Not sure what tubes you are using, but Sometimes one has to select out from a batch of tubes with lower noise.
Another possibility would be HF oscillation.
Another possibility would be HF oscillation.
@Michelag : I will try today with another amp
@analog_sa : will it affect both sides of the IV converter ?
@analog_sa : will it affect both sides of the IV converter ?
I spoke with someone in France who knows :
In an electronic way, the iv stage works.
In a tube way, it just cannot work without noise because of the 1M, 1M5 resistors and the CCS - so my quest of noise is endless...
In an electronic way, the iv stage works.
In a tube way, it just cannot work without noise because of the 1M, 1M5 resistors and the CCS - so my quest of noise is endless...
This seems quite unlikely. I have experienced socket related noise in only one half of a dual triode and usually with horisontally mounted tubes.
Not sure the big resistors here have any meaningful noise contribution. Nor do i understand why are they quite as big.
From my experience, I would first say that some depletion mosfet has a gate breakdown, the DN2540 is especially sensitive when soldering to the PCB.
Which depletion mosfets were used, what is their Vds and what is the voltage at the anode of the tube?
1M and 1M5 have no influence on noise, they can be higher values, it doesn't matter. That someone who knows must not understand how this CCS works and what these resistors are for.
Attachments
I am pretty sure he knows more about tubes than anyone on this thread 😉
This IV stage should work with low efficiency speakers, but not with high efficiency headphones. I have no noise with an AOP stage, so this tube stage has an issue. Are you currently using it ?
This IV stage should work with low efficiency speakers, but not with high efficiency headphones. I have no noise with an AOP stage, so this tube stage has an issue. Are you currently using it ?
I used this or a similar stage with this CCS in my DAC and hybrid amplifier with tubes that have a much higher gain than the ECC88 and without any noise, nor has anyone who uses this I/V reported a problem with noise. . My friend even used a stage like this, but with a 6S4P in the phono preamp and without any problems, so I don't believe that the problem is in the design, but the way it was made or the implementation.
Attachments
Maybe about tubes, but a little about depletion mosfets, it's neither the first nor the last to get into a trap with them 😉 .
Otherwise, he would never have brought the R15,R16 in the CCS in connection with the noise. But as I already wrote, they can make noise in the event of a gate breakdown.
I can send you my board so you can check it, but with my tube amp and my headphones, there is a background noise - and I can say it will not bother anyone who does not have the speakers on his ears 🙂
Another AD1862 ready! I tried the tube output with 6n23p-ev and 6522 and it works fine. At first I had a noise, it turned out to be a bad solder on C2, C5. I moved them parallel to Riv1 Riv2 and everything was fine. After listening to old favorites songs the sound is superb. I have completed almost all the schemes from the thread, this is the DAC that plays best for me. Once again, I want to thank Miro1360, Grunf and Michelag for the wonderful moments with my favorite music!
Attachments
Last edited:
