Hello,
in the last few months I designed a tube-driven active DI-Box with these specs:
-stereo version (not dual mono)
-input is a cathode follower stage for high-resistance sources - gain is 0,9
-followed by a simple passive EQ (highboost, lowcut, lowboost) gained by a srpp stage very similar to gyrafs pultec concept
- output is a transformer 2:1 - I used the OEP A262A7E wired 2k4/600 Ohms
Here are the schematics and some pictures of my prototype:
http://groupdiy.twin-x.com/displayimage.php?pos=-1721
First of all - my tube di works fine - no problems at all! No noise, no undesirable distortion, good frequency response (+/-0,5dB). The EQ is much better than the EQ's of several mixers.
But what I expected was more 'tube sound' (without the EQ). It sounds very clean and I can't here really a difference compared to semiconductor amplified DI.
I tried several tubes in the input stage:
12AX7 JJ
12AX7 SED
12AT7 JAN Philips
E88CC JJ
The sound differences are very very small. And compared with a solid state mixer channel, there's no "tube" effect or something else. It is subjectively the same sound. So I'm a bit dissapointed because tube circuits are much more expensive than semiconductor ones...
What I've built is a good (from technical side) active DI-Box. As good as a semiconductor DI-Box - but that's not what I wanted!
Any suggestions concerning the schematic? Are there possibilities to get a more "tubelike" sound?
Thanks to the experts here and best regards!
in the last few months I designed a tube-driven active DI-Box with these specs:
-stereo version (not dual mono)
-input is a cathode follower stage for high-resistance sources - gain is 0,9
-followed by a simple passive EQ (highboost, lowcut, lowboost) gained by a srpp stage very similar to gyrafs pultec concept
- output is a transformer 2:1 - I used the OEP A262A7E wired 2k4/600 Ohms
Here are the schematics and some pictures of my prototype:
http://groupdiy.twin-x.com/displayimage.php?pos=-1721
First of all - my tube di works fine - no problems at all! No noise, no undesirable distortion, good frequency response (+/-0,5dB). The EQ is much better than the EQ's of several mixers.
But what I expected was more 'tube sound' (without the EQ). It sounds very clean and I can't here really a difference compared to semiconductor amplified DI.
I tried several tubes in the input stage:
12AX7 JJ
12AX7 SED
12AT7 JAN Philips
E88CC JJ
The sound differences are very very small. And compared with a solid state mixer channel, there's no "tube" effect or something else. It is subjectively the same sound. So I'm a bit dissapointed because tube circuits are much more expensive than semiconductor ones...
What I've built is a good (from technical side) active DI-Box. As good as a semiconductor DI-Box - but that's not what I wanted!
Any suggestions concerning the schematic? Are there possibilities to get a more "tubelike" sound?
Thanks to the experts here and best regards!