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Jempie 15th February 2013 05:23 PM

Single Ended Solid state preamp
Im looking for an single ended solid state preamp only with one transistor design.

I have looked everywere to see if there is an design with only one transistor
use in an line preamp. does it exist

Mooly 15th February 2013 05:25 PM

You have to define things a bit more. Do you want gain with this preamp or is it just to be a "buffer" ?

jan.didden 15th February 2013 05:26 PM

What you need is a common emitter (or common gate) stage. These are very basic, and google will turn up a lot of examples.


Jempie 15th February 2013 05:34 PM

i have a lot of KT603A
i also need gain

Mooly 15th February 2013 06:15 PM

That appears to be an NPN transistor. To make a one transistor amplifier we would need to know the supply voltage and the gain needed. Also using one transistor means the design will have several compromises such as fairly high output impedance.

AudioSan 15th February 2013 06:40 PM

J-fet BOZ.

Jempie 15th February 2013 10:52 PM

Not an amplifier but an preamplifier

jerluwoo 16th February 2013 04:57 AM

1 Attachment(s)
A simple common emitter stage like in the pic attached will work. The 2n2219 is supposed to be nearly the same as KT603A. The distortion is going to be quite high, 5% at 2 volts rms out. Of course it will require a regulated supply or noise will be an issue as well.

Jay 16th February 2013 10:29 AM


Originally Posted by Jempie (
Not an amplifier but an preamplifier

JFET-BOZ is a preamp. It uses NJFET instead of NPN. If you have many NPNs, why do you want a single transistor preamp? NPN/BJT is not suitable for single ended gain stage. There's nothing wrong with two or more transistor, would you think so?

BTW, I always buffer the input of my low power chip amps with NPN-BJT. The chip amp uses single ended supply, so low that very low noise NPN can be used (many of them have maximum Vce of 15V). Schematic topology is similar to what Jerluwoo posted except that output is taken from emitter (instead of collector). My favorite NPN for this purpose is gold plated 2N2222A.

EDIT: For more than one transistor you'll need PNP. Sorry. But eww... they are cheap.

Mooly 16th February 2013 11:42 AM

Why would you need a PNP to use more than one transistor ?

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