guitar stereo tube preamp

[accmeint]

Hello,
 I built the tube preamp project:

http://www.el34world.com/projects/images/stereopreampschematic.gif

I typically run my guitar through one channel at a time...In retrospect I probably should have built the pedal.
The problem I am having is that the "volume" and "output" controls are hard to control.   For example, if I have the output pot set at 6 o'clock to get some crunch, (12 o'clock is off),  There will be very little output until he volume control goes past 3 o'clock, then at 3:01 The volume goes from essentially "off" to something like an icepick in the ears!

The same scenario happens with the volume set at some level, say 4 or 5 o'clock.  When I turn the "output" pot beyond a certain level, it's hit the deck time!!!

Has anyone seen this behavior before?  Could it be an audio vs. linear taper thing with the pots, although I thought I followed the schematic very closely.

Thank you

[sluckey]

That preamp is meant to drive a power amp. You're not plugging it into the instrument input of another guitar amp are you?

[accmeint]

Hello,

Thank you for the reply...Yes, I am plugging it into the input of a guitar amp.

[Geezer]

Hello,

Thank you for the reply...Yes, I am plugging it into the input of a guitar amp.

Then you will have to "insert" the preamp into the power amp in some way, by either using the "preamp in" jack of your amp (if it has one) or by modding your amp to have a "preamp in", which would be a switching jack placed in the circuit between the amp's last gain stage & the phase inverter.
I did that on a build for a friend. He uses a Digitech amp modeler & wanted to be able to insert it directly into the power amp (bypassing the existing preamp, just like you need to do).
I used a standard Switchcraft jack (12A?, just like is used on the input) wired so that when the jack is not used, the stock preamp signal passes to the PA as normal. When a plug is inserted into the jack, the stock preamp is disconnected & the "new" signal from the external preamp is routed to the PA.

The schematic for that amp is attached.........

[kagliostro]

In the schematic Volume and Output are shown as Audio pot not linear pot

which kind of pot did you used ?

and yes, if you mean you put the output of this preamp in the input where you connect guitar to your amp the problem is there !

Kagliostro

p.s.: a personal question - which is your AC High Voltage before to rectify it ?

[EL34]

Guitar amps are expecting a very low instrument level signal.
Preamps put out a much larger signal.

It's not an effects pedal, it's a pre amp.

As the guys said, plug it into a line or return on an amp or right into some sort of power amp.

I feed my Stereo pre amp into the line in on my computer soundcard.

[accmeint]

Hello,

Thank you for the info.  I have built 2 amps one is the GA-5,

 http://www.el34world.com/projects/images/GA5.jpg

and the other is the 5f6a bassman

http://www.el34world.com/Hoffman/images/5f6aOld.gif

could you recommend the best place for a "preamp-in" connection on these amps?

Thank you for your time and info.

[sluckey]

See pics...

[accmeint]

Thank you very much for the info!