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Author Topic: Low voltage "space charge" tube designs  (Read 10079 times)

darwindeathcat

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Low voltage "space charge" tube designs
« on: September 22, 2009, 09:37:56 PM »
I was just perusing the internet and came across this site http://www.junkbox.com/electronics/lowvoltagetubes.shtml about certain types of tubes that were meant to be run at low voltages (both on the heaters AND the plates). 20v or less. Most of the info at that site is about building low voltage tube radios radios, but there is no reason on can't build instrument amplifaction stages with these tubes. The sopht amp uses common space charge tubes (12u7 in the preamp and I forget what the power tube is). AFAI understand space charge tubes will sound  different than "starved cathode" designs that use regular tubes in a low voltage mode. Anyone know of any other designs, specifically preamps or overdrives, that use space charge tubes. I searched google, but got a lot of useless repsponses. The idea is to use a space charged tube circuit as the preamp to a chip amp. I've got one chipamp that runs at +-24, and another at +18 that I'm fooling with the preamp sections on. Of course I can use a regulator to get whatever voltage I need for the space charged tube preamp design.

Cheers,

DDC
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darwindeathcat

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Re: Low voltage "space charge" tube designs
« Reply #1 on: September 23, 2009, 01:12:41 PM »
I should add that I have on hand several 6au6 and 6ba6 tubes. The two circuits I'm aware of that can use these in fairly low voltage are the Jon Anderson "Lonewolf" (and the derivative "werewolf", designed by Adriano "Renegadarian" of the diystompbox forum), which runs at +36 volts(werewolf at +50 volts), and the Doug Hammond "Pentode driver" that runs at +/- 12volts.

   It's likely that I'll give one of these a go (prob the pentode driver first), but would appreciate any other suggestions.  
« Last Edit: September 23, 2009, 02:01:11 PM by darwindeathcat »
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Brymus

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Re: Low voltage "space charge" tube designs
« Reply #2 on: September 23, 2009, 04:58:12 PM »
Why not try a 12V version of your fav tube amp?
Maybe 12V F2B or SLO100 at 12V could be interesting.
even a scaled down 5e3 would be an easy start.

darwindeathcat

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Re: Low voltage "space charge" tube designs
« Reply #3 on: September 24, 2009, 05:47:15 PM »
Thanks, I'll check those tubes out. I'm a total Tube newb, so i'm not sure I have the engineering knowhow to convert a high voltage tube amp circuit to 12volt one (I think that's a pretty tall order). I'm interested in circuits that run within the range of voltages that most common chipamp have already. I'm interested in building this as a hybrid amp. Let the chipamp make it loud,and let the tube preamp color the sound. I'm aware of the valvcaster and derivatives (Valvelitzer, etc.) and definitely am interested in those. I happen to have those 6au6 and 6ba6 pentode tubes already (from an old radio), so it would be cool to use them, especially because i've read that "cranked pentode distortion" is a good sounding thing.... I've got a few schematics, so I at least have a place to start with these tubes, but i was just fishing here for some sage advice to keep me from heading ff in the wrong direction! I suppose it's time to just breadboard it and see!

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PangCat

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Re: Low voltage "space charge" tube designs
« Reply #4 on: November 13, 2009, 10:25:01 PM »
           I am a Tube newbie also , So I am researching more about this I am so glad I saw this thread I got some details that Is helpful.


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Re: Low voltage "space charge" tube designs
« Reply #5 on: February 26, 2010, 01:44:41 PM »
You can make a valve version of the Noisy Cricket:

http://www.beavisaudio.com/projects/TubeCricket/