Hello all. I have a buzzing amplifier which has been isolated to an issue with what else is connected alongside. Whilst I recognise different amplifiers have different designs and that some are better and some are worse when it comes to buzzing I'm stuck with this one (I have another two which are ok) and want to make it work rather than rolling back.
The issue is the power coming in is not clean. If you have a PC on the same mains circuit with a typical switching power supply the amplifier will pick this up and create buzzing through the speakers. It's a JLH 1969 variant and supposedly class A so gets hot and runs at full power all the time. So potentially more sensitive than my other amplifiers.
The guy who diagnosed the cause (i.e. if you switch off the PC the buzzing stops) said I should fit something into the line before the power reaches the amp to clean it up. Is anybody else doing this and what have you used?
The issue is the power coming in is not clean. If you have a PC on the same mains circuit with a typical switching power supply the amplifier will pick this up and create buzzing through the speakers. It's a JLH 1969 variant and supposedly class A so gets hot and runs at full power all the time. So potentially more sensitive than my other amplifiers.
The guy who diagnosed the cause (i.e. if you switch off the PC the buzzing stops) said I should fit something into the line before the power reaches the amp to clean it up. Is anybody else doing this and what have you used?
I would first try to find out where the noise enters the amp. Does it buzz also with inputs disconnected? If that's the case that's probably an easy fix because that means the noise is entering via the AC line and a mains filter will do the trick. There are lots of mains filters available out there, look for example here:
Spannungsversorgungsleitungsfilter – Mouser Deutschland
As your amp seems to draw quite some power make sure that the mains filter is rated for sufficient current. You have to take peak currents into account as the current will be flowing in spikes when line voltage is at it's peaks and will charge reservoir caps. If for example the amp draws 250W at 240V that's ~1A RMS current - I would at least suggest going a factor of 5 higher! Maybe even better 10. If the common mode chokes in the filter start to saturate their filtering abilities will get a lot worse...
Spannungsversorgungsleitungsfilter – Mouser Deutschland
As your amp seems to draw quite some power make sure that the mains filter is rated for sufficient current. You have to take peak currents into account as the current will be flowing in spikes when line voltage is at it's peaks and will charge reservoir caps. If for example the amp draws 250W at 240V that's ~1A RMS current - I would at least suggest going a factor of 5 higher! Maybe even better 10. If the common mode chokes in the filter start to saturate their filtering abilities will get a lot worse...
I'm not extremely interested in the small details but I was of the view that a class-A amp (like what we're discussing here) does not peak as it is always drawing the full load. The unused power is converted to heat and radiated out through the casing.
That mouser website is interesting but selecting 240v from the menu brings up 5+ pages of recommendations so not sure I'd really be that confident picking out the right part at the first attempt.
That mouser website is interesting but selecting 240v from the menu brings up 5+ pages of recommendations so not sure I'd really be that confident picking out the right part at the first attempt.
But the reservoir caps are only charged when the mains voltage is at it's peak, i.e. 100 times per second. Look here: https://media.monolithicpower.com/wysiwyg/6_18.png
Before selecting a filter I'd recommend you first answer my question in the previous post.
Before selecting a filter I'd recommend you first answer my question in the previous post.
I've done a fair bit of testing of various household equipment for energy consumption and power amplifiers probably draw less than you think.
The 250W were just an example, you will have to calculate it yourself as I don't know the power draw of your amp. You still did not answer my first question though 🙂
Your first question was whether or not it continues to buzz with inputs disconnected. I actually answered that question before you asked it. So finding it close to irksome that you asked it and keep asking it.
OK, I cannot see it anywhere, maybe I'm blind 🙂
So what's the rated power draw of your amp? I could then give you my recommendation for a power line filter.
So what's the rated power draw of your amp? I could then give you my recommendation for a power line filter.
That wasn't your first question. "Does it buzz also with inputs disconnected?" = your first question...
I've done some testing, just for you.
The results confirm that it doesn't spike, like I said. It's rated as 18w per channel but maybe we can see whether or not that is accurate from the results.
Each test is more or less 10 minutes long. One with about a minute of loud music, one no music. You will see the ratings for the JLH while playing nothing are higher in the second test because it has been connected to the power for longer.
JLH 1969 - 10 minutes with music
JLH 1969 - 10 minutes without music
NAIM NAP 200 - 10 minutes with music (test overran a little!)
NAIM NAP 200 - 10 minutes without music
I've done some testing, just for you.
The results confirm that it doesn't spike, like I said. It's rated as 18w per channel but maybe we can see whether or not that is accurate from the results.
Each test is more or less 10 minutes long. One with about a minute of loud music, one no music. You will see the ratings for the JLH while playing nothing are higher in the second test because it has been connected to the power for longer.
