Battieries for B+ - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 31st July 2008, 05:31 PM   #1
diyAudio Member
 
whitelabrat's Avatar
 
Join Date: Dec 2006
Location: Maryland
Default Battieries for B+

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?
  Reply With Quote
Old 31st July 2008, 06:55 PM   #2
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
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.
__________________
Aerodynamics are for people who can't build engines. Enzo Ferrari
  Reply With Quote
Old 31st July 2008, 07:21 PM   #3
diyAudio Member
 
Join Date: Jul 2008
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.
  Reply With Quote
Old 31st July 2008, 09:36 PM   #4
diyAudio Member
 
Join Date: Apr 2007
We used to Sola constant voltage transformers to clean up commerical and locally generated power sources for computer controlled process equipment.

I just checked ebay and looks like you can get on for between $100 and $200. Don't see why it wouldn't work for your situation.

Steve
  Reply With Quote
Old 31st July 2008, 09:53 PM   #5
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
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.
  Reply With Quote
Old 31st July 2008, 10:13 PM   #6
Tweeker is offline Tweeker  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Cincinnati, Ohio
Quote:
This isn't actually something new.
Understatement of the year. The origin of the term B+ comes from batteries.

Quote:
. 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!
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.
__________________
Be sure your foil hat has a good low impedance ground.
  Reply With Quote
Old 1st August 2008, 01:58 PM   #7
diyAudio Member
 
whitelabrat's Avatar
 
Join Date: Dec 2006
Location: Maryland
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?
  Reply With Quote
Old 1st August 2008, 02:03 PM   #8
diyAudio Member
 
Join Date: Jul 2003
Location: Ann Arbor, MI
hey-Hey!!!,
Go to the junkyard and get a hybrid battery. These will be NiMH of ~7 A-hr. Avoid the Honda, as it is only 144V( or get two ). You'll need to run their disconnect contactors somehow, but that is a fairly simple task( and needs no super-clean/audio-grade DC ).
cheers,
Douglas
__________________
the Tnuctipun will return
  Reply With Quote
Old 1st August 2008, 03:14 PM   #9
diyAudio Member
 
whitelabrat's Avatar
 
Join Date: Dec 2006
Location: Maryland
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.
  Reply With Quote
Old 1st August 2008, 03:39 PM   #10
diyAudio Member
 
Join Date: Jul 2008
Isolation and balanced power not the same thing. very informative website below.

http://www.equitech.com/articles/articles.html
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 11:23 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2