What is the best plan of action?

naturephoto1

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I wasn't sure where to post this, but if one of the Moderators can find a more appropriate place that would be fine.

I am having an issue since I just received my new Oswaldsmill Audio OMA New Yorker Prototype horn speakers:





I like the speakers and their performance very much. But, they have an efficiency of approximately 105 dB/1w/1m. The issue is that I am hearing some hiss through the tweeter/midrange on the horn. Jonathan Weiss of OMA feels that an amp should be dead quiet. But, my Aragon Palladiium 1K monoblock amps are showing a little hiss. The issue is that the problem is worsened substantially when I turn on my ARC LS10 line stage preamp.

I use the system for both 2 channel and for multichannel/movies. I have some options open to me which though may improve the overall sound may result in a bit of inconvenience. For 2 channel listening I am using the Soundsmith Strain Gauge 410 phono preamp with the Strain Gauge Cartridge and my Teres Certus 450 turntable and Teres Illius Tonearm.

http://www.sound-smith.com/cartridges/sg.html





The Soundsmith Strain Gauge 410 phono preamp can use variable volume outputs directly to the Aragon Palladium 1K monoblock amps used for the front speakers. Additionally, the unit has a line input that would allow me to plug my DAC into to play directly through the Phono preamp and the amps. Of course, I could also plug the DAC directly into the amps as well. At this point, I run both my April Music Stello 100 CDT 100 transport as well as my NuForce Oppo 83SE through the DAC with different cables. To run the DAC through the Soundsmith though I would need to have a pair of 2m Balanced to RCA cables made up. This would probably be my cheapest option.

Another option would be to get something like the passive Silvercore Preamp One made up for my needs hopefully with Balanced inputs (the unit has 3 inputs). Jonathan Weiss of OMA is a dealer and is checking into this for me.

http://www.silvercore.de/index.php?preamp-one



If I went either of these 2 routes and removed the ARC LS10 from the system it would require that I change the inputs to the front amps when I wanted to watch a movie. The Onkyo would be used for movies, multichannel music, SACD, DVD-A discs, and FM with my Sanusi TU-9900 AM/FM tuner. I would have to run the cables for the front speakers directly from my Onkyo 885 to the amps. Also, I do not know if the Onkyo for the front speakers will sound as good as the ARC LS10 when used with Home Theater Bypass.

I have however at this point plugged the DAC, the Soundsmith 410 Phono Preamp, and the Onkyo 885 Pre/Pro directly into the amps and have not noticed additional noise as I did with the ARC LS10. I will have to listen to these options directly.

But, I would very much appreciate your input, comments, and suggestions.

Rich
 
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DonH50

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Turn down the treble? Not much help, but that looks like a very bright (live, reverberant, whatever) room and that may accentuate the issue. Have you considered room treatment (or maybe it's there, just well hidden? If so, my apologies.) That would increase the audibility of the hiss.

Does the ARC need to be retubed, or maybe just quieter tubes?

Have you tried playing with the speakers' toe-in a bit, maybe turning them out a bit (straighter to the back wall) so you are a hair off-axis?

When I had all tube equipment, I learned to listen through the hiss, low in level though it was. :( - Don
 

naturephoto1

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Hi Dom,

The ARC LS10 is the best solid state Preamp that Audio Research ever made. So, no tubes to be changed out. Room treatments will be coming later. As to the toe in, I am just playing with and making the adjustment. I can definitely hear a decided increase in the hiss when I stand near the horns. It is frustrating that the Preamp is adding that much additional hiss while the Phono Preamp, Pre/Pro, and DAC do not appreciably add to the noise.

Rich
 

RBFC

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Two thoughts:

1. Have you tried a different interconnection with the LS10 to be sure it isn't a damaged cable?

2. Could you send the LS10 to the factory to be sure it is meeting specifications? A high-quality solid-state unit should not introduce that much hiss into the chain, nor should properly functioning solid state amplifiers.

Lee
 

DonH50

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<Smacks head> Duh! I see "ARC" and automatically think "tubes", sorry!

I agree it's odd the lline preamp is the main culprit; you'd think the phon pre would do it if anything. In addition to what Lee said, have you measured the response in your room? Maybe the radiation pattern has added/increased an upper midrange/treble "hump" that wasn't as obvious before (?)

