Genz Benz Diablo Troubleshooting and Repair

Doing a routine service and repair on this Genz Benz Diablo 100 amplifier. Fortunately, it was not too difficult to track down the cause for each issue and fix everything.

In the video I briefly discuss the folly of the 100W/50W switch. Many amp manufacturers have used a version of this but this is basically the same switching method as used in the Peavey Ultra Plus. Output power is reduced by lifting the cathode to ground connection on two of the output tubes. When doing so, this changes the impedance of the output section and it would be advisable to use the next lowest output tap. For example, if you were running the amp at 16ohms and plugging into a 16 ohm speaker cabinet, you would want to use the 8 ohm output on the amp instead when using the "reduced power" or 50W mode switch. Personally, I don't think there is much benefit here. Pulling two tubes doesn't reduce the volume by much, likely no more than 3 decibels.

If you'd like to know more about output transformer and tube impedance matching, check out this video from Uncle Doug who does a great job in explaining the how and why!
   • Output Transformers: A Discussion of ...