I'm about to pick up a new BHA-1. I've read this thread over the years but can't recall seeing this question answered.
If I want to control volume from Roon and bypass the BHA-1 volume control, how do I do this? Is it simply a matter of adjusting BHA-1 volume control to max? Do the gain switches still work normally if volume is bypassed? Any other potential issues?
Thanks in advance.
Bill
Bypassing the volume pot is as simple as maxing out on the knob. Potentiometers are essentially a fancy resistor divider that chops off how much signal gets fed into the amplifier circuitry. When the knob is maxed out, the signal does not go through the pot and is basically a short circuit into the amp circuit. There's an argument made that it is still passing through a contact point inside the pot, but that's an argument for another day.
All amp circuits multiply what is fed into them. This is the "gain". In the case of the BHA-1, it has two different gain settings (some BHA-1 are also modded to have lower gain settings compared to stock). Gain is either expressed in decibels or as a multiplier. I'll use multipliers here for the sake of simplicity.
"Unity gain" can be interpreted two ways. The first is when the amp multiplier is x1 (ie: the size of the voltage signal going in equals the size of the voltage signal going out), which makes it essentially a current buffer. Very very few amps ever have unity gain (or fractional gain for that matter, which reduces the output relative to the input). The second way you get "unity gain" is when you chop the input with the pot, by an amount that exactly cancels out the multiplier from the gain stage. So let's say your gain stage is x4, that means you need to use your pot to chop down your signal down to a quarter, so your resultant voltage swing coming out of the amp equals what was put in.
So now that all said, can you "bypass" the pot in the BHA-1? Yes, I've done it. In my case I was feeding my dac into an SPL Phonitor2 then into the BHA-1 with the knob turned all the way up. Because my preamp also has gain to it, it left me with very little room to move on the preamp before things became too loud too fast. Good digital attenuation can work, or if you have a dac who's output isn't too hot then you may be ok. Or get a modded BHA-1 with lower gain.
