Maker Pro
Maker Pro

valve preamp modify to DI box?



Jan 1, 1970
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
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?


tempus fugit

Jan 1, 1970
Is the MC xformer an audio one? If not, it will probably trash the sound. If
you go to 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.