Forum about valves

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bancho
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Forum about valves

Post: # 19261Unread post bancho
Mon Apr 16, 2012 2:59 pm

Hi!
Could someone please point me to the ultimate forum dedicated to valves and circuits with them? Something like LatheTrolls to cutting...
I'm trying to make an triode astable circuit and I have to know some characteristics ... If anyone here has sufficient knowledge... also good!

Thanx!

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opcode66
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Post: # 19262Unread post opcode66
Mon Apr 16, 2012 3:25 pm

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markrob
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Post: # 19263Unread post markrob
Mon Apr 16, 2012 4:56 pm

Hi,

Here is one place to start:

http://www.duncanamps.com/

Also be sure to download a copy of the "RCA Tube Manual" and "The Radiotron Designers Handbook". Both essential reading.

Get the both and much more here:

http://www.tubebooks.org/technical_books_online.htm

What are you trying to do? A 12AX7 or simular dual triode will give you what you need to make a astable multivibrator.

Mark

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bancho
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Post: # 19269Unread post bancho
Tue Apr 17, 2012 4:17 am

yes I've seen all youtube videos and I've read that and some others books...

I'm trying to make tone generator (audio) at first then maybe something little more complex...
the 12AX7 was the first thought but then I found ECC86 (6GM8) which has low plate voltage - max 30V which is quite convenient. The other option would be maybe filament cathode triode but I'm a little bit skeptic because of life span (many working hours).
Is there any other low plate voltage triode than ECC86?

In ideal conditions you get square wave output, when not so ideal there are a lot of harmonics also... how can I get sine wave output (with/without harmonics)?

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dubcutter89
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Post: # 19270Unread post dubcutter89
Tue Apr 17, 2012 5:07 am

Hi,

I was already wondering why you need a tube astable multivibrator...
If you need a simple Sine-Wave Generator use a Phase-Shift-Oscillator (http://en.wikipedia.org/wiki/Phase-shift_oscillator) or a Wien-Bridge-Oscillator... Commonly used for tremolo circuits in guitar cicuits, and if made well also for labor-testing-whatever...

you can use a lot of tubes with less plate voltage - there is even a book about low voltage tube circuits - "Röhrenprojekte 6 bis 60V" - but in german

TUBES RULE! (valves und Röhren too ;)

regards
Lukas



PS:
In ideal conditions you get square wave output, when not so ideal there are a lot of harmonics also... how can I get sine wave output (with/without harmonics)?
square-wave has a LOT of (uneven - 1. 3. 5. 7....order) harmonics, so if you want single frequency + no distortion you need a pure sine wave!!!
Wanted: ANYTHING ORTOFON related to cutting...thx

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markrob
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Post: # 19271Unread post markrob
Tue Apr 17, 2012 8:00 am

bancho wrote:yes I've seen all youtube videos and I've read that and some others books...

I'm trying to make tone generator (audio) at first then maybe something little more complex...
the 12AX7 was the first thought but then I found ECC86 (6GM8) which has low plate voltage - max 30V which is quite convenient. The other option would be maybe filament cathode triode but I'm a little bit skeptic because of life span (many working hours).
Is there any other low plate voltage triode than ECC86?

In ideal conditions you get square wave output, when not so ideal there are a lot of harmonics also... how can I get sine wave output (with/without harmonics)?
For low plate voltage valves, check out the devices used in car and battery powered radios back in the day. They have max plate voltages under 100Vdc. For example, the 1R5 has a max plate voltage of 90Vdc and has typical operation down to 45 Volts.

Mark

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markrob
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Post: # 19274Unread post markrob
Tue Apr 17, 2012 10:29 am

Hi,

One other source for low plate voltage tubes are the submini's. These are cool because you can PCB mount them.

http://amps.zugster.net/projects/subminiature

Mark

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audadvnc
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Post: # 19284Unread post audadvnc
Wed Apr 18, 2012 9:30 am

Well, you can run tubes with low plate voltage, but why bother? It's like running a diesel automobile on cheap wine - I suppose you could get it to work with enough effort, but it's not worth the effort. The circuit will be starved for energy, and you'll spend more time & effort with those bizarre tubes & circuits than you need.

Run a standard vacuum tube in its designed supply range and you'll be fine. 6SN7 rules!

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