Jfet substitution for Dr.Boogie and other jfet dirt pedals!

[Denio]

Hi there,gang!
So I'd like to try out the dr.Boogie and maybe some other jfet-based pedals,but the problem is that it's impossible to find the j201(nor it's common equivalents,the mpf102 and the 2n5457 ) here in Bulgaria.
So would it be possible to exchange those for,say 2sk30atm or bf245c?
Looking at the datasheets I can see that they have a lower gate current(10ma compared to the j201's 50ma).Would that be a problem?
Maybe the pedal would have slightly less gain,but really that doesn't bother me much.
Thanks!

Denislav

[J0K3RX]

IDSS classification for a J201 is .2 mA to 1.0 mA - the BF245C is 12.0 mA to 25.0 mA 

The 2SK30A would be an excelent choice if you have the 2SK30A-R which has an IDSS classification of .3 mA to .75 mA

Problem is that the 2SK30A have R, O, Y and GR classifications and they are all different.. 

[Denio]

The 2sk's that they sell here are called 2sk30atm.I'll have a look at some other sites but this is what I got so far.

Thanks again for the quick reply! 

[J0K3RX]

The 2SK30's are made by Toshiba and they are all ATM... Look at the "Note" at the bottom of the first page under the "Electrical Characteristics" chart. You will see "Note: IDSS Classification  R: 0.30~0.75  O: 0.60~1.40 Y: 1.20~3.00  GR: 2.60~6.50

http://datasheet.octopart.com/2SK30A-Toshiba-datasheet-101654.pdf

You can tell by looking at the markings on the transistor package.. They will all have K30A on the top and the class on the bottom.

Here is "R" for example
http://i.ebayimg.com/images/i/181678316080-0-1/s-l1000.jpg

[Denio]

Ok.
So on our online electronic shop they haven't specified what type these are(and the pictures just show a blank transistor with no writings) so I will order a few and hope for the best!
By the way you said that the R version should work well because of it's IDSS,but if I grab another type with a higher IDSS,can I compensate the difference in current with the dr.Boogie s onboard trimmers?
Sorry if this is a bit of a dumb question.

[J0K3RX]

You could email your online electronics shop and ask them which ones they are carrying rather than hoping and then being disapointed... 

Can you order from here > http://www.mouser.bg/

Trimmers... no, you would have to redesign the whole preamp.

[Denio]

Nah,I'm a poor teenager so ordering from other countries will be painful.

I'm going to drop them a line and hope they have those particular ones...

Thanks again!

[J0K3RX]

How about 2N7000 or BS170 mosfets, can you get those?

[ggedamed]

Denio, what's the URL of your online shop? My impression is that the usual JFETs that can be found in post-socialist countries are BF245A/B/C and 2SK117-Y/2SK30ATM-Y.
2SK30ATM-R/O/Y and BF245A could work in Dr. Boogie with no modification other than trimmer adjusting. Because the bias is adjusted by the drain trimmer, the frequency characteristics of the Dr. Boogie builds are all over the place, along with the JFETs' parameters. So, no use chasing specific values. But if you want to replicate the frequency characteristic of the J201 stage, you could adjust the drain trimmer/resistor*, the source resistor and the source capacitor.
* To fight the noise it's recommended to replace the trimmer with a resistor.

[blackieNYC]

Americanmicrosemiconducto just quoted me -20pieces at $14.95 U.S.  each for 2sk30a-R.  Pass

[Denio]

J0KER3X:bs170-yes,and looking at the IDSS(I think it was 0.5mA) I think I'm going to get those.Thanks man!

ggedamed:The 2sk117 is available(they don't mention what type it is though,but judging by the  5mA drain current that they have specified it should work) and they only have the bf245c which I think would not be suitable.
And thanks for the tip about replacing the trimmer with a resistor.

You guys rock! 

[J0K3RX]

Americanmicrosemiconducto just quoted me -20pieces at $14.95 U.S.  each for 2sk30a-R.  Pass

These are the SMD version... 10 pieces - 0.35 cents 100 pieces - 20 cents
http://www.mouser.com/ProductDetail/Toshiba/2SK208-RTE85LF/?qs=sGAEpiMZZMv4z0HnGdrLjnwNZ9rg4nWl40oK3%2fTw9Rsiw81qNSYyVQ%3d%3d

http://www.digikey.com/product-detail/en/2SK208-R(TE85L,F)/2SK208-R(TE85LF)CT-ND/4503201

[smallbearelec]

Now that we are geared up to sort JFETs for phasers, we get many 2N5457, for example, with relatively low or relatively high Vp that would be good for lots of runoffgroove stuff. As soon as I can, I'll post a line item.

SD

[J0K3RX]

Denio, what's the URL of your online shop? My impression is that the usual JFETs that can be found in post-socialist countries are BF245A/B/C and 2SK117-Y/2SK30ATM-Y.
2SK30ATM-R/O/Y and BF245A could work in Dr. Boogie with no modification other than trimmer adjusting. Because the bias is adjusted by the drain trimmer, the frequency characteristics of the Dr. Boogie builds are all over the place, along with the JFETs' parameters. So, no use chasing specific values. But if you want to replicate the frequency characteristic of the J201 stage, you could adjust the drain trimmer/resistor*, the source resistor and the source capacitor.
* To fight the noise it's recommended to replace the trimmer with a resistor.

Agree with this.. I have seen and heard people who have used 2SK117-Y and BF245A with good results. I have not used them so I can't really say from personal experience but, many have and seems to work ok.. The reason I asked about the mosfets is because there are some really good sounding schematics based around the 2N7000 and BS170. I personally really like the sound of the mixed jfet/mosfet russian designs!