Preamp Switching

[dunner84]

I have two independent pre-amp circuits that I am combining into a rack chassis. The first is a classic dumble ODS type thing, and the second is the drive section of a soldano SLO. Combined this will give me Dumble clean, dumble OD, and SLO drive. These circuits are already built, and I am simply repurposing them from previous builds. I will also be including a switchable tube effects loop.
The relay logic will be controlled via an arduino, and that part is straightforward. Hopefully someone can take a look at my switching layout, and provide some insight. For example, I am not entirely sure that the effects loop in/out needs to be muted when not in use. The normally closed position of the relays is marked with a grey line.

My next question is the best way to include a panel switch when I'm just at my desk, and don't need the footswitch. Ideally it would be a single 3 pos switch for the channel selection, and 1 switch for the effects loop. I am thinking the channel switching can be done with an on/off/on switch where the middle position is clean (normally closed state for all the relays), but I could be missing something. The footswitch cable is a 7pin din (thats just what I have on hand), so I can't disengage the panel switch simply by plugging the in the jack.

[tubenit]

I am NOT familiar with an arduino.    So, this is how I would approach it.  I'd use relays with with spst toggle switches or foot switches.  The Dumble amps use both a toggle switch and footswitch for the relay switching.

I'd use a simple A/B switching between the Dumblish and Soldano preamps.

I can not tell if the preamps are going into the same LTPI and poweramp based on your post?

I am sure there are other ways also of making this work.

With respect, Tubenit

[dunner84]

Thanks for the feedback. The preamp will be a standalone unit, so sometimes it will feed a "power amp in", a dedicated power amp, or direct into my interface via a buffered out, so the channels will only ever be used discreetly.

A/B box wont work for my planned setup because it complicates the switching logic when I use it in a live scenario. Using a small controller like an arduino allows me to program switching logic with respect to the channel and state of the effects loop. For example it makes it really easy to go from dumble clean to soldano drive with the effects loop engaged with only one button press.

I realized I have an extra muting relay on the input and output of the preamps, so I removed them and updated the schematic. I also figured out the panel switching, so I will add that to a future drawing for anyone interested.

My remaining question is whether or not I need the muting relays on the preamps, or effects loop. My main concern is noise. Switching noise, or bleed from the unused preamp. The entire supply is well filtered, but anything to minimize noise will be worthwhile.