Finally, I got the Aikido preamp working in synergy with my main system.
I owe a huge debt to Sy who looked over my circuit diagrams for PSU and inspected a poor quallity photo of my layout. With his recommendations, the amp is now hum-free, except for very minor hum from the transformer which is not getting into the signal.
I am incredibly revieved.
So, I learned a few things:
1. Bias the heaters to 25% of B+ to the center-tap of the heater AC transformer.
2. Mount the volume pot to the chassis
3. Ensure that the signal wiring avoids the proximity of any AC wiring.
I do now need to buy a good stepped attenuator and then move my good quality jacks and source selector from my passive-preamp to Aikido.
Again, I want to thank Sy for his help, and metion that this forum really benefits from his expertise and experience.
Regards,
Charlie
I owe a huge debt to Sy who looked over my circuit diagrams for PSU and inspected a poor quallity photo of my layout. With his recommendations, the amp is now hum-free, except for very minor hum from the transformer which is not getting into the signal.
I am incredibly revieved.
So, I learned a few things:
1. Bias the heaters to 25% of B+ to the center-tap of the heater AC transformer.
2. Mount the volume pot to the chassis
3. Ensure that the signal wiring avoids the proximity of any AC wiring.
I do now need to buy a good stepped attenuator and then move my good quality jacks and source selector from my passive-preamp to Aikido.
Again, I want to thank Sy for his help, and metion that this forum really benefits from his expertise and experience.
Regards,
Charlie
Glad you are now enjoying the aikido circuit. My 6SN7-based aikido brings a smile every time I switch it on...it is just so darn musical...
One comment about the stepped attenuator. I have a cheap Alpha pot, and a nice ladder stepped attenuator. Honestly, the Alpha pot sounded more lively than the stepped, altho it was a bit thin. I swapped it out for the stepped, which sounded dull and rolled off.
In the end, I switched to a shunt-style setup, using a single resistor in the signal path, with just the wiper and the shunt resistors from the stepped providing a path to ground. That proved to be the ticket.
If I were to do it all over again, I would forget about dropping in the stepped, and just using the Alpha pot in shunt form.
All you need is 2 resistors which are the same value resistance as the pot. Start with that, first...
One comment about the stepped attenuator. I have a cheap Alpha pot, and a nice ladder stepped attenuator. Honestly, the Alpha pot sounded more lively than the stepped, altho it was a bit thin. I swapped it out for the stepped, which sounded dull and rolled off.
In the end, I switched to a shunt-style setup, using a single resistor in the signal path, with just the wiper and the shunt resistors from the stepped providing a path to ground. That proved to be the ticket.
If I were to do it all over again, I would forget about dropping in the stepped, and just using the Alpha pot in shunt form.
All you need is 2 resistors which are the same value resistance as the pot. Start with that, first...
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