An active loaded triode

[analag]

Mix a little SS with some GS (glass state) to really hear how great a tube can sound. One day I just got tired of plate resistors it's sublevel perfomance.

Analag

 

[gyraf]

Hmm..

I've been experimenting quite a lot with these hybrid designs through the years, but in the end I had to conclude that the "sublevel perfomance" of the classic circuits sonically outperformed all these modern thingys - although the moderns were MUCH better in both theoretical and measured specs...

Somehow the hybrids dosen't do well in (blind) listening tests..

Jakob E.

 

[bcarso]

Jakob, what kind of subjective responses did the hybrid circuits tend to receive?

I can think of a lot of reasons why sand state can create problems in many cases. But then there is the issue of hybrid circuits producing less 2nd harmonic sometimes (analag's one here in particular) and resulting in things sounding possibly less "alive" etc. Also, when there is substantial 2nd and even some 3rd the single voice/instrument mic feed etc. sounds great but the denser textures start to get congested a bit.

Then there are the issues with solid state being able to demodulate r.f. if any has gotten into the system, which may be occurring well below obvious audibility. Also the silicon tends to have some energy at much higher harmonic multiples where it is much more noticeable.

 

[analag]

This was just a schematic I tossed up there. I used the DN2540N5 when I active load a triode. This is a depletion mode lateral MOSFET. I normally don't cascode them. I use one per triode, it holds the tube, but not as stiff as the BJT's would, hence the lifeless sound. I let the tube swing a little. Using a tube as CCS is acceptible I take it, well it works for me, with this combination I am able to broaden the midrange focus tubes are famous for further into the bottom and top region of the audio spectrum. No more flabby bass and loose treble.

Analag

 

[bcarso]

The thing I do like about your current source is the relative freedom from self-heating shifts due to the common-base cascade.

 

[analag]

This is one that I'm particularly fond of. Very clean in your face type of sound. I listened to a CD going through it and I could hear the mixing board un-muting channels in the studio where the disc was recorded and I heard this CD many times over the years and never noticed it. Hmmm.

Analag

 

[Learner]

hey Analag,
That's a very intersting looking circuit, SRRP with a MosFet and tube? Any particular reason why you don't use a cathode decoupling cap?

Also, how do you choose what MosFet to use?

 

[Winston OBoogie]

...

 

[VacuumVoodoo]

A couple of articles and experiment reports on hybrid SE, unfortunately in russian are here:

Hybrid SE

They use MOSFETs in output but the input stages are similar to what is discussed in this topic.

Schematics, formulas and spectrum analysis pictures should be readable for all.

 

[analag]

I use it because it works in depletion mode just like a tube, it can handle higher voltage and current than a jfet, and is heatsinkable. Plus you can download the spice model from Supertex the maker of this wonderful device. I bought a shit load of them. Great investment.

Analag

 

[kevinc]

Add a parafeed output transformer to your circuit, like: http://www.kandkaudio.com/phonostage.html
and you have a great-sounding, low output impedance gain stage. With a 6N1P triode and 4:1 stepdown you end up with about 14dB of gain and Zout of 200 ohms.

 

[analag]

I've been meaning to order some Lundahls to provide galvanic seperation for some pieces I already have working. Suggest three good transformers (1) mic input (2) line input (3) line output. I will buy them.

Analag