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Questions about tetrodes for specialists

138.36.35.41
Posted on December 1, 2016 at 13:20:53
Aldovan
Audiophile

Posts: 113
Location: South
Joined: October 10, 2001



Friends

I found a type 36 tetrode and built the above circuit to test it as a preamplifier. However, I observed that from 20Hz to 15KHz the circuit provides 35Vpp at the output, but this voltage goes down to 27Vpp at 20KHz.
What can cause this loss of gain? The capacitances on the tube look ok.

Thanks

Aldovan

 

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RE: Questions about tetrodes for specialists, posted on December 2, 2016 at 05:58:41
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001
 with a 500K Rp I would expect that behavior even driving a scope probe.

dave

 

RE: Questions about tetrodes for specialists, posted on December 2, 2016 at 08:21:27
Triode_Kingdom
Audiophile

Posts: 10047
Location: Central Texas
Joined: September 24, 2006
 The Rp of the tube is in parallel with a 55K anode resistor. Even if the probe was as high as 20pF, the 1kHz - 20kHz delta should only be about 0.15 dB.



 

RE: Questions about tetrodes for specialists, posted on December 2, 2016 at 08:54:31
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001
 Ahhh... that changes things. I don't see the schematic..... just get a broken link.

so the next question becomes what exactly is the OP trying to drive and since I cannot see the schematic how is he trying to drive it?

dave

 

RE: Questions about tetrodes for specialists, posted on December 2, 2016 at 13:08:12
Triode_Kingdom
Audiophile

Posts: 10047
Location: Central Texas
Joined: September 24, 2006
 Right, there are a lot of unanswered questions. I highly suspect this all has something to do with the measurement procedure and/or test equipment.


 

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