Dax's dual Green Preamp FINISHED! - With AUDIO samples

Hey everyone!
I've finished off my dual Green pre!
(which I have cheekily marked as 909B :grin: )

First of all, I'd like to thank EVERYONE here at the P-P forum who has helped me out on this project (either directly or otherwise).


Large view: http://www.puzzlefactory.com.au/Green_inside.jpg
Face: http://www.puzzlefactory.com.au/face_sample.gif

I gotta say, this baby sounds great!
I'll put up a few samples of this preamp, recorded with a Sony C-800g in comparison with my console pres (Chilton CM2) and my Summit 2BA-221.

The samples will also include comparisons of 3 different signal path capacitors and 2 different PSUs. (One using fixed 7*15 regs and the other using the recommended LM3*7 adjustable regs.)

Notes:
1) The 1/4" socket on the front panel is the output, not a DI input. My patchbay is 1/4" so there was no point in fitting an XLR then having to make adaptor leads.

2) Yep, that's right - no phase switch. I find that I basically never need to invert phase when I'm recording and it's just another set of contacts (i.e. more noise) that I was able to avoid.

3) Klotz AEY-122 used for all signal path connections, inc gain. The light green wires connect from the braid shield to a ground point on the PCB. Gain and HPF are grounded on one end only.

4) The PSU has a sheet of tin dividing it from the rest of the preamp. The sheet is grounded to mains earth. (top right green wire)

Things left to do:

Change the HPF pre/post switches to DPDT and parallel the poles (to lower resistance & hence noise).

Lower the HPF cutoff frequency from 100Hz to 70Hz. (Just a personal preference)

Get someone to CnC rout the face plate and mount the metering LEDs.

Shit.
I just wrote this whole reply out then closed the page (IDIOT!)

Okay, take two...

The password is peterc

For an explanation why I did so many tests, see this post:
http://www.groupdiy.com/index.php?topic=14983

One thing I want to make clear is that I AM NOT A SINGER!
Please try to keep the comments focussed on the sound, not the singing :grin:
Microphone is Sony C-800g

http://www.puzzlefactory.com.au/Schematic-Caps.gif
Caps in red are directly in the signal path.
Caps in green are for phantom power blocking (also signal path).
7815 & 7915 voltage regs were initially used.

Sample set A:
http://www.puzzlefactory.com.au/Green-part-a.rar
*Green ch1 - Elna Starget caps - 2x22uF in 2x22uF positions, 7x100uF in 7x47uF positions
*Green ch2 - Panasonic caps - correct values in all positions.

Sample set B:
http://www.puzzlefactory.com.au/Green-part-b.rar
*Green ch1 - Elna Cerafine 47uF 100v phantom caps - Elna Starget 2x22uF in 2x22uF positions, 7x100uF in 7x47uF positions
*Green ch2 - Elna Cerafine 47uF 100v phantom caps - Elna Starget 2x22uF in 2x22uF positions, 7x47uF in 7x47uF positions

Sample set C:
http://www.puzzlefactory.com.au/Green-part-c.rar
*for comparison: Summit 2BA-221 (see below for important note)
*for comparison: Chilton CM2 console channel
*Final build of Green Pre (see below for final config & note)
*Dave Mann Collective - the backing music to clothe my naked voice :grin:

Final configuration of Green pre:
2x Elna Cerafine 47uF 100v phantom blockers (green positions)
2x Elna Starget 22uF 35v (red positions)
5x Elna Starget 47uF 35v (red positions)
Voltage regulators changed to LM317 & LM337

Billy (enthalpystudios) noticed that there is cricket noise (!) in the final Green pre sample. Maybe I should've used a green cricket (grasshopper) as the front panel logo :grin:

Summit note: All preamps were set to equal gain and I tried to keep the dynamics of my singing as even as I could. You will notice that there is one point where the Summit pre saturates (clips) internally. I left this intentionally to show the difference in headroom between the different pres.

Interesting side note: Voltage rails were over 16v with LM7*15 regulators that didn't get warm.
Voltage rails are 15v with LM3*7 regulators which now get warm.

Thanks for all the work , and many more pres to you sir

regards Greg

Thanks for all the work , and many more pres to you sir

regards Greg

pretty cool man, singing is pretty consistent.

the green sounds pretty good, interestingly its about the same sound I was getting on mine, when I had a channel going unracked for a minute. I was actually using either a soundroom oktava 012, an md421, and an AT3060, and all had a pretty decent HF sound, if not sometimes a little dangerous for sibilance, but pretty silky actually.

only thing that I can't get over is in c-FINAL Green (with LM3_7 regs) (C-800g).wav (didn't notice on others) is this sound... are there crickets, or is that the electronics???

cool stuff, good work,

billy

Damnit!
Yep, you're right Billy, it's crickets alright. I can't believe I missed that.

I will amend my earlier post to include that.

Thanks for spotting it!

no prob, thought I heard something. man, pcb mount components make for damn hard metalwork!

I just gave up for the day on my green metalwork...... i had my bottom drilled, all my spacers mounted, cards in place... measured my toggles, double measured, copied to frontpanel, double checked, and I totally messed it all up !

anyway, I drilled out the holes an extra 1/32 and moved my pcb's around... hopefully I can finish tomorrow.

No more pcb mount switches/stuff for me however.

nice work, however, it's good see someone finishing this guy.

billy

I kinda thought more people would be interested in hearing this, oh well :grin:

If this thread stays dead much longer, I'll be removing the audio samples from my server. There's about 50Mb of files just sitting there wasting my storage.