SEN I/V stage for BIII

[sbelyo]

Does anyone here have experience with the SEN I/V stage?  I want to try this with my BIII

http://www.diyaudio.com/forums/digital-source/195483-zen-cen-sen-evolution-minimalistic-iv-converter.html

[sbelyo]

looks like I need SEN I/V v18 boards and 4 2SK369V matched quads w/heatsinks

[mypasswordis]

Please let us know how it is when you finish. Do you know where to source the heatsinks?

[Bespav]

@sbelyo:
You can even add cascode:

[sbelyo]

I don't think the original boards are available and I think the 2SK369V are out of production.  As far as the heatsinks go they look like they were made just for the original group buy a few years ago and haven't been made since.

My thoughts and or questions are:

1. is there an equivalent to the 2SK369V through hole or smt that we could match?

2. would someone be willing to layout the board

3. we should be able to find a heatsinking solution

What are your thoughts

Edited February 1, 2017 by sbelyo

[Bespav]

is there an equivalent to the 2SK369V through hole or smt that we could match?

Any JFET with preferably lower noise, higher Idss and higher transconductance.
Say, LSK170 grade C or D

You can tie upper transistor gate to a potentiometer and correct DC shift at the output.

would someone be willing to layout the board

Yeah, nice joke.
Please let me use it from time to time!

Since when layouting of 2/4 transistors became a problem?

we should be able to find a heatsinking solution

1. Cascode.
2. Mount from bottom and thermalgrease to case panel
3. 2-3-oz PCB with thick traces and ground plane
4. 3/8" air conditioner copper pipe
5. Just bend JFET case to a ground copper plane and add some thermalgrease.

[sbelyo]

6 minutes ago, Bespav said:

Yeah, nice joke.
Please let me use it from time to time!

Since when layouting of 2/4 transistors became a problem?

 

 

It is indeed funny, but I have no layout software or experience. I know, I suck

[Bespav]

but I have no layout software

Multisim + Ultiboard (simplest way to begin)
Eagle
Diptrace
KiCAD
Pulsonix
Protel
Altium Designer
Cadence
Mentor graphics

or experience

Just start to try!
Even by curiosity!

[sbelyo]

I believe you're right...

Let me try

[mypasswordis]

Hm, how about mounting SMT versions of Linear JFETs to PCB and then attach normal heatsink with screw, like this? http://www.ebay.com/itm/like/391354463361?lpid=82&chn=ps&ul_noapp=true

Personally I would highly prefer not to mount directly to a case panel

[sbelyo]

That's what I was thinking was one possibility

Edited February 1, 2017 by sbelyo

[Pars]

Re: 2SK369V

This guy on diyaudio has them, but is in W. Australia with large shipping costs. Genuine devices though. You need 4 quads matched (16 devices)? You would probably need to buy 100 devices to guarantee this level of matching (and nothing is guaranteed). Might get lucky with 50...

http://www.diyaudio.com/forums/vendors-bazaar/297423-toshiba-2sk170-2sj74-fets-other-semis-sale.html

I had some stuff I needed and would consider piggybacking an order to split shipping if you decided to go this route.

 

[sbelyo]

That looks like a good deal.  He's not matching them right?  So we have to buy 100 or so raw correct?

[sbelyo]

found this

 

 

I'm definitely going to need help with this

 

Edited February 2, 2017 by sbelyo

[Pars]

luvdunhill might match these for you, but you would need to contact him. He has a curve tracer (locky_z), and likes doing this kind of stuff. I'd ask his opinion on how many devices you might need to get a good match for 4 quads. I could probably do the board layout for you and integrate the es9018 stuff if you wanted that on board.

Edited February 2, 2017 by Pars

[guzziguy]

He'll do anything for a couple of cigars.

[luvdunhill]

Heh, I even have the heatsinks. What is so appealing about this design, anyways? I think 100 would be a good start, yeah.

[sbelyo]

I saw a bunch of posts saying this was a whole different ballgame compared to the ivy or legato. But it seems like a lot of work and the cost of sourcing hard to get parts.

Maybe it would be worth it if there were parts we could use that are currently available. What do you think ?


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[Bespav]

Maybe it would be worth it if there were parts we could use that are currently available. What do you think ?

Yes.
LSK170D + Cascode 2SC3503.

Increase I/V supply to about +- 100-150 Volts.

And you just need to simply bufferize I/V output via some kind of good follower.

You can even take well known Pass F5 and realign it's input and ground like this:


Let your DAC output current to flow there.

[Pars]

You could do Colin Toole's I/V stage... he may even have some boards left (you would need 2 if you intended balanced). I built up a balanced set and used them in the Adcom CD player that recstar24 had. You could ask him what he thought of them?

http://www.head-fi.org/t/316795/discrete-i-v-converter-board

[luvdunhill]

What do you think?

Ditch the ESS. Feels like lipstick on a pig.

[sbelyo]

What's the next step up? Soekris?


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[sbelyo]

8 hours ago, Bespav said:

 

Yes.
LSK170D + Cascode 2SC3503.

Increase I/V supply to about +- 100-150 Volts.

And you just need to simply bufferize I/V output via some kind of good follower.

 

You can even take well known Pass F5 and realign it's input and ground like this:


Let your DAC output current to flow there.

High voltage, hmm  maybe worth a shot but there's this

http://www.diyaudio.com/forums/digital-source/195483-zen-cen-sen-evolution-minimalistic-iv-converter-188.html#post4961030

And, I heard back from someone that had it working with the BIII albeit in single ended config he said it sounded weak and sold the setup.  Then reading a bit further someone else reported the same.  There are two people that may have working ver 18 boards that they're willing to sell and are to get back to me soon.

Let me do some more research

[Bespav]

maybe worth a shot but there's this

Corner idea was posted much more earlier:
http://myelectrons.com/hotfet-pre-j-fet-audio-preamp/


Just tie it's input to the ground and blow your DAC's current to it's output.

[Bespav]

High voltage, hmm

Exact hmmm!

I can't forgive and keep in mind my first time i have heard an amp with +-150 Volts VAS supply. Truly different from common and usual +-15 V opamp-based and something like +-40-70 V discrete ones.