Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Modding a guitar amp schematic to run a different output stage
Modding a guitar amp schematic to run a different output stage
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 24th March 2020, 11:38 PM   #11
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Modding a guitar amp schematic to run a different output stage
Relocated to Instruments & Amps per forum policy.
__________________
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 24th March 2020, 11:42 PM   #12
rayma is online now rayma  United States
diyAudio Member
 
Join Date: Apr 2011
Quote:
Originally Posted by CaterpilarSK View Post
Well thanks for the feedback ill try it some day when the raw stock arrives and
come back to here to post my findings
You may need to experiment with the polarity of the feedback connection,
depending on how you wire the primary. Wrong way = oscillation.
  Reply With Quote
Old 25th March 2020, 12:16 AM   #13
Printer2 is offline Printer2  Canada
diyAudio Member
 
Join Date: Apr 2010
Quote:
Originally Posted by CaterpilarSK View Post
It was indeed a vacuum tube radio based with very weird and hard to find tubes from tungsram(by that I mean very hard to find data about them).

Best I can figure it used a load of 1S5T (or IS5T i really dont have an idea) IT4T DLLI something something(cant really recognise the writing) and there were 4 of the same tubes (judging by the internal construction of the tubes and similarities in writings) suggesting a paralel push pull arrangement.

I couldnt find any documentation on the internet for this radio, best I can figure its a west german radio and to be honest I am not really looking forward to replace every cap that has turned into a insanely brittle fossil.


Determining Output Transformer Impedance


Output Transformer Impedance

Last edited by Printer2; 25th March 2020 at 12:18 AM.
  Reply With Quote
Old 25th March 2020, 02:16 PM   #14
Kay Pirinha is online now Kay Pirinha  Germany
diyAudio Member
 
Kay Pirinha's Avatar
 
Join Date: Oct 2011
Location: Somewhere in Germany
Quote:
Originally Posted by CaterpilarSK View Post
It was indeed a vacuum tube radio based with very weird and hard to find tubes from tungsram(by that I mean very hard to find data about them).

Best I can figure it used a load of 1S5T (or IS5T i really dont have an idea) IT4T DLLI something something(cant really recognise the writing) and there were 4 of the same tubes (judging by the internal construction of the tubes and similarities in writings) suggesting a paralel push pull arrangement.


1S5T = 1S5 = DAF91
1T4T = 1T4 = DF91
Tungsram often put a »T« somewhere to their tubes' designators.
If there weren't any other tubes than these battery powered ones, I suspect that the OT you've ripped out might be too brittle for a EL84 design.
Best regards!
__________________
"I spent a lot of money on booze, birds and fast cars. The rest I just squandered." (George Best)
  Reply With Quote
Old 25th March 2020, 08:38 PM   #15
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Location: Slovakia, Nové Zámky
Quote:
Originally Posted by Printer2 View Post
Determining Output Transformer Impedance


Output Transformer Impedance
Thank you kind sir for the literature. I suspect you did not read the first post because I mentioned that the impedance of the transformer is 8K anode to anode (roughly).

I did not need to do math on the subject because I have an impedance tester and I just put a 4ohm load across the secondary and bam the meter shows roughly 8K (tested at 100Hz 1kHz and 10kHz)
  Reply With Quote
Old 25th March 2020, 08:44 PM   #16
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Location: Slovakia, Nové Zámky
Quote:
Originally Posted by Kay Pirinha View Post
1S5T = 1S5 = DAF91
1T4T = 1T4 = DF91
Tungsram often put a »T« somewhere to their tubes' designators.
If there weren't any other tubes than these battery powered ones, I suspect that the OT you've ripped out might be too brittle for a EL84 design.
Best regards!
I have the same concern on the matter. The DC resistance on the primary side was a bit high to my taste..

I dont really want insane power in fact 10W is more than enough because we will be using the original speaker (for vintage sake).

Dont the road it might get a toroidal output transformer but not any time soon.

