John Curl's Blowtorch preamplifier

[KSTR]

Re: Re: PIM

Hi Edmond. Yes, it's just a guess of mine that doing an AC analysis with different DC offsets would reveal PIM. I have not tried it yet.

Maybe you missed my Post #6530, where I just tried that, showing only the closed-loop amplitude response vs bias. Now here, for the same test conditions, the phase plot from 1kHz to 20kHz, showing some 1deg max delta between different DC bias values.

- Klaus

 

[Steve Eddy]

Steve that looks like 40yr old technology ala "High Times".

Yeah. They don't measure as well as some of the more modern stuff, but they sound fantastic!

se

 

[Charles Hansen]

These Sanyo FET's were only a tiny bit worse than the Toshiba ones at half the Ciss. I wonder if they make P-channel.

Unfortunately, no.

Scott, did you see my post a while back asking you if ADI would be interested in making an IC dedicated to high-end audio?

 

[Steve Eddy]

Scott, did you see my post a while back asking you if ADI would be interested in making an IC dedicated to high-end audio?

You mean perhaps something other than just an opamp?

How about a hybrid device? Seems that could get you a long way in the miniaturization department and would likely even be reasonably affordable.

se

 

[john curl]

Charles, since you are using this thread to communicate with Scott, I might interject an opinion. I don't think that Scott can help you in any real way, since he does not believe in what you and I do and know. IF you could get Barrie Gilbert or at least one of his circuits with some sort of fet input, then maybe we could all surge forward with a quality chip.

 

[EUVL]

> These Sanyo FET's were only a tiny bit worse than the Toshiba ones at half the Ciss. I wonder if they make P-channel.

Scott,

I searched the Sanyo website as well as Japanese DIY websites, and could not find any P-channel. See :

http://www.diyaudio.com/forums/showthread.php?s=&postid=1533270&highlight=#post1533270

While there were a few of those sites mentioning the use of 2SK223 (supposedly because of the high Vds rating) as frontend diffpairs, I could not even find a supplier on the net for any of them for small quantities, including 2SK222 (other than the usual Chip Inventory sites).


Patrick

 

[hitsware]

then hook some fets to the inputs of one of these

http://www.intersil.com/data/fn/fn475.pdf

isn't that a 'Gilbert" cell ?

 

[gerhard]

>
While there were a few of those sites mentioning the use of 2SK223 (supposedly because of the high Vds rating) as frontend diffpairs, I could not even find a supplier on the net for any of them for small quantities, including 2SK222 (other than the usual Chip Inventory sites).

www.segor.de

2sk223 EUR 0.70 @ 1 EUR 0.57 @10

no 2sk222, however.

regards, Gerhard

 

[syn08]

www.segor.de

2sk223 EUR 0.70 @ 1 EUR 0.57 @10

no 2sk222, however.

regards, Gerhard

http://www.tenfourltd.com/ it's the Sanken/Sanyo arm of bdent.com

Does not have 2SK222 in stock right now, but they'll stock it pretty soon.

http://www.bdent.com/ does have 2SK223 in stock but it's very expensive.

 

[Sigurd Ruschkow]

2sk373

If anyone wants to use a high voltage Nch JFET, Toshiba's 2SK373 is still available to buy at around a dollar a piece.

Maybe a bit low on the Yfs at around 4mS and high gate leakage, but noise is good for line level signals.
Well, I think I will stick with cascoding.....




Sigurd

 

[john curl]

We are approaching the bottom of the barrel in fets. Back several decades. It is OK to use these fets, but there are plenty to be had. They are not on the unavailable list.

 

[Steve Eddy]

Excuse me if this is a silly question, but, why the need for P?

There seem to be some good N channel FETs out there, but they're essentially rejected because they have no P compliment.

Is there no way at all to achieve as good or perhaps even better distortion cancellation using only N devices?

se

 

[john curl]

NO, and if you had been studying this thread, you would know this.

 

[Charles Hansen]

Oh, come on John. Two N-channels with a push-pull transformer have to be at least as good as a complementary pair.

Right?

Right???

Right?????????

 

[john curl]

If you say so.

 

[Steve Eddy]

Oh, come on John. Two N-channels with a push-pull transformer have to be at least as good as a complementary pair.

Right?

Right???

Right?????????

Hmmm...

Why not?

Take a look at the first and third quadrants of a B-H loop for a high nickel core. Are they any less complementary than any of the complementary JFET pairs out there?

se

 

[john curl]

Duh!

 

[PMA]

PMA, good that you are still here. Jack Bybee came over this week and we did some listening tests too. Lots of fun, and my hi fi needed some TLC, as I tend to neglect it. Jack brought over a NEW item of interest, then we got into his expensive Mercedes and went to lunch at a fancy restaurant. (You see, Jack is independly wealthy from other investments, not audio, he just does audio for the love of it)

John, just returned, and results of listening tests were great for discrete complementary - differential, against opamp based designs.

 

[PMA]

In fact it is only Blowtorch I am interested to compare with. If it is Hamburg, it is not impossible.

 

[Steve Eddy]

Oh, come on John. Two N-channels with a push-pull transformer have to be at least as good as a complementary pair.

Right?

Right???

Right?????????

Actually, after doing a little research, it seems that the answer is in fact, "Right."

With regard to distortion cancellation of the complementary differential, John has said "You people worry too much about superficial things."

According to John, the real advantage of complementary differential is "...that it creates two separate signals that are opposed in DC voltage from each other. This gives 2 times the gain, without any phase delay increase."

Ultimately, so does two N-channels with a push-pull transformer.

An externally hosted image should be here but it was not working when we last tested it.

se