Using a Variac to lower volume

[blackba]

After watching this video on the Soldano HR25 and hearing Mike talk about retubing EVH's amp and achieving the 'brown sound'. He then applies this to the HR25. So this got me thinking about using a variac to help lower the volume of some of my vintage amps a bit. I already have a variac and could get in a plug in voltage display easily. Any draw backs to using a variac and running the amps at a lower voltage, thinking 110 to 115VAC? Amps are a '66 Vox AC50, '60 Fender Brown Super, '69 Fender Bandmaster Reverb, and Masco MA-50.

 

[jlb32]

Not sure about your amps and a variac but I just recently bought one of the Soldano Hot Rod 25's and whatever Mike did it's awesome. The amp sounds amazing and lets you push it with lower volumes. Also with the bigger iron and big bottle tubes of 50 and 100 watt amps it doesn't lose any of the punch and dynamics of bigger wattages.

If the variac is the secret it's worth a shot IMO.

 

[PatF]

I think it would be ok to try it out with those amps. You could probably go down as far as 90v for a minute to try it. There a risk of tube damage if too low. Check bias if you want to keep it in there..

 

[PatF]

It's not the secret, but it helps.

 

[Stradazone]

I don't think using a variac will do much for the volume if you're only dropping to 110 to 115VAC, if you need a bigger reduction in volume you're better off with a attenuator or slaving, even at 90 volts you're only dropping maybe 3 decibels, at 90 and below is when it creates a little sag and loosens up the amp a bit, making it not so stiff. I usually use a variac with a attenuator. John Suhr says he was in the same room when EVH played his Marshall with and without the variac and it was pretty much the same tone.

 

[TrueTone500]

If you're going to run the amp below 110VAC, you should consider installing a dedicated filament transformer. On the other end... If the filament voltage is too high, not only will tube life will suffer, and the amp will begin to sound quite bad. You can run it lower, (down to 90 volts) and you'll be fine, but this too will place excessive wear on the tubes. 110VAC is optimal, but 116VAC sounds best with my particular rig.

Most home outlets can reach as high as 126VAC! My british made Cornford amplifier calls for 115VAC maximum input, with 110VAC being ideal. I stopped using a variac when I secured a Furman power regulator, which supplies 115VAC consistently. I also use a secondary Furman power conditioner w/LED output voltage indicator. It's not uncommon (in our area) that I see the Furman input voltage indicator lights reading 126VAC.

I tell players:
1. Get the supply voltage at 115VAC (117VAC modern) via variac.
Note: The dial indicators on a variac are not a 100% accurate depiction, so you will need a Furman (or other) power supply w/LED readout to monitor the output.
2. Bias tubes accordingly...
3. Actuate the voltage supply (via the variac) between 100VAC and 115VAC, and play... Let your ears be the judge.

You can go down to 90VAC, but you won't notice much of a volume drop. I don't refer to a low supply sound as brown... I refer to it as slow, because that's exactly what's happening. The lower the supply voltage, the longer it takes to charge the capacitors. If you run the supply voltage low enough, you will actually hear the charge/recharge effect. Think of the sound a distortion pedal makes with a dying battery... It's sort of a gating effect.

 

[blackba]

If you're going to run the amp below 110VAC, you should consider installing a dedicated filament transformer. On the other end... If the filament voltage is too high, not only will tube life will suffer, and the amp will begin to sound quite bad. You can run it lower, (down to 90 volts) and you'll be fine, but this too will place excessive wear on the tubes. 110VAC is optimal, but 116VAC sounds best with my particular rig.

Most home outlets can reach as high as 126VAC! My british made Cornford amplifier calls for 115VAC maximum input, with 110VAC being ideal. I stopped using a variac when I secured a Furman power regulator, which supplies 115VAC consistently. I also use a secondary Furman power conditioner w/LED output voltage indicator. It's not uncommon (in our area) that I see the Furman input voltage indicator lights reading 126VAC.

I tell players:
1. Get the supply voltage at 115VAC (117VAC modern) via variac.
Note: The dial indicators on a variac are not a 100% accurate depiction, so you will need a Furman (or other) power supply w/LED readout to monitor the output.
2. Bias tubes accordingly...
3. Actuate the voltage supply (via the variac) between 100VAC and 115VAC, and play... Let your ears be the judge.

You can go down to 90VAC, but you won't notice much of a volume drop. I don't refer to a low supply sound as brown... I refer to it as slow, because that's exactly what's happening. The lower the supply voltage, the longer it takes to charge the capacitors. If you run the supply voltage low enough, you will actually hear the charge/recharge effect. Think of the sound a distortion pedal makes with a dying battery... It's sort of a gating effect.

Good info thanks. So you answered my follow up question on if I needed to check the bias if i as lowering the voltage from 125vac to 115vac and I see the answer is yes.

I was going to get a plug in voltage readout to help me know where I am at with the variac.

I like the idea of using the power regulator, which one are you using exactly? The ones I am finding provide 120vac +/- 5V

 

[TrueTone500]

Good info thanks. So you answered my follow up question on if I needed to check the bias if i as lowering the voltage from 125vac to 115vac and I see the answer is yes.

I was going to get a plug in voltage readout to help me know where I am at with the variac.

I like the idea of using the power regulator, which one are you using exactly? The ones I am finding provide 120vac +/- 5V

I use the original Furman AR-117, which regulates to (what else) 117VAC. The newer replacement model regulates to 120VAC. I spoke with Furman last year, and recommended that they build a regulator with scalable variable output select... 90VAC to 120VAC. The Furman rep. thought it was a great idea, so we'll see.

 

[blackba]

Good info thanks. So you answered my follow up question on if I needed to check the bias if i as lowering the voltage from 125vac to 115vac and I see the answer is yes.

I was going to get a plug in voltage readout to help me know where I am at with the variac.

I like the idea of using the power regulator, which one are you using exactly? The ones I am finding provide 120vac +/- 5V

I use the original Furman AR-117, which regulates to (what else) 117VAC. The newer replacement model regulates to 120VAC. I spoke with Furman last year, and recommended that they build a regulator with scalable variable output select... 90VAC to 120VAC. The Furman rep. thought it was a great idea, so we'll see.

I emailed furman asking for the same thing. Now response as yet. Hopefully they get the message that there is a market for a variable regulator or at least one that you can ajust say to 110, 115, or 120vac.