Homemade high quality preamplifier tone circuit

I bought a high-quality pre-amplifier tone board kit. Due to the upgrade of the whole machine, the tone board and the whole machine were integrated and reproduced. The circuit principle and parameters are introduced as follows.

This circuit can boost or attenuate the frequency points of 25Hz, 200Hz, 1kHz, 10kHz, and 16kHz by ±18dB. The output stage adopts cross-coupled complementary emitter followers, which have good symmetry, wide frequency response, low noise, and low distortion.

The following improvements were made during the remake process:

1. Remove the original integrated power supply and process it separately, and connect power filter capacitors of different specifications in parallel.

2. The first-stage output interconnect capacitor was changed to a 1μF tantalum capacitor, the high-frequency capacitor of the tone part was changed to silver mica of the same specification, and the mid- and low-frequency capacitors were changed to Weimar capacitors of the same specification.

3. Replace the op amp 5532 with AD827, the high frequency is significantly improved, the mid-frequency is brighter, the low frequency extension is stronger, and the control is better.

suggestion:　　

1. Add 100μF+0.1μF in parallel before the ± power supply of the two op amps for decoupling, which is helpful in suppressing background noise.

2. Adding a small signal amplification stage before the input of this line will achieve better results.

Note that the power of the 2200 resistor in the figure is not less than 1/2W, and BC547 and 557 can be replaced by A733C945.