bi-amping NuPrime STA-9?

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peresmeshnik

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bi-amping NuPrime STA-9?
« on: 24 Feb 2018, 02:10 am »
Are any NuPrime STA-9 owners out there currently bi-amping, i.e. using *two* STA-9 units to drive two speakers? If so, I would be curious to hear your opinions of the results. I currently drive a pair of Wharfedale bookshelf speakers with one STA-9 + Mjolnir 2 preamp. Basically this setup works for me, but I feel like I'm hearing more noise from the speakers at louder volumes that I would like to (as well as an annoying hum --- more so via balanced outputs from preamp to amp, less so via UNbalanced connection). From what I've read, bi-amping --- in theory --- is one solution to less noise at the same volume, but I've never had the opportunity to hear a comparison between one STA-9 vs. two. Anyone with any thoughts or advice to share? Thanks in advance!

left channel

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Re: bi-amping NuPrime STA-9?
« Reply #1 on: 24 Feb 2018, 05:56 pm »
Do you mean running two STA-9 amps as monoblocks, one for each speaker? Or bi-amping as in using two amps on each speaker, giving each speaker separate amps for its woofer(s) and tweeter(s)? If you search the STA-9 thread for "monoblock" and "bi-amping" you'll find much discussion of both. I'm thinking about using two as monoblocks myself. http://www.audiocircle.com/index.php?topic=138614.0

peresmeshnik

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Re: bi-amping NuPrime STA-9?
« Reply #2 on: 24 Feb 2018, 06:40 pm »
I guess I mean the latter configuration, i.e. driving the woofers and tweeters separately. But I say that without ever having done it before, so maybe what I really want is the former (monoblock) setup. My understanding was that my single STA-9 lends itself well to coupling with a second unit, which can enhance the audio quality, esp. at lower volumes. But, to repeat, I have no direct experience with either configuration, so I would like to try and find out more from users who *have* tried and compared them both.

I also have a hum problem whenever I use the balanced Mjolnir-to-NuPrime connection. Have the same problem via unbalanced connection, too, but less severe; so I'd also be curious to know whether a second amp might reduce the hum still further.

Thanks very much, left channel, for the link to that very informative thread. From what I've read there thus far, some of it is rather abstruse for me, but the specific technical differences between both of these two-amp configurations is precisely what I would like to figure out. I will re-read the more relevant posts again (some discuss STA-10 & other amps, rather than STA-9) and then try to post more specific questions there.

left channel

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Re: bi-amping NuPrime STA-9?
« Reply #3 on: 24 Feb 2018, 07:09 pm »
Glad to help. There's also a bridged mode discussed there, which may be what you're really after. Not having tried any of those yet, I can't comment further on that topic. I can say more about the hum problem though, which those configurations may not solve.

A hum is usually caused by a ground loop. If you get the amp entirely off the same circuit as the Mjolnir, or at least off the same power strip, that may help. I had the same problem (STA-9 and Modi/Magni 2U), but because I wanted to turn everything off using the same power strip I instead inserted a Hum X filter: https://www.amazon.com/gp/product/B0002E4YI8/ The packaging says not to use the Hum X with amplifiers, but even the manufacturer's own sales videos show them using it with guitar amps. Go figure.

You should first move plugs around to confirm the hum is a ground loop and not a defect. Then you'll have those two types of choices for a solution.
« Last Edit: 24 Feb 2018, 10:09 pm by left channel »

John Casler

Re: bi-amping NuPrime STA-9?
« Reply #4 on: 26 Feb 2018, 05:56 pm »
Are any NuPrime STA-9 owners out there currently bi-amping, i.e. using *two* STA-9 units to drive two speakers? If so, I would be curious to hear your opinions of the results. I currently drive a pair of Wharfedale bookshelf speakers with one STA-9 + Mjolnir 2 preamp. Basically this setup works for me, but I feel like I'm hearing more noise from the speakers at louder volumes that I would like to (as well as an annoying hum --- more so via balanced outputs from preamp to amp, less so via UNbalanced connection). From what I've read, bi-amping --- in theory --- is one solution to less noise at the same volume, but I've never had the opportunity to hear a comparison between one STA-9 vs. two. Anyone with any thoughts or advice to share? Thanks in advance!

