ClefChef
New Member
I've been searching the web all over for Dared MP-2a3c schematics...
I tried to figure everything out myself, the difficulty is that this is two-sided PCB and all connections to it (leds, inputs, transformers) are soldered to it solid and removing the PCB requires un-soldering everything - not a great idea for two-sided PCB's...
Preamp stage consists of 12ax7 (voltage amp?) going to 12au7 (driver?), then the signal is off to 2a3c. It looks like the .47 coupling cap between ax7 and au7 is also bypassed by a resistor (and another small cap?), I wonder for what reason. It also looks like ax7 has cathode bypass cap missing (there is space for it on PCB) and au7 has one (100uf) in place.
On the PCB board I can see something like DC filament circuitry that was omitted and left as simple AC (with hum pots for 2a3).
The first two pics are of the "unmolested" amp, the third pic shows some mods in it: couplers are auricaps, silver signal wiring, twisted AC wires, small cap on the Omron delay relay (to prevent arching).
Since I don't have the schematics and I am quite recent in my experience with tubes I did not do anything else to it, although I feel that the signal path is somewhat cluttered.
I won't go into details on the sound of this amp - it's quite good for the amp of THIS level of construction (observe the "semi star" grounding in the center of the PCB!), my questions are purely technical: would it be possible to obtain the schematics of this amp (US version preferably, and Yes, I did email Dared US...), and what could be done to modify the circuit for cleaner sound?
Many thanks!
I tried to figure everything out myself, the difficulty is that this is two-sided PCB and all connections to it (leds, inputs, transformers) are soldered to it solid and removing the PCB requires un-soldering everything - not a great idea for two-sided PCB's...
Preamp stage consists of 12ax7 (voltage amp?) going to 12au7 (driver?), then the signal is off to 2a3c. It looks like the .47 coupling cap between ax7 and au7 is also bypassed by a resistor (and another small cap?), I wonder for what reason. It also looks like ax7 has cathode bypass cap missing (there is space for it on PCB) and au7 has one (100uf) in place.
On the PCB board I can see something like DC filament circuitry that was omitted and left as simple AC (with hum pots for 2a3).
The first two pics are of the "unmolested" amp, the third pic shows some mods in it: couplers are auricaps, silver signal wiring, twisted AC wires, small cap on the Omron delay relay (to prevent arching).
Since I don't have the schematics and I am quite recent in my experience with tubes I did not do anything else to it, although I feel that the signal path is somewhat cluttered.
I won't go into details on the sound of this amp - it's quite good for the amp of THIS level of construction (observe the "semi star" grounding in the center of the PCB!), my questions are purely technical: would it be possible to obtain the schematics of this amp (US version preferably, and Yes, I did email Dared US...), and what could be done to modify the circuit for cleaner sound?
Many thanks!
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