Monitor speaker hissing

[twotoedsloth]

Hello,

I seem to have gotten myself into a jam here. I'm recording and doing PA for a Jazz ensemble, they've asked for four monitor speakers. This is normally not a problem, but for some reason the third monitor is hissing quite loudly. This is not the speaker that I was having trouble with in the summer, that was buzzing (which is a lot more offensive). I've just turned off the third monitor and raised the level of the fourth. Fortunately in the last 15 minutes of sound check, no one has complained, so maybe they haven't noticed.

If someone has a suggestion to try in the next hour or so (the concert starts at 2pm) I would be very grateful.

Many thanks,

Peter

[Wonks]

Possibly an internal component like a capacitor that’s either failed or its capacitance has dropped to a point where it’s not smoothing the power supply enough.

Not something you’d fix quickly.

[James Perrett]

If you really want our help then makes and model numbers would be really helpful.

[twotoedsloth]

Sorry I didn't include the make and model number. Sincere apologies for the omission. They are Yorkville NX10C-2 10-inch/1-inch Active 500W. We have four of them.

They were plugged into a Allen & Heath SQ5 console, through a DT168 Dante stage box. It doesn't look like there was anything I could have done, but thank you for your reply all they same. If it matters, we have 9 Sennheiser e935 mics, with two Rode TF5s in the piano, and pairs of KM183s and KM184s (the Neumanns are being used as recording mics only, not being sent to the monitor or mains).

I just talked to the band during the intermission, and they said the monitors/stage level were great, I didn't tell them that one of the monitors was off. I guess they were hearing bleed from the front of house sound.

All four of the NX10Cs will get tested after the show. Two of them are brand spanking new, so they should have problems with internal components yet.

Best regards,

Peter

[Hugh Robjohns]

Step 1. Check connections and controls.

Connected to line input, not mic input.
Mic level control at minimum, line control at centre, EQ control at centre.

Step 2. Swap input connection with another good NX10C

If the hissy monitor remains hissy, it's a monitor problem. If the previously good monitor becomes hissy, it's a mixing desk problem or a defective cable problem.

[twotoedsloth]

Hello,

Concert just ended, must have been good as the band even thanked me from the stage!

I plugged the faulty monitor into what was previously feeding one of the working monitors. Hiss persisted. Plugged a working monitor into the what might be faulty monitor connection (same power and XLR), and there was no hiss.

So it is the monitor. I hope they'll repair it under warranty.

Thanks gentlemen,

Peter

[ef37a]

Good news in this day and age? This, https://yorkville.com/loudspeakers/nx/product/nx10c-2
Gives the specifications, user manual and...Lordy! Lordy! A service manual WITH schematics!
Bad new is I cannot find a figure for self noise or S/N spec for the amps.

Dave.

[twotoedsloth]

Wow Dave,

That manual is maddening. Why didn't I read this before? Apparently Yorkville speakers have a 10 year warranty. I had to get two NX10c repaired last summer, and it was not cheap! I can understand, perhaps, that the second one that I got recapped (sorry if I'm not using this term correctly) was not exhibiting a fault - yet - but the first one was clearly malfunctioning, as was confirmed and fixed by the repair department. I'm not sure exactly how old those speakers are, for sure they are pre-covid, but they are certainly not 10 years old.

I will be sure to bring this to my dealer's attention tomorrow morning.

Thanks Dave, for passing this along.

Peter

[ef37a]

You are very welcome Peter. Maybe consumer law is different in Canada?

Dave.

[James Perrett]

Having the make and model number really helps. First thing to check - where was the Eq control set?

[ef37a]

", that the second one that I got recapped (sorry if I'm not using this term correctly)"
Perfectly correct Peter but an outrageous thing to have done, if indeed it was necessary. Electrolytic capacitors have been very reliable for at least the last 30 years. Yes, they do fail in some designs but that is due to POOR design! In my world of TV there was notorious field output stage chip which failed (the electronics which waggles the electron beam up and down). It failed because the electro- caps around it failed but THEY failed because the chip was cooking them! I understand there was a mixer of decent pedigree that borked SMPSUs in a year or so? That was because one of the main caps was very close to a heat sink.
Other than that field OP stage above I replaced very few capacitors in the last 40 years or so I was fixing electronics. Active devices and bad soldering, either original or due to heat/vibrational stress were by far the biggest culprits.

