Hi again! While enjoing my just built Noir, I noticed some problems.
When there is a source connected to Noir but there is no signal going in, I hear some chirping or ticking sound in the tweeters of the speakers when the volume control is above the middle. Same is heard in the headphones. There is no this problem when the signal is going in. If you pause the music, the chirping starts in about 5 sec. from the moment you paused. It does not depend on the source: same happens with the DAC as well as vinyl player. This does not happen with the other pre-amp.
Another thing. If I connect the headphones, but the power amp is still on, the music plays fine in the phones, but there is a loud hum (probably the same chirping, but much much louder) in the loudspeakers.
Any ideas why this can happen and what is a problem with my build or setup?
Would be thankful for any help.
When there is a source connected to Noir but there is no signal going in, I hear some chirping or ticking sound in the tweeters of the speakers when the volume control is above the middle. Same is heard in the headphones. There is no this problem when the signal is going in. If you pause the music, the chirping starts in about 5 sec. from the moment you paused. It does not depend on the source: same happens with the DAC as well as vinyl player. This does not happen with the other pre-amp.
Another thing. If I connect the headphones, but the power amp is still on, the music plays fine in the phones, but there is a loud hum (probably the same chirping, but much much louder) in the loudspeakers.
Any ideas why this can happen and what is a problem with my build or setup?
Would be thankful for any help.
Yes, the phone jack is switching, same as in the BOM, this one:
NMJ6HFD2 Neutrik | Mouser Europe
NMJ6HFD2 Neutrik | Mouser Europe
The NOIR should be very quiet; mine is.
It sounds like you might have ground loop/s/not shunting incoming high-freq noise to ground. Did you put this into a chassis and connect together the current return paths? The NOIR is specifically designed to have grounding connection/contact points on the front/back panels that connect the panels to the chassis star ground point, including the POT which also needs to have its shell connected. These loops are a common problem when folks build chassis that are anodized too that don't connect the panels together for solid continuity. I sand off the anodizing on the places where the panels touch to get around this but on the NOIR you simply set up a common ground point on the chassis and bind it all there. You can see how I did this in the attached figure.
--Tom
Attachments
Yes, Thomas, I did connect the ground to the shield of the front and back pannels (the picture of my build is just a few messages above), and I sanded the contact points of the standups to the bottom as in the build guide. But thanks for the comment, I will poke with the ohmmeter around the chassis in a few hours to check if all chassis parts are in contact.
I recommend the experiment of temporarily installing RCA male "shorting plugs" into Noir's input jacks. These solidly short Noir's input signals to ground. If noisy misbehavior still exists then you know it's caused by something within the Noir chassis. If misbehavior goes away then it's likely a problem with external gear, or with the interface between the other gear and Noir itself.
You can buy pre-made RCA shorting plugs (here is an Amazon example) or you can make them yourself by soldering a shorting wire across the pins of an RCA male plug.
Mouser example 2
Mouser example 3
Mouser example 4
Depending on what's your idea of "fun", you might also enjoy making another pair of shorting plugs, but this time installing a low-value 250mW resistor (instead of a zero ohm wire) between the two terminals of the RCA plug. Popular values of resistor would include 49.9 ohms and/or 1.0 Kohms. Some people find it extra reassuring to also hear zero noise, when the input is terminated by a resistance "similar to" the output impedance of the upstream equipment. In case they think a zero ohm, pure shorting plug is an artificially "easy" test. I'm not one of them, I'm just mentioning it here so you can think it over before deciding whether to purchase 2 or 4 or 6 male RCA plugs.
You can buy pre-made RCA shorting plugs (here is an Amazon example) or you can make them yourself by soldering a shorting wire across the pins of an RCA male plug.
Mouser example 2
Mouser example 3
Mouser example 4
Depending on what's your idea of "fun", you might also enjoy making another pair of shorting plugs, but this time installing a low-value 250mW resistor (instead of a zero ohm wire) between the two terminals of the RCA plug. Popular values of resistor would include 49.9 ohms and/or 1.0 Kohms. Some people find it extra reassuring to also hear zero noise, when the input is terminated by a resistance "similar to" the output impedance of the upstream equipment. In case they think a zero ohm, pure shorting plug is an artificially "easy" test. I'm not one of them, I'm just mentioning it here so you can think it over before deciding whether to purchase 2 or 4 or 6 male RCA plugs.
Hi, Mark. I have shorting RCA plugs made for reseting M2X output DC offset, so I could test it right away. And there is no noise (chirping/clicking) with the Noir inputs shorted (as well as when inputs are not connected at all).
I also checked shielding (chassis connection to ground). 5 sides of the chassis are connected to ground, but not the top lid (one should scratch anodizing layer of the top lid and the sides to make them touch). Is that essential to do to protect Noir from picking up any noise?
But how could it be explained that the chirping is heard only when there is no signal on the input? There is no noise between the songs. And the chirping starts only about 5 seconds after you put the music on pause or stop it.
I also checked shielding (chassis connection to ground). 5 sides of the chassis are connected to ground, but not the top lid (one should scratch anodizing layer of the top lid and the sides to make them touch). Is that essential to do to protect Noir from picking up any noise?
