Line preamp for JLH/PLH?

[tmblack]

I'm looking for a line preamp for a receiver, and the ouput amp will require a single voltage supply, it maybe a JLH design or not.
It should run on 12V (no -12V), use up to 3 transistors and be single ended and have gain up to 20x.
So BOZ is out, way too high a voltage and current.

Any good circuits from Threshold/NP/ to diy ideas?

 

[tmblack]

I'm starting with a single BJT CE circuit with no bypass capacitor on the emitter resistor.
Not bad, but hums and not as much detail as even an op amp.
Am I asking too much from a single voltage power source?

 

[Zen Mod]

NS10
or J310 BOZ ( search for Juma's posts )

then you'll find his BF862 preamp , too

 

[tmblack]

Which do you like better?
I think the NS-10 should sound smoother and the J310 BOZ or k170 is brighter with more distortion.

 

[Zen Mod]

they're different

build both and decide

 

[tmblack]

K170 BOZ sounds like a little gem.
Solid bass, brash cymbals.
With Idss=6ma,17V in original circuit, I get almost all 2nd harmonic distortion 1% @0.3V output with 1kHz signal.
Should be very good for guitar preamp as well!
But I want less distortion.

 

[knutn]

Maybe you should try it with "indirect feedback"...http://www.diyaudio.com/forums/solid-state/197819-indirect-feedback-fets.html

 

[tmblack]

Very interesting design knutn.
Have you built one up? And with source resistors?

 

[knutn]

No, I haven't, but I would think it is worth a try. Alex Nikitin (x-pro) has tried it. Dependent on matching, it is wisely to use small source-resistors. The output is high-impedance, so you will also need a source-follower.

 

[tmblack]

I built the variations of JFET BOZ, first with feedback to reduce gain.
Tighter bass, treble still too crisp.
Then added JFET current source in place of drain resistor.
Even better bass, treble better but still too crisp/harsh.
Distortion is mainly 2H 0.1%.
Good but I like to get rid of harsh treble.

 

[tmblack]

I'm designing a BJT BOZ with a current source at collector end.
How do I control the gain?
Where do I add the feedback resistors?

 

[Zen Mod]

why with CS ?

 

[tmblack]

The BJT BOZ is just a CE amplifier and sounds ok/good, but with CS it should have less distortion and may sound better.