I tend to think the better method would be using the "bridge" function.

In bridged mode the specs are better in all areas, including SN.

You might also try using the XLR outs from you preamp to the STA-9 ins, but also run a single RCA (from an unused preamp rca out)


peresmeshnik

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Re: bi-amping NuPrime STA-9?
« Reply #5 on: 3 Mar 2018, 09:24 pm »
A hum is usually caused by a ground loop. If you get the amp entirely off the same circuit as the Mjolnir, or at least off the same power strip, that may help. I had the same problem (STA-9 and Modi/Magni 2U), but because I wanted to turn everything off using the same power strip I instead inserted a Hum X filter: https://www.amazon.com/gp/product/B0002E4YI8/ The packaging says not to use the Hum X with amplifiers, but even the manufacturer's own sales videos show them using it with guitar amps. Go figure.

Thanks, left channel, for that good suggestion. I actually researched the problem a bit when I first connected the two together (Mjolnir + NuPrime) and concluded the same --- that is was probably a ground loop. But running the two units into different power strips *&* outlets does not help, and I can't afford to do any major re-wiring of my current residence. So maybe I need to move... Oddly enough, one of the reasons I chose both the Mjolnir and the NuPrime (among competitors in their price range) was because they both allow for balanced connection via XLR cables. But the hum is actually *worse* when they are connected via XLR cables, so I've ended up listening to them via unbalanced/RCA cables instead, simply to reduce the hum. Like everything else in life, one gets used to it, particularly since it's not overwhelming, just annoying during soft musical passages and/or silence, of course. But even if I can't afford to resolve the problem --- i.e. re-wire the room or switch to a different city power grid --- I'd still love to know where the source of it lies...

As for the Hum X filter, after reading the many negative reviews on Amazon (by buyers for whom the filter did nothing), I decided it wasn't worth the $70 risk. I feel like I've already invested too much money in cables, connectors, adapters, etc., most of which are now just lying around, obsolete or unused. But maybe at some point, when the hum is *really* bothering me, I'll resolve to drop the money and give it a try. QUESTION: Did the Hum X filter actually resolve *your* problem completely?

peresmeshnik

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Re: bi-amping NuPrime STA-9?
« Reply #6 on: 3 Mar 2018, 09:40 pm »
I tend to think the better method would be using the "bridge" function.

In bridged mode the specs are better in all areas, including SN.

You might also try using the XLR outs from you preamp to the STA-9 ins, but also run a single RCA (from an unused preamp rca out)

Thanks very much, John, for your suggestion. If I understand you correctly, by "bridge" function you mean to set up two STA-9s as mono blocks and use each to drive one speaker (of the pair); but I don't exactly follow your alternative wiring suggestion. Do you mean run *three* out cables from the pre-amp (two XLR + single RCA) to a single NuPrime? Or to a second NuPrime? I have all *four* outs going to my single NuPrime right now, but I have it switched to "unbalanced" b/c it produces less hum that way (for reasons I can't figure out).

left channel

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Re: bi-amping NuPrime STA-9?
« Reply #7 on: 3 Mar 2018, 10:28 pm »
QUESTION: Did the Hum X filter actually resolve *your* problem completely?

Yes, it fixed the problem completely. YMMV, but perhaps some of the bad reviews come from people who do not have simple ground loop problems. I do perhaps have more money than sense, but am usually too cheap to spend $79 on such things. However this one turned out to be actual science not voodoo.

