• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

distance from power supply to amp modules

datrumole

Active Member
Joined
Mar 26, 2020
Messages
156
Likes
64
hey all,

have (2) L20.5 amp modules, and (2) SMPS to power them. is there a required distance they should be away from one another in the same enclosure? the amp modules will be mounted vertically on the enclosure's side heat sinks, while the SMPS will be mounted horizontally (so perpendicular to one another) and the space is somewhat tight, probably 2 or so inches from one another. will this be problematic?
 

Bob-23

Senior Member
Joined
Jul 3, 2019
Messages
425
Likes
379
Location
Berlin, Germany
You may consider using an external power supply - that's what I do with my builds. I have one good transformer in a separate case for the amps that want ac (Gainclones), and one good rectifier & dc-protection/muting in a separate case for the amps that accept dc (some headphone amps). And you have more room inside your amp's case for potential modifications.
 

bigguyca

Senior Member
Joined
Jul 6, 2019
Messages
477
Likes
617
Are you in a 220v country or are you using it on 110v in North America?


If the voltage supplied to your residence is 110V in the U.S. Then you need to contact your power company. The nominal voltage in the U.S. is 120V. Allowing a 5% +/- tolerance puts the minimum at 114V, but the full 120V is preferred.
 
OP
D

datrumole

Active Member
Joined
Mar 26, 2020
Messages
156
Likes
64
Are you in a 220v country or are you using it on 110v in North America?

sorry, should have specified, i'm in the US, and ordered the 110V

If the voltage supplied to your residence is 110V in the U.S. Then you need to contact your power company. The nominal voltage in the U.S. is 120V. Allowing a 5% +/- tolerance puts the minimum at 114V, but the full 120V is preferred.

i'm 122V at most outlets
 

Speedskater

Major Contributor
Joined
Mar 5, 2016
Messages
1,610
Likes
1,333
Location
Cleveland, Ohio USA
In the US the nominal voltage ah been 120V but it's now drifting towards 125V. The NEC/UL specs are now 125V.
But a SMPS (power supply) doesn't give a hoot if the voltage is 105V or 130V. They instantly adjust themself for changing line voltage.
 

tomchr

Addicted to Fun and Learning
Audio Company
Forum Donor
Joined
Nov 5, 2018
Messages
984
Likes
2,607
Location
Calgary, