variable autotransformer

[Dale]

Would the use of a variable autotransformer with Rockman gear have a negative impact? I was wondering if I were to drop the voltage to my gear what it may or may not do.

[GuitarBuilder]

Dale - that depends what voltage you plan on feeding into the Rockmodules. If you stick with 120V +/ 5% the voltage regulators in the power supply circuitry will probably be fine. They can typically tolerate high input voltages (30-40V) - as delivered by the bridge rectifier circuit. However they need a minimum 4-5 V over the output voltage (which could be as low as 6V) in order to work properly.

Using a variable autotransformer will likely have zero effect on the tone or audio quality if you stay within these limits; beyond them the circuit will either blow up or stop working.

[Dale]

Well I was thinking of running the voltage between 90 and 112V. The reason for my odd question is that a while back I experienced some problems with the electrical supply to my house. I would have brown outs and a loss of voltage to my house. I measured and was getting between 93 and 105 volts. Long story about this issue and electricians, FP&L and one special night the fire department.............any-who

I can tell you that it had a very negative effect on the following things that I had to replace....refrigerator, air conditioning compressor, and countless light bulbs, and most likely my wash machine.

But it seemed to a positive on the sound to my guitar sound in a way I can only explain as warming it up......similar maybe to what Eddie VanHalen described as his brown sound?

Problem is that I really don't know if I heard what I thought or not?

[RockmanCentralBob]

Hey Dale, it was nice meeting you in Clearwater... sorry we didn't have more time to talk, it was a pretty hectic time!!!

As for your inquiry here, in Japan, they run at 100 volts instead of our 110 volts. Of course I questioned how/why our products would work, and I was told that MOST electronics are designed to work within a 10~20% tolerance. In my experience, and from what my musician friends tell me, things like the Sustainor, XPR etc, don't sound as good when running at their lower voltages and tend to lack gain. Great if you are a blues player, I supposed, not so great if you like distortion!! So I'm told they always use a voltage converter to bump it up a little so that it sounds correct.

Also, my understanding is that the whole "brown sound" idea with Eddie and his variac was more about lowering the voltage so that he could blast it full volume without burning out the output tubes so fast while also controlling the volume somewhat. Of course, Tom's solution to that was the Power Soak, though he still ended up using voltage regulators because voltages vary from town to town. His ultimate solution was to eliminate the tubes all together, and design the Rockman to be as consistent as possible, regardless of the voltages, temperature, humidity, speakers, mic placement, etc.

In other words, the Rockman was designed to avoid all those problems Tom was dealing with, one of which you are trying to reverse.
If you really want to do that, I'd say just use an EQ in your Sustainors loop and lower the signal level and you should approximate the same effect.

On a side note, Tom's guitar tech was kind enough to explain the reason for all the heaters onstage.
Part of it is because of course they play some cold venues, so it get's chilly up there for the performers.
But those cold temperatures also affect the tuning of the instruments which the heaters help to alleviate.
Now you know....

[REO Speedweasel]

As someone who has modded their Marshall (JTM45) to run @ 100v via VariAC (and who owns Rockmodules etc):

There is a difference between fiddling with a tube amp and fiddling with solid state (obviously). The only case where I would use a VariAC with 110-120v solid state devices is to ensure said device was running at spec and being fed the proper voltage (as we know, voltages out of the socket vary quite a bit).

When using a VariAC with a tube amp, for optimal results, one has to bias the amp after the voltage drop, and this sometimes involves replacing a resistor because the stock resistor won't allow you to get in range for approx 70% (or whatever you like) max dissipation.

So, the VariAC concept can't simply be applied across the board.