Hi, just wondering if I can connect the RCA & XLR inputs on my BHK250 at the same time? I want to run my home theatre setup via RCA and my 2ch setup via XLR.
Obviously not intending on running them simultaneously but being able to connect them up at the same time rather than connecting / disconnecting when switching from HT to 2ch will be useful in my setup. Just hoping it’s possible and won’t risk any damage to the amp.
Thanks.
More likely to damage one or both of the two sources. Connecting outputs together is a Bad Idea ™
You should use a preamp with a Home Theater bypass function?
Yep, that’s the plan. I bought a new BHK pre but had a problem with one of the XLR outputs not working when it arrived. So now I’m stuck making ends meet while it’s off being repaired. 
Might be a pain, but for now, I’d connect and disconnect depending on what you’re listening to. There can be severe impedance mismatching between all of the pieces, and can cause harm to not only the gear but definitely the sound.
I’m not sure about the BHK 250 but my power amp has a switch on the back. You can use either RCA or XlR, but not both at the same time. The switch disconnects one or the other depending on what position it is on so there is absolutely no harm. BTW, in my system, XLR sounds much better than RCA. No contest.
Jamesh
So why is it okay to run XLR and RCA outputs from the BHK pre-amp to the 250 and a subwoofer respectively?
Subwoofers tend to have such a high input impedance that the preamp hardly knows that anything is connected. It’s just receiving a signal essentially.
Jamesh
How is that different from the 250?
You can split an output to go into the inputs of two different pieces of equipment. It may not sound good, but it will not hurt anything.
However, you cannot combine two output sources and send them to a single input without causing problems.
These two scenarios are very differently electronically.
Elk
Understand that- I thought the initial point of discussion was powering several speakers in a home theater situation. If running the a single output from the BHK Pre to the 250 (XLR) and a subwoofer (RCA) “may not sound good” why did Paul specifically recommend it and what is the alternate way of doing this?
To the pre, the amp and the sub present themselves as a load. The input impedance of both the amp and sub are relatively high, so the pre doesn’t really care about this load and is designed to handle this with a pretty wide tolerance.
If you have two preamps hooked up to the BHK 250 (RCA + XLR) the load on each pre is not only the BHK 250 but themselves. The RCA and XLR in the 250 are using the same positive terminal, essentially tying them together. This then can present a massive load on the preamps, harming their output stages. If by putting one of the preamps into standby flips a relay and completely cuts the connection, that’s fine because it’s essentially like disconnecting it. But if it doesn’t you might be SOL. We have no way of know for sure what other pre manufacturers are doing, so we just say not to do it.
Ok, I have a follow up curiosity… I have a similar situation in which I have the XLR outputs of my BHK Pre going to the mono amps. I also have a single ended stereo amp.
Can I plug both RCA and XLR into the pre and leave the other ends of the ones not in use disconnected? This is more convenient since the amps are not in the rack and the pre is.
Cheers,
Mike
Yes, shouldn’t be a problem as there won’t be any load on the output if you are unplugging the cables when not in use.
Yes Mike