You have excessive colophonium - rosin and this may mask some soldering problems as well. Use isopropyl-alcohol and clean the boards.A better definition pic
I will follow your advice. Thanks!!!d3A CCS will push ~20mA and other two for ECC88, ~10mA each. Disconnect tubes and connect a 10K/5W resistor between cathode and anode. Look on the scope for the noise across resistor.
This should indicate which CCS have problems.
In my case, higher depletion mosfet had problems. For future protection, I have added a zener between upper mosfet gate and lower mosfet source.
Hope this helps.
Regards,
Tibi
https://www.yumpu.com/en/document/read/47728837/his-masters-noise-s-yanigerAs this thread has been conceived almost twelve years ago, the schematics have vanished from the 1st posting. Is there any chance to see them again?
Best regards!
I bought 10 siemens d3a 5 years ago for 17 euros/piece from Germany.I could have bought 20 at the time but failed to consider that ...now its about 50 euro/tube...I built two different phono preamps based on d3a, both were my own designs , i was very happy with them , yet many tubes are good enough for phono preamplifiers.I consider d3a somewhat a waste of resources for phono preamps compared to ecc83.About 16...32 times more current and heat than ecc83 for the same job..You still need an input transformer for mc carts no matter what tube you are considering for the job while for mm carts there are lots of tubes good enough for that purposeThank you very much!
Well, D3a's may have been in the few bucks range ten years ago. Nowadays they aren't. So, what about paralleling PC 86 UHF frame grid triodes that still are dirt cheap to get this »impressive transconductance« and low plate resistance?
Best regards!
You waste much of the first stage gain with the passive RIAA network. It's a solution in search of a problem.I bought 10 siemens d3a 5 years ago for 17 euros/piece from Germany.I could have bought 20 at the time but failed to consider that ...now its about 50 euro/pcs...I built two different phono preamps based on d3a, both were my own designs , i was very happy with them , yet many tubes are good enough for phono preamplifiers.I consider d3a somewhat a waste of resources for phono preamps compared to ecc83.About 16...32 times more current and heat than ecc83 for the same job..You still need an input transformer for mc carts no matter what tube you are considering for the job while for mm carts there are lots of tubes good enough for that purpose
That's highly debatable...cause i made lots of very different phono preamps over time and none of them had the sound of the D3A with a passive network and I KNOW it's not because of the nature of the riaa network, but because of the tubes, while having passive or active network with very high GM tubes is completely irrelevant for the noise perspective because they allow one order lower impedance for both passive and active networks. We are already limited by the vinyl surface noise which is at least 10db higher than what a d3a with passive riaa design can get you...Do you think that a phono preamp with 120db SNR would bring you better vinyl experience when vinyl SNR is between 50...70db?You waste much of the first stage gain with the passive RIAA network. It's a solution in search of a problem.
I have two HMN's -- one I managed to fit into a PAS3 chassis!That's highly debatable...cause i made lots of very different phono preamps over time and none of them had the sound of the D3A with a passive network and I KNOW it's not because of the network, but because of the tubes while having passive or active network with very high GM tubes is completely irrelevant for the noise perspective because they allow one order lower impedance for both passive and active networks. We are already limited by the vinyl surface noise which is at least 10db higher than what a d3a with passive riaa design can get you...Do you think that a phono preamp with 120db SNR would bring you better vinyl experience?
I have two HMN's -- one I managed to fit into a PAS3 chassis!
It's just phono now, will post when I get back to NJ next wkCould you post a pic of the interior layout please. I have an old PAS4 collecting dust, which might be an option. TIA
jeff
Can you tell us more about the various boards?Finally finished my boards. Everything working. Needs final RIAA adjustment. Thanks Jackinnj for the PCB's