Maybe a bypass cap or two is bad in the preamp....
 

naturephoto1

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I checked the cables by replacing the Balanced ICs with an identical set. Both sets had the same affect on both speakers. So, I suspect that the cables are not at fault. Maybe I have exaggerated a little as to the affect, but I would say that I am hearing about twice as much hiss with both the amp and the preamp running through the speakers(meaning the ARC LS10 is contributing at least as much to the hiss as the amps). As mentioned, I did not notice any additional hiss when I ran the DAC or the Onkyo Pre/Pro directly into the amps (after they were turned on). In the case of the Soundsmith Phono Preamp again, it was only plugged directly into the amps and turned on. I will have to run some tests and change the set-up of the Soundsmith for variable output so that I can run a record directly into the amps. I will also run some additional tests with vinyl and CD running through the ARC LS10 as well through the Soundsmith and the DAC respectively.

Don,

I am listening so that my head and ear are directly in front of the horn so I do not think at that location and distance that I am experiencing very much of the affect of the room itself. We do know though that the room is a little live when we clap and that will be resolved later.

Rich
 

naturephoto1

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Without going to reinstall the older speakers as I recall there was a fairly low hiss. But, it was hidden and masked in the fact that the rebuilt Dahlquist DQ-10 speakers had a sensitivity probably of somewhere around 90 dB/1w/m. That is a far cry from the sensitivity of the new OMA New Yorker prototype horn speakers with a sensitivity of 105 dB/1w/m.

I am going to give Peter Ledermann of Soundsmith a call a little later and see what he suggests.

Rich
 

amirm

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I suspect you are stuck with the problem :). That said, when you change the volume, does the level of hiss change?
 

naturephoto1

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I suspect you are stuck with the problem :). That said, when you change the volume, does the level of hiss change?

Hi Amir,

I haven't noticed any increase in the hiss with the volume adjustment, but, I haven't really listened for it either. It just became a little irritating on soft passages in a movie and to a lesser extent in some music. The ARC LS10 is just adding more hiss to the background from the amps than I would like to hear especially since I am sitting only about 9 or 10' or so from the speakers.

I am really considering getting rid of the ARC LS10 and going with one of the options that result in my loss of some flexibility. Those being using the Soundsmith Phono Preamp (with one additional source) directly to the amps (much less hiss as far as I can tell) or possibly the Passive Silvercore Preamp with 3 source inputs. Either of these options would require that I swap cables in and out of the main amps when I wanted to switch from the main music sources to the Onkyo 885 mainly for movies and multichannel music. Also as mentioned I did not hear any appreciable increase in hiss when the Onkyo went directly to the amps.

I am waiting to speak with Peter Ledermann of Soundsmith to give me his input on the matter and I hope that he calls me back in just a little while.

Rich
 

amirm

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If the volume change also changes the level of hiss, it means that the noise is upstream of it (i.e. something at the input of the pre-amp). If it is there all the time, it means it has that baseline noise.

Doing a quick search looking for its noise specs, I ran into someone saying they had theirs modified to reduce input noise and hum! Seeing how your Onkyo works better, definitely points to the native device of this pre-amp being noisy.
 

Steve Williams

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If the volume change also changes the level of hiss, it means that the noise is upstream of it (i.e. something at the input of the pre-amp). If it is there all the time, it means it has that baseline noise.

Doing a quick search looking for its noise specs, I ran into someone saying they had theirs modified to reduce input noise and hum! Seeing how your Onkyo works better, definitely points to the native device of this pre-amp being noisy.

I agree
 

DonH50

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From what I recall of the DQ-10's sound, I suspect the horns have a lot more extended high end and are thus exacerbating the slight hiss from the preamp. I do know my old Maggie MG-IIIa's had/have a much flatter high end, with much more tweeter output, than the DQ-10's of that day (mid-80's). I was able to do side-by-side comparisons of the two back then (and measurements; I wanted to see how the pulse response compared, ever the geek). I do not know how flat your new horns are; it is also possible the hiss hit a response peak in the speakers and/or room (boo-hiss, no pun intended! :) ).

Your new horns certainly look terrific! I suspect a little response tweaking and they will be blowing you away. - Don
 

Nicholas Bedworth

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@DonHo... I was thinking the same thing... the horns have extremely extended high frequency response (the JBLs are spec'd to 50 kHz, as I recall). So the noise was probably always there.

Noise horror story of the day. You know how SCRs (dimmers) create a fast ticking sound? Which gets worse as one turns the lights down? So after installing some new gear, there was this annoying, episodic bzzzzzz bzzzzzz bzzzzz. Sort of like SCRs, but fuzzier. Sometimes there, sometimes not. Hmmmm. The fellow eliminated everything he could think of, but there was still some buzz. It would come on for a few minutes, go off, come back at a leisurely interval.

