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Topic: Clean tubes |
Shaun Swanson
From:
Wisconsin, USA
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Posted 28 Oct 2009 6:34 pm |
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Can different tubes make an amp sound cleaner (more headroom)? I've acquired a Peavey Classic VT Series 212 from the 70's. I need to replace the tubes anyway so I thought I'd ask.
Thanks
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www.swansonillustration.com |
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David Nugent
From:
Gum Spring, Va.
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Posted 29 Oct 2009 2:43 am Tubes
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| Groove Tubes offers (or did anyway)6L6 tubes that were designed to break up at different stages. They were color coded red, white and blue with the red ones offering the most headroom I believe. |
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Shaun Swanson
From:
Wisconsin, USA
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Posted 29 Oct 2009 6:36 am
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Other than speaker size and tubes what else effects headroom? I'm totally ignorant about amps.
Thanks
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John Groover McDuffie
From:
LA California, USA
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Posted 29 Oct 2009 10:04 am
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There are two different factors to consider. Headroom at the input and preamp, and ultimate clean power available.
Insufficient input/preamp headroom will often result in undesired distortion even at low volumes. Many pedal steel pickups have a much higher output than typical guitar pickups and will push the input stage into distortion.
The preamp stages in tube amps often use a 12AX7 tube (not familiar with this particular amp). Substituting a 12AT7 (same tube design with lower gain) will result in less preamp gain and a cleaner sound through the preamp. Sometimes changes to the value of the resistors in the input circuitry can also clean up the input.
Insufficient clean power will result in distortion at high volumes although the amp sounds clean at lower volumes. The amount of clean power headroom one needs is closely related to how loud one needs to play.
All amps (tube and solid state) have limits to the amount of power they can produce before the power stage goes into distortion. In tube amps changing to different power tubes of the same basic type can sometimes result in slightly more clean power available, and can also result in changes to the curve of how gradually or abruptly the power stage goes into distortion. (So you might not be able to raise the ceiling very much, but you could get closer to the ceiling before the amp starts to distort.) Groove tubes ratings relate to this parameter. |
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John Groover McDuffie
From:
LA California, USA
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Posted 29 Oct 2009 10:10 am EXAMPLE Princeton Reverb "pedal steel mod"
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| I have a late '70s Fender Princeton Reverb amp. After having it "gone through" so I know everything was operating correctly, I felt it was going into distortion too soon on the volume knob. Also the reverb seemed wimpy. So I swapped the 1st pre-amp tube - a 12AX7 - with the reverb driver tube - a 12AT7. This resulted in a cleaner sound through the preamp stage (lower gain tube) AND driving the reverb send hotter (higher gain tube). It makes the amp much more "steel friendly." |
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Jim Pitman
From:
Waterbury Ctr. VT 05677 USA
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Posted 29 Oct 2009 12:19 pm
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I've been using my tube amp, a Fender Blues Deluxe, for steel lately and am really liking it over my solid state amps. It seems to fill a room better with the tone I'm interested in even though it's 1/3 the watts. A few years ago I tried it and didn't like it because my pickup was overdriving the first 12AX7. The 12AX7 is a very high gain tube, > 100. I speculate the one in my blues deluxe has lost some gain over time. John M is right on the money with his comment about the lower gain 12AT7. Stevie Ray Vaghn substitued the 12AT7 so he would get less preamp tube distortion. Then he would turn up his master to get more power tube distortion which has a different quality.
Most steel guitar pickups will overdrive the gate of a 12AX7, and unfortunately, most tube amps using the 12AX7 are designed with no attenuator (pot) in front of the first stage. You can plug into the 2nd input on a Fender amp, however, which inserts a resistive divider network I believe. This makes a tube amp more steel friendly. |
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Brad Sarno
From:
St. Louis, MO USA
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Posted 29 Oct 2009 12:26 pm
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Or try snipping the cathode bypass cap on the first stage. Keep the 12AX7 in place. Cleaner, less gain, and more headroom.
Brad |
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Curtis Alford
From:
BastropTexas, USA 78602
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Posted 1 Nov 2009 6:30 pm Condensor snip
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Brad,
I cut the C1 out of my DeVille 60 watt, and changed all the filter cap to Ruby Gold caps, made a great sounding amp. I play it through 4-10" Fender speakers or 2- 12" Emenince speaker and some time 1- 12" speaker.Sound good with any of them. I always liked the 2-12" cabinet, maybe a hold over from twin days.
Still use the Session 400 if I really need to be heard in the next county over. |
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Eric Dunst
From:
Brooklyn, New York, USA
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Posted 2 Nov 2009 9:48 am
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| One thing to keep in mind about the Peavey Classic VT Series (and VTX series etc...) is that it has a solid state pre-amp. So the only tubes Shaun has to worry about are the 6L6's power tubes. I really don't know if some tubes are rated higher than others, but that is a loud and clean amp to begin with. |
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Shaun Swanson
From:
Wisconsin, USA
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Posted 3 Nov 2009 10:40 am
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"that is a loud and clean amp to begin with"
I can't get past 4 on the Brite gain channel with the master almost all the way up.
Different question then, can an old, bad tube take away headroom?
_________________
www.swansonillustration.com |
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John Groover McDuffie
From:
LA California, USA
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Posted 3 Nov 2009 11:10 am
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| Yes, one or more bad tubes can certainly cause an amp to lack headroom. It is pretty easy to envision a bad tube in the power section severely limiting the power available, and also it could make the push-pull circuit produce a lopsided wave which would add to the distortion. |
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Curtis Alford
From:
BastropTexas, USA 78602
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Posted 3 Nov 2009 11:16 am Tubes
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Shaun,
As long as I can remember starting with the Tweed amps, some tubes give a cleaner sound, some give more distortion, some give more gain before break-up. This is how I understand break-up, as more drive with out distortion, this is the clean sound. This headroom. The high gain pre-amp tubes cause earlier break-up in most cases at lower drive.
If I have misunderstood this please correct me.
Curtis |
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Ken Fox
From:
Nashville GA USA
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Posted 3 Nov 2009 1:28 pm
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I just had a Classic in the shop. It was the model just before yours. It has a discrete transistor front end and 6L6GC output tubes, yours has an op-amp (IC chip) front end and 6L6GC tubes.
A new set of JJ tubes and it sounded great. I use 100's of JJ tubes in my shop every year and I am more than pleased. I could use any tube I want, as my customer pays for them! These tubes have been very dependable and great sounding to boot.
Svetlana (SED) is also another very good sounding and reliable tube. |
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Shaun Swanson
From:
Wisconsin, USA
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