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Testing my new PM3000...White Noise, ARG!

Brantel

Brantel

Well Known Member
After spending about 4 hours building a beautiful harness for my new PM3000, I fired that puppy up last evening and found what several have reported and that is a high level of WHITE NOISE in the headsets.

Now I know all the discussion about you will never hear it when in the air with the motor running, I would most likely agree with that statement but the noise there does seem to be excessive.

Lets get a few things out of the way so this does not turn into a bunch of replies for troubleshooting:

1. Power supply is a clean variable bench model that was set at 14vDC
2. Harness was built by me and is a work of art and is exactly per the wiring diagram.
3. The jacks are isolated from the aircraft (not even mounted in the panel yet)
4. Proper cable shield treatment has been followed.
5. The noise is not ground loop noise, not 60hz hum, it is plain old white noise.
6. Everything else about the intercom works like a charm.
7. The noise is not affected by the squelch or the volume control, the noise is a constant level out of the intercom.
8. Headsets are Lightspeed passive mono/stero and they work in either mode and the noise is there regardles of mode. The headset volume control reduces the noise but also reduces the intercom volume.
9. It appears that the preamp's inside this box are amplifying the noise and there is nothing an end user could do to stop this.

I know Mark visits here and will respond, looks like my issue with the noise is considered within their quality standards from the post in history so I am not sure what could be done about it.

That being said, I am willing to wait and see how it works in the air. I don't like that as soon as I turn on my avionics my passengers will be greeted with a earfull of hiss but guess I will have to live with it.

I will try the suggestion I read about reducing the headset volume using the headset volume controls and increasing the intercome/radio volume to offset the noise floor more below the desired signals.

While not a intercom circuit expert, I am an electrical engineer with a degree in electronics. I have a working knowledge of how audio circuits work. I have also served as an audio engineer within my church so I understand issues that can exist in audio systems.

I was aware that some have reported this with the PM3000, but I decided to give PS Engineering my business if for nothing more than the fact that they are a local company for me and for the most part seem to have a good record of customer service as recorded here in the archives.

Do the other PS Eng audio panels have this issue? Does anyone using a PM3000 not have white noise?

At this point I am on the fence about if I would recommend this intercom to someone in the future or not. I will have to try it in real life for a while to make that determination.

PS: If you want to hear what I am experiencing, go here for a listen...
 
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Hi Brian,

Here's what I would say. Let's not try to find a resolution to a problem that we don't know exists yet. A lot of this stuff is very subjective, for example - your harness may indeed to you be a "work of art", but to me it may not. I use that point not to flame you, just to point out that it's subjective. Same with "white noise" while listening to an intercom without the plane running or the rest of the avionics all complete and interconnected. There are SO many variables here that it's impossible to do any real troubleshooting at this stage of your build.

I would say wait until you have the entire panel wired up and have the plane running. Sit in the plane with it running (and all of the avionics/EFISes/etc..) turned on and then see what you hear.

Mark is an extraordinarily busy person and well he does read these forums, I'd politely suggest that we not waste his time trying to troubleshoot something as subjective as this just yet.

I can tell you that you that it'll be hard to a better stereo intercom out there or a better company to deal with.

Cheers,
Stein
 
Stein,

Agree, like I said above, I did not want to make this a troubleshooting thread as I don't think there is any troubleshooting to be done.

My panel is complete as far as the intercom is concerned with the exception of the jacks not being mounted in their holes.(hanging in thin air)

Since I have an example of your quality of work in my Dynon harnesses (great by the way :)), I know that your idea of a "work of art" harness and my idea of one are very close to the same! :rolleyes:

My point is that I think this is how it is with the PM3000 and others should not be suprised when they turn them on and hear elevated levels of white noise.

White noise does not come from poor installation, bad harnesses, ground loops etc. it comes from amplifying the Black Body Radiation from everything in the Universe, end users have no effect on how good a pre-amp is or how good the shielding is inside the box.

I also agree that most likely the noise floor of the white noise will be overshadowed by the environment when the engine is running.

If Mark wants to respond, he can, if he does not, he won't. I don't think he will have anything more to say that what he already has in the past. I also would never waste any vendor's time with troubleshooting anything I build until I have exhausted all of my bag of tricks and have completely verified that all there recommendations and literature have been followed.
 
