We all know that one of the cleanest sources of power for just about anything is a battery. I've got some dirty dirty power, and I'm trying to think of the least expensive way to get off the grid. To prove my point, if I move my amp to super nice conditioned power, all noise is gone. Put it on unfiltered mains, and it's horrible buzzing time. Could be the grounding? Could be DC on the mains? Who knows.
So let's say I've got a target voltage for a B+ of 250vdc drawing about 30ma. I could use 208 1.2v AA batteries, but there goes the cheapo factor. I suppose I could get a 12v SLA battery and then use a voltage doubler circuit in a series to step up the DC. That would be a lot of stepping!
One positive of using a battery would be the elimination of expensive power transformers.
Then there are the heaters. I figure on just using 6.3v from a wall wart should do fine, since it doesn't need to be super clean.
Anyone every think of a graceful and inexpensive way to get a tube amp off grid power?
So let's say I've got a target voltage for a B+ of 250vdc drawing about 30ma. I could use 208 1.2v AA batteries, but there goes the cheapo factor. I suppose I could get a 12v SLA battery and then use a voltage doubler circuit in a series to step up the DC. That would be a lot of stepping!
One positive of using a battery would be the elimination of expensive power transformers.
Then there are the heaters. I figure on just using 6.3v from a wall wart should do fine, since it doesn't need to be super clean.
Anyone every think of a graceful and inexpensive way to get a tube amp off grid power?
This isn't actually something new. There are after all both commercial and DIY tube amps for cars. You can search both this forum and the car audio forum for some info.
As for what's most elegant, you would probably get some disagreement. IMHO, the most elegant way would be to use the tubes such as 6GM8 and the rest of the family that were designed for car radios and are happy with a 12V B+. Others might say that using a DC-DC upconverter to generate B+ in order to use the more popular audio tubes is a more elegant approach.
As for what's most elegant, you would probably get some disagreement. IMHO, the most elegant way would be to use the tubes such as 6GM8 and the rest of the family that were designed for car radios and are happy with a 12V B+. Others might say that using a DC-DC upconverter to generate B+ in order to use the more popular audio tubes is a more elegant approach.
lots of ways of dealing with dirty power...certainly going DC is one way.
As a consideration, not to rain on your parade, I had a major dirty power problem and decided to use a balanced power transformer at my sub panel. I bought a 5000VA medical grade transfomer and wired it up as a balanced isolation transformer. I think I paid 96 bucks for the transformer on ebay.
A balanced power transformer will cancel out noise and is reported to lower the noise floor by as much aa 18db.
It basically converts 120 - 0 to 60 - 0 - 60. There are some issues. You can't plug an incandesent lamp into one. reason being the metal cup of an incandesent socket is exposed and expects to be netural. In a balanced power arrangement the cup would be hot with 60 volts.
As a consideration, not to rain on your parade, I had a major dirty power problem and decided to use a balanced power transformer at my sub panel. I bought a 5000VA medical grade transfomer and wired it up as a balanced isolation transformer. I think I paid 96 bucks for the transformer on ebay.
A balanced power transformer will cancel out noise and is reported to lower the noise floor by as much aa 18db.
It basically converts 120 - 0 to 60 - 0 - 60. There are some issues. You can't plug an incandesent lamp into one. reason being the metal cup of an incandesent socket is exposed and expects to be netural. In a balanced power arrangement the cup would be hot with 60 volts.
There seems to be some anecdotal evidence (and even some engineering fact) to suggest that the chemical process inside a battery can be inconsistent and electrically noisy.
One method would be to use a low voltage battery and then use a DC-DC converter to step up the voltage. However I guess that you swap one set of problems for another though, as the converter can be noisy both with line spikes and RFI. Having said that, Nagra use the technique in their PL-L preamplifier with apparent success.
One method would be to use a low voltage battery and then use a DC-DC converter to step up the voltage. However I guess that you swap one set of problems for another though, as the converter can be noisy both with line spikes and RFI. Having said that, Nagra use the technique in their PL-L preamplifier with apparent success.
Understatement of the year. The origin of the term B+ comes from batteries.
You need an AC source for a doubler or a multiplier stack, your looking at a switchmode DC-DC converter, which is doable, but has its own noise issues to solve. 20 car batteries could be accumulated cheaply I suppose, but isnt exactly elegant.
