Hissing sound coming from tweeters

I was going to say that johnk really was listening to the sound of silence at 106db sound level until I realized it was the efficiency rating of the speakers and not the sound level.

Dtc, I ended up not going into the dealer. I got lazy and didn't feel like driving up to Seattle in the traffic. I'm probably going to end up buying a Mcintosh MC252 or Ayre V-5xe and sell the Emotivas. Before I dish out the big dollars, I might try a set of those Rothwell attenuators listed above to reduce the gain and noise floor.

Very often simple math saves lots of funds.
Bravo Al.

I sit in front of massive front horns honest 106db my tube amps on nothing playing only sound I hear is my heart pounding. No system induced noise at all....

Any update from your dealer visit?

My Tannoys are hissing since I changed preamps. The Cary SLP-05 was quiet, but the new preamp is very noisy. I won't mention the product, because the designer has promised to address the issue.

I'm taking the Ayre in to the hifi store on Saturday and will try hooking it up to some of their gear just to make sure there is nothing wrong with my preamp. While I'm there, I might as well demo it with some other power amps to get an idea of how it will sound. Only problem is they dont have any speakers with horn loaded tweeters, so it might be like comparing apples to oranges. I think my preamp just doesn't like the cheap emotivas for some reason. My system is lacking synergy.

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I agree you have more power and gain than you need but that is not causing your problem. In any case I think everyone is over thinking this.

Now that we know you did not have an issue with your previous preamp isn't the problem obvious?

......Before the Ayre hiss not a problem

......With the Ayre hiss is a problem

We're going around in circles here talking about gain. Either something is wrong with the Ayre or there is some weird interaction with your amps but probably the former. Maybe the reason the previous owner sold the Ayre is they had some annoying hiss? Have you contacted Ayre about getting it checked out?

I don't agree it could be a cabling or ground issue. A hum problem yes but hiss no.

How about building a little passive pre out of some Radio Shack parts and see how that sounds? May be all you need.

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Just tried it with the Klipsch KG4 and it the tweeters hissed just as much. I never had this problem before using my Marantz 2270 as a preamp with the Emotivas. Why is this Ayre preamp brining on the hiss? >_<

You're a smart guy Al. It's been a while since I have worked with that kind of math. It seems like there must be more to it than the gain on these amps that's causing the hiss. There are plenty of people out there running Klipsch with Emotivas/Mcintosh and don't experience the ridiculous amount of hiss I'm experiencing. Even if I picked up an Ayre V-5xe, that amp still specs gain of 26db which wouldn't help my case either.

I just want a good solid state amp that can rock hard and won't cause a bunch of hiss through my tweeters. I could hook up my old Klipsch KG4's and see what happens. They are rated at 94db.

Did you try the cheater plugs? It is a common solution to hiss/hum problems? May not be elegant, but it does work in lots of cases. If it has no effect, you are out $10 at most. You probably need different amps, but the cheater plugs may buy you some time. If it really is a ground loop problem, different amps may or may not help.

Al, how do you calculate the reduction in gain?

As a rough approximation, I neglected dynamic headroom and calculated the gain for the MC252 based on the continuous maximum power rating of 250 watts. Based on P = (Esquared)/R, 250 watts into 8 ohms corresponds to 44.7 volts. The specified sensitivity for the balanced inputs is 3.2 volts. Therefore the voltage gain, neglecting dynamic headroom, is 44.7/3.2 = 13.97. Based on 20log(Vout/Vin), that corresponds to 22.9db.

I now see in one of the spec sheets that dynamic headroom is specified as 1.8db. So depending on what power level the sensitivity spec is defined with respect to, the gain may be as much as 22.9 + 1.8 = 24.7db, which is only 7.3db less than the gain spec of your present amplifier.

how much reduction do you think is needed to obtain satisfactory levels?

