I have been experiencing the same system hiss discussed in one of the other threads, however, I believe the hiss is associated with the 770, not 950.

Whats happening to me is that with absolutely no external inputs connected to the 950/770 system (i.e. only the 950 connected to the 770 and the 770 connected to two speakers), and the volume set at the very minimum (-80db), I hear a very faint (but acceptable) hiss. But adjusting the volume from -80db to -79db immediately propels the hiss to a HISS (hiss=not so loud, HISS=loud ) in my tweeter, and adds a little noise to my mid-range speakers. Turn the volume back down and the HISS and noise remain until you either turn the 950 off or toggle to a different input.

Why do I think it’s the amp? The HISS is present when all connections between the 950 and 770 are removed (as per suggestion #2 in the 755/770 manual).

Is this a grounding issue?

Anyone else have the 950/770 combo with or without this problem?



[This message has been edited by tetra500 (edited May 22, 2002).]

I would think that the small "hiss" you hear is the *interaction* between the amp and the speakers. I have this too. Have to put my ear right up against the tweeter, and then actually angle my head specifically to hear it. (Just the amp connected to the speakers.)

But the big "HISS" that you hear that becomes apparent when you adjust the volume from -80db to -79db must be from the 950.

So that's at least 3 people now:

Prefect
Dealcatcher
Tetra500

That have experienced this...

I don't think it is coming from the amp. I've tried 3 diffrent amps and they all have the same problem. I also don't think it has anything to do with grouding. My Yamaha on the exact same setup has no hiss. Grouding problems usually induce a 60hz hum not a faint hiss. Overall I feel the 950 is great, I just want to be sure that there is not a handfull of defective 950's. Many people swear they can not hear the hiss past three inch's. I actually measured that I can hear the hiss pretty clearly from over 9 feet away, and this is with the volume at -79db.

I've been experiencing hiss in my 950 as well. It can be heard from several feet away, however it only occurs with certain inputs and certain degial modes.
Examples:
CD analog - hiss
CD digital (optical)with CD player on - no hiss
CD digital (optical) with CD player off - hiss
DVD digital (dolby 5.1) - no hiss
DVD digital (DPLII) - hiss
Video2 (TV with analog + DPLII) - hiss

This hiss comes from both my left and right Active/40's, as well as from the rest of the channels which is connected by my 5 channel amp.

For those people who are commenting on the hiss produced by the 950, I would like to suggest that they mention what power amps they are using (and the gain, if known, of the power amp) and what speakers they are using (and the speaker's sensitivity, if known).

The higher the gain of the poweramp and the more sensitive the speaker, the more likely hiss and other forms of noise will be noticed.

I am looking into purchasing a 950 (I am reading various user's comments). My main speakers are Acoustat 2+2 (reworked interfaces) which are not sensitive and my power amps are not particularly high gain.

Even a very quiet piece of equipment may have noticeable hiss when coupled with a high gain power amp and sensitive speakers.

Paul

There is a certain amount of hiss from any amp. Now whether you can hear it or not, thats where Paul's comments come in.

(I completely disconnected my pre/pro, and just had amp to speakers, and I have it. But like I said, have to put my ear right up to the tweeter, *and* angle it just right to hear it. My level of low level "hiss" is a function of the amp. In my case, when I went from a 150 W/channel Nak PA-5AII to an Acurus A200x3, effectively 300W per channel for stereo listening, the "hiss" did increase, but it never approached "HISS".)

But what dealcatcher is talking about is a lot more than hiss: but HISS.

If the amount of hiss changes from hiss (low level) to HISS (high level) due to the "state" of the 950 (i.e., volume level, input selection, etc.), then that can have nothing to do with the amp and must be due to the 950...

