Class A2 Direct MOSFET Coupled SE

[Wavebourn]

Originally posted by lineup
Can you be more specific, Wavebourn?
What is obvious to you, might need a bit of explaining to others, professor!

Not for the author of the thread. Some threads are not for dummies. High voltage kills!

[Sheldon]

Originally posted by smoking-amp
Nice circuit!

I think it's cool too. Especially nice, since it's a novel approach that's been built.

BTW, I agree with JC on his 10 points. But I still like tubes. They have such a nice glow, and they don't go phfft, if you abuse them for a bit.

Don,

Drifting further OT, and speaking of tubes, and something they might do that sand can't, did you ever get a chance to explore the DHT seasoning factor?

Sheldon

[smoking-amp]

OT, re: Sheldon

Everything (the parts) are sitting on the shelf for the DHT experiment, but I've been way too busy with some other major projects:
1) The toroid winder machine (what a pain trying to find all manner of little mechanical parts for it, I probably over-did it with spring suspension rollers for the toroid rotation supports), have to go get my lathe yet too.
2) I'm modding a Tek 576 curve tracer to do tube curves (increased the V step range to 250V to handle even screen grid drive), now I'm including Mu and gm curves via a HF grid signal injection and synchronous V or I detection at the plate.
3) One of the surplus venders has a switching supply card for sale that is cheap and easy to convert to HV (exposed toroid HF xfmr). So I'm tracing the circuitry out for that.
4) I just bought a used Jet-ski, Yamaha Waverunner. The trailer tongue is too short for my car (I have to back the car into the water to get it off), so another project there. B.O.A.T. = Break Out Another Thousand $

May be a while

Don

[Sheldon]

Originally posted by smoking-amp
OT, re: Sheldon

Everything (the parts) are sitting on the shelf for the DHT experiment, but I've been way too busy with some other major projects:
1) The toroid winder machine (what a pain trying to find all manner of little mechanical parts for it, I probably over-did it with spring suspension rollers for the toroid rotation supports), have to go get my lathe yet too.
2) I'm modding a Tek 576 curve tracer to do tube curves (increased the V step range to 250V to handle even screen grid drive), now I'm including Mu and gm curves via a HF grid signal injection and synchronous V or I detection at the plate.
3) One of the surplus venders has a switching supply card for sale that is cheap and easy to convert to HV (exposed toroid HF xfmr). So I'm tracing the circuitry out for that.
4) I just bought a used Jet-ski, Yamaha Waverunner. The trailer tongue is too short for my car (I have to back the car into the water to get it off), so another project there. B.O.A.T. = Break Out Another Thousand $

May be a while

Don

Ahh, just figger out a way to eliminate sleep from your schedule, and you can get it all done - no sweat. The curve tracer project does sound cool.

Sheldon

[kenpeter]

Feel like burnin some todes with that contraption?
Maybe a little non-beam-forming g1=g2 action?

[lineup]

Originally posted by Michael Koster

..get you copy for reading/thinking: J.C. On Audio matters - collected

Thanks for that paper from John Curl! The stories of Matti Otala and
TIM distortion brought back some memories of my own.

In the late 1970s I worked in an audio store in Alaska and we sold
mostly Sansui. I was into DIY audio design back then and working
on my own versions of comp-symm output circuits, blowing up a lot
of transistors but I was tired of my day job as an audio tech consisting
of mainly replacing from 4 to a dozen transistors in an amp and
hoping you get them all so the whole thing doesn't smoke again...
----

Anyway, enough of that. I only read the first few pages and need
to turn my attantion elsewhere now.
Thanks again!
Michael

Glad you got your Curl paper copy.
The woek to collect wasnt done by me. a member called Dimitri did a heluva job!

Regarding symbiosis MOSFET + TUBES or even tubes + transistors
I miss a lot anybody doing such projects.
I am of this opinion, that sometimes tubes do a better job in a circuit .. with all that high voltage across and their different good parameters.
And sometimes transistors does it better, from some angle seen.

But too seldome do they meet - due to division into 2 camps:
- nothing but tubes
- nothing but transistors or IC:s
This two separated clans - where nothing but clensed and fundamental thoughts count
is very unfortunate

Because I am sure there are such good things to find in the Hybrid Thinking.
There are a few that are handy with BOTH.
We have Wavebourn
we have one other Sheldon (stokessd) at his home SDS Labs http://www.quadesl.com/
Profile:
http://www.diyaudio.com/forums/membe...fo&userid=3901
and there are some others.
SY, our moderator, I think knows BOTH worlds, too.


