Power conditioners...can we DIY?

[Ed G.]

Check this out:
http://www.furmansound.com/products/pro/pwr_cond_seq/cond/pfpro.php
I was wondering what is inside that...I mean, I've seen RFI filters in the mouser catalog, add some capacitors for reserve current needs....what else?
Reason is, when playing out, I notice a change in the sound of my tube amp from club to club. Yeah, part of it is acoustic, but I know it's more than that in some places. I've played places where the electricity is pure crap, and it gave the PA fits as far as hum, noise, etc...
I figure there can't really be that much to a box like that, but maybe someone else knows what they stick in those things.

[aron]

I have no idea. But you can find out for a $$ here:

http://www.schematicconnection.com/store/asp/prodtype.asp?prodtype=114&ph=cat

[ESPguitar]

I have no idea. But you can find out for a $$ here:

http://www.schematicconnection.com/store/asp/prodtype.asp?prodtype=114&ph=cat

So we have to pay for schems?
:roll:

RB

[R.G.]

I figure there can't really be that much to a box like that, but maybe someone else knows what they stick in those things.

There can't be much - but what there is in there is high voltage, probably high current parts with safety rating requirements. Get it wrong, you pop fuses and breakers; get it really wrong and you start fires. Be very, very cautious about what you do with AC line power. You can not only start fires, you can get dead, or kill a friend.

I used to design power supplies for a major computer company, and so I can guess at what some of the contents are.

The transient protection is easy. Some high current inductors and some MOVs to clamp transient spikes. The filtering is also easy, some series inductors and shunt capacitors between phases. The exact values and current ratings would take some time to ferret out, but that's what it has to be.

The only thing I'm a little curious about is the supposed 45A reserve current. About the only electrical way to store AC is in a resonant circuit. It's possible that they have a whacking big inductor and (probably) a motor run capacitor in there resonant at 60Hz and that is what does the "reserve current" stuff.

There *is* a simple, easy way to get clean AC voltage for your rig, but you won't like it. The key is the constant voltage transfomer, CVT, or ferroresonant transformer. These are made by several companies, Sola being the big one that's commercially recognizable. There are always a few of these on ebay.

A good ferro will take in 95 to 140Vac, with any kind of spikes, transients, dropouts, voltage changes and other junk and turn it into pure sine waves at 118V +/-10%; that is, what the AC line is supposed to look like. They are simple, no adjustments, and so reliable that your amp will die long before they do.

The only catch is that they're ...h..e..a..v..y... a good one for maybe 3A output weighing 30 pounds. But they are a class solution.

The other thing you can do is buy a cheap computer backup supply, the kind that always runs, not just does a wait-and-changeover. Then the amp will always be running on (relatively) cleanly synthesized AC power.

There happens to be a band-sized one on ebay now, item 7507143147. It's 2KW(!!) of clean AC power . Probaby weighs 200lbs, but it's clean.

[Ed G.]

[quote="R.GThe other thing you can do is buy a cheap computer backup supply, the kind that always runs, not just does a wait-and-changeover. Then the amp will always be running on (relatively) cleanly synthesized AC power.
[/quote]

Great info, R.G. I think getting a used UPS might do the trick. I basically want my amp to sound more consistent from gig to gig and run on the same amount of voltage. I imagine that is especially important to tube amps, if you would bias an amp on AC line voltage of 120V and play somewhere with 110 or 130V, that would likely knock the bias off a bit, right? The UPS would give you clean AC power, but would it keep it at a consistent voltage?

[R.G.]

I think getting a used UPS might do the trick. I basically want my amp to sound more consistent from gig to gig and run on the same amount of voltage. I imagine that is especially important to tube amps, if you would bias an amp on AC line voltage of 120V and play somewhere with 110 or 130V, that would likely knock the bias off a bit, right? The UPS would give you clean AC power, but would it keep it at a consistent voltage?

You do have to be a bit careful about which UPS you get. You'll want one that touts "true sine wave power" or some such. The really cheap ones just do a square wave with a lower peak than the normal power line sine wave, but equal "area under the curve" so that for computers, all's well, but an amp would notice the difference in the peak voltage.

There are three kinds. Square wave UPS, which will not talk about waveform at all, "modified sine" wave UPS, which use a stair step approximation to a sine that may or may not be good in your amp, and true sine wave types.

You want the true sine wave; you might settle for the modified sine, although for your purposes, I'd try not to.

You might get by with a different piece of iron, a variac, or even a "Vintage Voltage Adapter". With these, you can use the existing power, but manually correct the voltage to be close. I would discourage the variac, even though it's the correct tool for the job, because there will inevitably be someone - the bass player, the singer's girl friend, someone - who will think that if 120Vac is good, 130 must be better, or who will wonder - gosh, what will it sound like at 80V?? The potential for abuse is there too. The VVA is mysterious enough that they're unlikely to turn the dial. Well, OK, there's no dial to turn.

How much AC line current does your amp use? Something like 3A? 4A? The premium solution really is the CVT, and a 3A CVT is not all that big.