I am DEEP in the experimentation stage. Here are some of my previous experiences:
1. In the '90s in college, I used a Barcus-Barry transducer mic drilled into my mouthpiece with preamp. This system picked up a bunch of valve clanking, and feedback was very bad when I wasn't performing with it. It lasted exactly 1 recital.
2. 10+ years ago I used an AT-35pro - clip on condenser mic: It had great sound, but had a directionality issue, as a quick tug on the mic cable could pull the microphone out optimal setup. I also tried this with a wireless setup, but the tech at the time had mediocre sound sound quality compared to the 35-pro. This is the setup I used years while performing with 3 bands in Indianapolis... The Tumbleweeds, Born Again Floozies, and Accidental Arrangements.
3. Recently, in NYC, I realized that performing on stage can be a challenge - not only due to the direction issue with the 35pro, but also dealing with multiple soundmen can be a challenge. Many don't quite understand how to address feedback issues, and end up just turning the tuba down, even if the problem isn't tuba related. Additionally, I began to get want to add other capabilities to my performance capabilities: volume control, octave doubling, even *gasp* overdrive distortion.
4. Current gear thoughts:
I own many microphones:
SM58 (great and low tech entry level stuff, has a bit of roll off in the low end.
Rode NT-2: large diaphram mic that is way to nice to bring out on gigs.
EV-RE20 -large diaphram dynamic mic. The sound is slightly better with the EV, and works amazing. I mount it to the horn with a Shu-composite mount. It inserts fairly deep, as it is a long microphone, and it is just great.
Preamp: Presonus Studiochanel - this is a rack mounted tube preamp, compressor, and parametric EQ in one. The compression helps even out the highs and lows in the sound, and the paraEQ can quickly address any runaway feedback caused by effects. For me, overdrive has a 105 Hz feedback loop. -3 to -6 dB fixes the issue.
Effects: I own 2 effects: a TC-electronics VoiceLive Touch2, and a Boss ME-20B. The VLT2 is a loop device with harmony function and a bunch of other really cool stuff. It has 1/4" and XLR inputs, but certain functions only work with XLR inputs, and its native EQ/compression needs to be turned off, as it is designed for voice. I use a stereo output from this device, a lead, and an FX send that I blend with a Boss LS-2 (2 channel mixer). The lead channel I send into the Boss ME-20B - with a volume/wah pedal with 8vb, overdrive/synth effect, and numerous delay effects. The Boss LS-2 is great to mix the two effects pedals, as some effects lack a nice wet/dry mix.
Amp: I had a few discussions with many fellow amped tubists. TubaJoe Exley gave some great advice to me, and I got a Gaillen-Krueger MB150/112S combo amp. Its small, light, sounds great, has versitle EQ, and a DI out. I hand off the DI to the soundman, and I have the peace of mind to adjust my own sound.
Power: I chose to get a Furman PL-Plus-C rack mounted power conditioner. I does a few things besides being a glorified surge protector/powerstrip. It removes line noise, transformer hum from powersources, and it regulates the input voltage to 120V. I can absolutely say that there is a difference without it in my NYC apartment. The power around here is NOISY.
That's about it. I am still experimenting with this setup. I feel that there is better "stuff" out there I could have employed... more up to date effects, loopers... I was tempted to go full out rack effects. It depends on your needs.