I built a Chassis that has an Aleph J in it right now but I built it with the idea that I would change out various amplifiers and I want to build a preamp to provide multiple inputs and volume control. Ideally, I would like to be able to bring both balanced and RCA inputs into it and provide a balance out to the amplifier. I have a DAC with a balanced output, a phono pre-amp with RCA, and CD with RCA. I was thinking of building a Balanced Output Son of Zen Pre (BOSOZ) amp and I hope to design a board for input control and maybe individual attenuation on it for each input if needed to get volume matching. If I get fancy I would design it to be selectable for XLR output to the Aleph or RCA output to my Tube amp or whatever. I don't think I need much gain but it seems nice to have some as an option. I have an FE 2022 connected which gives me 10 dB right now and I haven't needed more.
I would also need something for the output side for volume control. I was thinking of a relay-controlled step attenuator board for volume (does anyone have a design or PCB?) I don't need much gain in for the amps I have but it seems nice to have for the future. I like the BOSOZ because I have about 1/2 to 2/3s of the components and it seems simple.
My question is this a good solution or are there better options I should consider? Is the BOSOZ a good-sounding pre-amp? (seems like a silly question since Papa designed it)
I would also need something for the output side for volume control. I was thinking of a relay-controlled step attenuator board for volume (does anyone have a design or PCB?) I don't need much gain in for the amps I have but it seems nice to have for the future. I like the BOSOZ because I have about 1/2 to 2/3s of the components and it seems simple.
My question is this a good solution or are there better options I should consider? Is the BOSOZ a good-sounding pre-amp? (seems like a silly question since Papa designed it)
Take a look at the UGS Muse here in the Pass Labs forum. Very good sounding. An Aleph P could also fit your requirements.
ZM... thanks for the response! Is your "unbiased" recommendation mainly on the merits sound quality or something else?
mainly of the merits of sound quality
and then, it's dirt simple and dirt cheap - soon again available in Store, pretty much entire package already organized so not too much troubles with all things designing and mechanical
all in all - made by bunch of Sissies for bunch of Sissies
and then, it's dirt simple and dirt cheap - soon again available in Store, pretty much entire package already organized so not too much troubles with all things designing and mechanical
all in all - made by bunch of Sissies for bunch of Sissies
I would suggest the Iron Pumpkin. Can't comment on how it sounds (or doesn't sound) as I haven't finished building mine as yet.
that's blatant advertising 
I did suggest Iron Pre - more than good while certainly not expensive
what's not to like?
I did suggest Iron Pre - more than good while certainly not expensive
what's not to like?
Thanks, Is this the same as the BA-3 from the DIY Audio store? I don't have the JFETs and MOSFETs which I think are hard to source. I had boards made for the BOZOS and I have the parts. (Assembly starting this week). If I could get parts for the BA-3 and it is a better preamp I could tweak the power supply and change it out in the future.
^ Yes. You'll need two boards. https://diyaudiostore.com/collections/pre-amplifier/products/burning-amplifier-gain-stage-for-ba-3
JFETS - https://diyaudiostore.com/collections/jfets/products/matched-jfets
MOSFETs -
JFETS - https://diyaudiostore.com/collections/jfets/products/matched-jfets
MOSFETs -
Original Toshiba - Check swap meet. Few regular sellers.
Fairchild - Mouser, DigiKey, Arrow should have. Edited to add - Maybe not... showing out of stock/obsolete already. Either way... you should be able to get some.
BA-3B is a balance version of BA-3. Yes, you can use PCBs from the store. Try to find build guide topic here on the forum.
Member rhthatcher (great guy) offered the Fairchild mosfets at some point. Perhaps you can check with him.
If you can't find the Fairchild or Toshiba mosfets I would consider just going with the standard IRF510/IRF9510 or IRF610/IRF9610 parts.
Edit: Just found Randy's sales thread: https://www.diyaudio.com/community/...nd-irfp240-mosfets.365386/page-3#post-7646798
It looks like he doesn't have the Fairchild FPQ3P20 anymore. However, he still has some NOS Harris / Fairchild SFP9610. These are good parts and you can just pair them up with regular IRF610.
If you can't find the Fairchild or Toshiba mosfets I would consider just going with the standard IRF510/IRF9510 or IRF610/IRF9610 parts.
Edit: Just found Randy's sales thread: https://www.diyaudio.com/community/...nd-irfp240-mosfets.365386/page-3#post-7646798
It looks like he doesn't have the Fairchild FPQ3P20 anymore. However, he still has some NOS Harris / Fairchild SFP9610. These are good parts and you can just pair them up with regular IRF610.
I have the BOSOZ built except for installing the MOSFETS. I've never installed one where you want electrical contact to the board via the TO-220 tab however this board is designed with the FETs laying flat and a heat sink with screw attaching the drain to the board. I assume that I would still put thermal grease between the FET and the heat sink and electrical contact would be made through the screw on the bottom of the board and the top of the tab on the TO-220. (There is no trace connecting the middle pin of the FET).
Attachments
Is the screw pad connected to some trace on the board? Why do you think you should care about good contact to the pad?