valve preamp modify to DI box?

[Matt]

Can anyone advise me on following?

I have a simple valve preamp (based on a 12AX7) which I want to modify so
that it works similar to a DI box. What I want the device to do is provide
a
high impedence ( > 1 Meg) input for a device such as a guitar pickup, and
convert the signal to a lower impedence suitable to feed to a microphone
input or line input of a mixer. Prefereably the output would be balanced
but its not a requirement.

I understand that the output from the 12AX7 might need a transformer to
convert it to a lower impedence. I have a quality MC step-up transformer
(Dynavector DV-6A). Could this be used in reverse if the signal was
suitable attenuated first?

Can anyone advise me or point to schematics on the web?

Matt

 

[tempus fugit]

Is the MC xformer an audio one? If not, it will probably trash the sound. If
you go to http://www.jensen-transformers.com/ they have some application
notes that should help. I would think that you would also be looking for a
line level output, and since you're going to the trouble, you might as well
make it balanced.




"Matt" <not@this.address.com> wrote in message
news:406c256f$0$4543$afc38c87@news.optusnet.com.au...

Can anyone advise me on following?

I have a simple valve preamp (based on a 12AX7) which I want to modify so
that it works similar to a DI box. What I want the device to do is
provide
a
high impedence ( > 1 Meg) input for a device such as a guitar pickup, and
convert the signal to a lower impedence suitable to feed to a microphone
input or line input of a mixer. Prefereably the output would be balanced
but its not a requirement.

I understand that the output from the 12AX7 might need a transformer to
convert it to a lower impedence. I have a quality MC step-up transformer
(Dynavector DV-6A). Could this be used in reverse if the signal was
suitable attenuated first?

Can anyone advise me or point to schematics on the web?

Matt