Ah, no problem! Here it is (non mirror foil).
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Compact CFA (singleton)
A very good implementation of the Compact CFA in India. Experienced builder. Likes the sound a lot (tested with good JBL speakers).
Schematic and sink screen are attached so that you understand what design I'm talking about.
Cheers,
Valery
A very good implementation of the Compact CFA in India. Experienced builder. Likes the sound a lot (tested with good JBL speakers).
Schematic and sink screen are attached so that you understand what design I'm talking about.
Cheers,
Valery
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How critical is 43k for R9? Will 47k work? 43k is an odd value. I suppose I could stack a couple resistors to get there. I'm done aside from this.
Thanks, Terry
Thanks, Terry
Hi Terry,
You can do it this way - R9 = 47K, R 8 = 1.8K - for preserving 29db overall gain.
Cheers,
Valery
Hi Thimios,
I have attached the PDFs - it's double-sided, not the easiest for etching.
If you'd like me to send you gerbers - just let me know what e-mail to use 😉
Cheers,
Valery
The ALLFET is singing. Nice sounding amp. A little bit of low level noise. Maybe it is more sensitive to wiring that some of my other amps. You can see in the picture that the wiring is not real tidy but a couple other IPS hooked up the same were silent. Square waves look good but not as crisp as the CFA. Offset is <10mV.
I'm using the Mini Slew OPS. The lowest I can get the bias is 112mA with the stock setup. I will try it with the Tubsumo OPS a little later.
Blessings, Terry
I'm using the Mini Slew OPS. The lowest I can get the bias is 112mA with the stock setup. I will try it with the Tubsumo OPS a little later.
Blessings, Terry
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Hi Terry,
Looks good. Definitely not as crisp as CFA, but maintaining good stability margins and I like the way it sounds. My initial tests with TubSuMo showed some low-amplitude local oscillations at high output - I didn't even try to tame them, just switched to IRFP-based SlewMasters and those worked perfectly with this front-end. Regulaged supply for IPS boards is recommended.
Cheers,
Valery
Looks good. Definitely not as crisp as CFA, but maintaining good stability margins and I like the way it sounds. My initial tests with TubSuMo showed some low-amplitude local oscillations at high output - I didn't even try to tame them, just switched to IRFP-based SlewMasters and those worked perfectly with this front-end. Regulaged supply for IPS boards is recommended.
Cheers,
Valery
Yes, I didn't think about that. This OPS doesn't have the cap multiplier either. I only used this OPS because I just built it and was trying it out. I'll try it with the IRFP OPS tomorrow.
I played for three or four hours. It really does sound nice. It was a fun build and let me use some of the parts I had in the bin.
Blessings, Terry
I played for three or four hours. It really does sound nice. It was a fun build and let me use some of the parts I had in the bin.
Blessings, Terry
Sorry fellas but I seem to have entirely missed the IRFP OPS. Could you please point me to it?
It is a regular BJT board with a few parts jumper'd out, gate protection soldered under board and the bias circuit modified with a change in resistor plus LED added. It isn't its own version, but rather IRFPs impressed upon the regular boards.
It is a version of the Slewmaster OPS done with VFETs. Valery designed it.
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