A commonly cited rule of thumb is that a 10db reduction in volume is subjectively perceived as being about "half as loud." Based on that, and on your initial description of the present hiss level as "very annoying," my rough guess is that you would want to reduce the amplifier gain by significantly more than 10db with respect to what it is now, perhaps reducing the present 32db gain to the area of 16 to 20db or thereabouts.

Regards,
-- Al

I can hear the hiss 7 ft away from the speakers :( Anyone want to buy my amps?

Id rather have too much power than not enough. The specs for my speakers indicate that the power handling is 250W RMS. I don't want my equipment to have to work too hard to get some serious sound out of them. Al, how do you calculate the reduction in gain, and how much reduction do you think is needed to obtain satisfactory levels?

No, the hiss won't cause any damage.

The MC252 will reduce the 32db gain of your present amp to roughly around 23db, according to my calculations. Not sure that will be enough of a reduction to be satisfactory. Also, using a 250 watt amp with 101db speakers most likely means that you will be paying for a lot of watts that you'll never use, unless you are envisioning going to less efficient speakers in the future.

Regards,
-- Al

Well it looks like I'm stuck with the hiss for now. It won't cause any damage to my equipment right? I'm going to keep my eyes out for another power amp though. Considering the Mcintosh MC252 if I can find one for the right price.

Are there any ill effects from using the attenuators?

A lot of people are happy with them, but there have been some reports of adverse effects on dynamics, etc. I suspect that they would do fine when driven from a component having very low output impedance, such as your Ayre preamp, and assuming that the input impedance of the amp does not vary significantly as a function of frequency (which I would expect to be the case).

I wonder if any Mcintosh power amps would work well with the Ayre?

The key thing is that you want an amp having significantly lower gain than your present amp. More often than not that will correlate with having a lower maximum power rating than your present amp. The MC501 is an exception, though, having greater power capability but significantly lower gain. See JA's measurements.

The hum you are now hearing with rca's is most likely due to a ground loop problem, assuming that the interconnects are not running close to and in parallel with any power cords. I suspect that if you are hearing just hiss and not hum with the xlr's that the hiss is not being caused by ground loop issues, but you can verify that by using cheater plugs as DTC suggested. As I had indicated, xlr interfaces are inherently less susceptible to ground loop issues than rca interfaces, at least if they are well implemented.

Regards,
-- Al

The RCA cables were actually emitting a humming noise when I connected them in place of the XLR's. They have never done that before. I don't have any other amps to put in place of the monos. I know somone with McIntosh MC-501's mono blocks that are hooked up to Klipsch Chorus II, but they are too much work to bring over to my place. I wonder if any Mcintosh power amps would work well with the Ayre?

The attenuators might be worth a try. I have never heard of them, but it sounds like they would reduce the hiss. Are there any ill effects from using the attenuators?

12-28-11: Magfan
Pre / Power amp impedance mismatch?

No. Preamp output impedance is 31 ohms/62 ohms unbalanced/balanced (per JA); power amp input impedance is 23.5K/33K (per mfr). No problem.

Best regards,
-- Al

Pre / Power amp impedance mismatch?

Sounds like it could be a ground loop issue.

You should try cheater plugs on the power cables. These are the 3 prong to 2 prong adapters found at hardware stores. Cheap and easy to try.

I keep a CleanBox II around to try to detect ground loops. It lifts the ground on the cables (source to pre or pre to amp) to eliminate ground loops. It takes a 1/4" TRS jack, so you will need either balanced or singled ended XLR/RCA to TRS adapters or cables (Monoprice has XLR to TRS cables). Since you have mono blocks you could do one side at a time, meaning fewer adapters to buy. It is not a long term solution, but it can help identify if there is a ground loop carried by the ground. CleanBox II is $35 to $55 depending on where you get it. Alternatively, if you can make cables, you can try making either RCA or balanced ones with the ground not connected, as a test.

Do you have any other pre-amp or amp you can test to see if you still have the hum issue? So, the Ayre with another amp or another pre with the Emotiva?

