Peachtree Audio Nova - No subwoofer connection

I just switched from speakers (Martin Logan Ethos) needing no subwoofer to a pair of monitors (Reference 3A MMC Serie) which have an advertised lower limit of 40-42 Hz. This is fine for most of our listening but there are occasions, like when watching movies, when additional bass would be nice. I have a Polk Audio Micropro 4000 which seems very capable but the Nova has no dedicated connection for a sub. I talked to a Peachtree technician who said the only way to connect a sub is to use a splitter at the RCA pre-out connection dividing the signal between the Peachtree 220 amp and the sub. I tried this before and, of course, the sub works fine but it changes the overall sound in a not good way.....and I'm not good at judging minor changes.

I also use the Behringer Ultracurve 2496 in the system and separating the signal this way bypasses the sub's signal from the equalizer so auto room adjustments won't include the range of frequencies that would be produced by the sub. I suppose that if there was a dedicated sub out connection the result would be no different. Because base frequencies, though, are a big part of adjustments for the purpose of room equalization, this is a problem.

Because the 2496 has an unbalanced 1/4" aux out" it crossed my mind that it could be used for a sub. The manual doesn't seem to address this and I've not found discussions about this on the Internet. I've also not been unable to establish communication with Behringer for their help.

There's a good chance that I'm off base on some of these assumptions about this all works but if anyone has suggestions that might help with this dilemma it would be much appreciated.
it looks like your sub has speaker level connections--why not try using them (i.e. amp to sub)?
That's a good suggestion. Just run a cheap pair of speaker cables from your speakers to the sub. I know it doesn't sound like a good idea from an audiophile point of view, but there's really nothing wrong with doing it this way.
Thanks. I was just given the solution; Behringer called back and assured me that the 1/4" unbalanced aux out jack was ok to use as the sub out connection, so I hooked it up that way and it works fine. All I had to buy was 2 mono 1/4" jacks to RCA adapters. This is another example of what an incredibly competent device this EQ is. Now I'm going to use it to rebalance the room for the new setup.
What happened with your ML's? I thought they would be a good speaker for you.
ZD, the ML's are wonderful and I still have them but when I was looking for a pair of speakers for my little garage system, I came across these Reference 3A serie's and just couldn't pass them up. I don't know if you've ever heard them (these are the originals and, supposedly, only 100 were made) but IMO and for my personal taste they are one of the best I've heard. I like them as much but in a slightly different way as my ML's which are 20 yrs newer, and I was having a difficult time deciding which to keep. With the 3A's I have more latitude in amplification choices should I decide to look again into tubes and partly because of that factor the I have the ML's for sale on Audiogon, eBay and Craigslist. This takes first place in difficult decisions for change especially since I've had them for such a short time and I wasn't even looking for a change.
I appreciate the comments but I'm still having problems deciding how to go with this. I'm getting conflicting information not only from the Internet but from Peachtree Audio and Polk Audio as well. Peachtree says the only way to feed to the sub is to use a splitter from the pre out to deliver signal to the amp and powered sub simultaneously. I tried this and, of course, it worked but, and I have no idea why, it resulted in overall somewhat degraded sound.

Polk told me, and this is in the Micropro 4000 manual as well, that I should parallel out from the power amp to both the main speakers and the "speaker" terminals on the sub. These terminals look like speaker level inputs as would be the inputs on a passive sub and if this were the case that connection would bypass the sub's amplification circuitry; they assured me that this is not the case and all capabilities would remain operational such as volume, phase control, room balancing, filters, etc. I'm confused. Having a speaker level signal delivered to anything other than directly to a driver makes no sense unless their is some attenuation circuitry reducing the signal level. Also, what about the impedance reduction resulting from paralleling the speaker outputs.

I mentioned earlier that I have a Behringer DEQ 2496 that can accommodate a sub. I can put it back in the system if it comes to that but I prefer to keep it simple where I can. My experience with the use of subwoofers is limited to my years ago home theater listening at which time my amplification equipment all had dedicated sub outputs. As you all can tell my knowledge on the subject is also quite limited so I need help.
"These terminals look like speaker level inputs as would be the inputs on a passive sub and if this were the case that connection would bypass the sub's amplification circuitry; they assured me that this is not the case and all capabilities would remain operational such as volume, phase control, room balancing, filters, etc. I'm confused. Having a speaker level signal delivered to anything other than directly to a driver makes no sense unless their is some attenuation circuitry reducing the signal level. Also, what about the impedance reduction resulting from paralleling the speaker outputs."

