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Bad bar electrical systems: Use a variable transformer on the supply?

OogieWaWa

OogieWaWa

Mar 17, 2013
890
1,174
Oak Harbor, OH
#1
Long story short, we play at a number of venues (mostly bars, old buildings with poor maintenance) that I believe have crappy power. I can hear it sometimes, amps do weird stuff, and also think it was probably the cause for my tube amp bias power supply, failing during a gig.

Based on that, is there any reason to use a variable output transformer coming from the "mains"?

Long version:

It's a 300 watt Eden E300T, about eleven years old. It would sound "funny" at some places, some distortion and reduced volume, line noise. After the gig that broke it, I checked the bias current (actually voltage across resistors) and it would drift from below normal to zero over a few seconds after power up. (Normal voltage drop across a resistor for each tube is proportional to current in this case.) I'm pretty sure I'll have to get the power supply board repaired. And I really really like this amp, even though I'm using one of the newer, more "powerful" non-tube amps right now. I miss my tone!!! And grunt.

Other people have had power issues at the one place in particular, to the point that one band I know has their drummer/electrician run a line to them directly from the breaker box. Lots of fridges, neon signs, fans, etc. for loads, all noisy and potentially low voltage. It's at a campground off of one utility transformer, lots of A/C units running in summer. (And yes, the drummer/electrician thing is kinda scary! lol)

Let's face it, if nothing is seriously broke, no bar or older venue owner is going to spend anything on upgrading their wiring.

I see that you can pick up a 10 Amp variable transformer for less than a hundred bucks. They look like the pic below. Note that these are NOT auto-transformers, they don't adjust themselves. It would provide noise protection, prevent ground loop issues, really big surges, smooth out the sine waves, and allow me to dial in the right voltage, even at the expense of drawing another amp off of the outlet; I don't care as long as any voltage adjustments are minor, it's only going to add maybe another Ampere max by raising the output 10V.

Or is there an alternate solution for "conditioning" crappy power available that doesn't cost a small fortune? Some sort of filter at least? It's nothing that a surge suppressor or "power distribution box" would address.

Thanks in advance for any help anyone can provide. Oh, and no, we're not going to stop playing those places, this is the reality of being a cover band that plays 30 gigs a year at maybe 20 different rural-regional venues; it's the only client base we have.

shopping
 
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#3
OogieWaWa said:
It would provide noise protection, prevent ground loop issues, really big surges, smooth out the sine waves, and allow me to dial in the right voltage
Click to expand...
I doubt that a variable transformer would provide any of those benefits with the exception of the last one.

Are you sure that the voltage coming out of the wall is low? How low...have you measured it?
 
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#4
OogieWaWa said:
Long story short, we play at a number of venues (mostly bars, old buildings with poor maintenance) that I believe have crappy power. I can hear it sometimes, amps do weird stuff, and also think it was probably the cause for my tube amp bias power supply, failing during a gig.

Based on that, is there any reason to use a variable output transformer coming from the "mains"?

Long version:

It's a 300 watt Eden E300T, about eleven years old. It would sound "funny" at some places, some distortion and reduced volume, line noise. After the gig that broke it, I checked the bias current (actually voltage across resistors) and it would drift from below normal to zero over a few seconds after power up. (Normal voltage drop across a resistor for each tube is proportional to current in this case.) I'm pretty sure I'll have to get the power supply board repaired. And I really really like this amp, even though I'm using one of the newer, more "powerful" non-tube amps right now. I miss my tone!!! And grunt.

Other people have had power issues at the one place in particular, to the point that one band I know has their drummer/electrician run a line to them directly from the breaker box. Lots of fridges, neon signs, fans, etc. for loads, all noisy and potentially low voltage. It's at a campground off of one utility transformer, lots of A/C units running in summer. (And yes, the drummer/electrician thing is kinda scary! lol)

Let's face it, if nothing is seriously broke, no bar or older venue owner is going to spend anything on upgrading their wiring.

I see that you can pick up a 10 Amp variable transformer for less than a hundred bucks. They look like the pic below. Note that these are NOT auto-transformers, they don't adjust themselves. It would provide noise protection, prevent ground loop issues, really big surges, smooth out the sine waves, and allow me to dial in the right voltage, even at the expense of drawing another amp off of the outlet; I don't care as long as any voltage adjustments are minor, it's only going to add maybe another Ampere max by raising the output 10V.

Or is there an alternate solution for "conditioning" crappy power available that doesn't cost a small fortune? Some sort of filter at least? It's nothing that a surge suppressor or "power distribution box" would address.

