John Curl's Blowtorch preamplifier

[john curl]

Scott, better bearings.

 

[john curl]

PMA, what is this amp of Edmund's? Is it powerful? Is it single N ch? I don't have much to go on at the moment? 800KHz? Sounds like about what I make for Parasound, except that I have a higher open loop bandwidth and a lower amount of feedback.

 

[Edmond Stuart]

PMA, what is this amp of Edmund's? Is it powerful? Is it single N ch? I don't have much to go on at the moment? 800KHz? Sounds like about what I make for Parasound, except that I have a higher open loop bandwidth and a lower amount of feedback.

Hi John.

1. Usually I'm called Edmond, not Edmund. (can't you read?)
2. If you are really interested in my design you might put your questions to the person who designed it.

Cheers,
Edmond.

PS: Talking about communication, read Paul Watzlawick. I'm sure it'll help you to avoid blunders like this.

 

[john curl]

Sorry, your name is not usual to me. I do not make mis-spellings on purpose. However, it shows your level of communication with me, which is not very good, I am afraid.

 

[dimitri]

Edmond,
You are talking about MCP, aren't you?
Thanks

 

[GK]

Hi Pavel

>800kHz fT is very, very low.????

I don't think so. The fT of the (BJT) blameless amp is a bout 1MHZ, Bob's EC amp does about 2MHz. Remember, this is the fT of the NFB loop, not OLG.

Cheers,
Edmond.

I agree. That was a bit of a daft and misleading comment. It doesn’t matter if your open loop gain begins rolling off at 200Hz or 20kHz, if you have a reasonable amount of global nfb you aren’t going to have a stable amp with a ring emitter BJT or lateral MOSFET output stage with a unity loop gain much beyond 1MHz (if even 1MHz) and 2MHz with a vertical MOSFET output stage.
But maybe if you’re magically capable of defying the lays of physics. Such people that can abound. Their ears are sensitive to 2fs phase modulation and they have the authority to denounce any engineering effort beyond their capabilities and ingenuity on the basis of open loop bandwidth.

 

[john curl]

Every p-second counts, in my opinion.

 

[GK]

Every p-second counts, in my opinion.

Pico seconds !?
We're down femto seconds man!

 

[john curl]

p-seconds is good enough for me, maybe we should look for another measurement.

 

[GK]

p-seconds is good enough for me, maybe we should look for another measurement.

So how many of your power amps have p-second PIMD then?

 

[Edmond Stuart]

Edmond,
You are talking about MCP, aren't you?
Thanks

Hi Dimitri

No. I'm talking about the PCP amp, a new design. I'll let you know when I've put it om my website.

Cheers,
Edmond.

 

[Edmond Stuart]

Sorry, your name is not usual to me. I do not make mis-spellings on purpose. However, it shows your level of communication with me, which is not very good, I am afraid.

I was referring to my second point, what else? To avoid any miscommunication, I'll repeat it here:
2. If you are really interested in my design you might put your questions to the person who designed it.

Apart from the fact that Pavel doesn't even know my design, don't you understand how strange it is (to put it mild) to ask somebody else for inquiries regarding an amplifier of mine.

 

[john curl]

I find Pavel easier to follow, and more objective in his responses to me, so I would rather ask him first, even about your design, as it might be presented somewhere on this website, and I can then make up my own mind about it, without any 'salesmanship' added into it. You do appear to be advertising something.

 

[john curl]

Glen, I once built a 250W power amp with ring emitters that had an initial 6 MHz closed loop bandwidth. Would you like to buy it?

 

[GK]

Glen, I once built a 250W power amp with ring emitters that had an initial 6 MHz closed loop bandwidth. Would you like to buy it?

So?
No.

 

[john curl]

I thought you were saying that it was virtually impossible for a ring emitter with negative feedback to have a stable gain over 1 MHz. Did I read you wrong?

 

[GK]

I thought you were saying that it was virtually impossible for a ring emitter with negative feedback to have a stable gain over 1 MHz. Did I read you wrong?

Yes you did read wrong. I clearly said a unity loop gain frequency of 1MHz and reasonable amounts of global negative feedback (like ~34dB loop gain at 20kHz).

 

[john curl]

I would have thought that I had a fair amount of negative feedback at 20KHz in order to reach 6MHz and have some closed loop gain.

 

[GK]

I would have thought that I had a fair amount of negative feedback at 20KHz in order to reach 6MHz and have some closed loop gain.

 

[PMA]

10 years ago I would probably agree with Glen and Edmond on most of their points. After having passed many listening tests in the last 6 years, I do not agree, and my experience comes more and more close to that of John.