Stereomour + Subwoofer

[DesignTaylor]

I'm currently running some Horn Shoppe speakers with a powered subwoofer to round them out. My setup is a TT connected to an Apt Holmam preamp and then onto the Stereomour. The preamp has two sets of our outs (both controlled by the volume) so I pass one set to the Stereomour and the other to the sub. Not perfect but it works well. The sub has a built-in frequency and volume controls for fine-tuning.

While I think the integrated phono stage in the Apt Holman is pretty good, I'm interested in swapping it out for a tube based phono (maybe the
Eros 2). Since the Steromour has multiple inputs at that point it will be hard to justify having the preamp sitting in the middle of the chain doing very little.

So finally to my question... is anyone running a sub with a similar setup? Any recommendations on how to best set it up? Thanks!

[Paul Birkeland]

Does your sub have speaker level inputs? 

The amount of voltage that comes out of the Stereomour isn't so much that subwoofer line level inputs will be overwhelmed.  You can make a pair of banana plug to RCA plug adapter cables for this purpose.  If the range on the volume control of the subwoofer is too small, we can help you install some padding resistors to knock it down.  It's also important that the shell of each RCA cable is connected to the black binding post on each channel of the Stereomour. 

[DesignTaylor]

Hey Paul - thanks for the suggestion! I was actually just reading your comment on a similar thread (guess I didn't search enough before posting).

No line in on my sub, it was just an old home theater unit I had sitting around. Was happy that it had an integrated frequency control. I will likely swap it out in the future but not the highest priority right now.

With only one set of speaker terminals on the Stereomour would you just braid in the additional leads for the sub? I'm currently running Canare 4S11 Star Quad cable with one pair for the main drivers and the other allocated to some T90A tweeters.

I was also thinking that a Smash preamp might be an option since they have a few outputs and people seem to enjoy them as their phono stage. Not sure if I would be missing out on additional phono performance by going with a Smash but I see them used from time to time and they are pretty affordable.

Also wondering about losing tone balance control with this plan. I do tend to leave the bass levels slightly elevated on my preamp. Smash would take care of balance which I sometimes adjust when sitting on the couch vs. my "listening" chare (no dedicated listening room for me, yet).

Any thoughts / ideas welcome and appreciated.

[Doc B.]

Couple of things - line in is what your subwoofer seems to have. That is line level, i.e., what runs through interconnects into RCA jacks. Speaker level input would mean the subwoofer amp has speaker binding post inputs as well as RCA jack inputs.

Next - Smash would work as a way to split the signal between the Stereomour and the subwoofer amp, assuming that the sub amp has a level control. But Smash is not a phono preamp. It is a line, or control, preamp and to play vinyl you need a separate phono preamp like the Reduction or Eros ahead of it. We do have an assembled Smash preamp for sale.

[Paul Birkeland]

Does your subwoofer have one line level input or a stereo pair?  (maybe post a link to the product page for it here)

[DesignTaylor]

Doc B - thanks for the clarification, not sure how I got it in my head that the Smash was a phono/pre...? Anyway, my mission started by wanting to pull even more nuance out of my records. I've really been enjoying my Stereomour and high-efficiency speaker set up (after having a bunch of integrated tube amps and vintage speakers, it is a revelation!). I've tried a couple SS phono stages (the Schiit Mani probably being the highlight) and none of them bested the phono in the Apt. I'm wondering if the Bottlehead magic will strike again if I swap in a Eros or Reduction. But then I was thinking it would be great to just cut my current preamp out of the loop altogether and that's where the subwoofer, balance control and tone control questions started to arise.

Paul - my woofer has one line level (RCA) input. I currently have a two to one (stereo to mono?) RCA cable running from the Apt to the woofer.

thanks!

[Paul Birkeland]

Paul - my woofer has one line level (RCA) input. I currently have a two to one (stereo to mono?) RCA cable running from the Apt to the woofer.

For nearly all preamps, this will make your stereo signal into a mono signal (so the signal going to your amps will be L and R for each amp, not good).

To fix this issue, I made you an ugly drawing that you can implement to restore channel separation.  Resistor wattage isn't important. 

[DesignTaylor]

Paul - You are so right! I was trying to test some news drivers yesterday and couldn't figure out why my balance seemed to no longer work. Thanks for the drawing, super helpful.

On as more practical note, is there any good way to add this extra set of leads in without having to disassemble my current speaker wires and try and shoehorn more cable into my banana connectors? It's pretty tight in there already. Also, any thoughts on gauge needed to run to the subwoofer. Can't thank you enough for your help!

[Paul Birkeland]

Oh, if you already have bananas, then you can just use bare wire and put the resistors in on the RCA plug end (heatshrink is your friend).

[DesignTaylor]

Great, I've ordered in the supplies I'll need. Will report back later.

[DesignTaylor]

Just closing the loop in this one... I ended up swapping for another sub I had that has speaker inputs and then wiring out to that. Sounds good. Volume stays in line with my speakers, happy days.

To keep things tidy, I ended up using a banana plug extender that has a through hole allowing me to plug both the speaker wire to my main speakers and to my sub in. Seems to be working ok but let know if there's a better way to accomplish that.

[DesignTaylor]

LOOKING FOR ADVICE:

I've been enjoying this set up for a while now but I am getting a little bass hum from the woofer when the Stereomour is on. If I stick my ears up to my speakers I've always noticed a touch of background noise but it never bothered me (a small cost for the lovely tube sound). However, the sub seems to be amplifying that same background hum in a much more obvious and annoying way. Is there anything I can do to reduce that noise? I can limit the hz range on the sub. The lower I set the limit the less hum I get but I really like to have the sub support the lower mids so this is not a great solution.

As always, any advice would be appreciated.

[Paul Birkeland]

Well, this is a Steremour I, so the DC filament upgrade won't install onto it.  That would be the real solution to this issue, but other than that you could hack in a line level output that comes out of the amp before the 2A3.  I would also try a cheater plug on the power cord for the subwoofer if it has a 3 wire cord, just to be sure that isn't the issue.  (I'm assuming it's just picking up the hum at the output of the amp)

[DesignTaylor]

Thanks for the quick response Paul!

Yeah, the sub is silent until it gets the feed from the amp so I think it's likely the culprit. Can you point me to more info on hacking in a line level?

Long-term, an upgrade is probably in order.

[Paul Birkeland]

PJ had mentioned it in the past.  There's a 249K resistor between the 0.1uF brown coupling cap and ground. You can lift the ground end, then solder in a 2.49K resistor between the free end of the 249K resistor and ground.  The subwoofer out can be taken from this node.  I would run a twisted pair of wires from ground and this node on each channel to a pair of female RCA plugs and let them hang from the bottom out the back of the amp just to test this out.