Thanks in advance for any help anyone can provide. Oh, and no, we're not going to stop playing those places, this is the reality of being a cover band that plays 30 gigs a year at maybe 20 different rural-regional venues; it's the only client base we have.

shopping
Click to expand...

I used to be the bass player/electrician who did what that drummer does. I had a 4 conductor 6 gauge SO cable with one bare end and one "welding receptacle" end. Our power distribution rack plugged into that receptacle. I had breakers for most kinds if panels and I would run the cable to our breaker in their panel.

We also had a Monster rack mounted power conditioner..... thing..... that would correct for slightly low or high voltage. That was used mainly for our mixing board and power amps (this was before active speakers were affordable).

Both solutions were expensive.

Can you provide us a link to that transformer gizmo? I can't really tell what it does from the pic.
 
#6
And just to cut to the bottom line...there is very little you can do on your end to resolve issues of 'bad power'. And I must say, the campground scenario you described sounds pretty much 'worst case'...lots of small AC units cutting on and off on what is likely a marginal and over-loaded distribution system to begin with. Yikes!

Anyway, a Variac could help resolve a low voltage issue but really doesn't offer much else in the way of 'protection'. I recommend them to guys who have 50-plus-years-old tube amps for the opposite purpose...the power supplies in those things were designed when 110-volts was pretty much the standard household voltage, not the 120+ volts available out of a plug today.
 
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#7
Redbrangus said:
I doubt that a variable transformer would provide any of those benefits with the exception of the last one.

Are you sure that the voltage coming out of the wall is low? How low...have you measured it?
Click to expand...
Correct, all the information the OP provided about that auto transformer is incorrect except for the manual adjustment of voltage.
 
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#9
Good, exactly what I'm asking about. If I already knew I wouldn't be asking.

Here is the link:
https://www.amazon.com/Beleeb-Regul...ocphy=9015051&hvtargid=pla-585368213922&psc=1

Maybe this is similar to what I was thinking but not the right kind?

Isn't a transformer like this basically a low-pass filter that would reduce higher frequency noise? No reduction of noises from stuff like A/C units popping on and off?

FWIW the amp says 120 VAC input @900W. The unit says it's rated at 1000W.

Voltage showed 113 to 117 Volts.

Other bands have had issues enough that it seems to be common knowledge; our guitar player gets a lot of noise, like a background level buzz but not a 60Hz thing, more of a white or brown noise.
 
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#10
Agreed on most points here. Your friend who brought a power distro was on the right track. In the days of incandescent lighting, every venue supplied a 100 amp 220v. disconnect. They're rare now.
 
#11
OogieWaWa said:
the amp says 120 VAC input @900W. The unit says it's rated at 1000W.
Click to expand...
A 10% safety margin is the absolute minimum you should allow, so you're already at the maximum allowable load for the Variac. A 2400-watt version would be a safer choice, if you're determined to go that route...but of course, that's a whole lot more money. The 1000-watt version would probably do the job. But even if it does filter out HF noise on the AC line, that's not likely to be the predominant source of extraneous noises. And I'm not even sure it actually would do that, since an auto-transformer doesn't offer any isolation from the neutral line. The guitar player's buzz is more likely radiated RF energy (from dimmers, neon and fluorescent ballasts, etc.) being detected and amplified at the input stage. IMO, of course...without being there to check it out, it's all pretty speculative. There really is such a thing as 'bad power', but it's been my experience that the power often gets the blame when the problem is somewhere else.
 
#16
Paulabass said:
Agreed on most points here. Your friend who brought a power distro was on the right track. In the days of incandescent lighting, every venue supplied a 100 amp 220v. disconnect. They're rare now.
Click to expand...
All the venues that I work in still have disconnects for sound and lights. A 100-amp disconnect is pretty standard for a sound system...it wouldn't be much of a service for an incandescent lighting system; 100-amp, 220-volt service = 24 1K PAR cans. And even LED lighting needs some sort service...you can't plug much more than a 16-light show into 20-amp source with any sort of real fixtures. At any rate, carrying your own distribution and tying in to a large service is still SOP for any sort of real sound or lighting package. In part, for just the reasons outlined here...you can only be sure of the integrity of the whole power distribution system if you're providing the whole thing your own self.
 
#17
Wisebass said:
Hi twofer :)



Rack mounted? :hyper::hyper::hyper:

Must have been the best for "Hair Metal"! :laugh:


Link Removed

Afaik using a power conditioner can cause more problems (especially with class D amps)

than it solves!


greetings

Wise(b)ass
Click to expand...

Ha! I'm not talking about the little power strips people have always called "power conditioners". I'm talking about a really expensive unit that will correct slightly low or high voltage and costs hundreds.
monster-power-pro-power-7000-powersource-xl.jpg
 
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