I was expecting a call from Outlaw this week to help me sort out the hiss problem but have not been contacted yet. While waiting for their call, I think I discovered a third variation of the mysterious "hiss" that lies somewhere in-between the hiss and HISS (I'll call it the "hISs"). In order of loudness, my HiSsEs are:

hiss (very quiet, the one you have to tilt your ear just right just to hear) - occurs when the 770 and 950 are connected, turned on, but volume set at minimum -80db.

hISs (not really loud enough to complain about but present none the less) - occurs while the 770 is on but not connected to the 950.

HISS (annoyingly loud, distracting, and unacceptable) - occurs when the 770 and 950 are connected, powered up, and the volume set at any level that is -79db and above.

Although the problem could be in the amp, I'm back to thinking it’s the 950.

What ever the case may be, I am confident that the outlaws will do whatever necessary to "clear" things up for me.

Q. How hot have the 950s (770s) been running? I'm getting 110 easily (even while idle) and mine are sitting side by side in the open on a workbench.

Tetra- Have you tried to get in touch with Outlaw?

There are many of us (I'm sure!) who anxiously await any info on what's up with this new "feature" of the 950...

Tetra, based on your troubleshooting steps in your last post, it does sound as though the problem is in the 950.

In your description of hiss and hISs, the 770, when it's inputs are disconnected, is slightly noisier that when the inputs are connected to a low impedance low noise source (the 950 when the volume control is at minimum). This part seesm normal to me.
The amplifier input stage generates noise, and when the input is connected to a low impdance source (such as the 950 output) this noise level is lowered.

I am not familiar with the 950 internal design, but there may be a muting circuit that senses that when the volume control is at minimum, inserts a mute state (off) somewhere in the signal path. Similarly, some CD players and DACs, when sensing digital zero (all data bits in the word are zero) will mute the output, giving an artifically low noise reading in this state.

I would not be suprised if the noise increase a little as the volume contrl was increased to maximum, but I would not expect a large increase. If the amp has high gain and/or the speakers very sensitive, then levels of hiss (hiss, hISs, and HISS would be louder than the case of lover gain amps and lower sensitivity speakers.

Your description of your system that produces the hiss (950 connected to 770 with 950 volume control at min.) and HISS (volume control of 950 off of the min. setting) seems to point the finger at the 950 being the problem. To be more positve, does the HISS level change when all inputs to the 950 are removed? If possible, try the same test with the 950's inputs shorted.

Paul

p.s.

I looked at the specs for the 950, particularly the singnal to noise ratio specs. The digital preamp section has a worst case spec. of 98dB relative to 2v output. This corresponds to an output noise voltage of about 25.2microvolts, something you are not going to see on the vast majority of o'scopes or meters. The analog preamp secion has no signal to ratio spec. at all, suprisingly. I wonder if this omission is intentional.

[This message has been edited by Paul J. Stiles (edited May 27, 2002).]

Paul, the HISS is there regardless of what is connected. The way you described what might possibly be going on is exactly what seems to be happening. Something in the 950 is artificially chopping the base noise level when the volume is (initially) minimized. I hooked up my dvd player to optical 1 to check the zero word length thing you talked about for digital sources and this is what happened.

 With the DVD player either on or off, but not in play mode, volume at any setting (-80db to 10db) = no HISS (only hiss)

 With the DVD player in play mode, volume at –80db = no HISS (only hiss)

 DVD player in play mode, volume at –79db and above = HISS

 After HISS has been activated as stated above, it continues even when the volume has been returned to –80db, DVD player stopped, turned off, or disconnected. To put the system back into its resting (no HISS) mode I have to toggle to a different input source and the volume has to be at –80db.

BTW – the outlaws contacted me but we are still in limbo as to what to do next. My speakers are BA HD 10 with 90db/W/m sensitivity.

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

Lastly, to Scott, did anyone in Dallas receive a 950?

Thanks for you input
mt

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?

Tetra- The answer to your question is "yes". But also keep in mind that a lot of grounding problems come from the *interaction* between an incorrectly installed CATV or Dish ground, and presumeably your correctly installed house ground.

