Why not so common to split dual triodes between channels? - diyAudio
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Old 6th April 2007, 02:11 AM   #1
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Default Why not so common to split dual triodes between channels?

Maybe it is only my perception, but why is it not more common to see dual triodes split up such that each section is part of a separate stereo channel? Of course I have seen examples where it has been done, but I have seen more examples of designs, for example, where the 2nd triode has been used as a CF in the same channel, even if poorly suited for that task. Is it a practical issue where the wiring can get more cluttered, amp cannot be built as a monoblock, etc., or is there a strong technical reason such as resulting in poor channel separation, as an example?
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Old 6th April 2007, 03:25 AM   #2
Tweeker is offline Tweeker  United States
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Channel separation may be degraded, the two section can interact electrically. Often twin tubes are used such that this interaction is harmless. Some twin tubes, such as the 6n1p have an internal screen to prevent it.
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Old 6th April 2007, 07:09 AM   #3
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Heh, I've seen a few amps so carefully designed for channel seperation (seperate boards, even seperate supplies), then switch inputs through a $1 wafer rotary.... making a 130dB seperation design into a 30dB one with the crummy switch
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Old 6th April 2007, 02:29 PM   #4
Klimon is offline Klimon  Belgium
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Quote:
Maybe it is only my perception, but why is it not more common to see dual triodes split up such that each section is part of a separate stereo channel?
Strange, my experience has been exactly the opposite; a gargantuan number of diy se schematics use double triodes as driver tube, one half for each channel. In some (or all?) SRPP circuits using dual triodes, it's adviced not to use both tube halves for one channel (otherwise you would exceed ....... I hope someone can fill-in here ) so obligatory to share a tube between both channels.

Simon
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Old 6th April 2007, 02:36 PM   #5
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Geek
making a 130dB seperation design into a 30dB one with the crummy switch
Or with a phono cartridge - even the best ones.

Sheldon
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Old 6th April 2007, 09:08 PM   #6
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Quote:
Originally posted by Sheldon


Or with a phono cartridge - even the best ones.

Sheldon

You bet!


Bottom line - the tubes I believe are the *least* of the channel seperation worries
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Old 6th April 2007, 09:31 PM   #7
EC8010 is offline EC8010  United Kingdom
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Superstition. There's little reason not to share a twin triode across channels.
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Old 6th April 2007, 09:45 PM   #8
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by EC8010
Superstition. There's little reason not to share a twin triode across channels.

agree 158%

sometimes even best way.........especially with SRPP or Mu or whatever called thingies
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Old 7th April 2007, 12:42 AM   #9
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capacitive cross-coupling...... it isn't so much a problem if tube shields are used, but then nobody would see the orange glow of the filaments from the front of the amp.....

under the socket, you will occasionally see a grounded shield across the tube socket as well... reduces crosstalk and interstage coupling....
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