I'm beginning to think that the Ayre just doesn't pair well with my amps.

Given the findings you've described, I suspect that you're right. When you connect the cables to the preamp, you are introducing the possibility of ground loop-related noise, but I would expect the xlr connections to be much less susceptible to that than the rca connections, and you are saying that the results are fairly similar either way.

So even though the noise performance of the Ayre preamp is probably very good (I note that John Atkinson describes the noise performance of the presumably similar K5-xeMP as "superb"), the little bit of noise it generates in the circuitry that follows the volume control is being boosted to bothersome levels by the combination of the high gain of the amp and the high sensitivity of the speakers.

The only solution that occurs to me other than replacing the amps or the speakers would be to put in-line attenuators at the inputs to the amps. The Rothwell's, which are available in both balanced and unbalanced form, are an example, although the 10db of attenuation they provide might not be as much as you would want. I believe some others are available that provide 20db or thereabouts, but I'm not sure if they are available in balanced as well as unbalanced form.

Regards,
-- Al

When hitting the mute button the hiss doesn't change. Neither does selecting a different input or increasing/decreasing the volume. I tried plugging the Ayre in directly into the wall instead of being connected to the Panamax surge protector, but the results were the same. When I swap the XLR cables for RCA cables the hiss is still present as well. I'm beginning to think that the Ayre just doesn't pair well with my amps.

When I have the XLR cables hooked up to the pre-amp in balanced mode the hiss is amplified.

Does engaging the preamp's mute function reduce the hiss level?

Regards,
-- Al

Wow. You guys are extremely helpful and full of good ideas. Thanks for all the replies.

This morning I rearanged my equipment and made sure all cables, cords, etc. are nice and neat. Unfortunately when I powered everything back on the hiss is still there. I disconnected my XLR cables from the pre-amp and mono blocks again, and the hiss is much less noticeable. When disconnected you have to put your ear close to the tweeter to hear the hiss. When I have the XLR cables hooked up to the pre-amp in balanced mode the hiss is amplified.

A further thought. It would probably be worthwhile to invest a few dollars in a pair of shorting plugs such as these, and to put them on the unused rca inputs of the amps.

I see that the amp has a switch to select between the rca and xlr inputs. It is possible that noise being picked up at the rca input and its associated wiring or circuitry is coupling past the switch into the signal path, where it is then multiplied by the amp's high gain factor. Shorting plugs would probably help that.

Also, using the shorting plugs and selecting the rca inputs would allow you to make a more definitive assessment of the intrinsic noise levels of the amp, as others have said.

Before using the rca shorting plugs while using the xlr inputs, however, it would be a good idea to use a multimeter to verify that no continuity exists between the center pin of the rca connector and pins 2 and 3 of the xlr connector. Although I suspect it is not the case, I'm envisioning the possibility that the rca center pin may be connected directly to one of those two xlr pins, and the switch simply grounds the other pin when the rca input is used. In that situation using a shorting plug would ground one of the two input signals in the balanced signal pair.

BTW, be sure that the amp is turned off when and if you change the position of the input select switch. Also, for the benefit of others who may read this, shorting plugs should not be used where a component provides both rca and xlr inputs but does not have a switch to select between them. And of course they should not be used on the outputs of any component.

Regards,
-- Al

Your in a world of hurt.

It could be your system is not grounded properly. Our cable company, comcast was doing work and and did not properly ground the system. I was having hissing through the tweeters also. To pinpoint I disconnected the cable into the preamp and the hissing stopped.

Lots of good thoughts above. Given that the 89db s/n number is referenced to 1 watt (as opposed to full power), I would expect that with 101 db speakers it would result in a hiss level that can be heard at a typical listening distance in a quiet room, but not to a degree that is "very annoying." Even if the number is based on A-weighting, which would de-emphasize high frequency hiss somewhat.