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Brian,

There is an idiot amok, and once in a while he sneaks into my shop and does something that I would never be so dimwitted to do. I've spent hours trouble shooting noise, only to find that the idiot couldn't count pin positions on the D connector.

Your mileage may vary. No matter how certain and frustrated I am and get over something I can't find, sooner or later it is as obvious as an elephant in the living room, my mistake, not the electronics.

There shouldn't be any noise. Also, you say "elevated". Does that mean you hear something with the intercom off line? Track that down first.

And good luck.

John Siebold
 
White Noise

Hi Brian:

One of the VAF's member's complaint about the white noise level in the PM3000 was using a military type headphone (low impedance) and it was making the output amplifier work way too hard (GA impedance 150 - 600 ohms). THe white noise reduced significantly when a GA headset was used.

The white noise increased when we increased the gain of the music input. In the old days, CD players used 3 - 6 - 9 volt power battery sources and the output voltage swing from the audio was much larger than the typical output from the iPods of the world (at best 1.3 volts).

So, as you know as an electrical engineer yourself, engineering is an art of selecting from a series of tradeoffs to accomplish an optimum design. Years ago, we were getting LOTS of complaints that the music wasn't loud enough. The trade off was louder music with a little more white noise.

Anyway, as time permits, I will perform an analysis of all of the gain stages and see if there is anything that we can do. I am not promissing a fix, but I am promising to take a look at it.

To put it into perspective (and this doesn't diminish your complaint) we have well over 30,000 of our PM3000 series intercoms installed and flying, and except for the few complaints I have read here, it has not been an issue.

I suspect it is because, assuming the white noise level you have is typical of all of our PM3000, it is not being tested in an environment that it was designed to operate in. If you can hear the white noise once the engine is running, then there IS a problem and we'll go from there as well.

Oh, I just thought of something.....have you connected any of the unswitched inputs yet? If you have, you may want to turn off those sources, white noise into these inputs will be heard in the headset!

If you compare the fidelity, the VOX operation, reliability to our competition, I believe and hope that you will conclude that you've got a great overall system.

Thanks for trusting us with your audio stuff Brian, and I hope you won't regret your decision to purchase it.

Sincerely,
Mark Scheuer
PS Engineering

Brantel said:
Stein,

Agree, like I said above, I did not want to make this a troubleshooting thread as I don't think there is any troubleshooting to be done.

My panel is complete as far as the intercom is concerned with the exception of the jacks not being mounted in their holes.(hanging in thin air)

Since I have an example of your quality of work in my Dynon harnesses (great by the way :)), I know that your idea of a "work of art" harness and my idea of one are very close to the same! :rolleyes:

My point is that I think this is how it is with the PM3000 and others should not be suprised when they turn them on and hear elevated levels of white noise.

White noise does not come from poor installation, bad harnesses, ground loops etc. it comes from amplifying the Black Body Radiation from everything in the Universe, end users have no effect on how good a pre-amp is or how good the shielding is inside the box.

I also agree that most likely the noise floor of the white noise will be overshadowed by the environment when the engine is running.

If Mark wants to respond, he can, if he does not, he won't. I don't think he will have anything more to say that what he already has in the past. I also would never waste any vendor's time with troubleshooting anything I build until I have exhausted all of my bag of tricks and have completely verified that all there recommendations and literature have been followed.
Click to expand...
 
mscheuer said:
Hi Brian:

One of the VAF's member's complaint about the white noise level in the PM3000 was using a military type headphone (low impedance) and it was making the output amplifier work way too hard (GA impedance 150 - 600 ohms). THe white noise reduced significantly when a GA headset was used.

Thanks for the response Mark, one of the reasons I purchased your product is that you take the time to read your customers post! I am using a regular Lightspeed passive mono/stereo headset with no electronics.

The white noise increased when we increased the gain of the music input. In the old days, CD players used 3 - 6 - 9 volt power battery sources and the output voltage swing from the audio was much larger than the typical output from the iPods of the world (at best 1.3 volts).

