John Curl's Blowtorch preamplifier part III

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While they pretend measurements are the only way to evaluate the quality of an audio gear, they are absolutely not interested by the subject to improve the performance of their measuring instruments.
They just try to make their images shining with their little friends by trying to tarnish that of the others. In a constant inelegant and unfriendly way.
A phenomenon well known on social networks, they

Yes, measurements rule. Including ABX based hearing tests. I don't think you are addressing me personally, but if you were, let me assure you that improving measuring equipment and measuring technique is high on my agenda. But please leave my little shiny friend out of it.
 
First your amp will get the -140 test gear and if that shows promise, go to the full blown ultra low system.

I can't wait to see the measurements results on the "-140 test gear" and in particular on this magic "ultra low system". My guess, nobody is ever going to see a shred of coherent data from you, other than some "mine is longer" photos of measurement gear displaying some numbers, at best good to impress the n00bs. You haven't shown anything else, ever.
 
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What about the measurements of the room acoustics where you've done your listening evaluations to find out which amp is good sounding?

yes. what would you like to know from me about that specifically? What room acoustic measurements are of interest to you?

I use equalized flat low distortion headphones and near-field monitoring so there is very little room influence or none.

I use controlled directivity speakers for additional minimizing of first/early reflections; New QUAD ESL and JBL M2.

Both very flat and very low distortion. The ESL are in Bangkok. I have to get the big heavy M2 here some time in 2020.



THx-RNMarsh
 
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... If it is about stability of the final version, that is something that I master since 1970 and all the precautions has been took to can compensate-it nicely on the bench without any printed board modification. No other way, we don't cook on the restaurant table. Clipping behavior ? Look-at it.

I don't know a better way to verify the solidity of an amp, than torturate-it on the bench...
That is what I am concerned about. Compared to the < 1MHz ULGF amp, it is going to need more thorough tests and optimization to ensure stability on various load. Wide BW amps are notorious in oscillation dept.
 
That is what I am concerned about. Compared to the < 1MHz ULGF amp, it is going to need more thorough tests and optimization to ensure stability on various load. Wide BW amps are notorious in oscillation dept.
That is all the interest of this exploration. At least for me. No challenge, no fun.
This said, my actual CFA is rock stable and not lot slower.
One of my goal, too, was to see if any good to design an amp fully from simulations. This is new to me, i always worked on the bench from the early beginning. I like to learn by experiences. No risk, no experience ;-)

Happy Christmas to all of you and your families.
 
Can you describe in a general way what the amplifier circuit topology is?

mc head preamp - Quad MC with ZTX devices, but balanced in/balanced out
mm preamp - conventional balanced in/balanced out mike preamp with JFET input devices
preamp/headphone amp - fully differential (balanced in/balanced out) like OPA1632 with MAS6116 R-2R volume controls, input stage similar to LM6172
power amp - balanced input, input stage similar to LM6172
 
mc head preamp - Quad MC with ZTX devices, but balanced in/balanced out
mm preamp - conventional balanced in/balanced out mike preamp with JFET input devices
preamp/headphone amp - fully differential (balanced in/balanced out) like OPA1632 with MAS6116 R-2R volume controls, input stage similar to LM6172
power amp - balanced input, input stage similar to LM6172
Power fets or bipolars ?
I had a look at photos of the inside. Elegant.
 
mc head preamp - Quad MC with ZTX devices, but balanced in/balanced out
mm preamp - conventional balanced in/balanced out mike preamp with JFET input devices
preamp/headphone amp - fully differential (balanced in/balanced out) like OPA1632 with MAS6116 R-2R volume controls, input stage similar to LM6172
power amp - balanced input, input stage similar to LM6172

Thank you. something to look at and think about and learn from.

Is the over-all topology a VFA or CFA or CMA in line level?

(DAC level)


THX-RNMarsh
 
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