John Curl's Blowtorch preamplifier

[janneman]

Originally posted by 1audio
I set up a fixture similar to John Curl's with a few changes to measure the MLC sample I have. I used a Tek 7a22 preamp and a matched pair of P6055 probes to look at the differential. I revised the bridge a little, drove it through a transformer to reduce the HF common mode stuff and created a synthetic reference at approx the differential potential (the reason for the transformer isolation).

The top is the source waveform- a 1 mS pulse with a 10 mS rep rate, the middle is a cheap mylar (I couldn't find a generic X7R Ceramic) the bottom is the NPO multilayer ceramic. The scaling is accurate- the middle is X 1000 and the bottom is X10,000. Getting a balance at these ratios (CMRR of 10,000) at the higher frequencies is very difficult. The differences from the reference cap ( A Component Research film and foil Teflon in a plastic case with pure copper non-magnetic leads) is very small.

Demian,

Interesting and revealing. I might have missed it, but how is this measured? Sending the puls into the cap with the other side loaded to ground? What's the load impedance?

Jan Didden

[Sigurd Ruschkow]

I run 20dB gain and a few MHz at -3dB.
OL freq resp is a few 100kHz.
Pure class A. 30W.



Sigurd

Originally posted by syn08


Don't worry, that's not the reason I am currently running 8MHz unity gain for a 200W power amp, and nobody said anything about lunatic fringeness.

[Edmond Stuart]

Originally posted by Joshua_G
..................
I'm not an electronics engineer. I stated it over and over in this thread.
.................

Okay not exactly an 'electronics engineer', but according to your profile (i.e. your own words) 'Profession: Electronics technician'.
See: http://origin.org/ucs/profile.cfm?uid=114153

[GK]

Originally posted by ostripper
Glen ,I told andy that I don't have that anymore , since I was most
jealous and frustrated by it. Simulate it yourself, but don't use his input stage.. use what you know is best. This seems to
be like apples and oranges ,as I still am not not sure whether
he (steve) was referring to just the krill current stage or
the whole design (or some unknown mystery design).

I am absolutely objective and would love to gnaw on
that unknown design..
OS

OK, but after you edited with this:
"edit: I do 1k- 10k -20K now ,both at medium and pre clip power"
I figured that you were about to simulate it again

I did simulate it (just the OPS) myself and I'm utterly bewildered than anyone else here could have simulated it and found it working as advertised (especially with 0.005% THD), hence my request for your *.asc file.

Cheers,
Glen

[ostripper]

You are a hard man to please, MR. kleinschmidt..

It will be in my "WWW" in 12 hours using better devices
with good models (no ON's). (directory .... frugalamp\other)
edit: its there now .. original and just OPS

OS

[scott wurcer]

Originally posted by Steve Dunlap



Are you saying that only an "audiophile" would bother to design a circuit with a little bandwidth before the application of feedback?

Yes, in general as a "religious" stance. For instance putting a resistor to ground on a perfectly good VAS solely for the purpose of lowering the OLG to a 100k rolloff point rather than 100Hz (made up example).

[scott wurcer]

Originally posted by audiowolf
Its kind of like the same idea that some religious folks have that the Earth and Universe is only about 6K years old...that fossils and stuff tens of thousands of light years away in space was "created here" specifically to test and challenge the faithful. The TRUTH will indeed be different, for different people.

Funny this analogy keeps coming up. I sort of think of the guy grinding up stuff in his kitchen and baking it in his oven and then wrapping it around his speaker cables explaining the "sonic" results with a heretofore undiscovered quantum grain boundary effect.

After all it's the creation "scientists" that need a new model of the atom to invalidate carbon dating. Sounds familiar to me, Peter Belt, etc.

[Joshua_G]

Originally posted by Edmond Stuart


Okay not exactly an 'electronics engineer', but according to your profile (i.e. your own words) 'Profession: Electronics technician'.
See: http://origin.org/ucs/profile.cfm?uid=114153

So?

[PMA]

I do not understand that turmoil and attacks here. As a technician, and not an engineer, Joshua does not necessarily need to know what is FFT. He asked a normal, polite question, and has got a normal answer. Then a crowd of spiteful posters has appeared.

[Steve Dunlap]

Originally posted by ostripper


Yikes, I would completely redesign that one.

.0005% at 400w/w out NFB , you should be designing ALL the linear circuits for the "big boys". .05% is more realistic, giving
.0003% after NFB. Come on' ..at least divulge the topology for
this magic amp..words are cheap.
(I know it is not the "krill")
OS

I think you have added an extra zero.