I get why you think this might be a bad idea, but its not. Its perfectly OK to use the speaker cable connection the way Polk recommends.
ZD, with nearly all systems you would be correct, but not in this case.

Jim (Broadstone), I'll start with what is most important:

DO NOT CONNECT THE SUB TO THE OUTPUTS OF THE PEACHTREE 220 AMPLIFIER, unless Peachtree says it's ok, and they have said that it's not ok. I and Kijanki explained the reasons in this thread.

Although powered subs which provide speaker-level inputs almost always do in fact incorporate attenuation circuitry to reduce the signal level provided to the sub's amplifier, and although such subs almost always provide a very high input impedance to a power amplifier they may be connected to (resulting in negligible loading), the design of your specific amplifier appears to completely rule out the use of that kind of connection. At least without the use of a very specialized adapter incorporating DC blocking capacitors, as explained in the other thread.

Regarding connection of the sub to the preamp, can you tell us the exact model name or number of the Peachtree Nova? If it is this one, for example, it appears to have two individually buffered sets of outputs, each having low output impedance. Connecting one to the power amp (preferably Pre Out 1, which is described as being "discrete class A") and the other to the sub should work fine in that case. Aside, perhaps, for subtle possibilities such as ground loop issues that may arise when interconnecting three components.

Best regards,
-- Al
ZD and Al, I'm always glad when you guys respond to my concerns and I've applied your advice more than a couple of times. This one, though, is a bit scary and I probably could have provided more information for you to consider in the first place.

First, the component I'm using as a preamp is the Peachtree Nova 80WPC integrated amplifier. It has two outputs, one marked "pre out", the other is labeled "line out". I accidentally connected the amp to the line out plugs once and thought I'd blown my speakers with the incredibly loud resulting volume.

Also, Peachtree didn't tell me NOT to use the speaker level signal to the sub; they simply said that the splitter from the pre-out connections was the only way. I tried to discuss the specific issue with Polk sub but they, like me, didn't know enough to feel comfortable giving more advice than that concerning the pre-out splitter.

It strikes me that there are 2 ways to do this; the first is to use the splitter method but, and it could have been my imagination, I thought that this resulted in some sound degradation. The other is to reincorporate the equalizer. Is this a good assumption and is it the sonically the best choice?
Jim, I couldn't find an output impedance spec on the pre-outs of the Nova 80W integrated. However the Nova 65SE, 125SE, and 220SE all have the corresponding output impedance specified as "< 50 ohms." Assuming your Nova is similar in that respect, I don't know why it wouldn't be able to drive your power amp (which has a very high input impedance) and the sub at the same time, without perceptible sonic degradation.

I recall from the other thread I linked to that you have a multimeter. What I suggest is that you set it to measure DC volts, and while the amp is powered up but no music is playing measure the DC voltage between each of the output terminals of the amp and the ground sleeve of an RCA input connector on the amp. You can do that while the amp is connected to the speakers and the Nova.

If you measure a high voltage, such as 40 volts, that rules out use of speaker-level connections to the sub, at least without the specialized adapter I referred to. If you read a tiny fraction of a volt, then an approach that should work would be to connect the positive speaker-level inputs of the sub to the positive output terminals of the amp, and to connect the negative speaker-level inputs of the sub to a ground point on the amp. The chassis of the amp MIGHT be a suitable ground point, but a surer bet would be the ground sleeve of an RCA connector, or pin 1 of an XLR connector.

Good luck. Best regards,
-- Al
P.S: Subsequent to submitting the previous post, I did find an output impedance spec for the pre-outs of your Nova 80W integrated, that spec being "<30 ohms." So, again, I don't know why it wouldn't be able to drive the sub and the amp without sonic degradation.

