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Topic: Tube amp distortion. |
Austin Tripp
From:
Nashville TN
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Posted 30 Dec 2010 6:33 pm |
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1974 Fender Vibrosonic. Nothing wrong with the amp, I just have a few questions about the "natural" distortion.
Should the "master volume" be set higher than the "channel volume" to minimize distortion?
Is it natural for the distortion to be really noticeable on the bass strings above the 12th fret?
Will higher reverb contribute to the distortion rather than minimal reverb?
When playing on stage, is it safe to turn the "master" volume to 10 and use the "channel" volume as the main control?
I don't mean to sound dumb hehe. I'm sort of new to the vintage tube amps and I'd like to know more about them.
Thanks everyone in advance!!
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"Hotrod"
Steel guitarist for Cody Jinks
Member CMA |
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Don Hinkle
From:
Springfield Illinois, USA
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Posted 30 Dec 2010 7:21 pm
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You will always run the master considerably higher than the channel / gain knob.
I normally try to run the master as high as I can while avoiding any "hiss" or noise that might be present and a wide open volume.
I had a 74 twin that the amp was as quiet with the master on 10 as it was on 5, so I could run it wide open, normally leaving the channel gain at 3 or 4... maximum clean.
I wouldnt think that you should be getting more distortion on bigger strings unless are you pushing the volume up as well.
Reverb should effect either from my experience.
ps. I have tried to chat you a couple times on facebook.. not getting thru to you apparently!
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Emmons Legrande III SD10
Emmons Legrande III D10
Session 400
Fender guitars
Fender amps |
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Austin Tripp
From:
Nashville TN
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Posted 30 Dec 2010 7:36 pm
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Hey brother Don! I usually don't get on the computer. I'm in the woods and don't have great internet connection so I'm usually on my phone. Thanks for the info about the amp. I will try that!
Austin
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"Hotrod"
Steel guitarist for Cody Jinks
Member CMA |
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Tim Marcus
From:
San Francisco, CA
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Posted 30 Dec 2010 8:26 pm
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yeah - leave the master volume on 10 or just rip the whole MV circuit out of the amp.
Preamp distortion is a pretty nasty thing - you can get that by turning the master down and turning up the channel volume, but its fairly unpleasant. Especially on pedal steel.
reverb should not add distortion - the signal usually peels off the vibrato channel and then mixes back in to the tone recovery amp stage. It does not add any additional gain. Are you getting strange sounding reverb?
a fender amp from 1974 may be distorting because the bias is not set properly. The silverface amps usually had a fixed bias, and some of them are not adjustable. If the tubes are biased cold, you will get a really hideous distortion - especially on the low strings as the amp tries to push low end. I would check the bias and set it properly if its below 35mA (my '74 silverface twin was idling at a pathetic 8mA before I rewired it)
or if you want distortion you can cathode bias, but I don't recommend that for pedal steel. A good steel amp should be as clean as the sky is blue.
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Milkmansound.com |
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James Morehead
From:
Prague, Oklahoma, USA - R.I.P.
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Posted 31 Dec 2010 8:23 am
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Ken Fox rebuilt my '75 Vibrosonic. I leave the master AND the channel volume on 10, and it is clean all the way up, using my shobud pedal with 500K A&B pot. All that volume is controled with the volume pedal anyways and sounds great, allowing the tubes to "bloom". Before Ken worked this amp over, no way could I run it like this. So maybe a rebuild is in order?
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"Good judgement comes from experience, and a lot of that comes from bad judgement"~old cowboy proverb.
shobud@windstream.net |
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Ken Fox
From:
Nashville GA USA
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Posted 31 Dec 2010 6:24 pm
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I went through the amp and repaired a few things for Austin:
-Re-install audio coupling caps in the correct polarity
(Often Silverface amps had the caps with the foil ends installed backwards)
-replaced 1K screen grid resistors with 470 ohm
-replace 10K B+ dropping resistor
-checked all tubes and replaced 2 tubes
-re-soldered chassis grounds, tightened transformer nuts
-cleaned jacks
Bias was OK on the amp |
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Austin Tripp
From:
Nashville TN
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Posted 1 Jan 2011 7:37 pm
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Ken did a fantastic job on the amp. I must say its the best tone I've ever had. I turned the master up to about 9 and it sounds great. No booming distortion. Thanks for tips everyone!
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"Hotrod"
Steel guitarist for Cody Jinks
Member CMA |
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Ken Fox
From:
Nashville GA USA
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Posted 2 Jan 2011 4:51 am
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| That's great, Austin. If you every are int he area bring it by for a free checkup as well! |
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Dan Tyack
From:
Olympia, WA USA
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Posted 6 Jan 2011 8:10 pm
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| Austin Tripp wrote: |
| Ken did a fantastic job on the amp. I must say its the best tone I've ever had. I turned the master up to about 9 and it sounds great. No booming distortion. Thanks for tips everyone! |
Hey Austin,
If you have some booming tube distortion left over you can send it to me. I can probably figure out how to use it. 
Looking forward to hearing you in Phoenix! |
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