I had recently plugged my subs into the RCA connections on the BHK while the DAC was using the XLR inputs and it worked, which surprised me as they are both inputs. Is this ok as I have read that this is not a good option from the Directstream?
Itv really depends on the sub’s input impedance. What happens is you unbalance one side of the XLR output of DirectStream by the load of the sub input. If its impedance is high enough it will limit the impact, but it’ll not be perfect.
Thanks Paul
So subs with Directstream and BHK not such a great option.
The introduction of next years pre amp will no doubt provide the solution in this regard?
My old integrated has only one pre out so this only has enough for the BHK and no subs so looks like I’ve run out of options 
I shall wait patiently
Loving this amp by the way, absolutely loving it!!!
You can run your subs this way; it will not hurt anything. The only potential issue is the XLR connection becomes unbalanced to a degree and common mode noise rejection provided by this output may e compromised. This rarely will make any difference whatsoever.
If you can do so, it is better to send a signal to the sub from the amplifiers’ speaker level output.
Thank you Elk.
I am still curious as to why they can work at all from the input on the amp,as opposed to an output like a speaker level output.
pichi said Thank you Elk.I am still curious as to why they can work at all from the input on the amp,as opposed to an output like a speaker level output.
It’s simple really.
The single ended and XLR inputs on most power amps are really the SAME input to the power amp.
If there is a switch, it is merely to change the way the signals are grounded for single ended or balanced operation. It does not physically switch between RCA and XLR. A few power amps do in fact have two physical inputs for XLR and RCA but I am of the less is more camp when it comes to amplification complexity.
In effect connecting the RCA to your sub is like running a parallel set of wires from the DS to the sub. As Paul indicated - depending on the impedance/load on the subwoofer, this may affect the signal from the DS to the power amp (phase/attenuation etc).
I have the Audio Research Ref 5SE and I like that it has two separate preamp outs (each with either XLR or RCA) so I can run the subs in parallel on two separate pre outs. I think the PS Audio BHK pre will offer the same functionality.
.......I think the PS Audio BHK pre will offer the same functionality.Don't think so: believe there is only one set of outputs (balanced and unbalanced).
amsco15 said.......I think the PS Audio BHK pre will offer the same functionality.Don’t think so: believe there is only one set of outputs (balanced and unbalanced).
Which could be alright for the OP’s requirements if they can be used in parallel - something that was not recommended on the DS
Thanks for that guys,much appreciated.
DoggieHowser I have heard the difference that the Ref 5se made to someone else system and it really was stunning,nice pre mate.
REL and some other subs like to use “high level” connections off the amp speaker terminals instead of a line level feed from the pre-amp. This has proved to be a problem amps of a certain design, though I don’t recall what the variable is. Does anyone know whether this connection method will be successful with the BHK amps?
Welcome, drubin!
I have not heard of this ever being an issue. What “amps of a certain design” exhibit difficulties with this?
I recall reading about this problem with a balanced bridge amp design when used to drive certain subs due to an incompatibility with their grounding scheme.
Yep, it’s been a long time since I looked at that, but if I remember correctly the REL had a 3 wire high level connection which presumed a common connection with the left and right channels: this won’t work with a balanced output amp with no output ground.
Yes, that’s right, Ted. There were problems with some Pass models as I recall and undoubtedly others. Does that description apply to the BHKs?
Thanks, Ted. I was unaware of three-wire input connectors on any sub.
Is there any other circumstance where connecting a high-level input on a sub is an issue for an amp?
Drubin are you contemplating connecting a three-wire inout REL sub, or is your query more generic?
(I cannot answer your question either way. 
)
I am using a REL S/3 wired to the speaker terminals of my BHK250 with no issues…
I should really do a post about my whole system with the BHK 300’s but I am using a pair of velodyne Dd10+ powered by the BHK to great effect. I was powering the subs from an XLR y splitter from the DS. I used to run RCA out of the DS for the subs and XLR going into a preamp, but I found I lost impact and dynamics on the XLR when the rca was in use.
I have found using the high level input to the subs from the BHK blended quite well, perhaps better than via the XLR but I really should switch back and test again now that the BHK is broken in singing so well.
I have the PS Audio Pre-amp and the S300 mono’s feeding my Quad 2905’s. I’m thinking of purchasing 2 subs to augment the bass but I’m trying to work out the connections that will have the least impact on overall sound quality.
My initial thoughts are Pre SE out to Subs and use the XLR outputs to the power amp’s. Without internal modifications I do not believe the 2905’s can have their Bass panel by-passed or bass output lowered - e.g. the Quads are a full-bandwidth speaker design.
The sub’s may be custom built by a very knowledgeable person who specializes in speaker builds, room analysis, passive and active correction etc. has recommended using DSP for digital XO and time alignment.
A while back I was all for this but then I got to thinking (bad idea
) ;
One of my sources is the PWT/DS DAC and I think in the DSP scenario there will be another ADA conversion for the XO & corrections - I doubt that the conversion in say a DEQX or MiniDSP is equal to what preceded it in the DS DAC - so why bother?
Am I just putting up an imaginary wall to better sound? Are there very good ADA converters that won’t take away from the great OP from the DS DAC?
Do the inbuilt XO and phase correction in sub’s do a good job or would an external analogue XO be better?
I am still confused about how to add a sub to the system. Now I have a Mcintosh C2300 pre and I am using two different outputs to feed the BHK 250 and a B&W DB1 sub at the same time. However, I read elsewhere that you not only need 2 outputs from the pre, but also to reach some kind of impedance matching. The DB1, for instance, has 15k Ohm which is supposed to be low, in comparison with the 200k the BHK amp has. Could this be a problem? Even in you use separate outputs from the preamp, are those impedances correlated anyway?. (and btw, the absence of a second output has left the BHK pre out of my short list, even when I really like my amp, and for sure, my DStream)