DOD FX-10 Bi FET PREAMP

[ironman28]

Okay I tried a PNP layout for the 410. quick and dirty unverified.
corrections appreciated
http://i232.photobucket.com/albums/ee168/ironman-28/dod%20410/410pnp.gif
http://i232.photobucket.com/albums/ee168/ironman-28/dod%20410/410pcb.gif

I didn't leave any space for the mechanicals for mounting. Also the circuit would benefit from a power supply filter and polarity protection.
Maybe a good circuit to install inside a guitar 

[Ben N]

Either of these circuits would also be a good candidate for one of those RS IC boards, I think.

[sevenisthenumber]

[comfortably_numb]

Anyone care to point out what can be removed for true bypass switching?  Probably benefits from the buffer, but I'm not going to fool with relays, and like to keep things as simple as possible.

Thanks

[Ben N]

I love how the jfet switches only touch the feedback loops of the opamps. We're so used to clunky Boss-style fet switching requiring two buffers to be added to the circuit just to deal with the low R-off of the switches, yet this is so elegant. I thought about changing the switching so that only one opamp is left in the signal path in bypass/buffer mode, but that would require putting a jfet switch in the signal path.

Just sayin'

[Steben]

I don't believe much in the JFet Opamp rage (don't forget most JFet Opamps only have fets in the input). They "could" be pleasant, I don't feel it. There is always the "mojo" 4558, LM308 and the low-noise 5532, which all are bipolar AND have high input impedance as well, since any "opamp" should.
I really like the rail-to-rail (like the 2262) opamps however, since they boost just to power voltage as no other (which is ideal for low supply voltage) and for the simple fact most are CMOS opamps. They ARE full Fet chips.

[ironman28]

Anyone care to point out what can be removed for true bypass switching?  Probably benefits from the buffer, but I'm not going to fool with relays, and like to keep things as simple as possible.

Thanks

Remove the JFets and replace with a wire, the resistors across the D-S should be removed too. Every thing on the lower right is part of the switching and can be eliminated.
You could use mechanical switches in place of the JFETs to keep the opamps in the signal path.

[Ben N]

... and the low-noise 5532, which all are bipolar AND have high input impedance as well, since any "opamp" should.

I guess it depends what you mean by "high input impedance." Unless I misread it, the datasheet for the 5532 gives min r_i as 30k and typical = 300k. Not exactly comparable to the input-r of a TL0xx. Of course, depending on where you place the booster in your chain, it may not matter. But first in line, right after a high-impedance pickup (and certainly after a piezo) it matters--the low-noise bipolar will affect your highs that the jfet-input preserves.

[ilcaccillo]

Hi,
anyone has the schematic for for the Low-Z XLR output?

thank you so much