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footswitchable channels
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myker
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footswitchable channels
hi, im the new guy..just built my first 18 watt TMB. is there a way to make the two channels footswitchable?
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zaphod_phil
- Builder, Admin
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The easisest way is just to use an A/B Box on the floor, with a cable out going to each input. If you get a box that also lets you have both A and B on at the same time if you want, it's even better, as that lets you "jumper" the channels together. This jumpering is something you can do on a TMB that you can't really do with a regular 18W.
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myker
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s2
- Senior Amp Tech
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I've been playing with the idea of channel switiching on my prototype amp. The cool thing about these 18 watts is they stop getting louder at around 6 and transition into adding distortion and compression after that. This lets you set 1 channel at about 6 and use your volume control to control the sweet spot. You can then set the other channel at 8 or 10 for your leads. The DB level stays pretty close from one channel to the next, with a nice volume boost on the lead channel. This assumes, of course, that you can switch between them.
This turns out to be a complex problem.
One of the issues is you need to shunt the channel which is not in use as the moment (not to mention the loud click-popping sound that needs to be buffered when you hit the switch). Otherwise, you will hear a nice amount of hiss from the unused channel.
The first thing I tried was routing the inputs from each channel through a project box containing 2 A/B footswitches on the floor with stereo shielded cable. Each switch becomes a channel on/off switch with its A side going to the amp and the B side going to a 1M resistor. This works, but adds 2x15' to your input length. It's like using a 45' guitar cord. In a word, NOISY.
My next idea was using two 6 volt 2 way mini relays inside the chassis and using the heater power to switch them. My only concern here is having enough current to run the relays and adequately supply the heaters. The jury is still out on this one, but if it continues to work and proves to be stable, I'll draw up a schematic in Visio an post if for everyone.
Otherwise, I don't have any bright ideas.
This turns out to be a complex problem.
One of the issues is you need to shunt the channel which is not in use as the moment (not to mention the loud click-popping sound that needs to be buffered when you hit the switch). Otherwise, you will hear a nice amount of hiss from the unused channel.
The first thing I tried was routing the inputs from each channel through a project box containing 2 A/B footswitches on the floor with stereo shielded cable. Each switch becomes a channel on/off switch with its A side going to the amp and the B side going to a 1M resistor. This works, but adds 2x15' to your input length. It's like using a 45' guitar cord. In a word, NOISY.
My next idea was using two 6 volt 2 way mini relays inside the chassis and using the heater power to switch them. My only concern here is having enough current to run the relays and adequately supply the heaters. The jury is still out on this one, but if it continues to work and proves to be stable, I'll draw up a schematic in Visio an post if for everyone.
Otherwise, I don't have any bright ideas.
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