Snubber caps - 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 14th November 2008, 02:03 PM   #1
atmars is offline atmars  United States
diyAudio Member
 
Join Date: May 2008
Default Snubber caps

I have guitar amp that uses a 5E3 circuit built into a donor chassis. It's a lot like a 5E3 with some changes ( switch to parallel the first triodes, different iron, etc). Generally this amp is too bright. I have tried several solutions, but the one that works the best seems to be "snubber" caps over across the plate resistors on the first stage (.001 or similar) without trying everything, are there any guidelines to this technique? Value limits? What is the effect of adding snubber caps to the second stage instead of the first? Or somewhere else?

Thanks
  Reply With Quote
Old 14th November 2008, 03:55 PM   #2
m6tt is offline m6tt  United States
diyAudio Member
 
Join Date: Aug 2007
some of the older Fenders would put the cap between the two signal lines of opposite phase after the inverter. The later you put the HF bleed-off caps in the chain, the more you should be affecting the total response of the amp. Personally when an amp is too bright I start by removing the bypass caps and increasing the coupling caps slightly. Make sure it's not just that you don't like the tone stack. Try bypassing it with a wire and see if the bad sound persists (the bass may be boomy this way).

Removing the cathode bypass caps raises the output impedance, thus reducing high frequency response into the same load (as far as I can tell).

Increasing the coupling caps will change the bandwidth of the following stage, allowing more bass through. If the valve is amplifying more bass, it has less total bandwidth available for highs.

If that doesn't work, you can use larger grid stoppers in the input, like 220k or something fairly high. You can also add these to the outputs, for normal operation they're like 1.5-2k, you could make them 5 or 6k to really start rolling things off.

Finally, sometimes amps will sound shrill when they are oscillating at a few khz...I'd scope it for oscillations, especially if it sounds that way with the tone stack bypassed.
  Reply With Quote
Old 15th November 2008, 02:10 PM   #3
atmars is offline atmars  United States
diyAudio Member
 
Join Date: May 2008
Thanks for all the great info - a couple of clarifications:

Quote:
some of the older Fenders would put the cap between the two signal lines of opposite phase after the inverter.
Are there any values you have tried for the cap between the sides of the phase inverter?

Quote:
Personally when an amp is too bright I start by removing the bypass caps and increasing the coupling caps slightly.
Removing the bypass caps is going to cost me gain, right? If that's the case I probably don't want to do that.



Quote:
Try bypassing it with a wire and see if the bad sound persists (the bass may be boomy this way).
My tone stack is the standard "tweed" tone with lower values on high side. I thought taking the tone stack out increases gain and thus treble? No?

Quote:
Increasing the coupling caps will change the bandwidth of the following stage, allowing more bass through. If the valve is amplifying more bass, it has less total bandwidth available for highs.

Is this principle true globally? I mean, does increasing bass not just mask treble but actually reduce it?

Quote:
If that doesn't work, you can use larger grid stoppers in the input, like 220k or something fairly high. You can also add these to the outputs, for normal operation they're like 1.5-2k, you could make them 5 or 6k to really start rolling things off.
I have tried this technique, actually increasing the grid stoppers up to 1 meg. It definitely reduces the overall ice pick, but i worried that it was reducing gain and break up so I returned to the original values. Is there any evidence that high grid stopper values will reduce perceived gain and volume?

Thanks for any light you can shed.
  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
plain Big caps on psu vs. carlosfm style Snubber shiraz Chip Amps 25 9th September 2008 04:11 PM
Snubber AND non-snubber ? jimbo1968 Chip Amps 10 6th December 2005 08:49 AM
Just added caps and snubber bit from CarlosFM design PSU quickshift Chip Amps 2 23rd September 2005 02:38 AM
adding caps and snubber network to LM3875 power board quickshift Power Supplies 0 19th August 2005 03:12 PM
Snubber s2kov Tubes / Valves 13 30th November 2004 03:09 PM


New To Site? Need Help?

All times are GMT. The time now is 02:50 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