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Old 4th March 2008, 09:54 PM   #11
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Quote:
Originally posted by Johan Potgieter
Simon,

Mind giving me a website for that triode-trick if there is one? (All I find under Bill Perkins are a politician and a saxophone player!)
You can find it Right Here. It's a steaming, stinking pile of audiophoolery.
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Old 4th March 2008, 10:02 PM   #12
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Quote:
Originally posted by Miles Prower


You can find it Right Here. It's a steaming, stinking pile of audiophoolery.
A typical snake oil (proportions, diodes, etc...)
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Old 4th March 2008, 10:03 PM   #13
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Ah, that lot! But I have that under Grimwood, not Perkins. Same thing?

Nevertheless thanks Miles.
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Old 4th March 2008, 11:09 PM   #14
rdf is offline rdf  Canada
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Perkins recommended a string of cap-bypassed zeners from plate to screen to force a constant DC voltage between the two while maintaining an AC short.
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Old 4th March 2008, 11:22 PM   #15
mach1 is offline mach1  Australia
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Quote:
Mind giving me a website for that triode-trick if there is one? (All I find under Bill Perkins are a politician and a saxophone player!)
Johan,

I think this is what you were referring to:

http://www.t-linespeakers.org/tubes/triode-trick.html
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Old 4th March 2008, 11:30 PM   #16
mach1 is offline mach1  Australia
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And then there is this:
Attached Images
File Type: jpg triode tl431.jpg (15.8 KB, 382 views)
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Old 5th March 2008, 01:02 AM   #17
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Quote:
Originally posted by mach1


Johan,

I think this is what you were referring to:

http://www.t-linespeakers.org/tubes/triode-trick.html
Thanks, Mach1, that seems to be it.

...the advantage again appearing unclear. Not to belabour, but there seem to be certain guys who are constantly in fear of too much screen dissipation. When the data sheets show that Va=Vg2 is safe, and in fact give the g2-current, it can be easily seen that screen dissipation will be safe. With triode connection there is no "wasted energy" - it all goes to the anode.

Just for those new to this field of bewildering claims.
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Old 5th March 2008, 01:21 PM   #18
Klimon is offline Klimon  Belgium
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Old 5th March 2008, 01:21 PM   #19
Klimon is offline Klimon  Belgium
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Confessing I don't know the second thing about electronics but this little (despised ) circuit clearly sounds better to me than simple resistor: better bass-attack and better pace overall. The amp is an el84 set; I now actually use only three zeners + a single 1000F cap this sounds smoother than the published circuit. These are just my findings.

Simon
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Old 5th March 2008, 11:16 PM   #20
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Hi Simon,

Perhaps it was not said; I didn't check (I see that it is quite acceptable in some circles to say one is not feeling so well!). But yes, you have perhaps gathered that a screen grid can draw a quite varying current. Thus, using any resistor dropping more than a few millivolt (higher than the typical 100 ohm), will cause extra distortion. Triode operated pentodes are only that if the screen exactly follows the anode, otherwise an extra factor is introduced. Such a "close-coupled" condition is achieved by using zeners (or whacking big capacitors).

Thanks for that reference. I am greatly temted to be naughty and reply with some of Eddie's own advice: Do not listen to all the guru's! No further comment.
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