John Curl's Blowtorch preamplifier part II

[Trevor White]

Originally posted by dimitri
Trevor, I read it twenty years ago...

I might be wrong but from my recollection of the AES article the design bootstraps directly from the non-inverting input, whereas the thing that you are talking about takes its bootstrap from the output of the opamp.

regards
trev

[john curl]

Trevor, my associates and I are working on something similar. I have not heard and compared the results yet to a JC-1 power amp, but it will be revolutionary, if it works as well as my associates already tell me it does. It is under patent protection, already, so please look elsewhere for schematics. This is where I am using the AD825, kindly given to me by Scott Wurcer, (with advantages) to be a key part of the design.

Also, just yesterday afternoon, I got my 797 based phono stage in operation. It looks so 'wimpy' compared to my mighty Vendetta preamps nearby, but I have hopes that it will sound OK. The tech and I found a wrong valued part that kept it from working right from the get-go. Now, I have to align the RIAA to much better than 0.1 dB by using an HP3562 in sine-sweep mode with a Jung-Lipshitz designed inverse RIAA passive network that has served me well, over the decades. I can measure fairly easily to .025 dB, so why not get it right?
I am having lunch with Jack Bybee, who is bringing his latest QUANTUM filters to put into his Vendetta Research Phono stage to replace the existing quantum devices. I just love to solder and unsolder gold plated circuit boards, just to replace 'imaginary' devices. Especially with my bad eye, and no tech, today. Such is the life of a tired old man, well past his prime (this is true) with marginal test equipment. I hope that Jack will then take me to Chez Panisse, but I will settle for the restaurant, next door, because they don't insist on reservations, and the chef used to work for Alice, in the past. They make the 'perfect' martini, and I will have one, if I go there.

[dimitri]

Trevor, this is Sandman follower

[Bob Cordell]

Originally posted by john curl
It is under patent protection, already, so please look elsewhere for schematics.

Hi John,

Can you provide us with the patent number or the patent application number? I'm interested.

Cheers,
Bob

[Bob Cordell]

Originally posted by Wavebourn


Fortunately "P-type" tubes were not invented so we don't listen to horrible sounding symmetrical cathode followers.
I am joking Bob, but very seriously.

FYI, masking effect means the closer harmonics are to fundamental frequency, the less they are audible. But I know the rumor exists that high level of low order harmonics make high order harmonics inaudible, but it is not true. All of them, from fundamental frequency and up, mask closest higher order harmonics. 2'nd order does not mask 7'th, 8'th, 9'th, etc... harmonics. It masks the 3'rd order one, but up to some relative level only, and the higher is the loudness of the entire sound, the better it masks.

Hi Wavebourn,

I think I made a poor choice of words when I used the word masking, perhaps leading to confusion. I was not referring to audible masking of PIM. Instead, I was referring to the fact that an amplifier with, say, 0.05% distortion might have 0.01% PIM, and you would never know it from the measurement. At 0.05% distortion, that could be with or without PIM. The point I was trying to make is that while an amplifier with 0.001% THD-20 leaves very little wigglwe room for there to be PIM, one cannot draw much of a conclusion about PIM in an amplifier with 0.05% measured distortion without resort to a PIM analyzer.

I think that 0.001% THD-20 (or all CCIF spectra below -100 dB) is sufficient for confidence in extremely low PIM, but it is not necessary.

Cheers,
Bob

[john curl]

Sorry, I don't have the patent #'s available, not my patent.

[Wavebourn]

Originally posted by Bob Cordell



I think that 0.001% THD-20 (or all CCIF spectra below -100 dB) is sufficient for confidence in extremely low PIM, but it is not necessary.

Hi Bob;
nice to see you here again.
Do you know of some measurement system that is capable of drawing waterfalls with levels in decibels of error products in respect to input signal level, with frequency? Such graphs would be very revealing.

[KSTR]

Originally posted by Wavebourn
Do you know of some measurement system that is capable of drawing waterfalls with levels in decibels of error products in respect to input signal level, with frequency? Such graphs would be very revealing.

It's a bit unclear what you mean exactly, Anatoliy. Could you elaborate a bit?

- Klaus

BTW @all: I started a request for seperate boards to deal with measurement techniques, electrical and acoustical. Such are badly needed on this forum to seperate out (and find again later) these interesting topics, so please vote for it:
http://www.diyaudio.com/request/vote.php?id=131

[Wavebourn]

Originally posted by KSTR
It's a bit unclear what you mean exactly, Anatoliy. Could you elaborate a bit?

- Klaus

BTW @all: I started a request for seperate boards to deal with measurement techniques, electrical and acoustical. Such are badly needed on this forum to seperate out (and find again later) these interesting topics, so please vote for it:
http://www.diyaudio.com/request/vote.php?id=131

I did vote, thank you Klaus.

What do I mean is,

X: frequency,
Y: level of output signal in respect to input signal,
Z: level of input signal.

It is a spectrogram, but taken with many grades of input signal (in decibels). I am pretty sure it will reveal much more than any modern measurements about an amplification chain.

I used such a software when SY still lived here, in his laboratory, to check my Pyramid-V tube amp, but I had to dial input signal level manually observing an output behaviour. If to feed an input through D/A controlled attenuator such a procedure can be easy automated, data stored, and a waterfall picture constructed. It is better to have it 3-d, rotatable.

[Bob Cordell]

Originally posted by john curl
Sorry, I don't have the patent #'s available, not my patent.

John,

Can you just pick up the phone and ask your friend for it? If it is really something that is covered by a patent, the number itself is not something proprietary.

Otherwise, how am I to know you are not just blowing smoke where the sun don't shine?

Cheers,
Bob