Tuesday, July 24, 2012

I take apart my old amplifier, old circuits for sale

I "disassembled" my good old power amplifier. This version was very good but the part of this device needed to my new idea. I used this old version for 10 years, without problem. This amplifier contains two stereo devices, one for guitar, and one for microphones/keyboards. I built this double-stereo amp to 2 rack mounted cases: one for power supply, and one for the amplifiers.

The old power supply:
It was the old power supply on the rack case #1. The toroid transformer is  1200VA, the Greatz on the heatshink is 10A, softstart, stabilized power supply for preamplifiers and EQ, simple power supply for amplifiers. By the speakon connectors the output voltage can be changed from +/-10v to +/- 70V for poweramps only. One speakon is the output for poweramps, and one 5 pin connector is for preamplifiers and mixers. The toroid transformer have 4x10W and 4X15V output AC voltages for poweramps, and 2x15V for preamps, and 1x18V for LED, relays, and coolers.

This power supply is good solution for my new guitar amp project, but without speakons, because the different output voltages are not required for the new design. Now I have only one speakon for poweramps, and one 5 pin connector for all others:
This is the box of new power supply, assembled from the parts of old one. This case placed to the bottom of new combo. The required power voltages will be wired to the top of amplifier. The content of upper case not ready, and I want to design something new.

The old amplifier:

The poweramp, 6 input mixer,10 channel equalizer built to another rack mounted case. This is old photo with one poweramp on heatshink, but this part of amplifier has been duplicated. One of then used for guitar, the another one is for keyboard and vocal. This is all-in-one sulution, but for small or larger clubs was good solution:

There are the list of very good circuits what I don't  need for new amplifier design, so there are for sale:

4x200W poweramps with TDA7293 assembled to heatshink with cooler:
The poweramps are two stereo circuits with bridged TDA7293/7294 circuits. Very reliable circuits. All stereo boards have speaker protection with UPC1237 chip.

The equalizer:
10 bands stereo RANE copy equalizer. This is active filter circuit design, the "Q" of EQ is permanent for all bands, what is very interesting solution. See more... With small PCB relays the have true bypass, and the circuit can be switch between +/-6 and +/-12 dB modes.
6 input audio mixer:
Very simple audio mixer with 6 stereo inputs. All inputs have gain and volume pots. Two of them have jFET preamplifiers for guitars with 4x gain, 4 of them have op-amp preamplifiers for all others with 100x gain.

Here are the gallery of my "disasembled" but error-free circuits and prototypes. Write me if you need something:

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