School me on Variac

B

bjjp2

Power User
So VH sound is supposedly with Variac down? By how much? In anticipation of "use your ears" when I play with the Variac parameter it sounds more VH-ish to me with the parameter increased. What are others doing with it?
 
The generally accepted version is that EVH ran the variac lowering the AC voltage to 90VAC. To do this in the axefx lower to 75%, ie 75% of 120VAC = 90VAC
 
This has surprised me how subtle this effect is - I've been playing with it today on the plexi 100 - all negative values as per the EVH recipe, but couldn't say for sure it was really doing much TBH...
 
Maybe my ears are shot, but it seems to me that the volume lowers if you move the "dial" either way. It's loudest in the middle.

As to coloration, I've found it's pretty sweet at the 94% mark for the VH tone. Subtle change, but nice.
 
svl said:
Maybe my ears are shot, but it seems to me that the volume lowers if you move the "dial" either way. It's loudest in the middle.
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a real Variac lowers the volume a lot more actually. Cliff compensated for that already to keep it minimal.
 
seems if I turn it ccw things get louder, not sure what purpose that would be, other than volume change I hear no diff. in high gains. As with dynamics no diff. in high gain settings.
 
groovenut said:
The generally accepted version is that EVH ran the variac lowering the AC voltage to 90VAC. To do this in the axefx lower to 75%, ie 75% of 120VAC = 90VAC
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Agreed, however I think I remember someone (M@, Yek maybe?) saying the middle position of the variac parameter was 110V, not 120V. If that's the case, you'd want it around 82% (same math).
 
I guess we need Cliff to weigh in on that. The US standard for mains voltage is 120VAC so it seems strange to me that he would set it at a different level. Though I suppose he could have stuck his DMM into the socket closest to him at the time and went with that reading. :)


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symphx said:
seems if I turn it ccw things get louder, not sure what purpose that would be, other than volume change I hear no diff. in high gains. As with dynamics no diff. in high gain settings.
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This. I can't tell either.. I tried 3 of clock and 9 of clock
 
symphx said:
seems if I turn it ccw things get louder, not sure what purpose that would be, other than volume change I hear no diff. in high gains. As with dynamics no diff. in high gain settings.
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Wow, either you need better monitors or a hearing test.
 
groovenut said:
I guess we need Cliff to weigh in on that. The US standard for mains voltage is 120VAC so it seems strange to me that he would set it at a different level. Though I suppose he could have stuck his DMM into the socket closest to him at the time and went with that reading. :)


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I totally agree, which I think is why that struck me as odd when I read it...?
 
US voltage it usually around 117v... It is a "nominal" 120v, IIRC. Normal AC outlets will have some variance.




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Even so, the parameter in the Axe is definitely fixed at a particular value for 100%. Is it 110? 117? 120?
 
pacrec said:
If you were messing around like this with a real tube amp you would want to remember to bias the amp at that "90" VAC or where ever you end up.
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Fortunately for us, Cliff has made sure the AxeFx rebiases automatically no matter what voltage we choose to run at.


Though the question still remains if EVH actually bothered to rebias his amp after using the variac. If not those tubes would be running very hot, maybe even redplating. Might be the reason he had to use 6CA7's.
 
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Rotti said:
I totally agree, which I think is why that struck me as odd when I read it...?
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Thing to remember is that when your talking with a group of enthusiast, be it about amps, camera gear, stereo gear, wine etc, what may be considers a "huge" difference within the group, is likely one that the average layman couldn't tell apart.

Take wine for example...people in the know might discuss differences of the year of vintage...."oh, the spring way milder in 94, taste SO different than a 95..." while to a someone like me, I couldn't tell a merlot from a cab.

I used to post a lot on the SD pickup forum and guys would go on and about about switching a few winds, or wire gauge etc made this huge difference. I could hardly tell Alinco II's from V's lol

So just because you don't hear it, doesn't mean it isn't there, but likewise, just because some people on an enthusiast forum hear it, doesn't mean you might notice it
 
groovenut said:
Fortunately for us, Cliff has made sure the AxeFx rebiases automatically no matter what voltage we choose to run at.


