Well, both are good, this one utilizes some experience, gained with the first one, plus more comprehensive VAS and very careful stability modelling.
Very satisfied with this one. It came out as a rather "universal" design with a lot of "tuning" potential. Worth trying the version with JFETs at the input, especially bearing in mind Alex MM has developed a beautiful PCB for it >HERE<
For myself - I will leave the Low TIM with HEX-FET OPS and use this one with Lateral FETs, as originally planned.
Then, it will be interesting to run an A/B listening test between these setups 😛
Valery
Great job!!
Beautiful amplifier. Version with latFETs really rocks.
Looking forward your's listening impressions.
I think next step should be vacuum tube VAS 😛
Great job!!
Beautiful amplifier. Version with latFETs really rocks.
Looking forward your's listening impressions.
I think next step should be vacuum tube VAS 😛
Excellent work Valery!
It would be interesting to see if/how different tubes changed the objective and subjective characteristics of the amp.
Keep up the first rate work.
It would be interesting to see if/how different tubes changed the objective and subjective characteristics of the amp.
Keep up the first rate work.
Peter, Jim - thanks for the feedback 😉
I will write about listening in the nearest days...
Cheers,
Valery
I will write about listening in the nearest days...
Cheers,
Valery
TubSuMo Heater Supply
Valery,
You might have mentioned this somewhere (sorry if I missed it), but how are you powering the 12AU7 heater in the tube version?
Valery,
You might have mentioned this somewhere (sorry if I missed it), but how are you powering the 12AU7 heater in the tube version?
Heating and soft-start
Hi Ray,
I use a separate small transformer, giving me ~6.3V AC (1A) for the heaters.
Soft-start/protection board is setup in a way that it first switches the tube heaters on, and in about 20 seconds continues powering-on all the rest, as usual.
See my smart protection board description attached.
Let me know if you'd like to have the gerbers, firmware. etc.
Cheers,
Valery
Hi Ray,
I use a separate small transformer, giving me ~6.3V AC (1A) for the heaters.
Soft-start/protection board is setup in a way that it first switches the tube heaters on, and in about 20 seconds continues powering-on all the rest, as usual.
See my smart protection board description attached.
Let me know if you'd like to have the gerbers, firmware. etc.
Cheers,
Valery
I think, Terry's boards are still in production. I asked him to wait until I test everything to make sure there will be no necessity to cut the traces 😉
So he just ordered them recently...
P.S. I have fully soldered the second channel and now preparing a nice compartment - expect some pictures soon 😉
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Thanks, Valery. I would be interested in the Gerbers and firmware. I can PM you with my contact information if you can't get it from my forum profile.
One reason for asking about the tube heater supply is that someone suggested a version that uses a tube VAS (in addition to the tube IPS), and I was thinking about offering up a design to start the discussion. I've done mostly tube design in recent years (for non-commercial purposes), and I have a tube IPS and VAS circuit that I've used to good effect to drive a push-pull tube output stage. With minimal adaptation, that design could be used as a front end for a hybrid power amplifier. I was working on that design when I came across this thread. My front-end would need a separate power transformer but if one is already required for the TubSuMo then chassis space for it shouldn't be an issue.
If you have any interest in this idea, please let me know.
Ray
Cool! By the way, did you see >this one< - a fully tube-based voltage amplification, BJT buffer and no global NFB whatsoever. It's not as "high-end" (well, better say - "low distortion") as this one, however it's got a distinctive "tube" sound signature. Some 2-nd harmonic...
I am definitely interested to see your design, exchange ideas, etc.
Please drop me your e-mail for gerbers.
Cheers,
Valery
I am definitely interested to see your design, exchange ideas, etc.
Please drop me your e-mail for gerbers.
Cheers,
Valery
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I didn't see this one, so thanks for the link. My design uses a differential input stage feeding a second differential stage. It's a global feedback design (feedback applied to the grid of the second input tube). In the tube amp version, the second differential stage provides the out-of-phase signals needed to drive the push-pull output stage; in the hybrid version, the second stage uses a current mirror plate load to convert the balanced input to a single-ended output for the solid state OPS.
I'll be out of town for the next several days but I'll get you the basic design concept when I get back. This could be fun!
Ray
Lol, no still waiting on the boards. Should have the OPS boards in about a week but he IPS are probably 2-1/2 week out. I have been gathering parts though so should be able to fill them up pretty quick. Looking forward to comparing this the Low TIM hybrid. 😉
Blessings, Terry
