Russian Article about Fet tube emulation.

briggs · Post by **briggs** » 05 Sep 2007, 12:35

I've been looking at this: http://www.sugardas.lt/~igoramps/article68/article.htm

My russian, however, is crap. So I don't understand what the hell is going on! Can anyone explain what exactly the article is on about? Would it be possible to adapt one of these stages into a 9v tube type booster?

bajaman · Post by **bajaman** » 05 Sep 2007, 12:40

ah - those crazy Russians

bajaman

analogguru · Post by **analogguru** » 05 Sep 2007, 13:03

Hmmmm.....
And why don´t you read the cited patents (links at the bottom) from which this article has been derived ?
yes .....really.... they are in english...

analogguru

briggs · Post by **briggs** » 05 Sep 2007, 13:04

I never spotted them, I was too busy trying to fumble my way through the google translation!

briggs · Post by **briggs** » 05 Sep 2007, 14:59

When I go to click on the patent link it wants me to download a .djvu file? What the hell is this?

P.S : Has anyone got any ideas for suitable values for components here:

To have this thing run as a simple 1 fet buffer/booster off of 9v? Fet's and transistors are not my forte!

analogguru · Post by **analogguru** » 05 Sep 2007, 15:16

.djvu is a (special) fileformat like .pdf (or .jpg).

Hmmm....when you have some time, maybe you can look for an account at freepatentsonline or a similar possibilty for free download of patents ?
In the meantime you can try this:

US Pat. 5647004

US Pat. 5619578

analogguru

celadine · Post by **celadine** » 05 Sep 2007, 17:57

Patent to pdf:

http://www.pat2pdf.org/

You'll have to type in the patent numbers manually. It generates a single pdf file from that mess the U.S. patent office gives us.

briggs · Post by **briggs** » 05 Sep 2007, 19:18

Thanks Guru and celadine. I'll get reading. I would expect more questions though!!!!

I'm feeling stupid today

briggs · Post by **briggs** » 05 Sep 2007, 19:43

So basically what I can tell - I need to bias the drain to approx 0.5 of the supply voltage which would be around 4.5v of a 9v supply and I need to bias the source to around 0.2 of the supply voltage?!

I'm lost here.... Why did I never take those russian classes!?!??!

estragon · Post by **estragon** » 05 Sep 2007, 22:02

Drain is biased to 2/3 of the supply voltage, which means 6V for a 9V supply.

Regarding the calculation of the resistors, go to the original article (linked in the first post) and scroll down to Figure 7, then, just below there is a link to an MS Excel spreadsheet that does all the calculations for you.

From top to bottom enter 9 V for the supply voltage, 22 kohm for the drain resistor, 0.8 V for the JFET's pinch-off voltage, and 0,6 mA for Idss (this data is for an average J201), then you get the following for the source resistors:

r = 0,68 kohm (680 ohms)
R = 2,39 kohm (use 2k4 or closest available value)

If I understand correctly, the diode should be a germanium type. You may use 1N34A or 1N60.

Good luck.

briggs · Post by **briggs** » 05 Sep 2007, 22:07

Thanks a bomb Estra, I've been fiddling with that Excel thing for about an hour now trying to work out what all those symbols were... I'm just moving into learning all about Fet and the like, I've done opamps - fully versed in their operation. I've been reading this too - a good resource for Fet N00bs: http://www.runoffgroove.com/fetzervalve.html It has the required data for a J201 too

Thanks again!!!

estragon · Post by **estragon** » 05 Sep 2007, 22:14

briggs wrote:Thanks a bomb Estra, I've been fiddling with that Excel thing for about an hour now trying to work out what all those symbols were... I'm just moving into learning all about Fet and the like, I've done opamps - fully versed in their operation. I've been reading this too - a good resource for Fet N00bs: http://www.runoffgroove.com/fetzervalve.html It has the required data for a J201 too

Thanks again!!!

Hi, that Fetzer Valve article is exactly where I took the J201 values. Really handy.

I noticed that changing the drain resistor to 22k is not really necessary. In my spreadsheet the "R" value didn't fit in the cell and appeared as "####", thus I assumed it was invalid. Now I noticed it is a problem with the cell being too small to display the value. 100k drain resistors do work here. Too small resistors may give a negative value for "r".

In this example it is interesting to put a 12k drain resistor, as this makes the "r" vanish to 0, so you omit one resistor.

briggs · Post by **briggs** » 05 Sep 2007, 22:24

So would it be best to stick in a 100k trimmer for the biasing of the fet drain to 6v?

I'm looking forward to playing with this tomorrow. I've got to read up that fetzer valve article fully, it looks like just what I need to understand these little bastard Fet's! At the moment I'm completly lost....

ubersam · Post by **ubersam** » 05 Sep 2007, 23:21

briggs wrote:...

I could be completely off but, that looks just like a booster but with a lone clipping diode at the input. The full schematic, http://www.sugardas.lt/~igoramps/articl ... age090.jpg, looks like three of them in series after the first booster w/o diode. Looks interesting.

grolschie · Post by **grolschie** » 05 Sep 2007, 23:30

In English.... well kinda.

briggs · Post by **briggs** » 06 Sep 2007, 09:15

Yeah, I battled through a Google translation - Not easy to understand. I read that RunoffGroove article and I think I just about understand Fets now

I just want to see if I can make a nice single stage booster out of this thing

Jim777 · Post by **Jim777** » 06 Sep 2007, 13:10

I have that page from a few weeks ago there was a complete schematic of a preamp at the bottom of the page that isnt there now.

Jim777 · Post by **Jim777** » 06 Sep 2007, 13:12

Oops it's there just not in the translated one

Jim777 · Post by **Jim777** » 06 Sep 2007, 13:16

There's some interesting stuff here about tube emulation http://www.pritchardamps.com/pritchardamps.cfm

soulsonic · Post by **soulsonic** » 06 Sep 2007, 20:34

That diode is for biasing, not clipping.
In the text, it says that the diode should be a low voltage-drop type; either a Schottky or a germanium. I'd use a germanium for extra mojo.

Viktor Kempf is the MAN! I highly recommend all his articles that can be found at http://www.rusblus.ru
Just click on stuff until the tech articles come up - that's what I did!

I believe these are the original articles that Igor based his on.

I'm planning on having my own version of these ideas in my blog sometime. I understand Russian well enough to be able to "read between the lines" of the garbage Babelfish translation to get what's going on. My understanding of Russian vocabulary is very poor, but I can read the alphabet well and I've come to realize that many electronics terms are very similar phonetically to the English equivalents. It comes in handy when translating Russian transistor and valve datasheets.

I really love the ideas presented in these articles, and I think it's important that we give them a serious look. Viktor has done alot of really good work and I think it's something that deserves to be shared. Thanks for starting this thread up Briggs! I've seen it mentioned here and there, but no one's really followed up with a deep discussion of it.