To disassembly Topping PA3s (MA12070) you need long (at least 14-15cm) thin 2mm hexagon key (front panel is screwed from the inside), use it through the rear screw holes. You can make it yourself from scraps of any small 2mm wrench by welding a long handle if it's difficult to find such size in local stores.
Attachments
Yo need to use a balanced input attenuator helper board connected to XLR input of audio interface. Make sure not to let ground shield connect to speaker output. There is a circuit I used described in the REW distortion measurement thread. For Class D amps, you also want to use a passive brick wall 100kHz filter to prevent aliasing the data in the FFT.
Filter:
Also this is right script for ATtiny85, that switch MA12070 to PMP2 and than put ATtiny85 to deep sleep state, with ADC off and BOD off for minimize EMI.
You need to use special LowPower library that support ATtiny85 - this is it https://github.com/sej7278/LowPower
You need to use special LowPower library that support ATtiny85 - this is it https://github.com/sej7278/LowPower
#include<Wire.h>
#include <LowPower.h>
void setup()
{
Wire.begin();
//Change PMP from 0 (default) to 2
Wire.beginTransmission(0x20); // 0x20 = default MA12070 I2C address
Wire.write (0x1D); // 0x1D = PMP Register
Wire.write (0x02); //Set to PMP2
Wire.endTransmission();
LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
}
void loop(){}
If you don't bypass the opamps you will not get close to the potenial of these Boards. The way I use them they are better than the Accuphase E303 I owned. With a differential signal straight to the input pins of the Merus Chip, you get stunning performance. I never gave any sonic impression of these boards in stock form so please don't blame me for suggesting these boards if the sonic result is just mediocre.
It is planned to remove the entire preamplification part...
It's still in progress...
The multichannel dac (balanced) on the right in the photo will be connected directly to the inputs of the chip with a balanced signal !
