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Pentode to Triode trick.
Pentode to Triode trick.
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Old 6th November 2005, 02:19 PM   #1
Diy martin is offline Diy martin  Netherlands
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Join Date: Apr 2003
Location: papendrecht
Question Pentode to Triode trick.

Any one tried this trick to turning Pentodes into Triodes.

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Old 6th November 2005, 03:19 PM   #2
James D. is offline James D.  United Kingdom
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Join Date: Nov 2002
Location: North Herts, UK
Yes, I've used it with El34s and 807s. It works nicely and is slightly better sounding than using a 150R resistor only. Not sure it's worth the extra expense or bother (actually I am sure as I stopped using a couple of years ago..)

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Old 6th November 2005, 05:57 PM   #3
dhieber is offline dhieber  United States
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Join Date: Sep 2004
Location: Illinois
James, have you tried a UF4007 between screen and plate as an alternative to using a zener?

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Old 7th November 2005, 06:56 AM   #4
Alex Kitic is offline Alex Kitic  Serbia
Join Date: Dec 2004
Location: Zemun
Default Is that necessary?


Not to get too much into the topic's schematic, I would say that there is no particular reason to enter into so much fuss.

First of all, because a pentode will not become a triode, whatever you do with it, except if you can open it, take out all the g2 and g3 material between g1 and the anode... and close it back again. Or better still, do it at the factory, while it is being constructed. Imagine having a time-machine and visiting a Telefunken factory during WW2 or somewhere at that time -- and ordering a batch of tubes to your convenience ) Just try to imagine the engineer's faces when you ask them to make you this batch (ha, ha). They would probably take you for f..l

Whatever you do to the connections, it will still be a pentode wired as triode. Meaning whatever that means, including the loss of power, which you can certainly afford since you own Lowthers and other 96dB+ efficient speakers...

Further on, there are ways to use the pentodes in a better way, making them sound like if they were wired as triodes, while enjoying the higher power of pentode wiring... and very low distortions overall. I.E. my RH series... just think about it while you sit in your favorite imagination experimenters armchair.

Regards to all,
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Old 7th November 2005, 11:00 AM   #5
James D. is offline James D.  United Kingdom
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Join Date: Nov 2002
Location: North Herts, UK
Hi Dean,

No I've not tried just diode between anode and screen. I've only used the zenar string bypassed by a cap or a low value resistor.

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