What is happening is all the low frequency noise from the pre is triggering the protection circuits. You probably noticed woofer cone pumping as well. There are several ways to attack the problem but the more practical ones are to limit the input bandwidth severely in comparison to what it now is. That would be replacing the amp input caps with .047-.1UF. This might be enough to do it. The other thing would be to reduce the time constant of the preamp's power supply to so low to noise can’t pass. This would require 5-10 times more DC filter capacitance being added. This is a better fix as it corrects the real problem, a preamp with low frequency stability issues.
The other thing would be to reduce the time constant of the preamp's power supply to so low to noise can’t pass. This would require 5-10 times more DC filter capacitance being added. This is a better fix as it corrects the real problem, a preamp with low frequency stability issues.
would like to do that but how? by putting bigger cap ?
I assume this was addressed to me? The stereo UcD400AD amp I put together replaced an amp of my own design. This original was an all out A/B design that had been compared favorably to the best there are! It kicked over a lot of sacred cows for sure.
The UcD based amp was implemented in exactly the same way with the same power and chassis as well as all the support stuff so a direct comparison could be made to the A/B design. This means it is a non optimum layout for the UcD as it only will deliver 110W. This appears to be no real disadvantage as it immediately became our new reference. It has all the advantages everyone talks about but the bottom line is that it is just way more enjoyable to listen to. In fact you soon forget the system and concentrate on the music. Listening sessions can now last way too long as you don’t want to stop.
It is just more right and I can’t give it any higher praise than that.