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Author Topic: I can't think of a better preamp...  (Read 6754 times)

cb951303

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I can't think of a better preamp...
« on: April 23, 2006, 05:52:37 AM »
http://www.tonepad.com/getFile.asp?id=79

this is the schematic of the famous Sans Amp Gt-2, it's a great great preamp.
Also if you don't want to mess with PCBs and soldering etc. and if you don't have money for the genuine Sans Amp, you can always go with Behringer GDI21, it's very cheap and it's a sans amp gt-2 clone.

turbolx5oh

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Re: I can't think of a better preamp...
« Reply #1 on: July 27, 2006, 11:32:21 AM »
How would you change it for +-15v?

teemuk

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Re: I can't think of a better preamp...
« Reply #2 on: July 27, 2006, 01:51:17 PM »
Basically, by 1) removing the supply bias circuit (2 x 10k resistors and 220uF filter cap), 2) connecting the opamp Vee pins to -15 instead of ground, 3) connecting Vb nodes to ground instead of Vb (which would not exist anymore) and 4) reselecting parts with proper voltage and wattage rating. Also, the jack input on/off switching would need some rework and the Vee side would need a 220uF filter cap as well.

turbolx5oh

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Re: I can't think of a better preamp...
« Reply #3 on: July 28, 2006, 03:17:21 PM »
I'm going to give it a try as the preamp for my LM3875 chip amp.  I just ordered a 22-0-22 160VA Toroidal tranformer and I've got the power supply and amplifier board done.  All I need to do is build this preamp, test it a bit with a couple of batteries (+-9v) go from there and then see if I can keep from electrocuting myself.  I still need to find a cabinet for it though.  The plan is to build a 1x12 combo with a Celestian Vintage 30 in it.

turbolx5oh

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Re: I can't think of a better preamp...
« Reply #4 on: September 05, 2006, 09:30:23 AM »
Well I tried putting a dual power supply on a Sans Amp Preamp and it didn't like it.  Great distortion but not a whole lot of change between all of the different settings.  Someone with more electronics background is going to have to sort this one out.  I went ahead and used the ESP Project 27 premap.  I used my own circuit board and made several options for the clipping diodes (diodes, LEDs and soft/hard clipping).  It sounds pretty good.  I need to change a couple of caps to get a bit more low end out of it though but other than that it sounds pretty good.  I'll probably go with this config for my LM3875 Chip Amp.

Stompin_Tom

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Re: I can't think of a better preamp...
« Reply #5 on: September 11, 2006, 04:20:50 PM »
Did you make a perf board layout (or etch your own pcb)? Any chance you could post or send to me?...
myspace.com/bestinventions

turbolx5oh

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Re: I can't think of a better preamp...
« Reply #6 on: September 13, 2006, 10:06:06 AM »
Yea, I made a PCB of the ESP Project 27 preamp.  I made a few changes.  After I get the amp all together I'll see if it sounds as good as it does with a +-9V supply as a stomp box which is how I tested it.

Stompin_Tom

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Re: I can't think of a better preamp...
« Reply #7 on: September 13, 2006, 11:04:19 AM »
Yeah, I keep looking for a preamp for my chipamp project and I keep coming back to the esp project... seems relatively easy and straight forward. I'm not interested in anything that does too much, I got stompboxes for all that. Just something with good boost, tone stack, and can take pedals ok.

In any case, please let me know how yours turns out and what mods you did... and if there's anything you would've done differently!
myspace.com/bestinventions