But how could it be explained that the chirping is heard only when there is no signal on the input? There is no noise between the songs. And the chirping starts only about 5 seconds after you put the music on pause or stop it.
You've proven it doesn't originate inside Noir. So expand your investigations wider.
One thing to try, is to use another different source to drive Noir; perhaps your phone. A TRS-male-to-dual-RCA-male cable lets you try that quickly. Does the chirping clicking also happen with your phone?
Another thing to try, is to connect the same source to a different headphone amp. Does the chirping clicking continue, even without Noir?
Be creative, dream up as many A-versus-notA experiments as you possibly can. Test them all and see what the experimental data is telling you.
One thing to try, is to use another different source to drive Noir; perhaps your phone. A TRS-male-to-dual-RCA-male cable lets you try that quickly. Does the chirping clicking also happen with your phone?
Another thing to try, is to connect the same source to a different headphone amp. Does the chirping clicking continue, even without Noir?
Be creative, dream up as many A-versus-notA experiments as you possibly can. Test them all and see what the experimental data is telling you.
I agree. Try a different source. The NOIR doesn't lift the negative from the input RCAs and shunt them to earth ground like say on the Whammy, and so if you have a misbehaving source you can get noise/hum that way. The hum on the headphones I've had happen when the body of the POT is not solidly grounded too. For kicks, try attaching a clip+wire between it and the rear panel's ground point, and even touch around the chassis. Does the hum/noise go away when you physically touch the chassis or POT or move the clips to different points? That is a sure sign of a grounding issue if you do, but not necessarily with the NOIR but with how the source is setup, so try a different source to confirm.
Thank you very much to all for suggestions. I made some experiments and now I am absoutely sure that my Noir is totaly fine.
These was no noise when sourcing from the phone. But there was a noise when sourcing from DAC or Vinyl. But I found out that absolutely the same happens with my Shiit Magni pre-amp (I did not notice that before, as with a 5.5x gain of Magni I never needed to crank the volume so high as to hear that noise). So, finaly, I think my M2X is at guilt here. It is a bit capricious. It stays fine and quiet by itself, but start making a lot of noise immediately when you connect a mere RCA cable to its inputs! But goes quiet again as soon as you plug the other end of the cable to pre-amp and turn the pre-apm on.
I think my M2X is so whimsical that it also starts making noise as soon as you plug headphones to pre-amp and make M2X devoid of a signal! That happens with both my pre-amps, so it's definitely a "feature" of the power-amp. Will have to study that later. But for now - it's time for some good music, as everything is perfect when all cables are connected and the signal is flowing...
Thanks again!
-Alvis
These was no noise when sourcing from the phone. But there was a noise when sourcing from DAC or Vinyl. But I found out that absolutely the same happens with my Shiit Magni pre-amp (I did not notice that before, as with a 5.5x gain of Magni I never needed to crank the volume so high as to hear that noise). So, finaly, I think my M2X is at guilt here. It is a bit capricious. It stays fine and quiet by itself, but start making a lot of noise immediately when you connect a mere RCA cable to its inputs! But goes quiet again as soon as you plug the other end of the cable to pre-amp and turn the pre-apm on.
I think my M2X is so whimsical that it also starts making noise as soon as you plug headphones to pre-amp and make M2X devoid of a signal! That happens with both my pre-amps, so it's definitely a "feature" of the power-amp. Will have to study that later. But for now - it's time for some good music, as everything is perfect when all cables are connected and the signal is flowing...
Thanks again!
-Alvis
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Psychoaudio, by all means try the experiment and find out whether the results are pleasing to you!
I imagine that since the parallel resistance of (R25 // R26) is pretty low, namely 34 ohms, you are thinking that the new capacitor to be installed should probably have a pretty large value, like maybe 470 microfarads or even more. Fortunately that capacitor doesn't need to have a super high voltage rating; 16V or 25V would be perfectly fine. This means the capacitor will be physically smaller, so it will be easier to fit inside your Noir chassis.
You could consider using a capacitor whose package has axial leads, becausee the resistors it connects to, also have axial leads. Axial electrolytic caps are slightly uncommon these days, but Mouser does carry some of them:
470 microfarads @ 25VDC
1000 microfarads @ 25VDC
I imagine that since the parallel resistance of (R25 // R26) is pretty low, namely 34 ohms, you are thinking that the new capacitor to be installed should probably have a pretty large value, like maybe 470 microfarads or even more. Fortunately that capacitor doesn't need to have a super high voltage rating; 16V or 25V would be perfectly fine. This means the capacitor will be physically smaller, so it will be easier to fit inside your Noir chassis.
You could consider using a capacitor whose package has axial leads, becausee the resistors it connects to, also have axial leads. Axial electrolytic caps are slightly uncommon these days, but Mouser does carry some of them:
470 microfarads @ 25VDC
1000 microfarads @ 25VDC
Dave, the size is ok, but you should be looking for the Low Frequency series material (LF), the one in your link is High Frequency. I bought that one when building my Noir, but it's on back order now on Mouser.
LFB143064-100 Laird Performance Materials | Mouser Europe
LFB143064-100 Laird Performance Materials | Mouser Europe