Simple 500/51x preamp design

Hello DIY gurus,

I've just finished building a 51x rack and I need something to populate it with.  While I'd like to be able to afford 10+ commercial modules at $500 a pop, I'd prefer to DIY something.  I am a professional EE/PCB designer, so I'm looking for suggestions of designs to "port" to the 500 format.

Options:
- Green pre
- THAT 151x reference design
- ???

Would anyone like to steer me toward a design that the community could use?  I of course would make available all schematics/gerbers and hopefully some bare boards.  I'm shooting for something that's fairly simple; a gain knob, +48 switch, and that's about it.

Best regards,
Tim

well, the sky is the limit really. But there are some 9k, 4k pres in 51x offered here, as well as the f76, a 51x 1176 type thing. the seven circle SC-1MK500 is a THAT based design, although it's bought as a kit. I just finished up a 1512/1646 in 51X format that I haven't had the chance to etch up yet, if you like I can send gerbers so you can check it out, though the design isn't tested yet, it is pretty much pulled from a commercial product that is tested and true.

If you're looking to design something that doesn't already exist on the forum in 500 or 51X format may I suggest the Green Pre (A great idea I think), or perhaps the JFET "Fetboy" design proposed by Scott Hampton in his Tape-Op article? The Hampton design is a shoe-in for the 51X format with that +24v rail.

This simple pre is awesome: http://www.forsselltech.com/downloads/schematics/JE16%20Mike%20Preamp.PDF

Footprint the input tx for some of the 1:2s out there and sign me up for some. If they can fit the Classic API faceplate and sled, even better...

PeterC did a 500 version of the Green...not sure what the status is on that.

I think one of the most underated/undermentioned mic pre's & DI around here is this one:

http://www.groupdiy.com/index.php?topic=33492.0

1073  Neveish, awesome sound, only Euro275 for a complete kit, you don't have to go hunting high and low for parts and it looks great in my rack. The step by step documentation is fantastic, you cant go wrong if you follow it. Its not the simplest of designs, there are a lot of parts, but great quality, sound and price ..... and they have a neveish eq coming soon to complimenty it!

Michael

Thanks for the replies!

Whoops, I neglected to mention I wanted to start with a transformerless design, so that outs the Hampton and Forssell circuits.  (This is mainly because there's a bunch of trafo-based designs out there already, and not too much for discrete.)  I think I may just whip up a couple options quick and post some schematics in the coming week or two for everyone to mull over.  babyhead, good call making it fit the existing classicapi faceplate/tray; great idea.

Cheers,
Tim

Ok, I've done some research and I'm leaning towards making a fully IC based preamp from THAT/TI datasheets:
http://standingwaterstudios.com/gdiy/SWSthat.pdf
You can use THAT 1510/1512 or TI/BB INA217 for the input and a THAT 1646 or DRV134 for the output.

Otherwise I could do a "green" style, but I'm not 100% happy with the circuit (like why buffered polarity flip, and I would prefer a cross-coupled output driver):
http://standingwaterstudios.com/gdiy/SWSgreen.pdf

I could perhaps put both input stages (transistorized vs IC) on one PCB and let people choose.
Any thoughts?  Layouts coming soon.

Best,
Tim

I must say, The idea of an IC/transistor switch for the input stage is very interesting and appealing. Looking forward to watching your progress.

Ptownkid said:

PeterC did a 500 version of the Green...not sure what the status is on that.

Click to expand...

I think it was retail-only. No DIY option.
I recall the first 13 units were for sale at gearslutz. Don't know what happened after that...


BTW, the green pre sounds wonderful. Haven't heard any comments about the sound of the that.

Right, I'm a bit hesitant to release a green pre in 500 format because of that one.  I suppose I ought to ask PeterC for permission, but then again that Mozart circuit is public domain, I believe?

I think I'll throw in pads for a HiZ plugin module option too.    Stay tuned...

I think we could use a DIY option for the green! I didn't mean to discourage.

Looking forward to where this goes.

I just finished up a 500 version of the that1512/1641 app notes, well actually I took a lot from the rane ms-1, which seems to be basically an app notes design, but with signal/overload leds... pm me I can send you the gerbers to take a looksie. Thinking about doing a group buy, as I really want to get some pcb's ordered, but can't afford to pay for a whole panel myself.