Just build your own adapters. I hope you have room.
Then get an RCA splitter adapter and feed the Left channel of your signal source to both channels; use your balance control to switch from listening to one channel's tubes, versus to the other channel's tubes.
But what do you do for the extra filament current load on the preamp?
Hint: The balance control of many preamps does not have the same frequency response with it set to the center;
versus set to one channel only, or versus to the other channel only.
Good luck!
Then get an RCA splitter adapter and feed the Left channel of your signal source to both channels; use your balance control to switch from listening to one channel's tubes, versus to the other channel's tubes.
But what do you do for the extra filament current load on the preamp?
Hint: The balance control of many preamps does not have the same frequency response with it set to the center;
versus set to one channel only, or versus to the other channel only.
Good luck!
Are there any advantages/disadvantages to use each triode of a dual triode separately for different signals, besides saving an extra tube?
Anecdotally the mind can correct distortion badness in one channel if it gets a clean signal in the other channel, its really weird but the brain combines left right and fills in gaps in ones perception.
About 10 years ago I had one of those little $35 USB DAC headphone amps, it was only 2 inches wide and deep by 1 inch high. I used it for listening in bed because it was so small and volume control was right there in hand. Plugged into a laptop USB on the nightstand playing my lists using JRiver. I thought it sounded decent for what it was. Then one day I only had the plug half inserted so only the left channel was playing, it was horrible, distorted. Then when I pressed the plug in the right channel played and I was hard pressed to notice the horrible left channel anymore. Very weird. I then rigged up a wire to hear only the right channel, it was clean, no distortion, flipped the wires, left channel was indeed still distorted. After this happened to me I realized how handy an output mode switch might be to verify your Amp once in a while, both for LR balance and timbre. Don't know if speakers would show this phenomena but headphones fooled me along with my brain into thinking both channels were equally clean! Is what happens in our brains 99% of the reproduction chain I wondered? I have to conclude yes in this case. For amps with independent tubes across channels, a left/right to mono mode switch is an elegant and costless solution for comparing each tube swap as you go. IMHO tube swapping really should be all about human perception not testers, scopes, etc. Just make a rig of some kind to do fast flipping. Sharing a dual element tube across the channels does complicate it, so if someone wanted to design an amp that was "tailored made" for tube swappers, one should not go across the channels with any of the dual element tubes I suppose.
