SE 50c5 amp for guitar - 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 2nd December 2011, 06:00 PM   #1
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Default SE 50c5 amp for guitar

Hi guys, I'm planning on re-using this little amp extracted from a 60's turntable as a guitar amplifier, obviously the first part of the circuit should be changed from piezoelectric pickup to the impedance of the guitar and adjust the eq., that's where I mostly need help, also what about the output transformer, I have a few others slightly bigger in size and similar impedance's would that make any difference? perhaps for 2-3W max.


extracted as it is.
Click the image to open in full size.

Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 2nd December 2011, 07:10 PM   #2
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Good for not quite 2W, they usually have a 2-2.5K OPT. The one's i've seen are invariably run directly off 115v AC, so that is what you want for the power transformer secondary. I'd change to a full wave bridge.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 3rd December 2011, 01:32 AM   #3
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
You have 100 V.? marked on the schematic. Add up the voltages of the 150 mA. series heater string and you get 97.6 V.

Ceramic carts. produce substantial fractions of 1 V. as their O/P level. A guitar pickup's O/P is more in line with the mV. O/P of a mag. cartridge. You need additional gain.

Dave pointed you in the proper direction. Get rid of the 35W4 1/2 wave rectifier and use a bridge of 4X UF4007s to create the "raw" B+. Eliminating the vacuum rectifier makes room for another 150 mA. heater small signal tube. Install a 12AX7 and you'll have all the necessary additional gain. I leave the simple calculations for the value and wattage rating of the dropping resistor that must be added to the 150 mA. string to make the voltage come out right to you. If you get a resistance between available values, take the higher of the 2.
__________________
Eli D.
  Reply With Quote
Old 4th December 2011, 03:38 PM   #4
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Thanks guys, excellent help as always.
  Reply With Quote
Old 4th December 2011, 10:08 PM   #5
diyAudio Member
 
Join Date: Apr 2010
You have a 12AT6 which is 1/2 of a 5751, about 70% gain of a 12AX7. I have a small guitar amp with both triodes of a 12AX7 feeding a 50C5, I think you will find yourself short of gain. You could get yourself a 12AU6 and rewire the 12AT6 socket for it and end up with a lot more gain. Lots of schematics out there with this lineup. As an example,

http://dogbarkmusic.com/Harm/harmony.pdf

What I would do though is to use your tone pot as a volume control going directly to the 50C5 leaving out the 250k. I would then use your 1M pot with a 500pFand 5nF capacitor as a Tweed tone control across the volume rather than C4.

Could also use a cathode biased 12AU6 rather than grid leak for more headroom.
  Reply With Quote
Old 5th December 2011, 01:48 AM   #6
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Per forum directive this thread has been moved to Instruments & Amps.

I think there are a number of participants there who can build on the already good advice contained in previous posts.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 8th December 2011, 04:16 AM   #7
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Quote:
Originally Posted by Printer2 View Post
You have a 12AT6 which is 1/2 of a 5751, about 70% gain of a 12AX7. I have a small guitar amp with both triodes of a 12AX7 feeding a 50C5, I think you will find yourself short of gain. You could get yourself a 12AU6 and rewire the 12AT6 socket for it and end up with a lot more gain. Lots of schematics out there with this lineup. As an example,

http://dogbarkmusic.com/Harm/harmony.pdf

What I would do though is to use your tone pot as a volume control going directly to the 50C5 leaving out the 250k. I would then use your 1M pot with a 500pFand 5nF capacitor as a Tweed tone control across the volume rather than C4.

Could also use a cathode biased 12AU6 rather than grid leak for more headroom.
Hi, I was playing with it a bit today, and as you said, the radio triode doesn't cut it simply. Even using a guitar pre-amp wasn't enough. The 12AU6 is interesting I would have to get one and try it just to not do the obvious and replace the first stage with 12ax7 triodes and try something different.

I already got rid of the tone pot and tried something with the volume pot, but always before the triode. I think I will follow your advice though.
  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
SE P-P guitar amp. Printer2 Tubes / Valves 10 7th April 2011 02:51 AM
50c5 push-pull for guitar? freefallingegg Tubes / Valves 33 18th October 2010 10:27 PM
5w SE guitar Amp N9VOC Instruments and Amps 16 18th August 2010 06:34 PM
SE 7868 Guitar Amp - some issues... Stormrider Instruments and Amps 2 28th April 2009 08:33 PM
Edcor In SE Guitar Amp Trout Tubes / Valves 9 14th September 2007 11:59 PM


New To Site? Need Help?

All times are GMT. The time now is 01:54 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