JLH 1969 - 10 minutes with music
JLH 1969 - 10 minutes without music
NAIM NAP 200 - 10 minutes with music (test overran a little!)
NAIM NAP 200 - 10 minutes without music
Images don't work.
And I tried to explain that the spikes don't come from the music signal but are inherent to power supplies that use a rectifier and smoothing capacitor. The spikes occur with 100Hz (if you're in a 50Hz country, 120Hz in a 60Hz country) or every 10ms. For a class A amp that always draws near constant power, the current spikes will also be consistent but will still be there.
So please fix the images or state power draw of your amp(s) as text. And if you want to use one filter per amp or per stereo pair.
And I tried to explain that the spikes don't come from the music signal but are inherent to power supplies that use a rectifier and smoothing capacitor. The spikes occur with 100Hz (if you're in a 50Hz country, 120Hz in a 60Hz country) or every 10ms. For a class A amp that always draws near constant power, the current spikes will also be consistent but will still be there.
So please fix the images or state power draw of your amp(s) as text. And if you want to use one filter per amp or per stereo pair.
Weirdly this forum doesn't seem to allow editing posts!
Here are the four images. I uploaded them to this forum initially but don't download when checking from my mobile phone! They still display on my desktop computer!
JLH with music
JLH without music
Naim with music
Naim without music
Here are the four images. I uploaded them to this forum initially but don't download when checking from my mobile phone! They still display on my desktop computer!
JLH with music
JLH without music
Naim with music
Naim without music
OK, then thats ~75W for one amp?! Do you want to run one or two amps with the power line filter?
The second amp is just for comparison.
Does the 4th measurement (peak watts) on the last two images from the NAIM amp interest you at all?
And what do you think about the first two images where the class A amp appears to be running at full power all the time regardless whether or not it is being used.
Anyway, those are just side-points...
Does the 4th measurement (peak watts) on the last two images from the NAIM amp interest you at all?
And what do you think about the first two images where the class A amp appears to be running at full power all the time regardless whether or not it is being used.
Anyway, those are just side-points...
What I meant by the qquestion if you want to run one or two amps off the filter - is the JLH a stereo amp consuming 75W? or do you plan to run two mono amps off one filter, i.e. consuming 150W?
As you already correctly stated - class A amps draw more or less the same power regardless of music is playing or not, so the ballpark of 75W for one amp is enough to make a filter recommendation. Once you answer the question if you need 75W or 150W for two of these amps...
As you already correctly stated - class A amps draw more or less the same power regardless of music is playing or not, so the ballpark of 75W for one amp is enough to make a filter recommendation. Once you answer the question if you need 75W or 150W for two of these amps...
Just one stereo amp... It seems to be saying 77.1w in the second set of images after the amp has been turned on for 20 minutes. Could go up a bit.
OK, so i assume a RMS current draw of ~0.3A. To be on the safe side I assumed peak currents for the rectifier of 10x.
Here is a filtered mouser result for filters 250VAC/50Hz, single phase, 3 to 10A:
https://www.mouser.de/Power/Power-C...pZer6tZ1y8d2jiZ1y7gjaoS1y5uythGT&Ns=Pricing|0
PS: I'm not in any way related to mouser, I just know their parametric component search very well...
Here is a filtered mouser result for filters 250VAC/50Hz, single phase, 3 to 10A:
https://www.mouser.de/Power/Power-C...pZer6tZ1y8d2jiZ1y7gjaoS1y5uythGT&Ns=Pricing|0
PS: I'm not in any way related to mouser, I just know their parametric component search very well...
I have not checked all 128 results for absolute best performance, that wold be up to you, to be honest.
The cheapest dual stage filter that seems to have decent performance is this one here:
https://www.mouser.de/ProductDetail/ARCOL-Ohmite/AH-06?qs=xZ/P%2Ba9zWqYYsvE3i2atpA==
The cheapest dual stage filter that seems to have decent performance is this one here:
https://www.mouser.de/ProductDetail/ARCOL-Ohmite/AH-06?qs=xZ/P%2Ba9zWqYYsvE3i2atpA==
Ok, I've ordered that one. It's not too expensive so if it doesn't work out it's not the end of the world. Either way I'll update this topic with the results.
Trial installed without a component box but it makes absolutely zero difference. Or at least so little you can't hear any difference.
I suppose there is the option of disconnecting the earth which might make a difference but you're not supposed to do that. I have heard that disconnecting the earth can stop buzzing but it's not really the right way to do things.
I suppose there is the option of disconnecting the earth which might make a difference but you're not supposed to do that. I have heard that disconnecting the earth can stop buzzing but it's not really the right way to do things.