Znak m- Your MFA 200 uses octal base front end tubes 6SL7 or the mil spec version 5691, if I remember correctly. If
you've never replaced these tubes, you should try some new ones. They last longer than the output tubes, but they do
wear out.
As I posted above, not all tube preamps can drive long
cable runs. The Hovland's high output impedance of 2500 ohms can cause interactions with long cable runs, unless
it sees a high input impedance on the amps. Their amp's
input impedance is 680K ohms.
I'm not suggesting you replace your 30' cable run with another brand of cable, just try a shorter run between the
preamp/amp and see want happens.
If you need help with the MFAs, suggest you contact Scott
Frankland.
you've never replaced these tubes, you should try some new ones. They last longer than the output tubes, but they do
wear out.
As I posted above, not all tube preamps can drive long
cable runs. The Hovland's high output impedance of 2500 ohms can cause interactions with long cable runs, unless
it sees a high input impedance on the amps. Their amp's
input impedance is 680K ohms.
I'm not suggesting you replace your 30' cable run with another brand of cable, just try a shorter run between the
preamp/amp and see want happens.
If you need help with the MFAs, suggest you contact Scott
Frankland.