Does it or does it NOT matter if there is a emi/rfi line filter before the transformer in a linear psu ?
Since transformers have very limited bandwidth wouldn't that filter out the high frequency noise anyway ?
Since transformers have very limited bandwidth wouldn't that filter out the high frequency noise anyway ?
It depends on the type of transformer and it's VA rating. You only need a filter if you have noise problems.
can you please tell me more. I am curious about this subject.
by type and va rating do you mean if a transformer has sufficient bandwidth it might let the noise in, otherwise not ?
I don't have hum or hiss if thats what you mean by noise problems. Otherwise I don't have a scope with wide enough bandwidth to actually see if there is any 'noise' or not.
by type and va rating do you mean if a transformer has sufficient bandwidth it might let the noise in, otherwise not ?
I don't have hum or hiss if thats what you mean by noise problems. Otherwise I don't have a scope with wide enough bandwidth to actually see if there is any 'noise' or not.
Hi,
get someone to do some electric arc welding in the garage or adjacent property. Now listen for EMI coming in through the mains.
Or remove the spark suppressor from the switch of your mains operated electric drill and get someone to repeatedly switch it on and off while listening in another part of the house.
These mains borne noises will be completely different from noise produced inside the amp as part of the amplifying process.
If your amp and ancilliaries are completely free of external mains borne noise then don't bother adding input suppression. There is a body of opinion that says these reduce the quality of the audio output.
But, in my opinion, that reduction is always better than being plagued by variable external interference.
get someone to do some electric arc welding in the garage or adjacent property. Now listen for EMI coming in through the mains.
Or remove the spark suppressor from the switch of your mains operated electric drill and get someone to repeatedly switch it on and off while listening in another part of the house.
These mains borne noises will be completely different from noise produced inside the amp as part of the amplifying process.
If your amp and ancilliaries are completely free of external mains borne noise then don't bother adding input suppression. There is a body of opinion that says these reduce the quality of the audio output.
But, in my opinion, that reduction is always better than being plagued by variable external interference.
I was concerned about smps hash, flourescent light and motor static that gets dumped back on the line.
A shortwave radio will pick up that nasty noise easily because the house wiring acts as a gigantic transmitting antenna. I was trying to find out how much of that noise really affects an audio device with a linear psu using a step down transformer in any way.
A shortwave radio will pick up that nasty noise easily because the house wiring acts as a gigantic transmitting antenna. I was trying to find out how much of that noise really affects an audio device with a linear psu using a step down transformer in any way.
Try this if you've a mind to -
This is essentially the topology of the Audience Adept, PSAudio UltraOutlet and many other line filters. I've not had good luck with the metal encased filters from Corcom, Shafner, etc....
Common mode noise is attenuated by the common mode inductance of the choke, and normal mode noise is attenuated by the caps and the leakage inductance of the choke.
In my experience, line noise whose elimination is highly beneficial, is rarely percieved as noise. I'm unwilling to describe changes wrought as it requires 'audiophile terminology' and if I want to recieve ridicule, I'll talk to my wife....
For CMCs I recommend the JW Miller 8100 series in the States, available for reasonable cost from newark.com
http://www.newark.com/jsp/search/br...LS_001_PRICE1|1&Ntk=gensearch_001&Ntt=81&Ntx=
For a small system - 100wpc AB solid state amp and sources, I'd suggest a 8120-RC. For just sources, a 8118-RC
Outside N.A. RS carries the Wurth CMB common mode chokes. Search on 'WE-CMB XL'
At worst, and your power is wonderful and/or all powerconditioning is nonsense, you're out about $20.
FWIW
An externally hosted image should be here but it was not working when we last tested it.
This is essentially the topology of the Audience Adept, PSAudio UltraOutlet and many other line filters. I've not had good luck with the metal encased filters from Corcom, Shafner, etc....
Common mode noise is attenuated by the common mode inductance of the choke, and normal mode noise is attenuated by the caps and the leakage inductance of the choke.
In my experience, line noise whose elimination is highly beneficial, is rarely percieved as noise. I'm unwilling to describe changes wrought as it requires 'audiophile terminology' and if I want to recieve ridicule, I'll talk to my wife....
