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F4 power amplifier
F4 power amplifier
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Old 7th November 2017, 12:34 AM   #4291
soldersmoker is offline soldersmoker  United States
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I had a pair of Wild Burro Betsys a few years ago, so I'm familiar with the OB magic those were able to pull off (even though they aren't the best drivers ever). Again, thanks for the great suggestion!
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Old 19th November 2017, 04:31 PM   #4292
xrk971 is online now xrk971  United States
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F4 power amplifier
Just wanted to give a heads up that Hugh Dean and I have developed a nice preamp with 40v p-p output with low distortion and SE Class A harmonic profile. It's been tested in prototype stage already. JPS64 will be releasing Gerbers for easy construction soon. It's a 5 transistor affair, very simple but clean output. Sound is superb and can drive any amp to clip without adding hardly any distortion.

AKSA's Lender Preamp with 40Vpp Output

Incidentally, we are running sims of a boosted 100v rail version that can swing 90vpp into 10kohms and looks like this:

AKSA's Lender Preamp with 40Vpp Output-aksa-lender-preamp-hv-v2-1-90vpp-10kohms-fft-jpg

Here is the schematic of the souped up 90vpp version:
AKSA's Lender Preamp with 40Vpp Output-aksa-lender-preamp-hv-v2-1-schematic-jpg

The JPS64 design of the 40vpp version has SMT daughter boards on a main board with selector switches and PSU and looks like this:
Click the image to open in full size.

Here is a closeup of the actual preamp daughter board:
Click the image to open in full size.

For comparison, here my hand-made SMT prototype that I am listening too now:
Click the image to open in full size.

Measured FFT for 20vpp into 7kohm load:
Click the image to open in full size.
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Last edited by xrk971; 19th November 2017 at 04:33 PM.
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Old 18th December 2017, 11:05 AM   #4293
wdecho is offline wdecho  United States
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F4 power amplifier
Quote:
Originally Posted by Zen Mod View Post
1. yes
2. build it exactly as shown on attached pic ; you can omit R2 - it's there for cap bleeding purpose and not needed if entire shebang used as permanent OS
I decided to convert my F4 to the crippled F4 using Zen's schematic and installing a BA-3 pre board inside the case. It has made the F4 more in line with the BA-2 with BA-3 driver and made the amplifier much more versatile. Not hard to do and I have a set of spare j-fets for another project being that I already had the stuffed BA-3 board.
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Old 18th December 2017, 11:08 AM   #4294
Zen Mod is online now Zen Mod  Serbia
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F4 power amplifier
I decided to make LuDEF amp , as soon I have time
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Old 18th December 2017, 11:20 AM   #4295
wdecho is offline wdecho  United States
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Quote:
Originally Posted by Zen Mod View Post
I decided to make LuDEF amp , as soon I have time
I'm in.
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Old 18th December 2017, 06:40 PM   #4296
Zen Mod is online now Zen Mod  Serbia
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F4 power amplifier
you can be faster than Mighty Moi , if you wish

Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

fit M2 FE on it , et voila!

Click the image to open in full size.
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Old 2nd January 2018, 07:40 AM   #4297
marconi118 is offline marconi118  Germany
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Is it possible to build an f4 with only a pair of verticals and omit source resistors?
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Old 2nd January 2018, 08:04 AM   #4298
lhquam is offline lhquam  United States
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Quote:
Originally Posted by marconi118 View Post
Is it possible to build an f4 with only a pair of verticals and omit source resistors?
That would be fine if the transconductance of the verticals was high enough.
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Old 2nd January 2018, 08:06 AM   #4299
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by marconi118 View Post
Is it possible to build an f4 with only a pair of verticals and omit source resistors?
Yes I did it
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Old 2nd January 2018, 10:22 AM   #4300
marconi118 is offline marconi118  Germany
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And how it sounds?
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