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A guide to building the Pass F4 amplifier.
A guide to building the Pass F4 amplifier.
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Old 18th May 2019, 04:43 PM   #1281
wdavis009 is offline wdavis009  United States
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Quote:
Originally Posted by cal3713 View Post
And you're still driving directly, or through your DHT?

I've got an 8W DHT SET that I'll be using for voltage. Will be trying the F4 on bottom of a bi-amp setup and driving everything with the SET running a resistor. Really looking forward to hearing it this week/end, I've been trying to solve a bass problem for a year. Any amp I try beats the SET in bass, but loses too many other places... And bi-amping with an active crossover killed coherency. Hoping the F4 solves all of that.
Yesterday I hooked the F4 up as follows: PS Audio Directstream -> PassLabs XP10 -> Bottlehead S.E.X. -> F4 -> Harbeth 7es3. It sounds exactly as Nelson and everyone else has claimed: tone, texture and warmth of the S.E.X. with drive and bass of a much more powerful amp. I am thrilled with the sound and the flexibility of this amp. I have used tube amps for the past 15 years...various Audio Research and Conrad Johnson amps. I've tried a few solid state amps on occasion, the last being a PassLabs Int-60 that replaced an Audio Research VSi-75. I could live with that amp, as well as the F6 I built, instead of any of the Audio Research amps, except maybe my old CA-50 (it has a bit of a mid-bass bump and warmth not found in current AR models that makes it a very engaging amp to listen to). But no solid state amp I have heard to date has ever gotten me to consider giving up my Conrad Johnson Classic 60. It is the one I have always come back to. While there are certainly solid state and tube amps that are quieter, more detailed, more accurate, more of all the things high-end reviewers generally rave about, none have the the BIG sound that the Classic 60 has. The F4 driven by the S.E.X. has it. It sounds warm, rich and BIG with all the resolution I want. I built the S.E.X. for occasional headphone use and it is obviously not a state of the art DHT amp by any measure. So now I am wondering how good the F4 would be with an even better DHT driving it. I could easily imagine ending the amp game altogether with a pair of F4 mono blocks and just exploring different preamps in the future.
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Old 18th May 2019, 05:23 PM   #1282
Zen Mod is offline Zen Mod  Serbia
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A guide to building the Pass F4 amplifier.
now you know why I'm having Papa's Koan (F4) powered on behind my back in workshop, cruising all day long with whooping 1/2W to 1W

mostly FM program ,in my area - sole one left radio station worth listening

(so called cultural programme , all others are commercial )
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Old 18th May 2019, 06:05 PM   #1283
drpro is offline drpro  United States
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A guide to building the Pass F4 amplifier.
I have built a pair of F4 amps. And I agree it is fun to rotate the various preamps I have into the F4s. Of the amps I have built these are my favorites.
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Old 18th May 2019, 09:14 PM   #1284
Russellc is offline Russellc  United States
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A guide to building the Pass F4 amplifier.
Quote:
Originally Posted by 6L6 View Post
...maybe? It depends on how good a solderer you are.

What solder are you using? Is it lead-free? Might be part of the issue.,,
Good guess, when properly soldered I find enough flow both sides are good. Since I had a bad joint on Wayne's Line Stage, I check. If the leg through hole is a tight fit, I flip it over and hit it on that side too. Uh, after a third check for correct part and orientation!

Russellc
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Old 18th May 2019, 10:35 PM   #1285
cal3713 is offline cal3713
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Join Date: Mar 2014
Quote:
Originally Posted by wdavis009 View Post
Yesterday I hooked the F4 up as follows: PS Audio Directstream -> PassLabs XP10 -> Bottlehead S.E.X. -> F4 -> Harbeth 7es3. It sounds exactly as Nelson and everyone else has claimed: tone, texture and warmth of the S.E.X. with drive and bass of a much more powerful amp. I am thrilled with the sound and the flexibility of this amp. I have used tube amps for the past 15 years...various Audio Research and Conrad Johnson amps. I've tried a few solid state amps on occasion, the last being a PassLabs Int-60 that replaced an Audio Research VSi-75. I could live with that amp, as well as the F6 I built, instead of any of the Audio Research amps, except maybe my old CA-50 (it has a bit of a mid-bass bump and warmth not found in current AR models that makes it a very engaging amp to listen to). But no solid state amp I have heard to date has ever gotten me to consider giving up my Conrad Johnson Classic 60. It is the one I have always come back to. While there are certainly solid state and tube amps that are quieter, more detailed, more accurate, more of all the things high-end reviewers generally rave about, none have the the BIG sound that the Classic 60 has. The F4 driven by the S.E.X. has it. It sounds warm, rich and BIG with all the resolution I want. I built the S.E.X. for occasional headphone use and it is obviously not a state of the art DHT amp by any measure. So now I am wondering how good the F4 would be with an even better DHT driving it. I could easily imagine ending the amp game altogether with a pair of F4 mono blocks and just exploring different preamps in the future.
That all sounds great. Can't wait to finally get mine up and running.
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Old 20th May 2019, 04:20 AM   #1286
cal3713 is offline cal3713
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Missing a couple resistors, but stuffed and soldered a new board today. Much better. After soldering (the top again), I flipped the board and had fully soldered leads on almost all of the bottom. Just went ahead and hit those few from the other side too. Looks much better, thanks for all the tips...
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Old 21st May 2019, 02:08 PM   #1287
cal3713 is offline cal3713
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Got the remainder of the parts yesterday (thanks for the mosfets Wade!) and finished up the boards.

Started the biasing procedure, but unfortunately 10k at P9 is too high (can only get up to .10v bias at cold startup) and 4.75k is too low (can only get down to .15v at cold startup). Linked a couple 4.75s to try and get down a bit from the 10k, but didn't get a chance to bring it up before bed time. Hopefully I can finish today and order some 7.5k resistors to get the bias in the sweet spot.

Also, here's some pictoral evidence of the improved soldering technique... only needed to add solder to two leads on the bottom here, everything else flowed fully through.

Thanks again for all the help... and the super fast shipping Wade (wdavis009).
Attached Images
File Type: jpg 20190520_180915.jpg (645.4 KB, 63 views)
File Type: jpg 20190520_180831.jpg (591.4 KB, 63 views)
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Old 21st May 2019, 06:15 PM   #1288
cubicincher is offline cubicincher  Germany
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Join Date: Mar 2016
Location: Hechingen, South of Germany
Hello CAL3713,


your solderjoints look perfect now. Very good work!


Greets
Dirk
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