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Old 9th November 2008, 09:47 AM   #1
Cobra2 is offline Cobra2  Norway
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Default SSTART Preamplifier

Nobody tried the SSTART Preamplifier yet...?

http://www.enjoythemusic.com/diy/1108/sstart.htm

Arne K
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Old 9th November 2008, 10:07 AM   #2
Luke is offline Luke  New Zealand
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I was wondering the same thing.
I think this is the art pre Grey talks about in the article.

http://www.geocities.com/rjm003.geo/...io/diy_ls.html
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Old 10th November 2008, 12:35 AM   #3
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Quote:
Originally posted by Luke


I think this is the art pre Grey talks about in the article.

http://www.geocities.com/rjm003.geo/...io/diy_ls.html


Try this link, instead:

http://www.conradjohnson.com/It_just...ght/a-art.html

Note that the ART itself has been discontinued. There is a similar model called the ACT2 in the current CJ product line; the general idea is the same.
The circuit is inexpensive to build and as simple as you could wish for. It's also modular, which gives you the ability to change the gain to suit your needs.
Although I generally use PC boards, the SSTART is simple enough that it can be built using point to point wiring without undue difficulty. It can be built in an hour or two, which is nice if you're in a hurry, and there's not a lot of junk in the signal path to screw up the sound.
I happen to have about a zillion J271s on hand (a P-ch part very similar to the J310, though not technically a complement) and I keep meaning to throw together a P-ch version. Just never seem to find the time.

Grey
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Old 10th November 2008, 02:40 AM   #4
Luke is offline Luke  New Zealand
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Grey,

do you know if the circuit I posted is a clone of the ART preamp?
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Old 10th November 2008, 04:06 AM   #5
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Given that the original ART used ten tube sections (5 x 6922, all sections paralleled) and the one you linked to shows four sections, total, I'd say it's a definite no. Besides, he says it isn't--just read a review and got excited. He says he hasn't even built the thing.
I glanced at the schematic and saw something that looked a little odd, but I'm so tired I'm cross-eyed and might have misread things.
File it under "inspired by" and go from there.
I've got a small pile of 6922s and had thought about making a run at the ART, but decided to go with solid state. I've got another tube preamp circuit that I'd probably do first if I were to do tubes. Either 6SN7s or 6922s...remote chance I'd use 12AX7s, who knows? I'll cross that bridge when I come to it.

Grey
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Old 10th November 2008, 11:53 AM   #6
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Quote:
Originally posted by GRollins
I glanced at the schematic and saw something that looked a little odd, but I'm so tired I'm cross-eyed and might have misread things.

The absence of current sharing resistors in the cathodes?
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Old 10th November 2008, 12:22 PM   #7
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by GRollins
Given that the original ART ...

Grey

as you say ...... and to complete :

Ub=160V
Ua=90V
Uk=1V3

grid stoppers , each cathode separately biased , no degeneration

well , I'll not say that this operating point is best
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Old 10th November 2008, 05:41 PM   #8
Cobra2 is offline Cobra2  Norway
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How much gain does it give (or how do I calculate gain)?

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Old 14th November 2008, 01:38 AM   #9
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250 pieces of J310 on the way to me ... I'll give this one a shot. I can't promise anything before 2009 however

Thanks for this one Grey

P.S. Will it work as a headphone amp?
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Old 14th November 2008, 09:47 AM   #10
h_a is offline h_a  Europe
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Just by a short glance at the schematic, every jfet runs at about 5mA, so 20mA total current. That gives 0.04W into 100 Ohm headphones.

I would go for something stronger (more current).

Have fun, Hannes
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