How does the ACA compare to the other amps on the list from Post #38? It would be interesting to know what would be different should I try something beyond the basic ACA.
Thanks in advance...
Konstantin,
I still use the pair of Tea-bags's of assembled F6 board that you sold to me.
I use this with semisouth R125 jfets and I really like it as NP described.
That would be my favorite FW amp as well. I tried it with both jfets and mosfets and I can't say which one I like better. Mosfets have more sparkle on the top and jfets are more realistic in midrange... Bad thing I played with adjustable version when I was in that point of my life... looking for a lowest THD, so missed some sweetness most likelyI was thinking of revisiting maybe, but it will never happen as too many projects. Thinking of making B1 korg, that might give me what I need. Stay safe guys!
I still use the pair of Tea-bags's of assembled F6 board that you sold to me.
I use this with semisouth R125 jfets and I really like it as NP described.
Regarding FW amps, I have an M2 with overkill double mono power supply and an F6 built with ok/generic parts and simple stereo supply. The M2 has its merits but I allways return to the F6 and use it now with a moderately 2nd harmonic B1 Korg.
I have a F5 kit that I have not yet built and a 90% finished Sissy SIT and even an unbuilt Neurochrome Modulus-86. The F6 is so good in my system that the build pressure is greately reduced and my El34 and 300B amps are shelved and unused.
Conclusion: don't build an F6 as you might be too happy with it and stop building amps
I have a F5 kit that I have not yet built and a 90% finished Sissy SIT and even an unbuilt Neurochrome Modulus-86. The F6 is so good in my system that the build pressure is greately reduced and my El34 and 300B amps are shelved and unused.
Conclusion: don't build an F6 as you might be too happy with it and stop building amps
Conclusion: don't build an F6 as you might be too happy with it and stop building amps
Nah. You just need discipline to continue building, and rotate your amps.
True I need to pull myself togetherNah. You just need discipline to continue building, and rotate your amps.
Conclusion: don't build an F6 as you might be too happy with it and stop building amps
Agree totally
There is small to no need to try and improve on it. Unless one's Hobby is building amps...finding satisfaction in the building process
Forgive me, but I catabolized my F6 for Aleph J...I did keep boards, figuring on latter rebuilding it with a set of the proper outputs, which I have stashed somewhere...well the Semi south versions, not your special ones.
I don't remember the store boards having a P3? Maybe I forget. Is there another way to adjust "arbitrary 2nd harmonic character"?
I found my DIY F6 to be similar to DIY F5 which I still listen to. May be touching up 2nd harmonic would make a difference? My F5 needs updating, older build, my first build, and it is without P3.
Russellc
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Awesome thank you sir for the quick response!
Hmmm now I'm reading that a lot of the transistors for many of these amps are virtually impossible to find now.
Now I'm trying to figure out something else...Which Pass DIY amps use semiconductors (and all components really) that are fairly easily obtainable, today in 2020, for the average DIYer?
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I did something a bit different with my F6. Since I already had an M2x and an Aleph J, I wanted to explore a slightly higher power envelope. Using a pair of Antek AS-3222 transformers with SLB power supplies, I arrived at 26V rails with 1.85A bias current. The input stage is a Diamond buffer, and the output Mosfets are FQH44N10.
With these basic parameters, my F6 presented a different sonic character than either of the two large Papa amps. Perhaps a blend of the two, especially with the Austin IPS in the M2x. However, there was an extra level of dynamic detail that was further enhanced when I added 24,000 uF caps on the output of the SLBs. This variant proved to be very enjoyable with hard hitting music with good bass content. Also very clean sounding.
At the suggestion of 2 picoDumbs, I started fiddling with the H2 content by adding some AC degeneration resistance to the upper output device in each channel. I finally arrived at a value of 0.068 Ohms, which I happened to prefer over the cleaner measuring configuration. So that's how you can tweak the character of the F6 using otherwise fairly standard Mosfets. Worth a try.
I still listen to my Aleph J a lot, but the F6 is just fun to play with.
With these basic parameters, my F6 presented a different sonic character than either of the two large Papa amps. Perhaps a blend of the two, especially with the Austin IPS in the M2x. However, there was an extra level of dynamic detail that was further enhanced when I added 24,000 uF caps on the output of the SLBs. This variant proved to be very enjoyable with hard hitting music with good bass content. Also very clean sounding.
At the suggestion of 2 picoDumbs, I started fiddling with the H2 content by adding some AC degeneration resistance to the upper output device in each channel. I finally arrived at a value of 0.068 Ohms, which I happened to prefer over the cleaner measuring configuration. So that's how you can tweak the character of the F6 using otherwise fairly standard Mosfets. Worth a try.
I still listen to my Aleph J a lot, but the F6 is just fun to play with.
What about the Burning Amps?
I am curious about your opinions about the Burning Amps compared to the FW amps mentioned in this thread.
I have built the F5, BA2 and the BA3 with BA2 output stage. I found the F5 to be dynamic and fast, with great bass control but a bit cold sounding for my liking, still a great amp. The BA2 was more laid back, with a smooth, warm mid-range. The BA3 is my favourite, very natural sounding, a big soundstage, warm but detailed mid-range. Unfortunately I do not have any of them anymore. Got a new pair of speakers and they needed much more power. I am thinking of changing speakers again to something that is an easier load so I can go back to class A.
I am curious about your opinions about the Burning Amps compared to the FW amps mentioned in this thread.
I have built the F5, BA2 and the BA3 with BA2 output stage. I found the F5 to be dynamic and fast, with great bass control but a bit cold sounding for my liking, still a great amp. The BA2 was more laid back, with a smooth, warm mid-range. The BA3 is my favourite, very natural sounding, a big soundstage, warm but detailed mid-range. Unfortunately I do not have any of them anymore. Got a new pair of speakers and they needed much more power. I am thinking of changing speakers again to something that is an easier load so I can go back to class A.
Think I found my answer at the end of post #50...
" I later modified my amp to add AC degeneration to the upper Mosfet in each channel. That increased the relative amount of H2, and the overall THD. I liked the sound, so I kept it that way"
Thanks TungstenAudio….and Mr Pass whose quoted dialog says its possible in post #39!
https://www.diyaudio.com/forums/pass-labs/253334-sound-various-pass-amps.html#post6151356
Russellc
I agree the characteristic of the F4 is heavily influenced by what's driving it.
One of these days I'll try a 300B amp with the F4.
On Saturday I did a quick comparison of the F4 and AJ (both DIY).
The AJ felt a bit softer while the F4 had better bass control and a
crisper, more extended high.
I enjoyed both.
Dennis
One of these days I'll try a 300B amp with the F4.
On Saturday I did a quick comparison of the F4 and AJ (both DIY).
The AJ felt a bit softer while the F4 had better bass control and a
crisper, more extended high.
I enjoyed both.
Dennis