• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Tube Preamp Questions

MarmotDavid

MarmotDavid

New Member
These may be silly questions, but here goes....

I have an older Counterpoint SA-1000 hybrid tube preamp, circa 1988-1990 ish. It has a phono section with two 12AX7 tubes and line section with one 6DJ8 tube. I like it a lot and I'm in the process of upgrading tubes.

First question -When I am playing a turntable/phone source, is the signal going through BOTH 12AX7s AND the 6DJ8 tube, or just the 12AX7s?

Second question - How can a preamp have just one tube in the line level preamp section...is it processing both stereo channels?
 
Register to hide this ad
The 6dj8 is a twin triode (like the12ax7) and is literally like two tubes in one bottle. I'm not familiar with that particular preamp but it would be typical for the 12ax7s to handle phono amplification and the 6dj8 to handle line-level inputs. Sometimes additional stages are used for buffering etc but a single stage of the 6dj8 would provide enough amplification for line level signals to stereo channels.
 
MarmotDavid said:
These may be silly questions, but here goes....

I have an older Counterpoint SA-1000 hybrid tube preamp, circa 1988-1990 ish. It has a phono section with two 12AX7 tubes and line section with one 6DJ8 tube. I like it a lot and I'm in the process of upgrading tubes.

First question -When I am playing a turntable/phone source, is the signal going through BOTH 12AX7s AND the 6DJ8 tube, or just the 12AX7s?

Second question - How can a preamp have just one tube in the line level preamp section...is it processing both stereo channels?
Click to expand...
Why do you even consider replacing the tubes ? Chances are that they work perfectly well and
that you actually creates trouble by tinkering a working amp.
 
peterh said:
Why do you even consider replacing the tubes ? Chances are that they work perfectly well and
that you actually creates trouble by tinkering a working amp.
Click to expand...

The preamplifier was in storage for 22 years. When I recently put it back in service, it seemed fine but I wanted a new reference set of tubes for comparison. Also, my hearing has changed in 22 years so I wasn't quite sure. My matching Counterpoint amplifier did not successfully make the 22 year slumber successfully (with 4 6dj8 tubes) and has some yet underdetermined problem. The repair technician for the power amp suggested I replace the tubes in that unit. So, in summary, it just seemed like a good idea to have a comparison set of tubes for the preamp.
 
You must log in or register to reply here.
Back
Top Bottom