I understand the re-capping "fashion" started because a shed load of computer MOBOs were produced with faulty capacitors? In most circuits a cap could lose half its value and you would never know!

Dave.

[James Perrett]

", that the second one that I got recapped (sorry if I'm not using this term correctly)"
Perfectly correct Peter but an outrageous thing to have done, if indeed it was necessary. Electrolytic capacitors have been very reliable for at least the last 30 years. Yes, they do fail in some designs but that is due to POOR design!

I'd have to agree with Dave here. Wholesale recapping is only needed in certain, well defined, circumstances. The main ones are where early surface mount capacitors are used and where the gear is working at high temperatures for a long period. It isn't needed for most gear.

I've had 50 year old electrolytic capacitors that measure better than the equivalent new ones. I would go as far as to say that anyone suggesting wholesale recapping should be treated with suspicion unless the above circumstances apply.

[twotoedsloth]

Hello,

Sorry to bother you again, just another possibly stupid question.

You've recommended NOT changing the capacitors in the faulty monitor, however, in the summer one of our Yorkville YXL12p monitor speaker had to be recapped, as the capacitors on the power supply and the power inlet had to be replaced.

Prophylaxis had me get the same procedure done to the working monitor. Both of those speakers are now working fine, though I don't use them as I'm always afraid of the same buzzing noise returning. I bought two more NX10cs, as they are affordable and up to now, reliable. However, one of the NX10cs is hissing quite loudly.

So, is getting the faulty NX10c recapped a waste of time and money? I'm still going to ask them to fix the hiss, just wondering if we should recap it while it's at the shop.

Thanks,

Peter

[ef37a]

Hello,

Sorry to bother you again, just another possibly stupid question.

You've recommended NOT changing the capacitors in the faulty monitor, however, in the summer one of our Yorkville YXL12p monitor speaker had to be recapped, as the capacitors on the power supply and the power inlet had to be replaced.

Prophylaxis had me get the same procedure done to the working monitor. Both of those speakers are now working fine, though I don't use them as I'm always afraid of the same buzzing noise returning. I bought two more NX10cs, as they are affordable and up to now, reliable. However, one of the NX10cs is hissing quite loudly.

So, is getting the faulty NX10c recapped a waste of time and money? I'm still going to ask them to fix the hiss, just wondering if we should recap it while it's at the shop.

Thanks,

Peter

So the capacitors were replaced to cure supply hum? That would be reasonable but I have to think, either the original components were a bad batch ('t'appen) or they are badly sited and get heated by a heat sink or transistor. I would talk to the tech who did the original work and find out. Your bog standard caps from CPC or RS Comps will be fine. If heat is the problem resite if possible and/or go for 105C replacements IF they can be fitted...bit bigger you see. Do NOT be bounced into paying for some "low ESR" Audiophool rip offs.

3300mfd 63V caps will not cause you to lose limbs and if the guy is "in there" anyway to sort the hiss, should not add too much to the labour cost.

In any case I would try to get in touch with the manufacturers.

Dave.

[James Perrett]

You've recommended NOT changing the capacitors in the faulty monitor, however, in the summer one of our Yorkville YXL12p monitor speaker had to be recapped, as the capacitors on the power supply and the power inlet had to be replaced.

A quick look at the service manuals show that they use completely different power supply designs. The 10" speakers use a linear power supply while the 12" speakers use a switch mode power supply.

Anyone replacing smoothing capacitors on a switch mode power supply to cure hum obviously doesn't know what they are doing.

Or are we not hearing the whole story?

Edit - having gone back to the old thread I definitely think there's something weird here. Nothing makes sense to me....

[ef37a]

Yes James, I expected to see a switching supply but it is a linear 50/60Hz jobby (with auto 230/115V switching...clever!)

