Hi,
I have built the OTL amp described in the thread:
As i was building it and fitting into a case all seemed fine but now it sounds awful at even moderate volume. I am a newbie to valve amps but i think the problem is the power supply, which is basically:
115v-0-115v toroid - bridge rectifier (1.2kv, 16A UF soft recovery) - 4700uf 250v in both the +ve and -ve rails and 1000uf 400v between the rails. This provides +150v / -150v.
When i turn the PS on i get +-150v at the final cap as expected but then when i turn the 6C33C heaters on the PS output drops to approx +- 40v with only 9v across the cathode resistors (was about 40v when the amp was working OK).
If i pull the tubes on one channel the voltages improve slightly.
Im guessing its the caps (Evox Rifa PEH169's) which were NOS are failing after only a couple of months of use.
Would be grateful for any thoughts / advice.
Thanks
Gav
I have built the OTL amp described in the thread:
HTML:
https://www.diyaudio.com/forums/tubes-valves/189282-vacuum-tube-otl-power-amp.htmlAs i was building it and fitting into a case all seemed fine but now it sounds awful at even moderate volume. I am a newbie to valve amps but i think the problem is the power supply, which is basically:
115v-0-115v toroid - bridge rectifier (1.2kv, 16A UF soft recovery) - 4700uf 250v in both the +ve and -ve rails and 1000uf 400v between the rails. This provides +150v / -150v.
When i turn the PS on i get +-150v at the final cap as expected but then when i turn the 6C33C heaters on the PS output drops to approx +- 40v with only 9v across the cathode resistors (was about 40v when the amp was working OK).
If i pull the tubes on one channel the voltages improve slightly.
Im guessing its the caps (Evox Rifa PEH169's) which were NOS are failing after only a couple of months of use.
Would be grateful for any thoughts / advice.
Thanks
Gav