[dancremeans]

In the Nuforce manual it says, "WARNING: Do not connect NuForce speaker-level outputs to the line-level inputs of active devices such as active subwoofers or semi-active speakers with powered woofers."

I have done this with all the other amplifers I owned. I hook up the main speakers using spades, then I plug in the subwoofer to the same speaker-level outputs using banana plugs. I just want to confirm, this is NOT ALLOWED with the NuForce amps? I'm just trying to find out because I don't want to damage anything.

Thanks,
Dan

[John Casler]

In the Nuforce manual it says, "WARNING: Do not connect NuForce speaker-level outputs to the line-level inputs of active devices such as active subwoofers or semi-active speakers with powered woofers."

I have done this with all the other amplifers I owned. I hook up the main speakers using spades, then I plug in the subwoofer to the same speaker-level outputs using banana plugs. I just want to confirm, this is NOT ALLOWED with the NuForce amps? I'm just trying to find out because I don't want to damage anything.

Thanks,
Dan

Hi Dan,

The "key" terms here are "line level" and "speaker level".

I can think of NO circumstance where you would use "speaker level" output from an amp, to power the "line level" input.

"Line level" connections will ususally be either RCA or XLR terminations.

"Speaker Level" connections would be spades, bananas, pins, o-rings, or bare wire.

It would usually be hard to "mix" them (although I have seen very cheap speakers with RCA connections)

[dancremeans]

Thanks for clarifying that! I'm glad to find out I'm OK connecting the sub via the speaker-level input/outputs.

Dan

[Occam]

Thanks for clarifying that! I'm glad to find out I'm OK connecting the sub via the speaker-level input/outputs.

Dan

Please don't do that until you check specifically with the folks at NuForce. Both speaker outputs/channel are sitting at 1/2 the positive rail voltage of the Nuforce amps. This is known as a single rail bridge tied load output. Most [EDIT:powered] subwoofers with speaker level inputs expect one of those outputs to be sitting at ground potential and the other to be swinging above and below that ground potential which is not the case. Check with NuForce to see if this is the case and if they have a workaround.

Edit: If you're talking about a passive subwoofer, which takes the amps outputs with its own passive crossover, and directs low frequencies to its driver and higher frequencies to the 'satellites' it might not be problematic assuming the subwoofer has dual voicecoils or drivers.

[rustydoglim]

We usually point the finger back to the active subwoofer manufacturer  since we can't tell how the active subwoofer is wired internally.
Martin Logan Submit is one such example where ML upgraded the speaker in 2006 to allow for active woofer with amps that have half rail DC offset on the speaker terminal.  With so many amps using Icepower module internally (Icepower also has DC offset), I think a lot of active subwoofer manufacturers will have to accommodate this issue.

[favresj]

Brand new to the site... Can anyone tell me if Vandersteen Model 5's with internal powered subwoofers would present a problem for the 9.02?  I will be getting a pair very soon and hadn't thought about any possible compatibility problem, but now I am a little concerned.   The way these speakers work is by having a high pass filter between pre and amp and then sending speaker level connection to the speakers.  The signal is rolled off at 100 hz by the HP filter and then the  100hz and below content is actually recreated by the Vandersteen Model 5's.  So, there is no line level connection, only normal speaker connections.

Can anyone give me their opinions if this would present a problem for the Nuforce?
Thanks,
Seph

[Occam]

Hi Seph,

When I posted my caveat, I was thinking specifically of the Vandy 2w subwoofers, which the Vandy 5 [Great speaker by the way...] basically incorporates internally. If the implementation is like that of the 2w, I'd guess that it would be problematic to run the 5 with the Nuforce amps.
As Jason has put the onus on the subwoof manufacturers, I'd suggest you contact Vandersteen directly and ask, giving them a link to this thread if needed. They may have made internal modifications to deal with these outre' amplifiers. Be sure to mention the specific model of the 5 you're planning on using, as some versions might take the NuForce in stride, others might not. I doubt if you'll be the first to ask this specific question.

Regards,
Paul

[dancremeans]

Based on what I had read so far in the thread, even though as you are saying, it should be checked out with the sub-woofer manufacturer (well, that wasn't said yet), I hooked up the sub to the Ref9 using the banana plug inputs (my main speakers are hooked up to the spade connectors). So far it's been working fine, even though my next question would have to be..... "when can something bad happen," (to the amps) and "what will that bad be?" And...would it have already happened by now? javascript:void(0);

The sub-woofer is the HSU Research VTF-1 MK2

Thanks,
Dan

[nuforce-casey]

Hi Seph,

When I posted my caveat, I was thinking specifically of the Vandy 2w subwoofers, which the Vandy 5 [Great speaker by the way...] basically incorporates internally. If the implementation is like that of the 2w, I'd guess that it would be problematic to run the 5 with the Nuforce amps.
As Jason has put the onus on the subwoof manufacturers, I'd suggest you contact Vandersteen directly and ask, giving them a link to this thread if needed. They may have made internal modifications to deal with these outre' amplifiers. Be sure to mention the specific model of the 5 you're planning on using, as some versions might take the NuForce in stride, others might not. I doubt if you'll be the first to ask this specific question.

Regards,
Paul

Specific to the Vandy 2W, I spoke with Richard, and he said no problem to work with Nuforce.  You can double-check again.   Good designs and executions usually wouldn't have any problem.

[favresj]

That is great news.  Thank you for your response.  I really believe the Nuforce will mate very well with the Vandersteens.

[favresj]

I just wanted to let everyone know that I had also posted this question on whether or not the Nuforce 9.02 would work with his Model 5 speakers, on Vandersteen's techincal information page, and he responded; not good news.  Please see below for his response...I've pasted the relevant portion:

Answer: HELLO JOSEPH, THEY ARE NOT COMPATIBLE. THE NEWER VERSIONS OF THE ICE POWER AND MANY OTHER MODULES NO LONGER HAVE THE DC ON THE OUTPUT. IT IS IMPORTANT TO KNOW THAT THESE AMPLIFIERS ARE ANALOG IN YES, BUT ARE STILL SWITCHING AMPLIFIERS.

Thoughts?

[jkscherk]

I find myself in a similar situation.  I have ACI Jaguar/LFM speaker combination.  The LFMs are essentially subs with a bulit-in fixed 100Hz crossover for the Jags.  You can get the signal to the LFMs via speaker cable connections and ACI provides a speaker-level converter which can go from a speaker cable input to the line-level input connections on the LFM internal amp.  I think it's some type of capacitor maybe.....

Will I have the same problem??  Assuming I use the Ref 9.

[nuforce-casey]

Hi,
First of all, if the ground is isolated on the subwoofer amp, then the DC offset on the amplifier is not relevant, as the subwoofer amp will see an AC signal regardless of the offset. There is no reason for the subwoofer amp to share the ground with the system and usually they don't (check the AC plug, they either have a 2-prong, or check for conductivity between ground and the RCA shell).

The other issues are related to how the subwoofer amp circuit interfaces with the incoming signal.   First of all, a mono-subwoofer amp would be summing the 2 monoblocks, and that is not going to be compatible with Nuforce as they do not share grounds.   2nd, if the input is not differential, then it could be intpreting the signal with an artifical offset - the 2nd issue can be fixed, as long as the ground is being isolated, the subwoofer amp input can be decoupled with a 2-3uF capacitor on both the +ve and -ve leads.