Heavily modified revebr unit by BJFe, treated by Chris Stelloh.
A couple of the tweaks are from Björn - in particular, the 2k2 resistor from the source of Q1 to ground. Lowering that value fixes a volume drop that can happen when the 50k dwell pot is maxed. I replaced the second dwell pot with a 10 ohm fixed resistor, so that it is almost at maximum. I also added a flat-mids BMP tone control and BC337 recovery stage that sounds really great paired with this circuit. Using a PN3269a in Q2 can squeal with feedback (a GOOD thing in my world) so dialing in the 10k output trimpot is a necessary step. It is possible to set it so that it only howls when the dwell+mix are turned to maximum. The charge pump is something I redrew from an old tagboard layout. The 555 doubler puts out 30mA of current which this verb circuit needs most of (the schematic says it draws around 20mA, and that was before I added the extra transistor) no matter what voltage you are running it at.
Hey all - the transistor in Q2 is a Pn2369a (which I listed correctly on t6he layout but mislabeled when I sent Anders an explanation that he cut and pasted here). I chose this because of it's tendency for high frequency feedback when pushed but it can be subbed with Bjorn's original 2n1613 (which is an NPN silicon BJT around 70-80hfe) or one of the Fairchild low gain silicon dot transistors that Small Bear has.
ReplyDeleteThe right 1/3 of this drawing is the BMP tone control and recovery stage and if you can identify the bits from the many available schematics of this popular circuit (the 2x10nF caps, the 22k & 39k resistors for the tone control/ the 2x100nF caps, the BC337, the 390R+10k+100k+1m resistors from the LPB-1 recovery stage) you can, of course, change them to your preferred values if you want.
Where can I the schematic?
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DeleteSo... you can find the schematic linked in the original post on here of the BJF Analog Reverb - however, I did not use that schematic for the same reason that I am skittish about drawing up layouts for any of Bjorn Juhl's circuits... he hand-scribbles the circuit diagrams and they are very hard to read. In the case of this circuit, I simply modified what Anders (who is better at this than I am) had all ready drawn.
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