Isolation transformer (balanced helps too, but any electrostatically shielded transformer can make a big difference) and/or common mode filtering is another route worth considering. If your waveform is particularly distorted it could be hard to clean up though. Also, avoid things like triacs (seen in many light dimmers) in your house. Sola keeps voltage steady but can distort the waveform.
Another possibility is synthetic power, essentially a 60hz (or whatever) signal made from another amplifier. This is very expensive and inefficient (at least if a switcher isnt involved), but makes very clean power.
You may want to look to amp designs with high PSRR.
Actually I've got three isolation transformers. I don't think they do anything useful clean up the grounding though. My dilemma is that the dirty power I speak of is at my office, and I don't want to scare the natives. They already are spooked by my tube headphone amp. The little guy only draws about 22 watts total which I figure would be doable with batteries, especially if I keep the heaters on the mains AC.
I could also improve the amp's power supply. I'd say there's a good chance the noise is coming from the mains grounding. The soil around here has a lot of mica in it that makes getting good grounding difficult. That and there are a lot of industiral motor thingies like pumps and who knows what in close proximity.
My power supply should have some good filtering with a 10H choke in it. There's nothing between the mains ground and the chassis, and then a 150ohm resistor that goes to the center tap of the power transformer. That may be part of the problem. The 6.3v for the heaters are ruff, tuff, and in the buff too. They come straight off the power transformer, but are twisted very tightly.
My mission it to be cheap, and safe, but also to not scare the folks in my office. Black and Decker sells an inexpensive NiMH battery that includes an AC inverter. The inverter is noisy from what I've read.
Curious though. Am I mistaken or do these constant voltage transformers clean up the grounding too?
I could also improve the amp's power supply. I'd say there's a good chance the noise is coming from the mains grounding. The soil around here has a lot of mica in it that makes getting good grounding difficult. That and there are a lot of industiral motor thingies like pumps and who knows what in close proximity.
My power supply should have some good filtering with a 10H choke in it. There's nothing between the mains ground and the chassis, and then a 150ohm resistor that goes to the center tap of the power transformer. That may be part of the problem. The 6.3v for the heaters are ruff, tuff, and in the buff too. They come straight off the power transformer, but are twisted very tightly.
My mission it to be cheap, and safe, but also to not scare the folks in my office. Black and Decker sells an inexpensive NiMH battery that includes an AC inverter. The inverter is noisy from what I've read.
Curious though. Am I mistaken or do these constant voltage transformers clean up the grounding too?
I'm beginning to think that the safety issues of having high voltages without grounding negate any benefits of using a battery. A short could get ugly. Could you imagine shorting 208 AA batteries?! An arc welder comes to mind.
I'm sure a hybrid battery would work splendidly, but I would expect those to go for a mint, considering the popularity of hybrid cars these days. That and 200lbs of battery would look funny on my desk.
Back to the ranch. Gonna have to devise a more robust AC --> DC power supply.
I'm sure a hybrid battery would work splendidly, but I would expect those to go for a mint, considering the popularity of hybrid cars these days. That and 200lbs of battery would look funny on my desk.
Back to the ranch. Gonna have to devise a more robust AC --> DC power supply.
Isolation and balanced power not the same thing. very informative website below.
http://www.equitech.com/articles/articles.html
http://www.equitech.com/articles/articles.html
If you only need headphone power, something like a 3V4 or 3Q4 will deliver almost 300mw at about 100 volts B+. The filament is center tapped so it can use 1.5V or 3V.
These were routinely used as the output tube in battery operated radios and can easily drive small efficient speakers.
22, 45, and 67 volt B+ batteries are still made. Antique Electronic Supply has them. If you need some gain before the PA, there are lots of tubes in the 1xxx family to pick from.
I have toyed with 3Q4 as low as 36 volts, but to me they sound best (and obviously make more power) at 90 volts or above.
Win W5JAG
I ran a string of Dewalt 18v batteries into several preamps & some small amps all witjout loosing power, but needed my batteries back for work. I have ran them to almost 200v. I did short out some test clips one time, they dissinigrated instantly.. nothing left but the smoke in my house.., on the plus side they were of course dead quiet & creepy black background.I am to start using the 18v Dewalts in bias suppies for output tubes, this is for sure, I allready have actually, works excellent.
J & G
J & G
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