John Casler

Re: bi-amping NuPrime STA-9?
« Reply #8 on: 3 Mar 2018, 11:09 pm »
Thanks very much, John, for your suggestion. If I understand you correctly, by "bridge" function you mean to set up two STA-9s as mono blocks and use each to drive one speaker (of the pair); but I don't exactly follow your alternative wiring suggestion. Do you mean run *three* out cables from the pre-amp (two XLR + single RCA) to a single NuPrime? Or to a second NuPrime? I have all *four* outs going to my single NuPrime right now, but I have it switched to "unbalanced" b/c it produces less hum that way (for reasons I can't figure out).

Yes, try the following:

Use your XLR cables from your Preamp outputs, to the STA-9 inputs.

Then take a "single" RCA cable and run it from any unused Preamp out, to an STA-9 RCA input.

This hum seldom occurs, but once it was eliminated by this (strange as that seems  :scratch:)

To answer your other question, the reason you have less hum from RCA, is that the RCA voltage output, is often 1/2 the XLR. 

Eisener Bart

Re: bi-amping NuPrime STA-9?
« Reply #9 on: 10 Mar 2018, 08:36 pm »
I've implemented so called "vertical bi-amping" with great result last year. 2  pcs of STA-9 are feeding now a pair of Avanti from Audio Physic (floor speakers). Control of 2 NuPrimes are done with assistance of PS Audio PreAmp HPA-2.


peresmeshnik

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Re: bi-amping NuPrime STA-9?
« Reply #10 on: 17 Mar 2018, 06:13 pm »
Yes, it fixed the problem completely. YMMV, but perhaps some of the bad reviews come from people who do not have simple ground loop problems. I do perhaps have more money than sense, but am usually too cheap to spend $79 on such things. However this one turned out to be actual science not voodoo.

Yes, I'm usually too cheap, too, but then I remind myself that --- in my experience --- opting for cheaper electronics in the long run often saves me nothing since I have to replace cheap equipment more often b/c it dies faster (or causes something else in a chain to wear/die faster)... In short, thanks for the feedback, left channel --- I've decided to kill my china pig and invest in (what I hope will be...) a technical solution to my metaphysical (?) hum problem...

peresmeshnik

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Re: bi-amping NuPrime STA-9?
« Reply #11 on: 17 Mar 2018, 06:19 pm »
Yes, try the following:

Use your XLR cables from your Preamp outputs, to the STA-9 inputs.

Then take a "single" RCA cable and run it from any unused Preamp out, to an STA-9 RCA input.

This hum seldom occurs, but once it was eliminated by this (strange as that seems  :scratch:)

To answer your other question, the reason you have less hum from RCA, is that the RCA voltage output, is often 1/2 the XLR.

Thanks very much, John, for your suggestion. I tried this and, unfortunately, it didn't affect the hum on my setup at all. But I'm glad it resolved your problem, and I will keep it in mind as a possible solution for other (different) hums that may arise...

Thanks also for pointing out that difference between the RCA and XLR connection. I did not realize that there was such a significant difference in voltage output between the two; I always presumed it had more to do with the way/degree the voltage is carried, distributed, resisted, etc. I guess I'll have to read up more on the origins of the definition of "balanced" (vs. "unbalanced") inputs, which apparently I don't understand completely...

peresmeshnik

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Re: bi-amping NuPrime STA-9?
« Reply #12 on: 17 Mar 2018, 06:35 pm »
I've implemented so called "vertical bi-amping" with great result last year. 2  pcs of STA-9 are feeding now a pair of Avanti from Audio Physic (floor speakers). Control of 2 NuPrimes are done with assistance of PS Audio PreAmp HPA-2.

Thanks, Eisener Bart, for your post and remarks. Good to hear that someone else out there has had success with this arrangement. Wow, your tunes must sound fabulous after running through that PS Audio PreAmp, two bi-amped NuPrimes and your Avantis. Good listening!!

I think I'm now virtually convinced that this a second NuPrime is a worthwhile investment, so now I just need to find the will to fork out another $650 in the name of finer aural experience(s)...