Also not common is the linear bass amp which they call "Class H" where a higher rail voltage switches in for peaks. Such designs can compete with class D for efficiency and deliver lower distortion than many of them.

Dave.

[twotoedsloth]

Hello,

I'm not deliberately withholding information. Sincere apologies for any confusion.

We have four NX10 (c may be a subvariant), and two YXL12p monitor speakers.

I'm not sure about the different power supply choices.

Not sure where to go with this. I will post again after I get the speaker back from the shop, but in the mean time perhaps this thread should be archived?

Thanks,

Peter

[Hugh Robjohns]

Also not common is the linear bass amp which they call "Class H" where a higher rail voltage switches in for peaks.

Are you thinking of Class-G which switches the power rail voltage between two or more discrete levels — higher levels for louder peaks.

Class-H continuously modulates the power rail voltage following the audio envelope, rather than jumping between discrete values.

Class-H is even more ower-efficient than Class-G and closely approaches the efficiency of Class-D. It is obviously much more complex than traditional Class-AB amplifier, but has the advantage of avoiding all the ultrasonic switching noise issues of Class D.

The only professional Class-H amp I know of is the Benchmark Media AHB2.

PSI Audio monitors use Class-G amps.

I'm sure there are others, of both types, of course.

[James Perrett]

Hello,

I'm not deliberately withholding information. Sincere apologies for any confusion.

I'm sure that you are giving us all the information that you can remember but your tech's explanations don't quite add up. I'd say that your last speaker was probably fixed by luck rather than technical skill. I wouldn't be surprised to find that something carrying a ground connection had come loose so the real problem was fixed simply by disassembling and then re-assembling the speaker.

Mind you, I remember our local TV repairers were just as bad. With our first TV in the 1960s, the local shop's solution to our regular TV problems was always to just change a valve. The new valve would work for a few months and then the same problem would re-appear again. In the end we took it to a different repair place a bit further away and they found the real problem.

[ef37a]

Also not common is the linear bass amp which they call "Class H" where a higher rail voltage switches in for peaks.

Are you thinking of Class-G which switches the power rail voltage between two or more discrete levels — higher levels for louder peaks.

Class-H continuously modulates the power rail voltage following the audio envelope, rather than jumping between discrete values.

Class-H is even more ower-efficient than Class-G and closely approaches the efficiency of Class-D. It is obviously much more complex than traditional Class-AB amplifier, but has the advantage of avoiding all the ultrasonic switching noise issues of Class D.

The only professional Class-H amp I know of is the Benchmark Media AHB2.

PSI Audio monitors use Class-G amps.

I'm sure there are others, of both types, of course.

Note Hugh that I said "THEY call Class H" Yes, from the looks of the circuit it is class G with two supply rails each side and commutating diodes.

I am sure I read in one of Phils reviews of a speaker which use class H?

Dave.

[ef37a]

Hello,

I'm not deliberately withholding information. Sincere apologies for any confusion.

I'm sure that you are giving us all the information that you can remember but your tech's explanations don't quite add up. I'd say that your last speaker was probably fixed by luck rather than technical skill. I wouldn't be surprised to find that something carrying a ground connection had come loose so the real problem was fixed simply by disassembling and then re-assembling the speaker.

Mind you, I remember our local TV repairers were just as bad. With our first TV in the 1960s, the local shop's solution to our regular TV problems was always to just change a valve. The new valve would work for a few months and then the same problem would re-appear again. In the end we took it to a different repair place a bit further away and they found the real problem.

I blame the government...all of them. At least since I was about 20. Before that in the 4 years I was a'larnin' I recall at least four visits from the factory inspectors at two workshops. I went on to work at a large TV/audio* workshop on an industrial estate for 15 years. Never came close. I did ten years in a factory making data network products again, neither hide no hair.

In this country you can set yourself up as an electronics service tech, a builder, a computer expert and you don't need any qualifications. Can't do gas work or house wiring though I bet many have tried until they blow themselves up or get electrocuted.

* The audio room alone was almost the size of my bungalow's footprint!
Dave.