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Chip Amps Amplifiers based on integrated circuits

simple guitar preamp with bass treble distortion
simple guitar preamp with bass treble distortion
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Old 7th April 2007, 03:27 AM   #1
garydmd is offline garydmd  United States
diyAudio Member
Join Date: Dec 2003
Location: west virginia
Default simple guitar preamp with bass treble distortion

Hi there,

Here is just a post of an amp I built. I am posting the results because I am personally very happy with the sound, and I would like comments from anyone who is more experienced. The schematic is shown below. The power amp is simply the 4 resistor amp with gain 33 and 1 uf capacitor on the input and it is not shown here. The preamp is shown below. I disassembled an old defunked gallien krueger amp and got 13 op amps LF353 JFET. Yes I am new, and I have never built anything with an op amp. So I thought I would tinker around with these 8 pin ic's.

When I started, I was going to be happy if I got a half way decent sound. I hooked up the following schematic, and boy, I was surprised. Call me crazy, but I thought this sounded awesome. It really reminded me of an old gibson amp I had as a child when the gain was down(kinks), I felt like I got a decent tube type sound with the gain in the middle (ac/dc), and when cranked, the amp seemed good for old school heavy metal, iron maiden, etc. In fact, to me, I don't feel like I had as good as sounding amp since my tube gibson.

I have been running amp simulators through clean/flat power amps and I think this preamp shown does a better job at simulating an old tube amp.

I ran this preamp into gainclone with gain of 33 and it was suitable and loud for a guitar amp. To me it sounded nearly as loud as my behringer 120 watt head.

The second op amp stage was used because the lf353 is a dual op amp and I wasn't using it for anything else.

I tried to run the circuit into a fender tonestack and marshall tonestack, but I never really got a good sound. I tried the basic high pass, low pass filter for bass and treble and I was able to get good sounds, so I left the configuration alone.

I thought about using the second op amp in the chip for channel switching, which is very common nowadays with guitar amps. You could use diodes/higher gain with input A, and no diodes lower gain with input B, and then use a footswitch.

However, I loved the simplicity of this amp and kept it like it is. The volume pot goes after the circuit shown and then into the capacitor and then the 4 resistor amp.

This amp seems entirely giggable and I am impressed with the sound and volume acheived through 2 12 inch speakers. I have also included the schematics for the tone control section and a wiring diagram which shows how easy the tone controls are to implement. The pictures are borrowed and modified from Adam's Amplifiers (http://amps.zugster.net/articles/tone-stacks)
But the design is my own and are simply high and low pass filters.
I included the picture because it is so easy to hook up, you just wire the components right to the pots. Place this tone control between the preamp and amp section.

Click the image to open in full size.

Click the image to open in full size.
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