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Old 13th December 2009, 10:54 AM   #1
Stee is offline Stee  Italy
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Default Jfet audio buffer

Hi Collegue,
my new project is a Preamplifier with 3dB gain
and original architecture
see drawing

values are not true - never tested - just an idea
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Old 13th December 2009, 11:31 AM   #2
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I would prefer Andrea Ciuffoli's Power Follower - that have unity gain (0 db)
http://www.audiodesignguide.com/my/Follower_99c.gif
modify for use as preamp: only 9V supply voltage and 1A idle current (and therefore relatively low loss power)
unfortunately I don't know commercial preamp models with such parameters and such superb sonic quality.
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Old 13th December 2009, 08:03 PM   #3
Stee is offline Stee  Italy
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Default mosfet instead FET

intresting
this buffer can be used 3 times in chain
to have a complete amplifier
for example with resistors A/B= 3
the gain is G=3 in every stage and at last G=27
final stage can use IRFD 110 & C - the little Hexfet @ +/- 35V
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Last edited by Stee; 13th December 2009 at 08:09 PM.
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Old 14th December 2009, 02:19 PM   #4
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A power follower is not intended as preamp. A preamp has gain, otherwise it's a buffer.

I would not build that particular power buffer - it's an ordinary current sourced follower with esoteric comments.

Have fun, Hannes
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Old 14th December 2009, 04:32 PM   #5
Stee is offline Stee  Italy
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Default you are right Hannes

it's an ordinary current sourced follower with esoteric comments
and fets current source
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Last edited by Stee; 14th December 2009 at 04:36 PM.
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Old 14th December 2009, 04:33 PM   #6
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Quote:
Originally Posted by h_a View Post
A power follower is not intended as preamp. A preamp has gain, otherwise it's a buffer.

I would not build that particular power buffer - it's an ordinary current sourced follower with esoteric comments.

Have fun, Hannes
Why you prefer voltage gain by your line stage in your preamplifier?
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Old 14th December 2009, 04:41 PM   #7
Stee is offline Stee  Italy
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Default a little gain need

because I would like use Fet preamp instead my 6SN7 TUBE SRPP
so my idea is 3 or 6 dB of gain need to expand signal like SRPP
also I think this new preamp need 6 times PSU of output peak voltage
again for "open sound" - a sound with air around
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Old 14th December 2009, 06:16 PM   #8
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Mirror symmetric topologies (push-pull LTP and push-pull output buffer) looks very symmetric at the schematic and it is also in theoretic world very symmetric. But in real life this symmetric behavior don't exist, even by best possible performed selection work. Both at complementary jFETs and BjTs (go to the datasheets).
Harsh sound is still to expect and nothing compare to the mentioned power follower from Andrea Ciuffoli (if you have a possibility to compare both topologies in real life, please perform this).

A great amount of symmetric behavior you get there
http://www.passdiy.com/pdf/Build%20T...Circlotron.pdf
also appropriate for pre-amplifier with a small amound of voltage gain and much more better than the previous mentioned topology

6 times PSU of output peak voltage for "open sound"? Certainly by this mirror symmetric topology but not by Circlotron and clean power followers. To get better sound by already existing mirror symmetric topologies there is one possibility: the introduce of an offset voltage (2 times of output Vss value) and the introduce of caps in the signal line.

Please read in this case carefully the basic articles regarded "single ended" about www.passdiy.com

Last edited by tiefbassuebertr; 14th December 2009 at 06:23 PM.
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Old 14th December 2009, 06:43 PM   #9
Stee is offline Stee  Italy
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Default thanks

Ciclotron with FET is a genial project
but need balanced signal...
do you think it's possible introduce
a pseudo-SRPP configuration in a standard mirror?
of course, with FET - like tube sound
with minimum gain and optimum ratio between peak/Vss
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Old 14th December 2009, 07:16 PM   #10
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Default somethink like this

but with P and N rails
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