John Curl's Blowtorch preamplifier

[alansawyer]

I care more in how it sounds, or how it may impact the sound – I care less in how it works.
I DO know that there are things I neither know nor understand and I'm fine with it.
Concerning my audio system, I have it to enjoy music, rather than increase my knowledge.

Thanks.
I bought recently 100 of them on eBay from a fellow from China.

Hopefully you are not a victim, but there is a lot of counterfeiting going on with components. I have seen more evidence with Power Transistors than anything else but be aware.

 

[gerhard]

everything else away. NOW, Toshiba jfets rule the scene, except that they are disappearing from existence.
The next manufacturer who will mostly fill in for Toshiba is Linear Systems, and they will probably be what we will have available in future, in jfets. They will be more expensive, but they should do for most applications.

Or Interfet http://www.interfet.com/pdf/DS_IF3602.pdf
Not without merit, but the capacitances are too high for my purposes.

Crystalonics may have sth. useful, too.

I went back to bipolar, b/c I need a very low 1/f noise corner and FETs just
don't cut it there. And I hate it that JFET producers barely can fill the
first page of a data sheet.

regards, Gerhard

 

[Joshua_G]

Hopefully you are not a victim, but there is a lot of counterfeiting going on with components. I have seen more evidence with Power Transistors than anything else but be aware.

I DO trust my ears, therefore, it's quiet unlikely that anyone is going to sell me snakes oil.

 

[scott wurcer]

Or Interfet http://www.interfet.com/pdf/DS_IF3602.pdf
Not without merit, but the capacitances are too high for my purposes.

Crystalonics may have sth. useful, too.

I went back to bipolar, b/c I need a very low 1/f noise corner and FETs just
don't cut it there. And I hate it that JFET producers barely can fill the
first page of a data sheet.

regards, Gerhard

They must figure it's cheaper to sample and let the customer evaluate. It's a shame, the LSK170's actually have less Igx than the typical 2SK170.

100mV on a dual, why bother? We used to buy hand matched pairs at 15mV, they must be sandbagging that spec.

 

[alansawyer]

I DO trust my ears, therefore, it's quiet unlikely that anyone is going to sell me snakes oil.

This wasn't to do with the sound and getting persuaded to buy something that was not effective, it is a serious awareness warning that fake components are being made and sold.

See http://sound.westhost.com/fake/counterfeit-p1.htm#mj15003 for a picture of an example.

I have no idea if tantalums caps are being made this way but anything is possible.

 

[Joshua_G]

This wasn't to do with the sound and getting persuaded to buy something that was not effective, it is a serious awareness warning that fake components are being made and sold.

See http://sound.westhost.com/fake/counterfeit-p1.htm#mj15003 for a picture of an example.

I have no idea if tantalums caps are being made this way but anything is possible.

Indeed, anything is possible, especially with Chinese. I'll test the capacitors.

 

[syn08]

At CES there was a strange metal ball that was placed between the speakers. Talk about a 'graven image' BUT it did something right, at least in that demonstration setup.

I care more in how it sounds, or how it may impact the sound ? I care less in how it works.
I DO know that there are things I neither know nor understand and I'm fine with it.
Concerning my audio system, I have it to enjoy music, rather than increase my knowledge.

I just finished a listening session where one subject was always placed between the speakers.

We noticed a net improvement in the sound, which means the ball(s) number and material is not critical.

I don't need to understand why this is happening, but I really enjoyed the music.

 

[alansawyer]

What was strange about the metal ball?

Was it a round ball like for soccer, or was it more like a rugby ball? What size was it?

Was it shiny like silver, chrome or stainless steel or more yellow shiny like gold? or maybe dull like Aluminium?

Did you get a chance to see how massive it was? Was it solid?

 

[john curl]

If they are heavy and have a kink on one side, they are probably real. If they tarnish on the outside, then they may be silver. I wouldn't worry too much.
The caps MUST be DC biased or they break. But then, their DA and impedance is very good. It is the SOLID tantalum, especially dipped in plastic, that are the most difficult to use without adding low frequency distortion and significant DA. I published the distortion in an IEEE paper back in 1978.

 

[dimitri]

They must figure it's cheaper to sample and let the customer evaluate. It's a shame, the LSK170's actually have less Igx than the typical 2SK170. 100mV on a dual, why bother? We used to buy hand matched pairs at 15mV, they must be sandbagging that spec.

Scott, pardon my ignorance, but what is Igx?
You mean 'tight' matching Ugs1-2=20mVmax?

 

[Joshua_G]

If they are heavy and have a kink on one side, they are probably real. If they tarnish on the outside, then they may be silver. I wouldn't worry too much.

It's almost 1 AM here. I'll post some photos tomorrow.

 

[john curl]

They will get better. (I hope)

 

[hifimaker]

I spoke with the Linear Systems rep a few months ago. They are a boutique fab house and will customize the parts for you if you are buying in quantity. The rep said they will customize the performance of their parts and build to specific performance parameters.

-David

 

[john curl]

Talked to consultant to Linear Systems. Fur will fly!

 

[hifimaker]

Talked to consultant to Linear Systems. Fur will fly!

Hi John,

I bet more than nearly anyone else, you could max out their ability to customize. I've often thought "what if an accomplished audio application designer and builder spec'ed jfet properties"

We would certainly have some very interesting parts to experiment with!

-David

 

[john curl]

They are smart people, but they still lack experience.

 

[scott wurcer]

They are smart people, but they still lack experience.

Dr. John Hall, lack experience? Again you're speaking without thinking first.

If you think they can make a 1nV FET with 5pF of capacitance think again. They could parallel 4 - 2SK170's on one die, but that's essentially what that Interfet part is. The LSK170 noise is pretty good, a least the ones I measured. They have low Ron P-channel switches, has anyone even looked at their noise? (forget what the data sheet typ is). I tried some Vishay J111's and they were pretty good actually.


Igx is excess gate current at high Vgd. I'll bet they can't fix that either.

 

[dimitri]

Igx is excess gate current at high Vgd. I'll bet they can't fix that either.

It's a shame, the LSK170's actually have less Igx than the typical 2SK170.

please, Scott, which one is correct?

 

[scott wurcer]

please, Scott, which one is correct?

The LSK is a"little" better maybe you get a volt or two more Vdg. I am using Gig-Ohm gate resistors so it matters a lot. Sanyo's FET''s are good too BTW.

 

[john curl]

Scott, why don't you give some feedback to Dr. John Hall? Why expect me to do so? Pch is the real problem.