John Curl's Blowtorch preamplifier part II

[bcarso]

next time I won't just clik thru the "user survey" - they have broken the site for engineers who know what the part they want is called

That's a good idea! They need feedback, and my reflex, nearly, is to bypass the damn surveys --- but this is an opportunity.

 

[morinix]

JC is playin' hard to get "Last Activity: Today 09:25 PM"

 

[jacco vermeulen]

He's on the phone with Snowden.

 

[Kindhornman]

Jacco,
He is probably offering Snowden sanctuary in San Francisco as that is a sanctuary city!

 

[jacco vermeulen]

Can I apply too ?

 

[scott wurcer]

Scott Wurcer,
In the thread where you have your discrete opamp design how would you take that basic premise and use it in a preamp? I have tried to stay up with that thread and was wondering how you would practically implement that design into a working circuit rather than the old obsolete and almost impossible to obtain devices that so many still are designing around?

Not quite sure what you mean. It is workable with just the BF862 type FET and I hope Linear Systems keeps up at least some availability of P-channel devices if you want those. The folks that insist on the rarest of the old Toshiba parts, I can't help. I am not into magical properties of a select few discrete families. I've used ordinary parts right from Digi-Key for the most part. Not sure if the J310 family is still made by somebody.

I plan to present something at Burning Amp.

 

[simon7000]

Not sure if the J310 family is still made by somebody.

In current production as a preferred device J309 & J310 from On Semiconductor.

Mouser stocks them in depth.

 

[31697B]

I plan to present something at Burning Amp.

Hi Scott---- I've looked from time to time and maybe missed it.... do you have FFT's for your design... where?

Thx-RM

 

[scott wurcer]

In current production as a preferred device J309 & J310 from On Semiconductor.

Mouser stocks them in depth.

Thanks, they make a good high Vgs cacode for BF862's that does not need another reference rail (just the gate (J310) tied back to the source (BF862)) and of course they are VERY cheap.

 

[scott wurcer]

Hi Scott---- I've looked from time to time and maybe missed it.... do you have FFT's for your design... where?

Thx-RM

Somewhere, in any case I will be building a clean prototype (the patches got a bit messy) and repeating everything. I remain pretty convinced a 20dB line stage can drive 600 Ohms at < 10ppm at 20V p-p and 20kHz with the single gain stage. The first prototype looked to be 3ppm or so but my setup at the time was not great.

Jason will be welcome to put any presentation into the permanent archive.

 

[bcarso]

Off topic here but briefly tossed around in this thread, and of possible interest, the subject of the effect of I-V converter input impedance on current-output DAC performance, based on some calculations and simulations: http://www.diyaudio.com/forums/digi...-makes-r-2r-dac-nonmonotonic.html#post3565135

I decided it was best to start a new thread.

Brad

 

[31697B]

Where is JC ?

 

[simon7000]

Where is JC ?

He is visiting other sites where folks don't abuse him. After a break he will come back to this brawl.

 

[SY]

Where is JC ?

Berkeley. MLK Blvd, if memory serves.

 

[jacco vermeulen]

isn't that TMI ?

 

[SY]

No, but it's near OAK.

 

[jacco vermeulen]

It's OK, Buffalo Bill says it's not the right type of skin.

 

[DF96]

He is visiting other sites where folks don't abuse him.

So asking reasonable questions and offering alternative opinions is now 'guru abuse'?

 

[jan.didden]

So asking reasonable questions and offering alternative opinions is now 'guru abuse'?

It's in the eye of the beholder...

 

[Bonsai]

Maybe he's with Thorsten? 😀