MSG To Paul Stamler

[kornowsd]

Hi Paul;

I was going to attempt the mods on the Oktava MC012 that you had published in Recording Magazine a few years back. You note, in that article that you can only use the Toshiba 2SK170BL J-FET. This part is no longer in production and I can't find a datasheet that shows the differences between the original 2SK170 and the BL-series.

Linear Devices (I think that's the company) now reproduces the 2SK170-series, but not the BL. Can I use that???? Or, what would you recommend as a modern-day counterpart? Why the BL series in the first place?

Thanks.

Dar

 

[bcarso]

Toshiba , for the moment at least, still does manufacture the 2SK170. The BL is just the Idss code for 6 to 12mA (GR 2.6-6.5, V 10-20). You will not find the part number directly with the Idss codes but in the "fine print" at the bottom of the first page of the datasheet the Idss codes are there.

Linear Integrated Systems is second-sourcing their version of the SK170. Thier Idss code is the same as Toshiba's. In addition to the through-hole part LIS also offers an SMD package.

If you only need a few pieces of an equivalent part I have quite a few 2SK364's in the BL binning. These are identical, the part number only reflecting the characterization for switching apps rather than amp apps. If you have difficulty finding someone to sell you the SK170 in BL, PM me and I will send you a couple.

 

[adrianh]

Dar;

Toshiba make this part buy the zillions.
It is in EVERY junky asia mic made.

I typed "2SK170" into google and gor 1600 hits.
Look around you will find.

OK to be real honest that part is a little easy to get in asia.
But a little hard here.
But check www.bdent.com and www.mcmelectronics.com

NOTE MCM is lost in space and they do not know what part they have.
ASK then to look on the part and tell you if not do not give them your money.

Do a search here for that part. Lot of good info from "bcarso"
These FETS are made with the diffusion process this and the fact it is a JFET the transconductance varies greatly for wafer to wafer and even
over the surface of the wafer.

Since the part's (gain, simplified) varies a lot the part is made by the zillions and on the end of the production line the part is graded in 3 different Idss grades.
See the bottom of the first page of the datasheet.
that says;
Note: IDSS classification GR: 2.6~6.5 mA, BL: 6.0~12 mA, V: 10~20 mA

Datasheet here

The reason for the BL cond for that mic is they were running
that mic from phantom power and the fet still needed to be
turned on and not fully saturated.

This reply has taked me too long and bcarso has beat me to the punch.

To learn a lot about FETS go to Mr. Borbely site here.
http://www.borbelyaudio.com/special_articles.asp

Down load the 2nd and the 3rd articles there "The New Frontiers"
articles.

Read them 10 times. Then download his other articles. You will learn something reading his articles.

 

[pstamler]

Hi Dar and other folks:

Looks like y'all came up with the answers before I saw the thread. That's good, because I didn't write the Oktava mod article; that was my colleague at Recording, Scott Dorsey. He doesn't hang out here, but he's a regular on the rec.audio.pro newsgroup. If you need to ask him questions about the mod, that's the place -- he's very helpful. And a nice guy, too.

Peace,
Paul

 

[kornowsd]

EVERYONE - Thanks for the quick comments and professional response. I certainly appreciate it.

Paul - My sincere apologies... I can't read, either. :roll:

BTW: I read your article in "Audio Express" on caps. What stopped your op-amps from oscillating finally? Interestingly enough, I did the same thing on my Fender Hot Rod Deluxe, the other day, and the op-amps in the reverb circuit are now feeding back uncontrollably. Thanks again.

Dar

 

[Flatpicker]

Get them here: http://www.bdent.com/search/search.jsp?contains=2sk170&category=ALL They have a minimum order charge, though.

You want the 'BL versions.

If you only want to buy 1 or 2, it may be cheaper to just get them straight from Scott if he still sells them. His website is http://www.techwood.org/kludge I think his email address is on there somewhere.

 

[pstamler]

[quote author="kornowsd"]EVERYONE - Thanks for the quick comments and professional response. I certainly appreciate it.

Paul - My sincere apologies... I can't read, either. :roll: [/quote]

Not to worry -- getting mistaken for Scott Dorsey is no insult!

BTW: I read your article in "Audio Express" on caps. What stopped your op-amps from oscillating finally? Interestingly enough, I did the same thing on my Fender Hot Rod Deluxe, the other day, and the op-amps in the reverb circuit are now feeding back uncontrollably.

A ceramic disc, 5 or 10nF as I recall, connected between the V- and V+ pins of the offending packages, tack-soldered right to the bottom of the board, with short leads.

Peace,
Paul