I've experienced the same behavior on my DM4800 and on other 48s and 32s. Try the following:
1. Go on the Monitor tab
2. Select one of the Sels (1 - 6), say Sel4
3. Select OSC as input, press Enter to lock it in
4. Press that selected Sel button, (in this example, Sel4)
5. Go to the Osc/Com tab
6. Press the Oscillator button and adjust the level with Pod 4
Now, you'll have Pink or White noise or a Sine wave signal emanating from your speakers. The ONLY WAY to control its amplitude is with the Level control (Pod 4). None of the faders, including the Stereo fader will have any effect. You can also select different frequencies if putting out a Sine wave.
If you turn this off and stay on the Osc/Com tab, you can select Stereo, one or more Busses, or one or more Auxs with the Data Wheel and Enter button and the signal WILL BE routed to those busses. You will see the signal level on the meter bridge and on the display meters. BUT, you will not hear sound from the speakers. No matter how I have re-configured the routing, I have not been able to hear the signal with these latter selections.
It's not clear whether or not this is intended behavior or a software bug. It could be intended if the latter approach is to be utilized solely for setting and/or calibrating levels — it does work and the levels displayed on the meters are exactly that which you've dialed in using Pod 4. I haven't measured the output voltage with a meter to determine whether that is also correct, but I believe it is.
It's possible that Tascam intentionally turns off the output when using this approach to protect our ears and monitor speakers from a loud blast should the levels be set too high. Or, it could be a bug and was supposed to work how we have intuitively presumed.
We would need ask a Tascam rep to get an answer this question.
