Any opinions or suggestions about this hybrid tube preamp ?

Thread Starter

gaetan8888

Joined Nov 14, 2008
50
Hello

Any opinions or suggestions about this hybrid tube preamp ?

Here's the circuit with parts values.

Thank

Bye

Gaetan

519C3hkh8yL.jpg
 
Last edited:

crutschow

Joined Mar 14, 2008
24,716
My opinion is that a tube amp is an archaic amplifying device, and there is no good reason to use one (unless of course you have that magical "Golden Ear" that can hear the difference). :rolleyes:
 

danadak

Joined Mar 10, 2018
4,057
Looks OK. Biasing seems unusual, eg, static grid bias at ~ -18V.

Same for plate current, looks right on.

Regards, Dana.
 

Thread Starter

gaetan8888

Joined Nov 14, 2008
50
Hello

I have done a Ltspice simulation using 12AU7 tube and with differents values for somes parts.

The thd spectrum look good.

Any thought or suggestions about it ?

Thank

Bye

GaetanCapture hybrid amp.jpg

Capture hybrid amp-thd.jpg
 

BBee

Joined Dec 6, 2018
35
I am not sure about this one. I do quite a bit with tubes, and have made hybrid preamps, but my general approach has been to replace a fet front end with valve. Maybe a backward step, but it does work well and one big advantage is that front end overload damage is unlikely (I should say most of my work is with RF). I can see that the input circuitry is similar to tube circuitry. Putting aside the information given for the moment, I see one good reason for using fet input is lower noise. I suppose my thought would be to see the results compared with a purely tube design though, as I don't really see the point of sacrifice of (possible) advantages of tubes and placing one in a less advantageous position with attendant complexity.

Tracy
 

bertus

Joined Apr 5, 2008
20,451
Hello,

I would have expected a capacitor between the pot and the gate resistor of jfet.

Geatan_Capture hybrid amp_comment.jpg
I think that without the capacitor the DC settings of the jfet will be influenced, depending on the pot setting.

Bertus
 

TANDBERGEREN

Joined Jan 20, 2014
90
Theese old people is more drawn to the fact that tubes are "warmer". (Yes, actual temperature, not the sound)
All to often they confuse the two terms.

Somebody bring them wood-amps?
 

Audioguru

Joined Dec 20, 2007
11,249
Even harmonics distortion produced by a vacuum tube are exactly octaves apart and do not sound awful, but should not be there. Odd harmonics distortion is not musical (sounds awful, something like a buzzer) and is usually caused by push pull tubes close to and beyond symmetrical clipping.
 
Top