Biasing Zen vs PowerFollower99C - diyAudio
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Old 18th October 2001, 11:35 AM   #1
diyAudio Member
Join Date: Oct 2001
Hi all,
can somebody explain the difference between Zen2 Biasing
(Voltage ref R8 is not constant) and Andrea Ciuffoli`s
PowerFollowerC (fixed voltage Level).
chio andreas
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Old 20th October 2001, 03:16 AM   #2
diyAudio Member
Join Date: Sep 2001
Location: Salt Lake City
I'm not really mathematically inclined so can't tell you much about how each biasing scheme works, but the power follower 99 is a dynamite circuit to build. Great sounding and VERY quiet too. Of course there's no gain here but the virtual battery technique is a nice added touch. Mine run REALLY hot! Built on a 8" long piece of wakefield 1245. Pictures are at:
Mark Gulbrandsen
Salt Lake City, UT
P.S. This is my first audio construction project in over 15 years! Far from perfect, I threw them together in a weekend, but the performance is there....

[Edited by Mark A. Gulbrandsen on 10-19-2001 at 10:19 PM]
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Old 20th October 2001, 03:35 AM   #3
fcel is offline fcel  United States
diyAudio Member
Join Date: Sep 2001
Location: LA County
Mark, You built them in one weekend but how long did it take you to get all the parts together?
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Old 20th October 2001, 03:57 AM   #4
diyAudio Member
Join Date: Sep 2001
Location: Salt Lake City
I had ordered the mosfets from digikey the week before so I already had those, couldn't find them locally. The rest of the stuff came from a local surplus electronics supply firm which I make stops at frequently to get parts for work. Really, it was done in only one weekend! That included making the PCB's, which I could ahve used a bit smaller drill on, and painting and assembling the chassis. I baked the paint on in my kitchen oven. Gives the hammertone in from can a really high gloss finish and wet to dry time is less than an hour. They worked perfect on first run up on the variac. I am still looking for a good front end for it, possibly tube. Any suggestions here would be appreciated.

I've been an electronic tech for 25 years and build all sorts of stuff for large light dimming systems we install, sometimes in short order so I have a tendency to fly through things sometimes. I also have extensive metalworking experience so that made things go right along. The PCB's took about an hour and a half start to finish to make. Floating the boards in hot etchant makes em go real fast. The copper literally falls off the board as its heavier. This keeps fresh etchant at the copper always. The heatsinks and toroids were also from the surplus place. No more heatsinks but they still have many cases of the toroids if you need any....15.00 each. Its a lot larger than needed for this amp and has dual secondaries. Could easily power a stereo version of the follower. This IS a capacitor coupled amp but you'd never know it. Drives my Dynaudios pretty well.
Mark Gulbrandsen
Salt Lake City, UT
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Old 20th October 2001, 09:07 AM   #5
Freddie is offline Freddie  Sweden
diyAudio Member
Join Date: Oct 2000
Location: Sweden
The power follower 99 is a quite nice amp. I've been using for 2 years now. Very easy to build too. I'm running the PowerFollower with a 38V 500VA transformer, and I think that 38V is a little too high voltage, cause I've had to replace a couple of Mosfets, even though the heatsink temperature is reasonable (55 degrees Celsius).

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