I dont plan to run all that horrible idle currents on it aswell. I am considering grid biasing and tweak it with a scope to the exact point where I dont get crossover distortion.

Overall low B+ (320V) low current low power. I hope the OPT will survive.
  Reply With Quote
Old 25th March 2020, 08:45 PM   #17
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Location: Slovakia, Nové Zámky
Quote:
Originally Posted by rayma View Post
You may need to experiment with the polarity of the feedback connection,
depending on how you wire the primary. Wrong way = oscillation.
The usual thing for every build
  Reply With Quote
Old 26th March 2020, 11:12 AM   #18
CaterpilarSK is offline CaterpilarSK  Slovakia
diyAudio Member
 
Join Date: Jan 2018
Location: Slovakia, Nové Zámky
Quote:
Originally Posted by kevinkr View Post
Relocated to Instruments & Amps per forum policy.
I have a feeling that thanks to this, this thread does not get the same attention.. I was looking for technical advice on tube gear not general live audio. It appears more people go trough the tube section than live audio.

Last edited by CaterpilarSK; 26th March 2020 at 11:13 AM. Reason: misstipe..
  Reply With Quote
Old 26th March 2020, 03:13 PM   #19
Printer2 is offline Printer2  Canada
diyAudio Member
 
Join Date: Apr 2010
Quote:
Originally Posted by CaterpilarSK View Post
Thank you kind sir for the literature. I suspect you did not read the first post because I mentioned that the impedance of the transformer is 8K anode to anode (roughly).

I did not need to do math on the subject because I have an impedance tester and I just put a 4ohm load across the secondary and bam the meter shows roughly 8K (tested at 100Hz 1kHz and 10kHz)

You suspect wrong, I did read your first post.


Quote:
Originally Posted by CaterpilarSK View Post
It was indeed a vacuum tube radio based with very weird and hard to find tubes from tungsram(by that I mean very hard to find data about them).
Quote:
Originally Posted by CaterpilarSK View Post
Best I can figure it used a load of 1S5T (or IS5T i really dont have an idea) IT4T DLLI something something(cant really recognise the writing) and there were 4 of the same tubes (judging by the internal construction of the tubes and similarities in writings) suggesting a paralel push pull arrangement.

I couldn't find any documentation on the internet for this radio...

You sounded like you had no idea on the tubes operation and were trying to find information. You did not say how you determined the transformer was 8k, you never said you are versed in electronics or that you have any equipment to use. We get some that show up with less than a multimeter and want to design amplifiers. Up to the point of my replying you did not show where your capabilities lie.



Just build a JMP preamp on a 18 Watt.
  Reply With Quote
Old 26th March 2020, 03:36 PM   #20
Gnobuddy is online now Gnobuddy  Canada
diyAudio Member
 
Join Date: Mar 2016
Quote:
Originally Posted by CaterpilarSK View Post
I have a feeling that thanks to this, this thread does not get the same attention.
That's true, but what attention you do get, will come from people who understand that guitar amps are very differently engineered than Hi-Fi amps, and for good reasons.

The tube Hi-Fi forum has a lot more participants, but many of them have discarded logic, science, and engineering, in favour of subjective beliefs in "tube woo-woo", which often boils down to the belief that if you pay a lot more for a component, it will always sound better.


-Gnobuddy
  Reply With Quote

Reply


Modding a guitar amp schematic to run a different output stageHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
JVC XL-V1100 output stage schematic ? Bernhard Digital Source 6 11th March 2019 06:59 PM
S.S. guitar amp output stage hitsware Instruments and Amps 0 26th March 2017 11:41 PM
schematic/kit recommendation for low gain output stage gary h Tubes / Valves 6 23rd August 2016 12:10 AM
Help the mod of the schematic (DAC output stage and OP-Amp dilemma) ljames Digital Source 5 26th November 2011 02:08 AM
Output solid stage SCHEMATIC to NOS 2xTDA1541 DAC Katapum Digital Source 4 28th October 2005 07:00 AM


New To Site? Need Help?

All times are GMT. The time now is 08:07 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki