Anyone using a Variac with their Marshall Head?

sct13

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Yea. I'm a little confused by claims that you can go down to 90v Ac input and get a better tone . The 6.3 v AC heater supply is not stabilized in these amps . Going from 120 to 90 may drop your heater voltage to less than 5V , and it's going to cut the emissions from the cathode of each tube substantially. Having faulted a number of amps with low heater voltage over the years, IME they usually sound like pud. Dropping the HT sounds like a better idea to me.
You do need to watch that heater volage, and with that the bias changes,,,,so you need to "set it up" for that voltage your running ....you cant just plug up and go...
 

WesChilton

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it is not all about the power the voltage the grounding can be the problem . a lot of plugs are hooked to lights and other stuff . a power conditioner does not fix this.

it doesn't fix it, but a quality one will warn you about it.
 

flyinguitars

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I just ordered a variac with digital output display. I'll post a demo once we get it and get it figured out.
 

Matthews Guitars

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Yes, you can just drop the line voltage and go. It's not ideal but it won't harm anything. Cathode emission will be about 85 percent of normal output, and with about 25 percent less voltage in the amp on all circuits, bias current will be reduced but so will plate voltage, and the amp will only be able to deliver about half power. It's really not in any danger.

I've done it for some time, and it's hard for me to put my finger on how it changes the tone but definitely there is a change. And there is a substantial change in output level.
 

flyinguitars

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Ok I got one yesterday. From Amazon with the digital output display. The display is about 1 volt lower than what my fluke meter was reading, so it's not way off....but the manual dial that is used to change voltage is way off...lol ..like 30 volts . lol. I have to loosen it and adjust it later today. The 12 yr old who put it together must have missed that adjustment.
So we tried it with a 100w jcm 800. It lowered the volume significantly and seemed to bring out more of a fuzzy sizzle in the high end and a more loose feel as far as attack. I think we can eliminate the attenuator because of the volume decrease. We didn't have much time to fool with it yesterday but found that it sounded best to our ears even lower than the EVH sweet spot of approx 90v....our sounded best around 75v. We didn't play much at that setting in fear of doing damage, so I want to check if it's not safe for the amp before going back to that setting.
I'll get some clips and post asap.
 

Labjr

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Ok I got one yesterday. From Amazon with the digital output display. The display is about 1 volt lower than what my fluke meter was reading, so it's not way off....but the manual dial that is used to change voltage is way off...lol ..like 30 volts . lol. I have to loosen it and adjust it later today. The 12 yr old who put it together must have missed that adjustment.
So we tried it with a 100w jcm 800. It lowered the volume significantly and seemed to bring out more of a fuzzy sizzle in the high end and a more loose feel as far as attack. I think we can eliminate the attenuator because of the volume decrease. We didn't have much time to fool with it yesterday but found that it sounded best to our ears even lower than the EVH sweet spot of approx 90v....our sounded best around 75v. We didn't play much at that setting in fear of doing damage, so I want to check if it's not safe for the amp before going back to that setting.
I'll get some clips and post asap.

How can the dial be off that much? Does max out at the line voltage or go all the way to 130+
 

flyinguitars

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How can the dial be off that much? Does max out at the line voltage or go all the way to 130+
I probably wasn't clear about the dial....what I meant is the dial was tightened down on the shaft with the little arrow in the wrong position. All I have to do is loosen it and set it in the correct spot and then tighten.....kinda like how a guitar volume knob can be adjusted on the pot shaft. My son just sent me a clip...I will upload in a few and share it here ...he played some VH and it sounds really good. He's loving it so far.
 

flyinguitars

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I've heard some bad things about those Chinese ones on Amazon...


Yea that is similar .....our has a digital gauge and is larger and can handle more power... I'll post a vid as soon as get get freed up here at work..lol.
I saw that same video a few days ago so the first thing that we did was to verify the output with our own fluke meter.
 

Dogs of Doom

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I've seen others too, but couldn't find one right off, where the guy did a total rebuild (might have even been a member here) & he was saying that, if you're not prepared to do a total rebuild, you shouldn't buy one of those ones.

Play around w/ it. Keep an eye out for a good used one, that's US made. I see them every so often around here, but, they go quick, if the deal is good. Many of them, go for about $400 & up. To find one working for under $100 is a good deal. That's why they go quick!

Good luck w/ it. I don't think you need to bias after adjusting the voltage. I don't think Beato did, in that video, as they did it on the fly, & that's how they got that loose feeling from the sag. I think Randy did bias it after dropping voltage, which may account for his more stiff sound.

Try it out, both ways & maybe even somewhere inbetween.
 

Labjr

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I've said it before. I usually rewire Variacs to max out at the line voltage since I don't see any need to go over the line voltage. I definitely wouldn't want to by accident. Then I change the dial plate if I can get one. It's pretty easy to do with old Powerstats. I haven't looked inside those Chinese made ones.
 
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flyinguitars

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Demo recorded by iphone.

My son posted this to FB so I ripped it and put it on YT to share here. This was today probably after messing with it for 2 minutes...lol...he doesn't like to script and practice..... he's all about getting it done...lol

 

Amadeus91

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Here is mine. It always sits in a spot not readily accessible but easily visible with 2 pieces of bright tape, one on the knob indicator and another marking the number it should line up with.
American manufacturing at its finest.
IMG-2637.jpg
IMG-2639.jpg
 

jchrisf

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Demo recorded by iphone.

My son posted this to FB so I ripped it and put it on YT to share here. This was today probably after messing with it for 2 minutes...lol...he doesn't like to script and practice..... he's all about getting it done...lol


Whew!! he is a monster player like his dad! What were his settings on the amp.. the video wasn't that clear. Was he using a pedal?
 

Labjr

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Here is mine. It always sits in a spot not readily accessible but easily visible with 2 pieces of bright tape, one on the knob indicator and another marking the number it should line up with.
American manufacturing at its finest.

I have a 2.2KVA Powerstat on my bench. It seems quite a bit larger and heavier than a Chinese made Variac. A friend of mine asked me if it came out of a locomotive. :applause:
 
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flyinguitars

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Here is mine. It always sits in a spot not readily accessible but easily visible with 2 pieces of bright tape, one on the knob indicator and another marking the number it should line up with.
American manufacturing at its finest.
IMG-2637.jpg
IMG-2639.jpg
Nice!....? that's the real McCoy right there!
Whew!! he is a monster player like his dad! What were his settings on the amp.. the video wasn't that clear. Was he using a pedal?
Haha thanks! Yea the little Tyke can play! That kid can play anything any style and it always sounds good.
I'll check the setting and let you know what they are in the clip. We talked briefly when I got home and he mentioned that when he dimed the amp, it was cutting out. It the clip he was around 5 on the master volume. My first guess is that on 10 the amp was too starved for power at 75v.
At 5 he said it sounds great in person and was working with no issues.
 

junk notes

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Good to hear that he likes the affect. Wait until he gets the 1959!
@jchrisf
View attachment 115711
That was straight in but a very small of slapback delay.
Until he gets that 1959(x), max the Pre and Volume, listen and fine-tune and tweak the Volume's sweetspot, then dial something in with the variac. Can bet a paycheck he would not be on that 75 volts. What he likes now a NMV will change his thinking over time.

Some nice playing there!
 

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