Myself have only elementary knowledge in tubes.
I could build a SET (single end triode). No problem.
But a little angst I have. ..... Angst(german) = Anxiety = fear.
====


I have advocated Transistor+Tubes hybrid designs at a number of times here in forum:
See for example:
http://www.diyaudio.com/forums/showt...02#post1228902

Originally posted by lineup

beau2317

I am of the opinion ( I have expressed this in other contexts at our board, too )
that
There are too few designs done to explore Combination of Different Semiconductors.
MOS JFET BJT VALVES
Let each type do what does best and take care of this, in Amplifier.

I have started quite a number of such topics, over the years at www.diyaudio.com
Why so relatively little interest?

I have tried to explain such:
diyAudio builders are divided into camps, you 'belong' to one sort of builders
- a gang for mutual encouragement and exchange of applauds
We have:
1. The MOSFET maffia. FETdaMOSalists.
2. Solid State BJT Super Group. They do not make much Noise in circuits, but ...
3. Chim Amps Gain Crown rulers.
4. The only, The real AudioPhile Understanders: VALVES Lovers!

And we have not so many doing HyBride explorations.
And if they do, they do not get attention.
They do not Belong to 'Da Group of COOL People'
...as seen from view of 'those gangs'
---

Regards
lineup

Thanks. Michael, for you friendly post.
It pleases me to know I am not the only gentle man around here.

your lineup

[athos56]

I just finished a Mosfet/Aikidio hybrid (Moskito) there is a thread here somewhere. Its the only SS project I've ever got to work... I like tubes mosetly because they seem, to me at least, to be more forgiving. The picture at the beginning of the thread made me drool though.

[eboz]

Hey Michael,

Old thread I know, but was just curious about your project and A2 type tubes. Have you tried many other tubes in A2 or zero bias? Is the Meteor zero bias (sorry I have not checked myself). I am just curious if it's worth to try a tube like this versus another thoriated tungsten that is mostly in class A1 (211). It also makes sense to me to use a tube that will be in current production and perhaps Taylor would make this one. I don't think I'll ever do a 304TL because of how much heat it demands. Nice work though!! I am sure it's very snappy and scary good bass.

Regards,
-Michael Woods

[Michael Koster]

Originally Posted by eboz

Hey Michael,

Old thread I know, but was just curious about your project and A2 type tubes. Have you tried many other tubes in A2 or zero bias? Is the Meteor zero bias (sorry I have not checked myself). I am just curious if it's worth to try a tube like this versus another thoriated tungsten that is mostly in class A1 (211). It also makes sense to me to use a tube that will be in current production and perhaps Taylor would make this one. I don't think I'll ever do a 304TL because of how much heat it demands. Nice work though!! I am sure it's very snappy and scary good bass.

Regards,
-Michael Woods

The Meteor amp circuit ran with grid current for about 2/3 the positive half of the sine wave just before clipping in the driver. I think the bias was about -20V. The circuit would work great with 854 or 211 in partial-A2. I've even contemplated a 300B A2 using this circuit.

My current breadboard-in-progress (below) in this line of amps is using a high plate resistance triode (the 35tg) with local feedback to enable it to drive a readily available OPT. There is about +25V on the grid at idle.

The pentode driver is loaded by the current through the feedback resistor.

Michael

[eboz]

Originally Posted by Michael Koster

The Meteor amp circuit ran with grid current for about 2/3 the positive half of the sine wave just before clipping in the driver. I think the bias was about -20V. The circuit would work great with 854 or 211 in partial-A2. I've even contemplated a 300B A2 using this circuit.

My current breadboard-in-progress (below) in this line of amps is using a high plate resistance triode (the 35tg) with local feedback to enable it to drive a readily available OPT. There is about +25V on the grid at idle.

The pentode driver is loaded by the current through the feedback resistor.

Michael

Yes that is very cool from an engineering perspective, but you completely missed my question! How do these things SOUND???

Okay to be fair I must have been thinking (how do they sound) and should have asked more explicitly