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The plan is to take a quad 6v6 power amp complete with electrodynamic speakers I got from an FR-40 Hammond Tone Cabinet (schematic attached) and use it as a power amp for my mixer-preamp for voice and acoustic guitar. I followed the instructions for connecting the unbalanced signal from a preamp to the G-G balanced input of the FR-40 (below) and they seem simple enough.
So, the test failed. I tried connecting both a line-out and a headphone-out from a small practice amp to the new input, as modified in the instructions. There was complete silence, with zero sound from the speakers. All the tubes lit up, and everywhere I checked voltage it matched the schematic. I had a spare 6sn7 to switch, but no change. What did I do wrong?
If it's only a matter of input level, I got parts and room to add a 12ax7 stage, but I don't know how to connect it to the G-G input. Any suggestions?
(From a post by MikeFulk on TheHammondForum.)
To run a signal output into any HammondToneCabinet (in a quick-down-'n-dirty-but-it-works-and-is-harmless-way):
1. Connect two 200 ohm 1/4 watt, (higher wattage is OK), resistors in series.
2. Connect hot and ground of your signal output to either end of these "series-ed" resistors. (Do not connect ground of your device to tone cabinet ground.)
3. Connect these two ends of series-ed resistors with signal of your device connected to them to the G-G inputs (pins 1 and 6) of ToneCabinet.
4. Where the resistors in series meet, make a connection from there to tone cabinet ground (pin 2.)
5. The signal stength should be pretty high --- loudspeaker level or a little lower, and the lower the impedance of the source, the better.
6. Tried and true, and, incidentally, the way the Hammond Company reccommended hooking up a Solovox to a Hammond Tone Cabinet in 1941.
Voila.
So, the test failed. I tried connecting both a line-out and a headphone-out from a small practice amp to the new input, as modified in the instructions. There was complete silence, with zero sound from the speakers. All the tubes lit up, and everywhere I checked voltage it matched the schematic. I had a spare 6sn7 to switch, but no change. What did I do wrong?
If it's only a matter of input level, I got parts and room to add a 12ax7 stage, but I don't know how to connect it to the G-G input. Any suggestions?
(From a post by MikeFulk on TheHammondForum.)
To run a signal output into any HammondToneCabinet (in a quick-down-'n-dirty-but-it-works-and-is-harmless-way):
1. Connect two 200 ohm 1/4 watt, (higher wattage is OK), resistors in series.
2. Connect hot and ground of your signal output to either end of these "series-ed" resistors. (Do not connect ground of your device to tone cabinet ground.)
3. Connect these two ends of series-ed resistors with signal of your device connected to them to the G-G inputs (pins 1 and 6) of ToneCabinet.
4. Where the resistors in series meet, make a connection from there to tone cabinet ground (pin 2.)
5. The signal stength should be pretty high --- loudspeaker level or a little lower, and the lower the impedance of the source, the better.
6. Tried and true, and, incidentally, the way the Hammond Company reccommended hooking up a Solovox to a Hammond Tone Cabinet in 1941.
Voila.
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