For CMCs I recommend the JW Miller 8100 series in the States, available for reasonable cost from newark.com
http://www.newark.com/jsp/search/br...LS_001_PRICE1|1&Ntk=gensearch_001&Ntt=81&Ntx=
For a small system - 100wpc AB solid state amp and sources, I'd suggest a 8120-RC. For just sources, a 8118-RC
Outside N.A. RS carries the Wurth CMB common mode chokes. Search on 'WE-CMB XL'
At worst, and your power is wonderful and/or all powerconditioning is nonsense, you're out about $20.
FWIW
For those of you in Great Britan, a poster on another board (Thanks Darren!) is using this -
http://www.maplin.co.uk/module.aspx?ModuleNo=46830&doy=25m6
which is using a very similar topology. Given the economy of scale in the AV maket it appears to be quite reasonable. If its current constrained for power amps, it might well be quite good for source components. I've no personal experience with this product.
Towards the bottom of the referenced page, there is something about signing up for their newsletter and getting discount coupons.
http://www.maplin.co.uk/module.aspx?ModuleNo=46830&doy=25m6
which is using a very similar topology. Given the economy of scale in the AV maket it appears to be quite reasonable. If its current constrained for power amps, it might well be quite good for source components. I've no personal experience with this product.
Towards the bottom of the referenced page, there is something about signing up for their newsletter and getting discount coupons.
richie00boy said:
Or if you have an air conditioner, hair dryer, refrigerator, microwave oven...or if any of your neighbors are similarly situated.
not sure whether to start another thread about this or what because it kind of overlaps the subject, but what would you make of this -
I have a Yaesu FRG-100 communications receiver -
It behaves very differently in terms of audible noise when being powered by the ac adapter v/s batteries.
On ac I hear a lot of noise. Its typical RF noise - qrm/qrn if you know what I mean - not to be mistaken with hum or hiss. Even on a quiet area of a band (especially bc/am/mw band) with no signal the s-meter reads S-5. But when running on batteries it is very quiet. No noise from the speaker and the s-meter rests calmly at S-1.
I have tried putting an ac inteference filter/conditioner between the wall outlet and the adapter, and I have tried putting a 4700uf cap across the dc output of the adapter in case it is due to bad filtering, but to no avail. It does not have any effect.
But I switch to batteries and complete silence. No sign of noise. I use pretty much the same length of wire for the battery too.
Now what would you attribute this too ? How would you explain this ?
Line noise ? Something about the power supply ? What is it ?
And then it leads me to think what if it was a DAC, or a pre-amp or an amp at the dc end of that adapter ??
I have a Yaesu FRG-100 communications receiver -
It behaves very differently in terms of audible noise when being powered by the ac adapter v/s batteries.
On ac I hear a lot of noise. Its typical RF noise - qrm/qrn if you know what I mean - not to be mistaken with hum or hiss. Even on a quiet area of a band (especially bc/am/mw band) with no signal the s-meter reads S-5. But when running on batteries it is very quiet. No noise from the speaker and the s-meter rests calmly at S-1.
I have tried putting an ac inteference filter/conditioner between the wall outlet and the adapter, and I have tried putting a 4700uf cap across the dc output of the adapter in case it is due to bad filtering, but to no avail. It does not have any effect.
But I switch to batteries and complete silence. No sign of noise. I use pretty much the same length of wire for the battery too.
Now what would you attribute this too ? How would you explain this ?
Line noise ? Something about the power supply ? What is it ?
And then it leads me to think what if it was a DAC, or a pre-amp or an amp at the dc end of that adapter ??
Hi,
that description sounds like amplifiers with a poor PSRR and voltage regulators sending dirty power to the amplifiers.
The combination produces a dirty sound.
that description sounds like amplifiers with a poor PSRR and voltage regulators sending dirty power to the amplifiers.
The combination produces a dirty sound.
percy said:
I'd assume a really bad linear wall wart/brick, or a typical off the shelf switching wart/brick.
As your Yaesu runs of a 11-13.5 VDC 1.2 Amps ps, either run it off a 12v SLA with a recharger, or get/build a low noise 12vdc ps.
While circuitry with high psrr is allways a good thing, you're not talking hifi here. Nor is a redesign of the Yaesu's circuity overly practical. Its allways easier to to fix the problem as early as possible. The line filter topology above works well on dc, actually better as its into a lower load impedance, less prone to cause high 'Q' peaks, and you're not restricted to X type caps.
