Line preamp for JLH/PLH?

tmblack · 08:02 PM

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 · 25th October 2011, 11:00 PM

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 · 26th October 2011, 05:12 AM

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

then you'll find his BF862 preamp , too

tmblack · 26th October 2011, 09:16 PM

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 · 30th October 2011, 11:26 AM

they're different

build both and decide

tmblack · 31st October 2011, 05:57 PM

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 · 31st October 2011, 06:56 PM

Maybe you should try it with "indirect feedback"...Indirect feedback with FETs

tmblack · 31st October 2011, 07:17 PM

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

knutn · 31st October 2011, 07:23 PM

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 · 1st November 2011, 04:37 PM

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.

24th October 2011, 07:57 PM	#1
tmblack diyAudio Member Join Date: Jan 2005 Location: UK	Line preamp for JLH/PLH? 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? Last edited by tmblack; 24th October 2011 at 08:02 PM.

26th October 2011, 05:12 AM	#3
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	NS10 or J310 BOZ ( search for Juma's posts ) then you'll find his BF862 preamp , too __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

30th October 2011, 11:26 AM	#5
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	they're different build both and decide __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb

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25th October 2011, 11:00 PM	#2
tmblack diyAudio Member Join Date: Jan 2005 Location: UK	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?

26th October 2011, 09:16 PM	#4
tmblack diyAudio Member Join Date: Jan 2005 Location: UK	Which do you like better? I think the NS-10 should sound smoother and the J310 BOZ or k170 is brighter with more distortion.

31st October 2011, 05:57 PM	#6
tmblack diyAudio Member Join Date: Jan 2005 Location: UK	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.

31st October 2011, 06:56 PM	#7
knutn diyAudio Member Join Date: Mar 2006 Location: Oslo	Maybe you should try it with "indirect feedback"...Indirect feedback with FETs

31st October 2011, 07:17 PM	#8
tmblack diyAudio Member Join Date: Jan 2005 Location: UK	Very interesting design knutn. Have you built one up? And with source resistors?

31st October 2011, 07:23 PM	#9
knutn diyAudio Member Join Date: Mar 2006 Location: Oslo	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.

1st November 2011, 04:37 PM	#10
tmblack diyAudio Member Join Date: Jan 2005 Location: UK	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.

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