That makes sense... I tried an MP3 player last evening and it worked well and it seemed to be matched well with the gain of the intercom music input. It was plenty loud and did not require full throttle on the MP3 player.

So, as you know as an electrical engineer yourself, engineering is an art of selecting from a series of tradeoffs to accomplish an optimum design. Years ago, we were getting LOTS of complaints that the music wasn't loud enough. The trade off was louder music with a little more white noise.

How well I know about tradeoffs!

Anyway, as time permits, I will perform an analysis of all of the gain stages and see if there is anything that we can do. I am not promissing a fix, but I am promising to take a look at it.

To put it into perspective (and this doesn't diminish your complaint) we have well over 30,000 of our PM3000 series intercoms installed and flying, and except for the few complaints I have read here, it has not been an issue.

I suspect it is because, assuming the white noise level you have is typical of all of our PM3000, it is not being tested in an environment that it was designed to operate in. If you can hear the white noise once the engine is running, then there IS a problem and we'll go from there as well.

Don't spend too much time on it till I get the motor started. That will be the true test.

Oh, I just thought of something.....have you connected any of the unswitched inputs yet? If you have, you may want to turn off those sources, white noise into these inputs will be heard in the headset!

All devices that are connected to the unswitched inputs and the music input were turned off and the white noise was unaffected. I even went as far as grounding the unswitched inputs and this had no effect on the white noise. Tried it with the radio off as well...same thing.

If you compare the fidelity, the VOX operation, reliability to our competition, I believe and hope that you will conclude that you've got a great overall system.

Other than the white noise being somewhat high, I am very, very pleased with the other aspects/features/sound of the intercom.

Thanks for trusting us with your audio stuff Brian, and I hope you won't regret your decision to purchase it.

One other tidbit... I tested the effect that the volume control has on the white noise threshold. From minimum to around 5/8 clockwise, the white noise amplitude is totally unaffected, from there on up to max, it gets louder.

Sincerely,
Mark Scheuer
PS Engineering
Click to expand...

Thanks for the response!
 
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Its the intercom

This is a long term irritation of mine.

There's DEFINITELY a lot of white noise. I've had two of these now. One in a 9A and another one in my 8. The intercom works fine in general terms and does what I want it to do, BUT the amp just sucks. Plain and simple. You can even hear it with the engine running during taxi.

In the airplane, power on, power off, mic in, mic out, avionics on, avionics off, etc... doesn't matter
STILL HAS HISS.

And its not the headset. I've tried 4 different ones, Passive, ANR, you name it.
STILL HAS HISS.

And its not the harness/wiring.
I've had this thing hooked up to a 12 volt battery on the bench with NO harness except power ground and headset audio about 6" long, no mic, no radio, no nothing.
STILL HAS HISS.

And I'm not the only engineer that I've had look at it either.
STILL HAS HISS.

I suppose next they will tell me its the phase of the moon, or global warming, or something.:D

Frankly for the cost of the unit I would expect a better audio section.

And don't tell me that I can turn down the volume on the headset and turn up the volume on the intercom. Thats a doge, plus you can't do it with all headsets. ITS THE INTERCOM.

Rant off:(
 
Brian, I really appreciate the very kind words you have given us, thank you.

Currently our engineering staff (of 2) are really really busy working on something, and probably will be that way for about another month. When they come up for air, I'll give them this issue and see what, if anything, can be done.

I'd love for it to have no hiss, and we'll shoot for something like that if at all possible.

Thanks again.
Mark
 
I have a PM 3000 in my -8. I fabricated the harness myself like Brian did, and in my subjective opinion it is a work of art too :D On the ground, with nothing running except the audio system, there is white noise. However....even with a Bose X headset, when in the air in an airplane as noisy as an RV-8, I don't hear it at all. If I was flying a glider I might be sorta p-o'd. But in the -8 during normal operations the white noise is not an issue since I can't hear it.... YMMV
 
White Noise

Just a data point....I just installed a PM3000 and I do not have a high level of white noise. In fact, it's not hardly noticeable. I ordered the factory harness from PS Engineering and did the rest of the installation myself. I'm not flying yet so my avionics are being powered by my PC680. I've only got the PM3000 connected to a SL-40 and a Dynon D180 for audible alarms.
 
