Yes, that's it. I would just add 100u low ESR cap directly at LM3x7 outputs to ground - the chips like it.
You mentioned TL431 too, but there's none in the sch. ?
The sims do not show any improvement adding a cap directly from LM3x7 output to ground, but we know about the limitations of sims.
TL431 was a "brain fart", thinking about a different circuit.
I have been listening to an uncrippled F4 driven by the Curly-F4 gain stage for about 2 months and have not found anything definitive to complain about. However, I am having some issues with my B&W CDM1 in combination with my highly asymmetric and reflective listening room.
Today, I switched back to listening to another nearly identical, uncrippled F4 driven by my Impasse. My first impression is that the Impasse might sound better, but I am not sure that I can yet describe the difference. I intend to continue with the Impasse+F4 listening for a while. I currently do not have a good way to do quick switching for A/B testing. The biggest problem is the need for attenuators on one of the gain stages to equalize the levels.
Today, I switched back to listening to another nearly identical, uncrippled F4 driven by my Impasse. My first impression is that the Impasse might sound better, but I am not sure that I can yet describe the difference. I intend to continue with the Impasse+F4 listening for a while. I currently do not have a good way to do quick switching for A/B testing. The biggest problem is the need for attenuators on one of the gain stages to equalize the levels.
Something about the dynamics and esae of presentation you get from tube preamps is hard to match with SS. The only thing I have found that is similar is symmetric version of your Curlian FE. I have not built the exact stage, but something similar and in general, balanced/bridged amps seem behave more like what is described above.
Completely unsupported audio babel on my part, of course. Just opinion.
Completely unsupported audio babel on my part, of course. Just opinion.
You could be right, but in theory a balanced version would only have better cancellation of even harmonics and possibly better PSRR. I am looking forward to the results of your balanced build. Since I now have two F4s to play with, I could also try such a balanced front end. I will consider that.
I did another set of harmonic distortion measurements of 3 different front-ends for the F4. The front-ends are:
The Impasse and Curly-F4 sound much better than the BA3-FE. I currently give the Impasse the edge on sound quality.
- BA3-FE
- Impasse
- Curly-F4
The Impasse and Curly-F4 sound much better than the BA3-FE. I currently give the Impasse the edge on sound quality.
Attachments
Aleph J is amp with gain , so having some of own sound signature
F4 is power buffer , without voltage gain ....... and completely embracing sound signature of preceding voltage gain stage (preamp)
so - direct comparison isn't possible .......... while judging Aleph J on it's own , you need to judge preamp/F4 combo
F4 is power buffer , without voltage gain ....... and completely embracing sound signature of preceding voltage gain stage (preamp)
so - direct comparison isn't possible .......... while judging Aleph J on it's own , you need to judge preamp/F4 combo
Hi Ihquam,
Those graphs represent a serious amount of work. Thank you for posting them.
I am building a BA-3B + F4CR and I have to say that your results are somewhat discouraging.
I'm using the 313/2013 pair and I will place my faith in the hope that they will improve the sound over the Fairchild parts.
Graeme
Those graphs represent a serious amount of work. Thank you for posting them.
I am building a BA-3B + F4CR and I have to say that your results are somewhat discouraging.
I'm using the 313/2013 pair and I will place my faith in the hope that they will improve the sound over the Fairchild parts.
Graeme
A/B listening tests
This post reports A/B testing of the Impasse+F4 vs. Curly+F4. The Curly gain stage is a variant of the LSK Pre without an output buffer, intended to drive an uncrippled F4.
I recently finished my A/B preamp+amp testing setup. It consists of two DPDT 24V DC relays to switch the speakers between two amplifier outputs, and a pair of trimmer pot attenuators for the inputs to one of the preamps (the Impasse in this case). The relays are controlled from the listening position with SPST switch at the end of a 16 foot telephone extension cable. The trimmers were carefully adjusted for identical amp outputs at 1kHz. With the gains balanced, flipping the switch is virtually undetectable.
I have listened for many hours to a variety of music and cannot repeatedly detect any differences between the Impasse+F4 and the Curly+F4.
I would like to do similar tests using my STAX Lambda Pro headphones without the F4 amps to better isolate differences between the two voltage gain stages. This could be done by using a stereo RCA switch box to select between the two front ends, and attenuating the output to the STAX by about 10:1.
This post reports A/B testing of the Impasse+F4 vs. Curly+F4. The Curly gain stage is a variant of the LSK Pre without an output buffer, intended to drive an uncrippled F4.
I recently finished my A/B preamp+amp testing setup. It consists of two DPDT 24V DC relays to switch the speakers between two amplifier outputs, and a pair of trimmer pot attenuators for the inputs to one of the preamps (the Impasse in this case). The relays are controlled from the listening position with SPST switch at the end of a 16 foot telephone extension cable. The trimmers were carefully adjusted for identical amp outputs at 1kHz. With the gains balanced, flipping the switch is virtually undetectable.
I have listened for many hours to a variety of music and cannot repeatedly detect any differences between the Impasse+F4 and the Curly+F4.
I would like to do similar tests using my STAX Lambda Pro headphones without the F4 amps to better isolate differences between the two voltage gain stages. This could be done by using a stereo RCA switch box to select between the two front ends, and attenuating the output to the STAX by about 10:1.
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