Help needed from Spectral preamp owners

I have a Spectral DMC 30SL. I just realized that the "balance control" doesn't seem to work. At the extreme, it shuts off the speaker, but anything above that seems to make no difference. My dealer said that it's a very small effect, not like other balance controls. But I hear nothing. Any insights?
You can try measuring the voltage output from the left and right amplifier channels while playing a sine wave test tone and stepping the balance control. I've measured the size of the balance gain step this way.
Bypass the dealer; try contacting Spectral yourself & ask.
Where did you get your pre-amp? It is normal for the output to mute at the last setting. Also, the balance range is quite narrow. It is unlikely that there is a problem with the unit. Have you used a "mono" signal. Please call if you need additional information. We are an authorized Spectral dealer.

Terry Menacker