However the very high 32db gain, in combination with the 101 db speakers, means that the noise level that is heard will be extremely sensitive to any noise that is picked up or introduced at the input circuits of the amp, including rfi/emi (radio frequency interference/electromagnetic interference) that may be picked up through the air. Are the amps located away from other components? Are the interconnect cables routed so that they do not run close to and in parallel with other cables or power cords? Are there any fluorescent lights, dimmer switches, computers, or other known rfi generators in the vicinity? If so, try turning them off.

Another contributing factor, btw, which can't be helped, is that your ears are only 25 years old, which means greater sensitivity to high frequency hiss than most of us would have :-)

Regards,
-- Al

The amps have a 5 year transferable warranty. Maybe you can contact Emotiva and see if they will ship you another one to try - just in case it is something wrong with your amps. Or they may have suggestions to try. I have been reading the Emotiva board and a small number of people do seem to have hiss/hum problems - not common but certainly some reports of issues.

Have you tried cheater plugs on the amps? Works sometimes.

SS ammplifiers and sometimes preamplifiers can have a hi noise floor most never hear it because designers thought only low or average efficiency loudspeakers would be used. And most do such. But if using horns on SS it can be hard to find a low noise SS design. I do know NAD newer bee amplifiers are horn friendly and affordable. I design loudspeakers and trust me SS amplifiers can have more noise on horns than tube amplifiers.

89db snr @1 watt isn't high enough?

I'd experiment with cable placement / orientation before changes which cost $$$.
See if raising speaker cables off the floor or getting them away from the interconnects makes any change.....

I don't want to get rid of the speakers or the pre-amp. If I have to get rid of the Emotivas eventually it wont be a big deal. I think I got them for $279 each, which is minimal compared to the speakers and the pre-amp. I like having some headroom that the more powerful amps offer. Unfortunately I went cheap and bought the Emotivas. I couldn't find anything that packed 200 wpc that matched the same price/quality point as the Emotivas. When I bought all my equipment I wasn't thinking about s/n ratios or anything like that. Shows how little I know about building a quality system.

I agree that the concept of building a system around a great pre-amp is a good idea. However, very high sensitivity speakers and an amp w too high a s/n ratio is a v. bad match. If you want to stick w the Arye pre, then you should look for less sensitive speakers or an amp w a better s/n ratio. You would also want to look for a good speaker/amp match.

The RF7 II's and the Ayre are my favorite components of my system by far. I'm definitely lucky to have a setup like this. I bought the Ayre used, that's the only way I could afford it.

@josefm: I tried what you suggested by removing the interconnects. The hiss isn't as prominent, but it is still there. I think my new XLR cables may have enhanced the hiss slightly. Ayre states on their website that the maximum gain on the preamp is 4db with unbalanced outputs and 10db with balanced outputs. I guess there isn't a whole lot I can do about it until I upgrade the mono blocks someday. I need to get a bigger place so I can sit further back from the speakers. That way I probably won't even notice.

I would say you are one lucky 25 year old. The Ayre is a great piece to build the system around. I would move slowly. Start by trying to find what other RF7II users are using. There are lots of good, used amps out there from people like Ayre, Bryston, Classe, Edge, Naim, Parasound, Pass Labs, Plinius etc. Power is not the main issue here. Tubes are certainly possible, depending on how much you use the system for home theater and TV. You can probably sell your Emotiva amps pretty easily. Do your research. You have a great base to build on. Take your time. Good luck.

I was originally using a Marantz 2270 as a pre-amp, but began having some serious problems with it after it was "refurbished". I demoed a couple pre-amps, one was the Ayre K-5xe and the other was an NAD C326BEE. The difference between the two was night and day so I picked up the Ayre on Audiogon (the hi-fi store wanted $2,800 + 9.8% sales tax for a demo model).

I would have to hear the Bottleheads and see if I like them. I have always liked the sound of Mcintosh amps, but they are out of my price range for now.

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Since you asked......

