Please just send me the last ones you have which should align with what I posted recently, no time for an in depth dive here.
Absolutely agree, Vgs of the top device should be as high as reasonably possible for the reasons you state. This design uses TO-220 for both top and bottom fets in the cascode.
Hi all,
I red all this thread and seems to be very good preamp with only one tube. Something I am looking to build for myself.
I want to ask you guys, can ECC99 tube work with this design?
Thanks,
bekim
I red all this thread and seems to be very good preamp with only one tube. Something I am looking to build for myself.
I want to ask you guys, can ECC99 tube work with this design?
Thanks,
bekim
The plate resistance of the ECC99 is about 2X higher than the 6N6P so I would not recommend it as the top choice, but it should be OK. The 6N6P should be readily available, is much cheaper and works very well. You should purchase tubes of either type that are section to section matched.
Trying to figure out grounding and my power supply umbilical from the PSU box. I know I need B+ and its ground in the umbilical, and will need the + and - for the filament supply. That's 4 wires. Basically, I'm wondering how the signal chassis is grounded and if I need a separate (5th) wire to tie it directly to earth in the PSU box. That seems most likely to me, but it would mean the signal circuit needs to be isolated from it's chassis (including at the inputs and outputs). But then what if the source negative were tied to earth? On the other hand, if it were grounded via the B+ circuit (e.g. lifted like the B+ circuit), that would seem to be a problem since if the two chassis touched, that would short circuit the lift and become the path to earth.
I'm thinking I need a 5th conductor for that purpose (and then need to be very careful to isolate all inputs, which I try to do anyway for ground loops). So any help thinking this through would be appreciated. I'm very close to finishing my build and looking forward to hearing it.
Thx.
I'm thinking I need a 5th conductor for that purpose (and then need to be very careful to isolate all inputs, which I try to do anyway for ground loops). So any help thinking this through would be appreciated. I'm very close to finishing my build and looking forward to hearing it.
Thx.
There are a couple of options. We can discuss tomorrow when you are here. Mine was built in 1 box.
I would have to bet that any of that basic performance family would work. 7044, 5687, 6900 etc. are comparable too( though not pin compatible with 6H6Pi).
Douglas
Just don't ask me to support these experiments, but feel free to do so.. It essentially becomes a new design. 🙂 I would imagine lateral mosfets like the Exicon ECX10N20 would also work if one wanted to do a lower voltage version.
I'm biased so I hope someone else who was inspired to build this will weigh in. If there is interest I will gift the gerbers to the forum as long as people agree not to profit on my work. (Donations to the forum are totally OK as alternative)
Hi,
I have few questions regarding this circuit if you could kindly answer:
1. Can you provide information on maximum input (mV) and output before clipping, distortion..? Can I connect two different power amp and will be the signal enough. assuming their input is rated 2V for full power.
2. If I use another regulated HV power supply, i.e., Salas (shunt regulated) or Maida, will it make any difference in performance?
3. Regarding output from transformer - if is used SE (rca connector) instead of balanced, will it be any 'downside' of the audio quality? Is it preferred or no?
Many thanks,
bekim
I have few questions regarding this circuit if you could kindly answer:
1. Can you provide information on maximum input (mV) and output before clipping, distortion..? Can I connect two different power amp and will be the signal enough. assuming their input is rated 2V for full power.
2. If I use another regulated HV power supply, i.e., Salas (shunt regulated) or Maida, will it make any difference in performance?
3. Regarding output from transformer - if is used SE (rca connector) instead of balanced, will it be any 'downside' of the audio quality? Is it preferred or no?
Many thanks,
bekim
Volume control is placed ahead of the 6N6P, the input can handle greater than 3Vrms.
The Salas shunt regulator would likely be an upgrade. The CCS makes it less sensitive to PSU performance, but the improvement may be worthwhile.
Please read through the thread for the information you are looking for in terms of overall performance, it's all here and its been years since I finished this design. (Unfortunately I don't have time to dig for you.)
There should be no problem using parallel pairs RCA outputs and you can drive multiple amplifiers without issue. (The source impedance is a few hundred ohms) Output capability is > 2Vrms. I drove a solid state subwoofer processor/amp and a small tube amp without problems for years. Combined input impedances greater than 1K or so should be fine. (Higher impedances are fine as well)
I strongly recommend putting the power transformer and power supply in a separate box if possible. The magnetic field from the power transformer was difficult to deal with, and while the induced spectra was below the threshold of audibility it bothered me that I could not fully eliminate it. (I was able to reduce it significantly.)
The Salas shunt regulator would likely be an upgrade. The CCS makes it less sensitive to PSU performance, but the improvement may be worthwhile.
Please read through the thread for the information you are looking for in terms of overall performance, it's all here and its been years since I finished this design. (Unfortunately I don't have time to dig for you.)
There should be no problem using parallel pairs RCA outputs and you can drive multiple amplifiers without issue. (The source impedance is a few hundred ohms) Output capability is > 2Vrms. I drove a solid state subwoofer processor/amp and a small tube amp without problems for years. Combined input impedances greater than 1K or so should be fine. (Higher impedances are fine as well)
I strongly recommend putting the power transformer and power supply in a separate box if possible. The magnetic field from the power transformer was difficult to deal with, and while the induced spectra was below the threshold of audibility it bothered me that I could not fully eliminate it. (I was able to reduce it significantly.)
Also make sure to buy 6N6P that have been section to secion matched in order to avoid gain imbalance. I bought a number on eBay, the one I originally installed is still in there and is still as well matched as when new. Unmatched samples had slight to significant differences in voltage gain section to section. I may have mentioned this earlier in the thread as well.
The tubes have a long service life in this application.
The tubes have a long service life in this application.
SLOWWW progress, but progress nonetheless. I finally got the PSU working and checked out. Ready for connection to the signal chassis, but the signal chassis needs a bit of work. As for the PSU, I seem to have from 6.4-6.5v unloaded on the rectifier heater (I'm using an EZ80). The unloaded 6N6P heater voltage is about 6.2v and I'm wondering if I need another wind on the transformer. I'll try to measure it under closer to operating conditions. Unloaded B+ is around 275v (I didn't let it stabilize too long, but it had settled there for a few minutes).
What size mains fuse are people using? I did a quick calculation and it looks like total mains current should be less than 150mA, correct? I'm assuming 30mA at 240 or so B+ and 1.5A total filament current at 6.3v. So I'm thinking between 500mA and 1A fuse size? Thoughts anyone? Thanks.
Bit of a rat's nest of wires at the moment. Once things are working as I'd like, I will probably shorten wires and re-think routing.
What size mains fuse are people using? I did a quick calculation and it looks like total mains current should be less than 150mA, correct? I'm assuming 30mA at 240 or so B+ and 1.5A total filament current at 6.3v. So I'm thinking between 500mA and 1A fuse size? Thoughts anyone? Thanks.
Bit of a rat's nest of wires at the moment. Once things are working as I'd like, I will probably shorten wires and re-think routing.