Yuan-Jing 6N3 Tube Pre-amp from Parts Express

Anyone here interested in a little diy project?  Check this out: Yuan-Jing 6N3 Preamp

I don't know how good or bad this pre-amp is, but at $22.80 I bought two of them.

How bad could they be?  I guess I'll find out in a couple of days and I'll post back.  At the very least I'm hoping the circuit stops working when the tube is removed.

We'll see.

Tony

uum . . . interesting . . .! It's got 4 transistors and runs on 12v. yeah, see what it does with no tube in there !!!

Sigh, well,

It arrived last night.  A quick look at the board confirmed the tube is in the circuit, but it is a cathode follower, no gain.   OK, not a big deal, do more research next time.  The power supply must be 12VAC since the four transistors are used in a 30V+/- split supply and there is a 7805 voltage regulator for the tube heater.

online schematic

I'll see how it sounds this weekend.  In the meantime it does give me an idea to play with to maybe convert it to a gain stage.

Still easily worth the $22.80 I spent.

more to follow...

Tony

What is the input impedance? It could make a useful buffer to feed solid state equipment from a tube preamp phono stage that is sensitive to load impedance, like a Dynaco PAS.

GP49 wrote:What is the input impedance?  It could make a useful buffer to feed solid state equipment from a tube preamp phono stage that is sensitive to load impedance, like a Dynaco PAS.

Looking at the schematics input impedance is more then 1 Mhom
I'll have to adjust this, input impedance equals the pot on input, whatever it has.
But you may remove the pot and take the signal stright to the input caps, then input
impedance will be more then 1 Mohm

I don't see the point if unity gain. You are just adding noise and distortion to the audio signal if using as a line level volume control. Other than an impedance buffer perhaps but tube cathode followers do not necessarily have ultra-low output impedance which can limit connecting cable lengths to very short ones with low capacitance.

The pot measures 45k ohms. Not good for high impedance output devices. I will probably remove it and sub a 250k or 500k minimum of I think it's needed.

anbitet66 wrote:The pot measures 45k ohms. Not good for high impedance output devices. I will probably remove it and sub a 250k or 500k minimum of I think it's needed.

Or remove it and substitute with 470k to ground.

The pot and it's function could be used at the output instead, the tube will happily
load 45k and output impedans is still decent.