An SET amp is in my opinion the only amp to pair with them. Bottlehead is a great value if you can solder and follow directions, and you can easily learn to solder. There is a used pair of monoblocks for sale here now (no affiliation)

http://www.audiogon.com/cgi-bin/cls.pl?ampstube&1327718278&/Bottlehead-Paraglow-II-2A3-cus

http://www.bottlehead.com/store.php?crn=44

If it were me I would have put my money in a nice amp first and used a cheap passive pre until I could afford a better preamp. You just might find you really don't need an active preamp.

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No worries Herman, I appreciate the suggestions and didn't take it as criticism. What kind of amps would you recommend to go with highly sensitive speakers? I probably couldn't go wrong with an Ayre power amp to match my pre-amp, but I'm open to other suggestions.

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Yes sir, pay as you go. It wasn't a criticism, it was a suggestions. Sorry if it came off any other way.

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Thanks for all the helpful information. I'm at work right now, but when I get home tonight I will disconnect the amps from the pre-amp to determine if this is just a noise floor issue. I understand that the Ayre pre-amp might not pair well with the cheap Emotivas, or maybe the Emotivas have too much gain for my sensitive Klipsch speakers. Once the music is on you dont hear the hiss and it sounds amazing. The hiss is most annoying when you're trying to watch a blu-ray during a quiet scene.

@Herman: In this hobby you can't always afford to buy all the nice gear in one purchase. I just picked up the Ayre and will be looking to upgrade my mono amps in the future. I am 25 years old and my system is a work in progress.

Looks like the amps had been designed with insufficient feedback making them unstable and hiss the tweeters.

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What Dtc said

IMHO your amps are not an ideal match for your speakers. You have way too much gain and even though price does not always indicate quality you have a $3,500 preamp with $300 amplifiers. I think you need to pony up for an amp that is a better match; less power, less gain, higher quality.

To test it don't just power it up with the inputs disconnected, many amps will be noisy when run without inputs. You need some shorting plugs in the inputs then turn it on to see if it hisses by itself. Or disconnect the interconnects at the preamp and short the middle pin to the ring. Stuff a little aluminum foil in there or use a jumper with clips.

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To further elaborate on the test methods recommended when disconnecting the interconnects from the amp use shorting plugs at the amps inputs.

The speaker sensitivity is 101dB so you are going to need an amp with a very low noise floor to not get some hiss. As Joselm said, disconnect everything to determine if it is the amp noise floor or not. The amp certainly looks like it could be the weak link. If possible, borrow another amp to try. You probably do not need a lot of power for those speakers. The UPA-1 is 200 watts and has a gain of 32dB, which is a lot for 101 dB speakers. It is the entry level Emotiva which may just not be quiet enough for your very sensitive speakers.

What you may well be hearing is the amps' "noise floor." The higher the sensitivity of the speakers, the easier it is to hear it. Every component has a noise floor. Not that I'm an electrical engineer by any stretch of the imagination, but I think it's impossible to not have one. Some are quite lower than others, and some may be inaudible.

It could be something else, or a combination of several things. In my experience, hiss is usually amp noise floor. Humming and buzzing are usually something else - ground loop, EMI, RFI, dirty power, etc.

To verify its really the amps, you need to disconnect the interconnect connected to the amps (do so with the amps off of course). If the 'hiss' is still there, then you are hearing the noise floor of the amp's circuit.
Would a conditioner reduce this noise? Maybe, depends on the conditioner.
COuld also be a mismatch between speaker and amps...speakers being too sensitive for your amps.

It's the amps for sure, I just don't know why they're making my tweeters hiss, and I want to eliminate it. The hiss comes on and stays on when I power up the mono blocks. The pre-amp never actually turns off. Do you think the mono blocks are a bad match for the rest of my system, or can I fix this problem with some sort of line conditioner?

Try turning off everything but the amps and see if you still have it; if you do it is the amps. If not turn on the other components in order and see when you get it.