The above comments (IMO) apply similarly to HiFi components.
added note- Percy - given the esl (equivalent series indctance) of a 4.7mF electro cap, its not going to be particularly effective with hf noise. If the ps is a switcher, that noise will be a combo of common and normal mode, and a cap isn't going to do anything for common mode noise....
percy said:
Did you ever see the series of article in QEX on receiver noise, SNR - contributed to by nonetheless than Dr. Rohde -- I will stick with my SX101A and SX115 for the moment (I had a drake R-8 but traded it.)
" ... I have a Yaesu FRG-100 communications receiver ... It behaves very differently in terms of audible noise when being powered by the ac adapter v/s batteries. ... On ac I hear a lot of noise. ..."
Yes, you obviously have a noisy power line and this almost certainly does affect the quality of your audio gear as well.
(Your communications receiver is easy = just run it from a battery all the time with a full time trickle charger ... a battery is after all very much like a capacitor and it stores DC energy over time, releasing it to your receiver as needed, over time. I use 12 VDC motorcycle batteries and a charger for my DX gear ( http://industrialcomponent.com/opticis/optpower.html ))
I equip all of my DIY amps with a line filter in the power connector, ahead of the transformer, just like the designs used on laboratory test gear. In addition I have built into my plug strip(s) a nice little power line filter from a design from the ~1965 Radio Amateur Relay League Handbook. My office system (next to a machine shop) is likewise equipped with surge strips, line filters, etc. ... to keep all the switching computer supplies and machine shop EMF, etc., off the audio equipment ... mmmmmore is better IMOP.
" Does it or does it NOT matter if there is a emi/rfi line filter before the transformer in a linear psu ? ..."
Yes ... 😀
" ... Since transformers have very limited bandwidth wouldn't that filter out the high frequency noise anyway ? ..."
Yes, but not all ...
Yes, you obviously have a noisy power line and this almost certainly does affect the quality of your audio gear as well.
(Your communications receiver is easy = just run it from a battery all the time with a full time trickle charger ... a battery is after all very much like a capacitor and it stores DC energy over time, releasing it to your receiver as needed, over time. I use 12 VDC motorcycle batteries and a charger for my DX gear ( http://industrialcomponent.com/opticis/optpower.html ))
I equip all of my DIY amps with a line filter in the power connector, ahead of the transformer, just like the designs used on laboratory test gear. In addition I have built into my plug strip(s) a nice little power line filter from a design from the ~1965 Radio Amateur Relay League Handbook. My office system (next to a machine shop) is likewise equipped with surge strips, line filters, etc. ... to keep all the switching computer supplies and machine shop EMF, etc., off the audio equipment ... mmmmmore is better IMOP.
" Does it or does it NOT matter if there is a emi/rfi line filter before the transformer in a linear psu ? ..."
Yes ... 😀
" ... Since transformers have very limited bandwidth wouldn't that filter out the high frequency noise anyway ? ..."
Yes, but not all ...
jackinnj said:
Jack, do you remember which QEX issue that was in ? I have been away from the hobby for a while, but find myself touching base with it often.
I am beginning to think its a combination of RF(antenna) ground and the supply ground issue - maybe something to do with the fact that the RF ground and the supply ground are the same (chassis). But its still beyond me why running it off batteries eliminates the problem all together.
Waveform and Spectrum analysis of the audio confirms that the noise is 120hz with strong harmonics across the entire range - 240hz, 360hz, 480hz,....
It's not a ripple/filter problem because adding tons of filter capacitance does reduce the ripple a lot but has no effect whatsoever on that noise. Another interesting tidbit is that it is a menace mostly under ~2Mhz. Above that its not so obstrusive - audibly, that is.
jackinnj said:
I hear ya. This is my first "modern" receiver. The only receivers I have ever used for serious SWL/DXing were all boatanchors - an EAC R-390A, a National HRO-50T and a BC-348"K".
EMI/RFI interference
I had problems with noise on an amplifier I was building. Various electronic deviced sent 'signals' into my amp... these guys sell all sorts of bits that help screen or shield your electronics from this. I used the fabric over foam and fingerstrips, but there is other stuff depending on what you want. www.shielding-solutions.com
I had problems with noise on an amplifier I was building. Various electronic deviced sent 'signals' into my amp... these guys sell all sorts of bits that help screen or shield your electronics from this. I used the fabric over foam and fingerstrips, but there is other stuff depending on what you want. www.shielding-solutions.com
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