I thought you guys were goofy when the HISS thing first got mentioned.

I had my 950 before anyone mentioned this and knew I never heard this HISS.

I checked it out for myself just to be double sure what I thought.... No HISS, only the ear to tweeter hiss you'd expect.

But.... one day I was sitting there, and hit mute, and noticed the HISS from several feet away!? Dang! I KNOW that wasn't there before?? So what's diff. now? Nothing that I can think of?

In normal listening where I'm ~9' from the speakers I can't hear either HISS, so I'm just gonna except that the prob. happens sometimes, but since you guys are still talking about it, I'll experiment some more to hear when it happens for me, and when it doesn't.

For the record I use Audiosource AMP 7t's (200W per chan. digital amps).

I'm sure that the prob is in the 950, and NOT in anyone's amps though.

My set up is very simple...
I only have three audio inputs plugged into the 950. All three are optical cables from my...
-Pannie RP-56 DVD player
-DishNetwork 6000 Sat /over-the-air rec.
-and PS2

The probs. not there either. I'm sure it's the 950.

I never have the volume at -80 so I've never tested the -80 to -79 effect where the HISS kicks in for people. My 950's pretty much never set lower than -35-ish since that's pretty quiet with my amp and speakers.

The digital amps are VERY precise. No hiss being masked there.

My speakers are Newform Research. The 45" ribbons have no problem letting ANY hiss through, so there's nothing being masked on the output past the 950 in the chain.

I don't use a power conditioner, but I have a dedicated 20 amp line feeding my system (using thicker guage wire than the rest of the house for it's inherent noise supression), so there's no house induced noise getting in either.

I'm thinking this MUST be in all 950's.

tI really seems like a design flaw in the processing. I think many other people like myself did what I did and never noticed that the HISS is there -at times, 'cuz at normal listening disances it's not audible, or just slightly at most.

"Also, exactly how do you “short” the inputs, can this potentially damage anything, and what effect are you expecting?"

There are "shorting plugs" made (probably easier to make your own if they are not available locally). Perhaps radio shack has some, if not, purchase some RCA plugs (the kind that are on audio patch cords of the type that would be used to connect a tape deck to a preamp or (for single-ended use) a preamp to a power amp.

To make your own, solder a wire from the center conductor to the outer shield. Shorting jacks are sometimes used to lower the noise generated by an unused (open) input on a piece of audio equipment. Except when testing/experimenting, they are not needed and it sounds as though they are not needed in your case.

Shorting plugs were much more common back when pre-amps had really high gain inputs for tape heads and such and when the electronics were much more noisy than they are today.

As long as you are connecting shorting plugs to the INPUTS of audio equipment, you should be OK: no damage should result. Connecting shorting jacks to the OUTPUTS is a different story and should be avoided if you like your equipment.

Speakers with a 90dB sensitivity (usually rated at 2.828v [1 watt into 8 ohms] at 1 meter ... yada ..yada) is what I would call average sensitivity and should not "highlight" whatever noise is generated by the preamp and poweramp, provided the noise levels generated are reasonably low.

Paul

I always wondered:

I have never ever personally seen shorted RCA plugs for sale.

But, I have seen the Canare caps (?) many times. All these do, is to basically metallicly cover the jack. (Wraps the shield over and around the inner conductor without touching it.) But not shorted between the center condutor and the shield.

I always thought that inputs were meant to see ~50 - 75 ohm impedance. Shorted plugs? That's 0 impedance.

But I'm no EE...

"Standard" input shorting plugs have a 50 or 75 ohm resistor shorted across the center conductor and outer shield, so they do, in fact, present the proper impedance to the input jack.

[This message has been edited by bstan (edited May 30, 2002).]

My fronts have a sensitivity of 98dB; I guess you would call that high. The hiss I hear is very faint, and can only be heard by putting my ear to the tweeter. It's not what I would call bothersome and I'd be surprised if anyone with 90dB speakers would be able to hear it. Unless your units are putting out FAR more noise than mine, or you have an obscenely high gain amplifier (I'm using the 755).

------------------
Matthew J. Hill
matt@idsi.net

Some applications, RF for example, require terminators with a 50 or a 75 ohm impedance. An improperly terminated connection could result in "reflections" and signal distortion. Severe cases could result in equipment damage. Impedance MATCHING between source and load is required in these situations. The interconnect cable has to have a characteristic impedance (of 50 or 75 ohms) for maximum energy (not voltage, not current) transfer from source to load.

Audio frequencies are a different story. Audio frequency signal sources, at the "line" level (signals on the order of a volt or two), such as a pre-amp, cd player(analog out), dvd player (analog audio out), AM-FM tuner, etc, have output circuits that are voltage sources. Ideal voltage sources have 0 ohm output impedance. Real-world voltage sources are different. It is generally considered "good" if the above mentioned pieces of equipment have an output impedance in the low hundreds of ohms. Lower is better.

The line level inputs on equipment of the above mentioned type (and power amps also) have impedances that are very high compared to the equipment that is supplying the signal. These input impedances are usually tens of kilo-ohms. This allows near-maximum VOLTAGE (not current, not energy) to be transfered from the source to the load (examples: from the CD player to the preamp, from the preamp to the power amp and in the majority of applications, from the power amp to the speaker).

When an input (say, of a preamp) with nothing connected to it is selected, noise generated in the input section of the input stage is amplified by the input stage (and also the following stages of gain). With this (preamp) input connected to a source (with a low impedance output stage) such as a CD player, much of the noise generated by the input stage (of this preamp) is "shorted" out by the low impedance of the source device's low output impedance. Of course, any noise in the source component output will be passed onto the next piece of equipment.

Without breaking the noise into its component parts of current noise and voltage noise, etc., connecting an unused input (on a device like a preamp) to a shorting plug (a true short or 50 ohms or 75 ohms) simulates the low impedance provided by the connection to a signal source. The 50 or 75 ohm version of these shorting plugs can be used in situations that require a 50 or 75 ohm impedance. Compared to the tens of kilo-ohms input impedance of a pre-amp, the 50ohm or 75 ohm or near 0 ohm "shorting plug" placed at the input acts as a short for the majority of uses in this situation, yielding the same result: somewhat reduced noise.

------------------
the 1derful1


p.s. Edited to make spel and gramr mistakes less noticeable and to increase happiness of reading.

[This message has been edited by Paul J. Stiles (edited June 01, 2002).]

dealcatcher, prefect, are either of you still HISSING? I'm still waiting for some input from the Outlaw engineers. I kind of thought I might hear something after the NY show, but no one is answering phones in the outlaw service center. Since I was so close to the end of the 30-day return policy, I ask Mike to suspend my return date until resolution of the HISS is at hand. If you haven't already done so, you might do the same.

BTW - I didn't try the "shorting" suggestion. If that is the answer, I'll wait for Scott to send me some outlaw approved shorting plugs.

Yea, still hissing. I've also had some digital locking problems and some poping during movie playback. I havn't heard back from the outlaws yet, however they are taking this problem serously. Hopefully, everything will be fixed soon.

According to the following thread http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=144535 problems with hiss CAN be related to grounding issues.

Though the specific problem in this thread concerns balanced interconnects, the root problem and cause of the hiss here is lack of matching grounds, i.e. ground loops.

The thread also provides links to some interesting information on this topic.

Regards - Geno

For the sake of troubleshooting, could one eleminate (or at least test for) any possible grounding loop (aka HISS) by using one of those two prong to three prong adapters (ie isolate the chassi ground) and run everything (cd player, amp, and pre/pro) from that same electrical outlet, or do the effects of a gounding loop migrate their way into every outlet regardless of where the loop is actually located?