Blues Booster

[SoMeDaY]

Hi, I'm Jesus from Spain... I've just to build the Blues Booster that can be found in DIYstompboxes.com but I can't make it work with 2 N Channel JFET and 2 P Channel JFET as it can be seen in the schematics. If somedody has built this effect as described in this web, can you tell me how to put (D, S, G) these transistors in the circuit? With 4 N Channel JFET works but I don't know if it's sounds properly...

Thank you very much..

[Harry]

Hi, I'm Jesus from Nazareth...

[spudulike]

Can you post your layout ?

[Jaicen_solo]

If you can link the schematic here, that'd be helpful. Also which J-Fets are you using?? I'm guessing it will need N-Channel, not P-channel. Usually you'll need something like an MPF102 or J201. 2N5458's sometimes work as well.
If you've got a 2N3981 or similar Jfet, that won't work in most common circuits, but you can use it in the millenium bypass.
We need more details to help you more.

[SoMeDaY]

This is the link: http://www.diystompboxes.com/pedals/bluesbooster.jpg

N Channel are J204.. I can't find J201 here in Spain... And P Channel are 2N5460 (or 61)

[petemoore]

  A Couple of seriesed Mu Amps, by Ed Guidry, author of BSIAB, which also is a couuple seriesed mu amps.
  J201, NTE458, 2n5457 etc. Jfets will work and sound different...
  All four Jfets go in:
  Drain ['top' of transistors symbols shown on schematic]
  Gate [has the arrow]
  Source ['bottom' of transistor symbol
  For J201's usage in Mu Amps, I put the source in the middle of each transistors socket, for 'straight' pin plug in...If you put the source connection to the bottom socket lug [following schematic] you have to twist the leads of the transistor so the gate and source are reversed, then insert so drain is to the 'top' socket lug.
  The drain of Q2 connects to the Source of Q1.
  When I build these things I use 1 voltage divider [the schematic shows two of them, the two seriesed 1m resistors from V+ to ground], as per noiseless biasing...
  two 10k's make up the divider, then one large resistor per mu amp [something like 2m2 or 4m7 even, I think you can go smaller like 470k...not sure] for biasing...see GEO Mod your own mu amp.
  Might reduce noise [I haven't A/B tested noiseless bias to the setup shown], but can be fascilitated using fewer large resistors, and only one actual divider...each mu amp biased...each connected through a large resistor from 1/2v created by the two small, [I'd think at least 10k or a little larger, same value divider resistors.
 
 

[SoMeDaY]

Pete, thanks for your answer.. As you described it's the way I've put JFETs in the circuit... But, what about the P Channel JFETs below?  It's wrong that symbol?

[petemoore]

  I see all four transistors in this circuit as needing the same polarity, not up on the N' and P'...which one's which, but J201's are the type that will work, [I *Think that means N channel] others 'like the J201 will work also....2n5457, NTE 458 etc.

[roknjohn]

According to the schematic Q1 & Q3 are N channel and Q2 & Q4 are P channel. Been a while but if memory serves me, arrow to the right is N channel or NPN, arrow to the left is P channel or PNP.

[petemoore]

  Whoopes...assuming again...
  I saw what looked like 2 mu amps, and overlooked the little arrows 
  Please excuse and disregard my 'unenlightened' previous posts//

[spudulike]

Look, the schematic is fine. As said, there are two N-channel and two P-channel jfets. J204 N-channel will work and 2N5460 will work, if biassed correctly. I have built this a while ago using J201 and 2N5460.

I asked for your layout as I have not seen a layout on pcb/perf/vero published anywhere, so I used my own. If you have an error on your layout the pinout is irrelevant.

Please read the "What to do if it doesnt work" sticky and post the schem/layout links and voltage readings.

[SoMeDaY]

Spudulike... I think my layout is correct because with four J204 works fine.. Maybe I dont put correctly 2N5460's or were not fine biased as you said.

Then, with 2N5460 instead of J204 at Q2 and Q4, must I put the drain of Q2 connected to the source of Q1 as said above with J204's?

[Jered]

  They are all supposed to be N Chan. The P Chan were a mistake when the schem was thrown together. Check out Ed's BSIAB, basically an improved Blues Booster.
  Jered