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Old 27th January 2006, 08:41 PM   #1
yagas is offline yagas  Greece
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Talking Anode Follower

Anyone tried something like this ?
I plan to build it for a friend of mine who insists on having the gain adjustable.
How the anode follower compares to cathode follower in terms of sound ?
Other than low input capacitance any other comments please ?

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Old 27th January 2006, 09:49 PM   #2
Zen Mod is offline Zen Mod  Serbia
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long time ago invented

anyway-next time try to mark output load little different,in this case I just presume that your load is 47K?

in most cases,difference in sound between different stage topologys is more dependant of actual physical layout ;
speaking of same tube ,naturally

for anode follower ,tube with lowish Ra is preferred,even more than for cathode follower;
but I think that EC99 will do the job

edit-some of Audio Inovations preamps used that config,little Rafael from Germany too ,and they are pretty good judged in hifififi journals of this era
I tried that once,with ECC82 and I pretty liked the sound;
but with my overcomplicated shunt reged supply of that time
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Old 27th January 2006, 10:01 PM   #3
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Seely, in Electron-Tube Circuits (1950) covers an equivalent circuit for it on p.108-111; and points out that the anode-follower's output impedance is approximately twice that of the C.F.
However the input impedance will be much lower. It is phase-inverting.

TCD covers it at least once.

And there is a paper, introducing The Anode Follower from Charles P. Boegli, (Audio, Dec. 1960) in PDF format.

I'm sure it must have had some discussion on this forum at sometime in the past too.

I can't comment on the sonics not having built or compaired one, but I hope some of the above might be of use to you.
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Old 27th January 2006, 10:14 PM   #4
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Someone recently forced me to look through part of RDH4. In the section on pentode cathode followers Langford-Smith was showing different ways to keep the screen grid current out of the cathode load. One of his suggested solutions was to put the load in the plate circuit, but apply the input signal between grid and plate. The result is a true anode follower. Of course it's mostly academic as it's pretty difficult to apply the input that way. A transformer might seem ideal, but you would run into some serious capacitance problems.

I suppose it goes without saying that you don't need to use a pentode ...
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Old 28th January 2006, 07:40 AM   #5
yagas is offline yagas  Greece
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yes, the load is 47K and the ECC99@150V@18mA approx.
The output resistance as shown is 2K with 12db gain

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Old 28th January 2006, 09:02 AM   #6
bucurb is offline bucurb  Romania
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Default anode follower using 6N1P

Very attractive subject. But I do not have EC99. I have several brand new 6N1Ps. Does any one knows a schematic using this tube, please? Thanks!
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Old 29th March 2009, 12:53 PM   #7
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I have noticed that the cathode follower and anode follower have different kind of nonlinearities. While the anode follower uses the direct version of the transfer characteristic, the cathode follower uses the inverse.

Does this explain subjective differences?

I actually feel that the anode follower sounds better. Is this a consistent experience?
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Old 30th March 2009, 04:34 PM   #8
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I like Nelson's Aleph as an emitter coupled base follower.
Of course, tube heads will want the enhancement mode
MOSFET replaced by a screen driven Pentode.

If Aleph's base follows a resistive divider from the Cathode.
The cathode of that Pentode can have a useful voltage gain.

Its definately on the sandy side of hybrids. Pentode mostly
for dissipation. With NPN in the error correction control seat,
driving the screen, and sandifying all the flavoring decisions.

Also tried simming Aleph with a Triode in place of the NPN,
as a cathode coupled grid follower. I didn't find that config
working as good as a plain jane Pentode cathode follower
for unity gain. And Cathode input impedance sucks. But for
gains over unity, it might still find use somewhere someday.
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Old 30th March 2009, 05:08 PM   #9
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If this Triode were an NPN, gain would be 10.
As a purely glass circuit, gain here is maybe 5....

Havn't gone to any great lengths to optimize.
Input Z very very low.... So low, not too sure
this topology has a legit use or not???
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Old 30th March 2009, 05:11 PM   #10
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