Though the question still remains if EVH actually bothered to rebias his amp after using the variac. If not those tubes would be running very hot, maybe even redplating. Might be the reason he had to use 6CA7's.
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"The Power Supply Sags …. In fact, Dave Friedman said that in Eddie’s # 1, the power supply “sags about 70+ volts with normal wall voltage dimmed, and 50 some volts with a variac on it” ….
B+ and Plate Voltages drop …. Mark Abrahamson ( Rockstah ) said the B+ in the amps he’s measured were around 363 dcv, and while he evidently didn’t take the 120v measurement, he estimated that they would normally run between 410 dcv and 500 dcv ?
Tube Bias drops …, which is why everyone who uses a Variac says to “crank the bias” ! Again Dave Friedman’s comment was: “Now I have said this before, the amp is biased to like 85ma with normal wall voltage and then dropped with a variac to 90 volts. This will bring the bias down to around 50ma.” Of course “the” amp he was referring to was Eddie’s # 1 ….
You shouldn’t really have to worry about Cathode Stripping because Ed’s amp at 5.5V on the heater, and running them 5 - 10% lower has been shown to increase tube life and stability. Ed’s went from 6.6 with 115VAC at normal to 5.8 at 87VAC.John Suhr said, “You also have to get into much higher plate voltages to worry about that.”"
 
FractalAudio said:
Wow, either you need better monitors or a hearing test.
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Agreed. I hear a pronounced difference. When I dial a plexi back to 75%, it gets quite a bit grittier. It's a bit like a dirt pedal, but with no coloration. It seems like it sounds a bit more like power amp distortion though... hard to describe in words, but it's different than just adding drive or master volume, or a pedal in front. It has a hairy quality to it... and it really does emulate that early VH type distortion to my ear... There is just no missing it.

I would guess (and it's ONLY a guess...) that if your not hearing it that could indicate that you already have so much distortion going on that it's just lost in there. That is a pretty common mistake of many players... they just go nuts with drive and lack any kind of nuance to the tone. (Hey, I'm not suggesting you don't know what your doing... I might be WAY off base here... it's just a suggestion of something to look at... if I'm wrong... disregard.)

I know that supposedly VH's amp was dimed out on almost all the settings, but that is not sounding good to me on the Plexi. I have the tone controls pulled back a bit, and the drive is about 6-7ish with the Variac on about 80% for my taste. Using a phase 90 up front, and a tape delay on the back end effects the tone too... smoothing it out some.

I haven't tried it with other amps much, but a little goes a long way for me on the Marshall models. It is a cool new feature, and one that I'm really happy with.
 
Pinkycramps said:
Agreed. I hear a pronounced difference. When I dial a plexi back to 75%, it gets quite a bit grittier. It's a bit like a dirt pedal, but with no coloration. It seems like it sounds a bit more like power amp distortion though... hard to describe in words, but it's different than just adding drive or master volume, or a pedal in front. It has a hairy quality to it... and it really does emulate that early VH type distortion to my ear... There is just no missing it.

I would guess (and it's ONLY a guess...) that if your not hearing it that could indicate that you already have so much distortion going on that it's just lost in there. That is a pretty common mistake of many players... they just go nuts with drive and lack any kind of nuance to the tone. (Hey, I'm not suggesting you don't know what your doing... I might be WAY off base here... it's just a suggestion of something to look at... if I'm wrong... disregard.)

I know that supposedly VH's amp was dimed out on almost all the settings, but that is not sounding good to me on the Plexi. I have the tone controls pulled back a bit, and the drive is about 6-7ish with the Variac on about 80% for my taste. Using a phase 90 up front, and a tape delay on the back end effects the tone too... smoothing it out some.

I haven't tried it with other amps much, but a little goes a long way for me on the Marshall models. It is a cool new feature, and one that I'm really happy with.
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u werent wrong I love high gain, and most nuances are likely lost, as I suggested in my post I wrote "at least at high gain", I also am playing at fairly low volume levels.

ps wish I was perfect guess I am not. I re listened with plexi, yes makes a difference in low breakup gain. Good or bad Ill leave for someone else who lives in that world, unlike myself. I dare 98% of us to explain the diff. with all the adv. parameters. From what I read and hear, 98% dont even touch em, ironically I happen to.
 
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