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Old 23rd February 2017, 06:48 AM   #1
Trajan is offline Trajan  United States
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Default DHT Cathode Follower?

I would love to know if anyone has built one or if it is even possible.
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Old 23rd February 2017, 07:17 AM   #2
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Yes it is possible.

Use a separate filament winding that has very low capacitance to the other winding.
A dedicated filament transformer with only a primary and secondary is best, and that has the plastic separated winding sections.
Use a good DC supply that is powered from the low capacitance transformer, it needs to be Very well filtered.
Do not use that DC supply for any other filament.
i.e. you can not power 2 cathode followers off one supply.
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Old 23rd February 2017, 07:32 AM   #3
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Ηi if you use two shunt reg SSHV2 for power 2 cathode followers tubes with one power supply, it is problem that?
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Old 23rd February 2017, 07:38 AM   #4
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Yes, it is. Both cathode followers' heater supplies need to be separated galvanically.

Btw, why does one do the hassle of a DHT CF? I don't see any reason?!?

Best regards!
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Old 23rd February 2017, 07:53 AM   #5
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Ηi Kay
im refers to power supply HV not for the power supply for the heaters...
one common HV Power supply with two regs for the two cathode followers tubes.
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Old 23rd February 2017, 07:56 AM   #6
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Sorry, in your previous posting this was kept secretly.

A common plate supply will do, of course, given it is of low impedance.

Best regards!
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Old 23rd February 2017, 02:14 PM   #7
316a is offline 316a  England
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Quote:
Originally Posted by Trajan View Post
I would love to know if anyone has built one or if it is even possible.
It is possible but why bother ? A cathode follower is already linear and requires a high mu , high gm valve . Try finding a DHT with high gm and high mu , may as well just use a suitable IDHT and avoid all the extra complexity of sepearte filament supplies etc

316a
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Old 23rd February 2017, 03:29 PM   #8
euro21 is online now euro21  Hungary
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Quote:
Originally Posted by Trajan View Post
I would love to know if anyone has built one or if it is even possible.
My (all) DHT amp: CCS loaded, heater biased 841, C, CCS loaded 10Y CF, direct coupled to 801a PSE.
All tube has own DC filament PSU: separated transformer, raw supply, Rod Coleman regulator.
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Old 23rd February 2017, 06:37 PM   #9
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Yes, correction to my post # 2
I said: "Do not use that DC supply for any other filament.
i.e. you can not power 2 cathode followers off one supply."

I should have said "i.e. you can not power 2 DHT cathode follower filaments off one supply, unless they are going to be driven from exactly the same signal".
(but then that is simply a Parallel DHT cathode follower).
There, I have taken it to the two specific cases.

"ALL generalizations have exceptions"
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Old 23rd February 2017, 09:26 PM   #10
Trajan is offline Trajan  United States
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Thanks to all who replied! Thank you euro21 and 6A3 for the inspiration! I was more curious than anything; nothing on it on the net. (I have a stockpile of 841s, so drivers are OK for me.) I was just thinking about an all DHT preamp (for kicks) with no output transformer. I figured a CF might be helpful here and wanted to explore the possibility.
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