So, you can try cheater plugs, but also try to completely disconnect any cable TV or Dish TV systems too. Might make a difference. Let us know what you find...

This is my first post, so I am a little nervous. I have a 950/770. Got it few weeks back and I put my self on the wait list early January. I have learned a lot from reading all your posts.

I have noticed this hiss that everyone is talking about so I thought I would tell my situation and how I fixed it.

I have a Toshiba 5700 DVD
Sony TV
Bose 501 series 5 (till I get my B&W speakers)

First off, I am new to all of this, so as I upgrade my stuff piece by piece I notice improvements. I am using very cheap interconnects at the moment and I have a slight hiss when my ear is to the tweeter. I had a loud HISS (from at least 5 or 6 feet) and found that my cable TV was the cause. Now the cable TV was not connected to my system at all. It was only connected to my TV. I had a s-video cable to the TV from the DVD player. The DVD player connected to the 950 with analog, optical, and digital connections. Somehow, even with the DVD player OFF and the source on the 950 NOT selected to DVD, I would get a loud HISS. I figured out the bad link was that s-video cable. Once I unplugged it from my DVD player (breaking the link to the TV which is connected to the cable), the HISS turned into a hiss. I would imagine that I can reduce it even more with better interconnects than I am using now.

I should also note that with the 950 turned off and the 770 on, I do get a slight hiss but only hear it when my ear is up to the tweeter.

I simply disconnect the Cable TV from the TV when I watch movies so I don’t get that nasty HISS. So I hope this helps someone. Like I said, I am new to all this audio stuff and hope I did not insult anybodies intelligence.

sing_sgt: The Outlaws may owe you more than you can ever know. Hopefully some others will try your fix, or variations surrounding it (those "chokes" or isolators you can buy for the cable coax line).

Is anyone else out there as excited about this as I am? Hee, hee. (Seriously!)

Kevin,

Yes, I find this hopeful, but at the asme time, considering some of the folks running into this hissing issue ... I suspect that at least some of them have quite high quality interconnects so ... I'd not expect sing_sgt's solution to work for all of them. But, perhaps?, it might help some of them? {fingers crossed}

------------------
pat----

email: pat@sklenar.info ---===--- home page: Grumpy's Lair

Man, if only the hiss issue was that simple to solve! Still, if folks who have the hiss haven't yet tried these relatively solutions, give em a try.
You can put together a simple, cheap, homemade balun like this:
OR, you can buy something like the Mondial Magic($99) or another brand unit like this Holland one($7)(silver barrelled unit in pic):
I wouldn't imagine that any cheater plugs would have any effect since Outlaw has already made that fix when they went from three to two prong power plugs.
Good Luck!

------------------
Take Care,
merc

[This message has been edited by merc (edited June 06, 2002).]

In my case, I'd had a problem with a ground loop between the amp (which DOES use a three-prong plug) and the CATV line. Disconnecting the RCA cables from the TV to the pre/pro would solve it, but leave me audioless for TV. So I picked up one of those ground loop isolators and that fixed the problem marvelously.

My symptom, though, was not a hiss but a hum. A *quite* loud hum, too.

Interestingly, my grould loop isolator looks exactly like your FM trap.

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

Matthew: I actually had to put all my amps on seperate power circuits than my other gear in order to get rid of my hummmmm. Cheater plugs worked somewhat, but I didn't like the idea of externally lifting the ground on amps.
I also noticed that in my system I can tell when ANY connection between my 950 and a coax cable is made. For example, hooking up a coax cable to my VCR and then running ONLY my audio outputs to the 950 causes a humm unless I used the Holland isolator. Also, when I ran a coax cable connection to my TV and then also had ANY video connection from my 950 connected, humm. The only way I could remove all of the humm was to use multiple Holland and Magic Isolators between EVERY RF coax to component connection in my system.

------------------
Take Care,
merc

[This message has been edited by merc (edited June 06, 2002).]

