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Hello, for context I am building the Killer Bee pcb and was wondering if there were any alternatives to the transistors mentioned in the title. I planned on using a 5458 to replace the 5457 just because I have those on hand. In terms of the J113/MPF102, would the 5458 be an applicable replacement as well? If so what changes would have to be made? I tried to research relevant topics in regards to alternatives but found mixed results.
Thanks in advance
I do not have J201’s on hand at the moment. However I do have J112s.
I also have already socketed the pcb
If you lookout their respective datasheets, you’ll note that while all of those named JFETs have the same pinout, they each slightly different VGS, Vgs(Off) and other characteristics. So you may need to futz with the biasing resistor values.
Damn I was writing a novel and Cybercow beat me to it!
The only thing I’d add is perhaps socket R11 and increase the bias trimmer to 20K to help with biasing
Start with the stock 6K8 at R11 check Q1 drain voltage is around 5v and adjust up or down as required
With the Q2 bias trimmer all you’re doing is giving yourself more resistance to play with and if you decide to eventually use the specified transistor types you wouldn’t have to change it
Glad I was thinking along the right lines and upping the trim to 20k! I’ll try to take off R11 without destroying the board and socket that bad boy. You know the site is good when moderators are competing with each other to help out. Bless you guys and thanks for your help Cybercow and Billy!
I wouldn’t bother taking R11 out if it’s in
Only do it if it sounds bad and you can’t get it to bias
No point in doing anything till you know just stick the transistors in the sockets and see how it sounds
If you already have a 10K trimmer in leave that too
Well I took out R11 along with the solder pad at the bottom but thankfully the board is designed to have +Va as the common connection and a connectivity test with the + side of C14 shows that the socket is in the loop. I have a Tube Screaming Preamp and Fuzzy Bee builds I’ll try and finish tomorrow and pray they work so I can continue with my G02 Animal and Killer Bee builds.
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