Tell me about Variacs please.

fretmeister

I'm having a bit of a mid life moment and my desires for a plexi are not going away.

In the unlikely event I will get family approval to buy something suitable I would like to explore the original EVH tones (and others).
Obviously I can just go on the website of any electrical equipment vendor and pick a variac.

But what am I looking for that would be safe for use with a plexi style amp. I'm thinking 1987X or maybe the 1959 (older reissue with the FX loop, not a Handwired) and I don't want to make any mistakes.

Are there any specific variacs made for guitar amps that aren't snake oil?

If I go down this path should I get the amp rebiased for whatever voltage I want to feed it?

Or should I just stop with this silly idea and stick with my Helix?

ta

goldtop

It's a rabbit hole. VVR/PowerScaling/etc are the technologically superior modern equivalents (which is why so many EVH 'purists' don't like them).

But a VariAC between mains and amp has that MacGyvered-look that seems perfect for EVH folklore.

Modulus_Amps

Dave Friedman said on a podcast that lowering the heater voltage is critical to getting the sound. I have never played with that but playing with pre-amp voltages alone will make an amp "browner"

In theory you also have to re-bias the amp at the lower voltage with a variac. a lot of faff if you plan to use the amp with and without the variac.

You need a transformer that drops only 10%, which from a design point of view is much less onerous than one that drops more.

A Suhr SL68 is really the amp you want out the box.

ICBM

It’s a bit of a faff and not particularly good for the valves, but if you want to explore that sound you probably need to try it. I wouldn’t rebias - I don’t think EVH did, and it’s largely self-compensating since the bias supply tracks the HT as the voltage goes down.

Any variac with a rating of at least 2A, preferably 3A, will do the job - there’s no special magic. Remember that it’s only for turning the voltage *down*, not up, regardless of what EVH said in a notorious interview. (Unless he had the amp set to 240V on the selector with 120V mains and 150V from the variac, which is possible… hard to know.)

Boromedic

As Modulus says above, perhaps save yourself the chew and get something out of the box that's designed and built for it. The Mark II Suhr SL68 has all that built in, also Dave Friedman is about to release something similar. I'd get one of them tbh although I appreciate they'll be expensive, a modern Marshall was on my shopping list till I looked inside them.

I've bought a Friedman Runt recently, it's only 20w but it's right in that ballpark, more so than the PT15IR.

randella

If you're going to buy a Variac, you'll see a lot of the AliExpress red ones for £130 or thereabouts (for a 4A unit). I just bought one and had to make some adjustments to it. The arm holding the carbon brush was on the wonk - it's fixed to the main shaft by two grub screws at 90 degrees to each other.

I had to tweak those to stop it binding - I had a look at the rest of it whilst I was in there too. It's bog simple really, but some of the soldering isn't the best. Mine has a digital readout on the front which is accurate to about 0.5V tested with a meter at the output.

You can go more spendy and buy one from RS or some such, you'll possibly get a less shonky device designed for electrical testing. I'm not sure what the guitar-specific units bring along, there's really not much to an autotransformer - a toroidal tranny with a single winding and a wiper/carbon brush mechanism controlling the turns ratio. No idea how you improve on that specifically for a guitar amp, or if the ones that claim to are snake oil.

Anyway, just some thoughts (2p worth).

goldtop

I haven't seen any modern Chinese ones. The one I have is one of those RS ones, from about 30 years ago. No voltage display, just a multi-division dial and now built into a box with a digital read-out in parallel with the output. Works fine.

But as Mike says above, it necessarily lowers the heater current. Which isn't the healthiest thing to do to your valves. Whether Friedman is right about that being a necessary part of Eddie's secret recipe is a matter of ... marketing. IMHO.

fretmeister

Boromedic said:

As Modulus says above, perhaps save yourself the chew and get something out of the box that's designed and built for it. The Mark II Suhr SL68 has all that built in, also Dave Friedman is about to release something similar. I'd get one of them tbh although I appreciate they'll be expensive, a modern Marshall was on my shopping list till I looked inside them.

I've bought a Friedman Runt recently, it's only 20w but it's right in that ballpark, more so than the PT15IR.

Unfortunately there is no chance of me spending £3500+ on an amp.

I can’t afford that and it also crosses my internal limit of what I would spend even if I had a million quid in the bank.

Pete Thorn’s demo of the original and Mk2 of the Suhr is lovely though. But an amp like that earns him money. For me it would not. 

Boromedic

Yeah, I get it, it's a ludicrous amount of money TBF. 

randella

goldtop said:

I haven't seen any modern Chinese ones. The one I have is one of those RS ones, from about 30 years ago. No voltage display, just a multi-division dial and now built into a box with a digital read-out in parallel with the output. Works fine.

But as Mike says above, it necessarily lowers the heater current. Which isn't the healthiest thing to do to your valves. Whether Friedman is right about that being a necessary part of Eddie's secret recipe is a matter of ... marketing. IMHO.

They're... dunno. About what you'd expect really. I bought it for some projects I have on the go, I don't own any amps that would benefit from tinkering with the line voltage, in tone terms at least. It was more a word of caution to the OP on the off chance that they were looking for a cheapo option - it's possible to make them usable but there's a good likelihood you're not going to plug and play.

I guess that lowering the heater voltage was less of a risk for EVH in the late '70s when valves were more abundant, cheaper, and probably of higher quality than the generic Chinese JJs et al. we get now.

lespaulcustom68

 Euge Valovirta has recently started with this idea. He's using a modern hardwired plexi. Gives you an idea of the sound I guess.

fretmeister

lespaulcustom68 said:

 Euge Valovirta has recently started with this idea. He's using a modern hardwired plexi. Gives you an idea of the sound I guess.

I have seen that.
I really like his vids.