Brantel said:
Do the other PS Eng audio panels have this issue? Does anyone using a PM3000 not have white noise?
Click to expand...

I'd rate my PMA 8000B audio panel as perfection. I had a less than desirable intercom from another manufacturer.... before that.

L.Adamson --- RV6A
 
WOW-Thank you

Dear L. Adamson:

I want you to know you made my day. You can't imagine how wonderful I felt after reading your post. In all honesty, this is what it is all about for me, design and built a product that provides functionality that pilots will appreciate.

Don't worry, I won't let this go to my head after tonight, but for now, I'm going to just sit comfortably in my Lazy Boy and enjoy your accolades.

Thank you
Mark Scheuer
Founder
PS Engineering

L.Adamson said:
I'd rate my PMA 8000B audio panel as perfection. I had a less than desirable intercom from another manufacturer.... before that.

L.Adamson --- RV6A
Click to expand...
 
dedgemon said:
There's DEFINITELY a lot of white noise. I've had two of these now. One in a 9A and another one in my 8. The intercom works fine in general terms and does what I want it to do, BUT the amp just sucks. Plain and simple. You can even hear it with the engine running during taxi.
Click to expand...

A friend of mine has a RV9A. I've got quite a bit of time in it, and it doesn't exhibit "white noise".

I was shocked this evening, when I blew up a pic of the panel................only to discover that it's a PM3000..

BTW---- I just confirmed it with the owner. NO white noise!!!

L.Adamson ---- RV6A
 
L.Adamson said:
I'd still connect to a 12V. battery without any A/C power supplies connected. A/C can & will add background noise.

L.Adamson ---- RV6A
Click to expand...

Yep of the 60hz hum and harmonics of 60hz variety. That is not what I am hearing.....Thanks for the suggestion but I have already tried it on a standalone battery.

mark mentioned above that at some point PS Eng. changed some of the design of the units to give the music input more gain. Might be why some older units do not have the issue and the newer ones do????

Seems strange that all things being equal that some would have it and others would not unless there are factory tunning differences inside the box and or tolerance issues stacking up with internal components. Variables like the wiring have been minimized to eliminated due to the fact that most that have had the excessive white noise have taken the wiring down to bare minimums in order to rule out harness issues to no avail.

Like Stein and Mark have said, some people are more sensitive to white noise than others. All people's hearing responses are not the same.
 
I have.

L.Adamson said:
I'd still connect to a 12V. battery without any A/C power supplies connected. A/C can & will add background noise.

L.Adamson ---- RV6A
Click to expand...

As I stated, I've hooked the unit up on the bench with a 12Volt battery and 3 wires and a headset(several different types)

IT HAS VERY AUDIBLE HISS.

This is in both (2, count'em, 2) units from 2 airplanes bought 5 years apart!
 
I've had the PM3000 in my Cherokee for a couple years now and have never noticed any unusual amount of white noise hiss originating from within the PM3000 itself. I'm pretty picky about audio quality too, and have two sets of Zulus for my front seats & cheap QFRs for my rear seats, and the plane is wired completely stereo for all 4 seats. I run my portable music player into the PM3000's music input and the audio quality is crystal clear, especially with the Zulus.

My audio system does have a lot of white noise when I use my old Terra nav/com radios, since they are very noisy even when their volumes are all the way down, but my King radio that I use as primary comm is very quiet, and I usually just keep the Terras powered off unless I'm actively using them.
 
I did a test last evening where I turned off the intercom and left everthing else in normal mode...

The white noise completely goes away and the failover mode in the intercom works like a charm...

Without a doubt, it is 100% no question in my mind that it is in the intercom. Maybe Mark's guys will find the Gremlin.
 
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Brian

We had a thread running on this a few months ago (hmmm... maybe a year) and just never got anywhere. Mark really didn't seem to think that this was a problem at that time. Seemed sure that it wasn't the intercom, just had to be the install. It really frustrates me though. As I'm sure you know, this is NOT a little bit of hiss.

Maybe they'll look at. I like the basic intercom but I really really want an alternative that sounds better.

The kicker for me was when it performed this way on the bench connected to nothing but a battery and a headset.




