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Topic: Difference in Tube Amps |
Len Amaral
From:
Rehoboth,MA 02769
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Posted 10 May 2015 8:00 am |
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We all love a Twin Reverb and for a classic sound at a reasonable volume. My experience with a Twin type amp with a U12 is it will sag and clip a bit especially when playing the low end.
I recently bought a Mesa Boogie F-50 head from a Forum member thinking it would be a sweet guitar amp and it is. However, I play my U-12 through a 12 inch 50 watt Tone Tubby speaker and it has a cleaner more defined sound than any of my Twin type amps. The Mesa F-50 is 50 watts with two 6L6 power tubes and four 12AX7 preamp tubes.
A head scratcher for sure? |
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Jay Fagerlie
From:
Lotus, California, USA
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Posted 10 May 2015 8:50 am
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It is all about headroom Len.
You can eat that up with the output of a pedal steel pretty easily.
The first thing to do is lower the gain of the signal path-
Did you try a 12AY7 in the V1 spot of the twin?
That is usually enough to lower the pre amp gain to maintain headroom in the phase inverter/power sections.
You can also put a 12AY7 in the phase inverter stage to lower the gain there for even more headroom..... |
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Tim Marcus
From:
San Francisco, CA
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Posted 10 May 2015 10:06 am
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A 12ay7 will add more gain to the phase inverter of a twin, and may cause a bad hair day for the reverb tank
Maybe try a 12au7 if you want to lower the gain from the 12AT7 already in place
_________________
Milkmansound.com |
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Jay Ganz
From:
Out Behind The Barn
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Posted 10 May 2015 10:13 am
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| That's what I use in my old blackface amps. |
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James Hartman
From:
Pennsylvania, USA
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Posted 10 May 2015 11:10 am
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Any two old Twins (or whatever amp) you might compare are likely to have somewhat different headroom due to components drifting off spec, different tubes, etc.
As suggested, trying a lower gain tube in the V1 position is a good place to start if your amp lacks headroom.
Also, the bypass cap across the V1 cathode resistor can be changed to tweak the gain structure. That might be a experiment best left to an experienced tech. |
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Jay Fagerlie
From:
Lotus, California, USA
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Posted 10 May 2015 12:20 pm
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A 12AY7 has a gain of 45
A 12AT7 has a gain of 60
A 12AU7 has a gain of 20
I have never subbed a U for a T....good point Tim
What's the bad hair thing?
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Jay Ganz
From:
Out Behind The Barn
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Posted 10 May 2015 12:36 pm
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As far as the cathode bypass cap goes, the 25 mfd by 25V cap that's in there is designed to boost the gain of all frequencies.
Changing the value will also change which frequencies get emphasized, so your tone will change.
That's why Marshall amps use a different value cathode bypass cap in their amps (for example). |
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James Hartman
From:
Pennsylvania, USA
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Posted 10 May 2015 1:06 pm
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| Jay Ganz wrote: |
As far as the cathode bypass cap goes, the 25 mfd by 25V cap that's in there is designed to boost the gain of all frequencies.
(for example). |
Yeah, more or less. Of course, it's a safe bet that cap is no longer functioning at 25 mfd if its 30, 40 years old.
| Quote: |
| Changing the value will also change which frequencies get emphasized, so your tone will change. |
Not necessarily a bad thing. Cutting the bass response a bit at that stage can result in more headroom and better presence without noticeably altering the character of the amp. |
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Mark Fowler
From:
Minnesota, USA
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Posted 11 May 2015 8:53 am
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Always a good idea to have the 12AU7 and 12AY7 tubes around for tube rolling.
Also, my favorite other tubes are 5751, ECC823 and ECC832 for tube rolling and creating different gain structures without the need to open up the amp and change anode resistor values or cathode resistor/bypass cap values.
Mark |
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Brandon Schafer
From:
Indiana, USA
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Posted 13 May 2015 4:17 pm
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| I have a Mesa Boogie Mark III with the 75 watt Simul-Class option that most would assume is a crummy pedal steel amp. I have found the clean channel sounds fantastic with my pedal steel. I am running it through a 15" JBL, so that helps. I am not too surprised it works well for you! Keep on enjoying it! |
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Tom Wolverton
From:
Carpinteria, CA
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Posted 14 May 2015 7:37 am
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Here a nice clip of Mr DB playing a Sho-Bud into a SFTR with a K130. Just a passive vol ped. That's it. Nice sound. Just a pinch of break-up. A nice Bakersfield sound.
http://youtu.be/ZAcplscwc2U
_________________
To write with a broken pencil is pointless. |
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Len Amaral
From:
Rehoboth,MA 02769
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Posted 15 May 2015 5:24 am
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The Mesa F-50 is fairly light weight and more than enough head room for any gig I would play.
Not going to change any preamp tubes in my Twin type amps as I couldn't carry them anyway.
I also have a Mesa Mark 3 head that sounds very nice but on the heavy side. The clean side of the Mesa has a very nice vibe.
Thanks to all who responded.
Lenny |
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b0b
From:
Cloverdale, CA, USA
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Posted 15 May 2015 8:45 am Re: Difference in Tube Amps
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| Len Amaral wrote: |
| I recently bought a Mesa Boogie F-50 head from a Forum member thinking it would be a sweet guitar amp and it is. However, I play my U-12 through a 12 inch 50 watt Tone Tubby speaker and it has a cleaner more defined sound than any of my Twin type amps. The Mesa F-50 is 50 watts with two 6L6 power tubes and four 12AX7 preamp tubes. |
That sounds like a perfect tube amp for steel. The sweetest amp I ever had was a Mesa/Boogie Mark II, "60 watts" with two 6L6 power tubes. My favorite speaker for tube amps is the 12" Tone Tubby. I've never tried the F-50. I appreciate your positive review of it, Lenny. 
_________________
-𝕓𝕆𝕓- (admin) - Robert P. Lee - Recordings - Breathe - D6th - Video |
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Gary Cosden
From:
Florida, USA
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Posted 17 May 2015 9:28 am
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| So.... If I put a 12AU7 in P1 of my blackface Fender Twin what impact does this have on the overall volume of the amp? I would assume it would be noticeably less. |
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Mark Fowler
From:
Minnesota, USA
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Posted 21 May 2015 7:59 am
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| Gary Cosden wrote: |
| So.... If I put a 12AU7 in P1 of my blackface Fender Twin what impact does this have on the overall volume of the amp? I would assume it would be noticeably less. |
Yes but you may like it. |
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Gary Cosden
From:
Florida, USA
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Posted 21 May 2015 8:09 am
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| Thanks Mark. Pretty much what I was expecting but I was not sure. |
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