Thanks merc, I put together a homemade balun like your picture and it works great. You guys should put together a "home audio for dummies" book or something. I have learned so much from all your posts.

Been sitting on a balcony watching an ocean roll by, wish I could have stayed a month.
Got my combo, just before we sailed and did a down & dirty install.
I won’t post my probably worthless newbie review till I get some breathing space.
I’m thrilled and irritated by the 950/770 right now.

Irritated because nothing is rigged for convenience right now, and I’m running 3 remotes just to get satellite up, (did I state dirty install). Worried about how much I can tweak the system back to ease and simplicity, when I have time to rework hardware and train remotes. Grabbed a new DTC 100-satellite receiver the day before I left, and just put it on line yesterday, replaced it because the old Sat. box, did not have digital capability. Now I have to hit 2 buttons on the remote every time I want to change the channel instead of one, (the old unit). Hopefully all these frustrations will ease in the next weeks when I have time to actually read manuals and can see how all these new pieces will mesh.

The sound and the user problems posted.
Regarding Hiss: No hiss at all in my room, (which is very small) but because the speakers are all hung, (I haven’t gotten up on a chair to see how many inches out it might be. Absolutely no audible hiss at any listening location in the room so far.
Regarding Pop: loud relay click in the amp as its powered on, and the tinniest pop in the speakers, much much softer than the relay click. So I’m not worrying about damage too much until I have time to hardware and macro my setup to its final configuration.

Have not had time to level match the speakers, and I can ‘hear’ they are off. When the source is Satellite, - straight stereo on the 950 sounds ‘dead’ compared to my old PL JVC receiver but apply Stereo Seven or S5 and the sound becomes incredibly fuller than the old setup.

Prob. due to not calibrating the system yet, I am having trouble with tweaking constantly in the trim, on certain DVD’s, or while changing to different channels on Satellite. The main prob. seems to be, getting my center speaker, up or down enough, so that dialogue is crisp and clear, not under or overwhelmed. Will try to write a review in the next weeks, for those still waiting patiently and hungry for any news, - although mine won’t surpass much more than bathroom reading, but might pass the time!

Merc- Thanks for the pix!

Smart Little Lena,if you haven't already, go by RadioShack and pick up a Sound Level Meter (p/n 33-2050) and use it to set your speaker(s) trim. You'll be glad you did.
By the way, hope you had a great time on your trip- it's good to get away once in a while!

According to Prefect, the outlaws have identified the source of the HISS and are actively implementing corrective measures for those few with the problem (and, I assume, to those units in the existing stock that have apparently been halted from delivery).

Good job!

mt

PS For some reason, my system sounds (and feels) best at and above -15db. A few more weeks of listening to music and movies at that level in my small living room will most likely eliminate my ability to distinguish the HISS anyway.

Thanks Steve! Got one, and confirmed my ears last night, the levels are off, but it was too late to mess with making the noise, will try to do it this weekend. Looking forward to finding out how much difference it makes. We are tired and disoriented trying to damage control from while we were gone; it’s going to be a couple of ‘catch-up’ weeks. I also have lots of odds & ends like getting the reg. TV hooked in again etc. We really did install the bare bones; Sat/DVD/Outlaw with no consideration for how we eventually want it all routed.

The trip was great; it was quite interesting to see the US Navy and the Coastguard taking the ‘underwater terrorist attack threat’ seriously. 2 Navel destroyers were protecting our ship, particularly in 2 harbors where they lurked sending out tenders out to everything that came near our ship and reportedly had 2 subs on ‘training drills’ in the area. I think the general populace do not realize how hard our military is trying to protect us right now, with one hand (either logistically, monetarily or politically) often tied behind their back And the ‘muster drill’ (as req. by Port Authorities before sailing) was not cursory as it had been in the past. They actually lined us up at our stations with women & children first, etc. something not included on prior trips.