Brantel said:
I did a test last evening where I turned off the intercom and left everthing else in normal mode...

The white noise completely goes away and the failover mode in the intercom works like a charm...

Without a doubt, it is 100% no question in my mind that it is in the intercom. Maybe Mark's guys will find the Gremlin.
Click to expand...
 
I am only about an hour away from PS Engineering and I have offered to bring my unit into let Mark hook it up to his gear to let them understand my issue. Hopefully they will take me up on the offer.
 
White Noise

Brian,

Same issue over here in Aus with my 3000 unit. Harness manufactured by Pacific Coast and when first hooked up I thought there may have been a pin swapped somewhere. No such luck. I have Bose headsets and the white noise is disconcerting given the integrity of the rest of my panel. Hopefully Mark will work a fix for us all.

Cheers, Greg:)
 
Offer to visit PS Engineering?

Dear Brian:

We have always welcomed visitors.

Who did you ask to come visit? What was his/her response?

Come anytime you'd like. Please.

Mark Scheuer

Brantel said:
I am only about an hour away from PS Engineering and I have offered to bring my unit into let Mark hook it up to his gear to let them understand my issue. Hopefully they will take me up on the offer.
Click to expand...
 
Same issue here but..

I've had 2 PM3000's in the last 5 years and went through the exact same thing on my first install. I also made a harness with nothing but a battery and headset to isolate things with no change to the hiss level like has been mentioned.

However, after flying now for about 5 years I will say that "when flying" you can turn the intercom on/off and you can barely tell the difference, so it appears in the "real world" the background noise drowns out the hiss and it's not much of an issue. Just for ref I now use the clarity aloft headsets which have a very clear sound and you can still really hear it when on the ground but not in the air.

Bottom line for me is when flying you don't notice it. Being an old "sterophile" and electronic guy myself I thought how unacceptable this was at first and that I would never be happy, now I think it's a great little unit and maybe someday I'll upgrade to the 8000, but really don't see a need for a full fledged audio panel as I'm perfectly happy with the 3000. Would I welcome an upgrade to a quiter box, sure but either way I'm happy.

Nice thing is you never hear of any failures of these units which is very high on my scale of "things that are important in airplanes" :D
 
Mark,

Via the PM, upper right hand corner. Let me know if you got it...

Thanks,

Brian C.

mscheuer said:
Dear Brian:

We have always welcomed visitors.

Who did you ask to come visit? What was his/her response?

Come anytime you'd like. Please.

Mark Scheuer
Click to expand...
 
GOT IT!

I never look for private mail...my bad.

As I mentioned, you, as well as all of our current and prospective customers are always welcome to visit our manufacturing facility.

You might enjoy seeing our manufacturing capability as well as see how we test our products. It's really fun to watch the pic and place machines run!

Come on down anytime!

Mark

Brantel said:
Mark,

Via the PM, upper right hand corner. Let me know if you got it...

Thanks,

Brian C.
Click to expand...
 
Dynamic Range spec

A simple number would remove the subjectivity from the noise issue.

From the David Clark website, the H10-30 puts out 90db for a 1mw input into 150ohms. If we take this as the "standard", what is the PM3000's noise floor into 150ohms, relative to say, 100db reference level?

100db (0dbrl)
10mw into 150ohms = 1.224V

@40db down:
1uw into 150ohms = 12.24mv

As they say, one o-scope trace is worth a thousand expert opinions. :D

I looked on the PS eng. site for specs. Found 'em, but no specs. for dynamic range or noise floor. :(
 
mscheuer said:
I never look for private mail...my bad.

Mark
Click to expand...

I never do either, but I discovered that you can set up your PM so that you get an email every time you get a PM:

User CP
Edit Options
Messaging Notification
Private Messaging
check: Receive Email Notification ..... etc.
:D:D:D
 
No White Noise

I have a PM3000 in my RV-8. The harness was built by Stein Air.

No white noise and I am very happy with the intercom.

Paul
 
I also have a very loud white noise in the headsets before start up. Actually quite frustrating, so I keep headsets off before engine is running. In flight its too noisy to hear it though.
I originally thought it was the Lightspeeds and sent them back . They were returned as "no problem can be found"
I just live with it now.
 
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