 70 c3 dcb50 Introductions 1 30th September 2008 11:20 PM
6L6WXT in a Dynaco ST-70 Sal Brisindi Tubes / Valves 12 12th August 2007 11:11 AM
For Sale: Dynaco St.70 Bandersnatch Swap Meet 3 3rd October 2003 09:42 PM
Dynaco st-70 toenail Tubes / Valves 9 19th April 2003 11:08 AM


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