Best regards,
-- Al
Thanks again, Al. I agree and will make those connections again. It's certainly the most straightforward approach. Also, because the subwoofer has its own room balancing capability I don't need to rely on the EQ to do that adjustment which is one of the reasons I bought this particular EQ in the first place. I'll post the results. Jim
Well, it turns out that this is the way to go, Al. I hooked up the sub using splitters at the pre-out connections on the Nova and it sounds fine. When I tried this earlier I think it was during a time that I was also having trouble with one of my interconnects. In the past I've used splitters successfully in various other applications so probably shouldn't have been so slow to accept the idea.
Good news, Jim! Thanks for the update.

Another reason you may have been hesitant to accept the idea of a splitter might be the many negative comments about them you may have seen here in the past. Although on occasion positive ones do appear.

My belief, though, from a technical standpoint and also based on having used them at times over the years, is that the adverse effects people often seem to report as a result of using them are in most cases due to the inability of the component providing the signal to simultaneously drive two sets of cables and the two specific load impedances with good results. Rather than being caused by the splitter or y-adapter itself. And/or failure to realize, in situations where a preamp output is split to drive both a power amp and a sub, that the capacitance of the cable to the sub as well as the input impedance of the sub will affect the signal seen by the power amp. To a degree that may or may not be significant depending on the specific numbers that are involved.

As I indicated earlier, though, those factors don't appear to be applicable in your specific situation.

Best regards,
-- Al
Yes, now I'll have to learn how to best adjust the sub to mate with my new speakers. I'll be starting a new thread on that subject soon.
Al, which way is better / safer/ better sounding? Splitting the rca output on the pre amp or just running speaker cables to the sub?

Also, can we run them straight from the amp or do we need to run them from the speakers?

Im in the same boat as I'm considering a sub but knly have one set of outputs on my Schiit Asgard, which I'm currently using as my pre...
B_limo, it's hard to say which approach would be better in your case. I suspect that either one would work reasonably well.

I assume you are referring to the Asgard 2, as the earlier version does not appear to have provided pre-outs. Although I suspect that the <2 ohm output impedance spec that is provided for the Asgard 2 applies just to the headphone output, not to the pre-outs. But I would expect that the pre-outs on that unit probably also have fairly low output impedance, and the input impedance of the Classe CA-150 amplifier listed in your system description (assuming you are still using it) is a high 75K. So even if the input impedance of the sub's line level inputs is fairly low, as is often the case, the Asgard 2 most likely would have no trouble driving both components. And hopefully the cables you would be using to connect the sub and the Classe to the Asgard if you went with the line-level approach would not be unusually long.

In making those comments about the line-level approach I'm assuming, of course, either that the sub provides line-level inputs for two channels, or that you would be using two subs. If the sub also provides speaker-level inputs for two channels, or if you would be using two subs which provide speaker-level inputs, connecting at speaker level should also work well. And some would say connecting at speaker level is preferable because the sonic character of the amplifier would be reflected in the signals received by the sub as well as the main speakers. Some would also say that connecting at speaker level is preferable because it avoids the use of a splitter, but see the comments in my previous post relating to that.

Also, although it's probably not applicable in your case, be aware that special considerations come into play when connecting at speaker-level if the amplifier is bridged, or has balanced outputs, or is a pair of monoblocks. And as you've seen earlier in this thread, in the case of certain class D amplifiers.

Regarding the choice between connection of the sub to the amp outputs or to the speaker terminals, it may not make much difference but my instinct would be to connect to the amp outputs. Conceivably that could be beneficial by reducing the amount of "back-emf" generated by the speaker drivers that could find its way into the sub. On the other hand, though, it is conceivable that doing so might increase the amount of electrical noise generated by the sub's amplifier that would couple into the feedback loop of the main amplifier, assuming it has a feedback loop, so who knows? As I say, it may not make any difference either way.

So I suspect that both a line-level approach and a speaker-level approach would work in a reasonable manner in your case. My instinct, especially if I am correct in assuming that the amp is not bridged, balanced, monoblock, or class D, would be to go with the speaker-level method, connecting to the amp output terminals. But when and if practicable consider trying the splitter approach as well, and comparing results.

Best regards,
-- Al