JFET 2SK44SP substitute: 2SK30A or 2N5457?

[Bucksears]

I'm working out a DIY Ibanez CS-505 project and came across four 2SK44SP's in the schematic. Another thread I found here listed 2NSK30A's as a suitable replacement (that and the 2SK30 are $1 each at SmallBear).
Just wanted to know if there is a more common replacement for the 2SK44SP, something I might already have on hand.

Thanks,

[R.G.]

Depends on what they do in the schematic.

Link?

[armdnrdy]

The 2SK44SP is a commonly used switching JFET used by Ibanez for the FET switching. Are you planning to include the FET switching in your build or delete that section and make it true bypass?

2SK30s are fairly common. If you're looking at the cost......well the cost of through hole transistors just went up a couple of months back. Through holes are being phased out by most manufacturers.

As far as the price goes, you can shop around and find a more competitive price.

[Bucksears]

Depends on what they do in the schematic.

Link?

Here you go:

http://www.4thlevelmedia.com/smallpics/CS505schem.pdf

[R.G.]

OK. Switching JFETs with 1/2 of 9V to run the shutoff. 2SK30, 2SK30ATM, 2N5292, 2N5485, and I think 2SK117 or 2SK118. There are others, but none of them are really common. A J201 is not what you want. You're looking for the maximum value of Vgsoff to be between -3V and -4.5V.

[Bucksears]

Thanks R.G. - I'll look into one of these.

Are you planning to include the FET switching in your build or delete that section and make it true bypass?

I'd prefer to omit the FET switching section to save space on the board, but not sure EXACTLY what that comprises. This will be true bypass so I can incorporate a mixing trimmer so there's no volume boost when it's engaged.

Thanks,

[R.G.]

It might be easier to raise the value of R129 and/or lower R130 to lower the output level a bit.

In this circuit, the JFET switches Q105, 106, and 107 are open when their gates are near ground, and closed (i.e. passing signal) when their gates are pulled up and the diode in front of the gate lets the gate float wherever it will. Q105 and 106 select for whether delayed or dry signal goes into the output mixer, and Q107 is turned on all the time if there is no plug in the dry output. This means that there is a proper mix in the normal output if there is no dry output plug inserted. If a plug is inserted, Q107 is no longer allowing dry into the normal output all the time, so the normal output flips between only delayed and dry when bypass is flipped. This makes the normal output either dry only or delayed only, presumably for external mixing or something.

I don't know exactly what they were intending with all that.

[Bucksears]

It might be easier to raise the value of R129 and/or lower R130 to lower the output level a bit.

Correct - I was going to replace R130 with a 10K trimpot.

I'm guessing the two outputs was for stereo?

Do you know what parts I can omit for the bypass portion so I can use hardwire bypass?

[R.G.]

I'm guessing the two outputs was for stereo?

Don't know. The "dry output" was never going to get any delayed signal, only the ... well, dry signal, the way it's set up. When it was plugged into, the normal output became either delayed+dry, or dry.

Do you know what parts I can omit for the bypass portion so I can use hardwire bypass?

Pull out Q105, Q106, and Q107. Install a jumper from source to drain holes on Q105 and Q106. It now does the delay+dry mix all the time, no matter what the footswitch and LED say.

... or you could go to http://geofex.com/Article_Folders/bosstech.pdf for "The Technology of Boss and Ibanez Switching" and graft in a small relay using the flipflop circuit that's already there and not have to hog out a hole and fit in a hard footswitch.

Just a thought.

[Bucksears]

Thanks R.G.
Did you get my PM?