Eventually, he was visiting his neighbor, who proudly showed off their new fish tank, complete with thermostatically-controlled heater. These things broadcast noise through the air, over the power lines, etc. They're almost as bad as laptop switching power supplies. The audio guy tracked down a better heater and that did it.

@naturphoto1 these are beautiful speakers... with that kind of sensitivity, one could have fun with the QRP amps... The LCD panel is an excellent noise reflector :) but this problem isn't room acoustics...
 

naturephoto1

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Nicholas,

Thank you regarding the speakers.

I have now conducted a lot more testing on my equipment. I have found that without question that the Aragon Palladium 1K amps do provide some of the hiss in what I am hearing through the OMA New Yorker prototype speakers. I confirmed this by checking one of the other Palladiums in the system. The Krell amp in my system by comparison is quieter revealing just a hint of hiss or none at all through the OMA New Yorker speakers. The Audio Research LS10 does definitely add additional hiss to the system much more noticeable with the Aragon Palladium IK amp than with the Krell amp. In fact, I would venture to say that the hiss of the ARC LS10 with the Krell amp is probably about the amount of hiss of the Aragon Palladium 1K amps alone. The Onkyo 885 Pre/Pro on the other hand adds very little or no additional hiss to the playback through the OMA New Yorker speakers.

Now, this is quite interesting and I will have to run additional tests. The Soundsmith 410 Strain Gauge Phono Preamp running into either the ARC LS10 or the Onkyo 885 from the fixed outputs of the unit seems to add little or no additional hiss. However, with the special RCA to Balanced cables and using the variable outputs from the unit there is definitely more hiss running through either amp and into the OMA New Yorker speakers. If Peter Ledermann of Soundsmith is correct, it is possible that the cable that was made up is causing part of the problem. I think that I will order the special RCA to Balanced adapters from Soundsmith (though they are not as high quality as the cabling) and then run additional tests with a proper pair of Balanced cables. This will then allow me to determine whether the unit in the variable output mode both for the Phono and auxiliary outputs is noisy, the cabling and adapter is the issue or there is some combination of problems. I will then determine how I wish to use the Soundsmith 410 either directly into the amps or into the Preamp or Pre/Pro.

What I think that I am going to do at this point at least as far as a major change is to remove the front Aragon Palladium 1K amps running to the new OMA New Yorker Prototype speakers. Additionally, I think that I will place an order tomorrow for one of the new First Watt amps that will supply 25 watts of class A power into 8 ohms. That should easily be sufficient for the OMA New Yorker speakers which only require approximately 1/2 to 2 watts (they have an efficiency of 105 dB/1w/1m). Hopefully I will have the new amp next week and will be able to fill everyone in about my findings. If I don't like the amp, then I will return it to the store. I will leave the other 3 Aragon Palladium 1K amps in the system for the Nola LCR Reference Center Channel speaker and for the Nola Viper IIA speakers used for the side surround speakers. The amps for these speakers cause little or no noticeable hiss for these much less efficient speakers.

Rich
 
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Nicholas Bedworth

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Richard,

This is a great report... one can learn a lot from it. My recent experimentation has involved bringing in a high-spec power conditioner, which reduced audible noise slightly, but made a dramatic improvement in more subtle phenomena such as soundstage clarity, richness of timbre, and overall, a removal of grunge that one sort of puts up with, but when it's gone, it's very noticeably gone. The unit in question is the Audio Magic Oracle. My limited experience in very high power amps is that they're often inherently noisier, but this probably depends a lot upon the brand.

Another thought: Do you have any SCR-controlled lighting fixtures? They're the kiss of death for noise. Aquarium heaters? Same thing, even if they're next door...

Anyway, check with Jeremy Ramsey at Audio Magic to see if there's a dealer near you. He could also ship in a unit directly to see if you like it. They seem to be quite good. And of course such untis are made by several companies.

Seems to me that by trying QRP, you're going in the right direction.

BTW in another context, I've had some very pleasant interaction with Frans Lanting... great fellow; he's done some shooting here in Hawaii. There's a famous video clip in which he's on a fairly toasty section of fresh lava on the volcano here, and his wife is asking, "is it safe". Sure, honey, no worries :)



Nick
 

naturephoto1

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I just placed an order for the First Watt M2 amp from Reno HIFI. We discussed which amp to get and after much deliberation this is what Mark of Reno HiFi and I decided to order based upon my speakers, needs and usage. It is a single ended only amp and is scheduled for shipment tomorrow.

Here is the link:

http://www.firstwatt.com/m2.html

It is scheduled to be shipped by UPS Ground so I should receive it next week. I will fill everyone in once I receive the amp and make sure that it is to my liking.

Rich
 

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