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JGR comes clean.... with his new "Studio" preamp design!!!!

JGR

JGR

The "G" is for Gustav
Commercial User
Jun 29, 2006
5,148
3,216
Huntsville
www.facebook.com
Disclosures
President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
#1
Inspired by the rich sound of my Box-O-Tone which has a very pure, short signal path with no EQ, I started thinking about ways to retain that character but with powerful EQ. I wanted to do a cleaner, more HiFi design that still had the richness and warmth of an old studio console. All the random ideas finally ran into each other inside my head to form something cohesive and I came up with a design approach which I just finished prototyping on one of my old 12ax7 units. Worked 'till about 4 am today:eek: and it was a mess, so I went at it again this morning from a different angle and it all came together. Spent about 6 hours tweaking the EQ which was a beast, but I'm really happy with the way it turned out.

Fully inductor driven four-band EQ - was going to do peaking mids with shelving for the lows and highs, but I didn't like the way it was sounding so I ended up with peaking on all four bands, but I think they sound really nice. Preamp has a huge amount of clean headroom and output. It will get some nice mild overdrive at the very extreme gain settings, but it stays clean until at least 3 o'clock and just keeps getting richer. :bassist:

Here's a clip (long)
 
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#5
Thanks guys. Been busy in baby land for a while, but it hasn't stopped the ideas from creeping in and bouncing around the subconscious. I've finally found a bit of time to get a few done which actually helps me sleep better at night! Looking forward to doing a full amp with the big ICE module - definitely less daunting than trying to get the big tube heads done.
 
#6
I got the Ice 1200 watter out last night to you.

JGR sent me the stand alone working 1200watter that we've been kindof conceiving together. Along with the Box O' Tone which I guess is the basis for this amp. I'm hoping to see him at the guitar/bass show near his house in Reading, PA this August with the new integrated amp.

And a note to the mods---JGR and I have no commercial affiliation or relationship---we're just both uber--geeks about bass gear and bounce ideas around. I got a couple of Ice modules and sent him one that he hooked up with some add-ons of his own. And just sent him a second one to use in his amp.
 
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#10
y'all got me droolin'
Have you ordered a case yet? If so, what size? You thinking you can get in under 15#?

Is it peak/dip--in other words, is 12 o'clock supposed to be relatively flat?
 
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#11
Passinwind said:
Wow, you've been mighty busy lately Jonathan!
Click to expand...

Yeah--he has a full time job, a new baby, and has been on a mission since he checked out the Ice. He called a lot in a relatively caffeinated state stoked about the Ice and then totally driven as far as the new integrated preamp/amp. No way I expected him to get this far so soon. He already has the integration with the Ice module pretty much worked out. (I think)

Imagine state of the art tube pre with usable eq with an honest 1200 watts. And Passinwind with his killin' amp. It's a good time to be a bass player!
 
#12
Mike Arnopol said:
y'all got me droolin'
Have you ordered a case yet? If so, what size? You thinking you can get in under 15#?

Is it peak/dip--in other words, is 12 o'clock supposed to be relatively flat?
Click to expand...

Hey Mike. I ordered the case last week - got the 12x12x5; could have maybe got it into a 4" height but no reason to make it any harder packaging wise! My regular preamps are around 8 lbs so I think it should be around 12 lbs.

Noon on all the EQ controls is flat on all of my preamps. With this design, all of the controls are active so I'm not getting a big insertion loss which allows me to play with the gain staging. I went with sort of an interesting HiFi approach to the driver circuitry for the EQ which gives lower noise and drives the EQ a little better. I like the 12ax7 front end but the 6SL7 will add a smidge of goodness that folks seem to dig. This thing has crazy output to drive anything, and when I build it with the regular transformers from the 2U, I'll be running even higher voltage which will provide even more headroom.

Going to order some custom would inductors this week once I settle on the values.

I should probably draw the circuit out now that I think about it - I did it in my head on the fly!

Will try to play with it some more this week and see if anything else can be dialed in. I'd like to now but in wiped from working in the yard all day!
 
#14
JGR said:
I should probably draw the circuit out now that I think about it - I did it in my head on the fly!
Click to expand...


Link Removed

BTDT. Reverse engineering is a lot more hassle than keeping after schematic revisions. I still have all kinds of old undocumented DIY builds kicking around here though.
 
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#16
Passinwind said:
Link Removed

BTDT. Reverse engineering is a lot more hassle than keeping after schematic revisions. I still have all kinds of old undocumented DIY builds kicking around here though.
Click to expand...

Indeed. I actually keep pretty good control of the schematic and layout updates. I just need help keeping the shop straight, especially after a build - always looks like a tornado blew through.
 
#20
my question is, can we get all of that ^^^^
XXX-vin-diesel-1605102-450-320.jpg




into here... vvvvv

alembic2.jpg
 
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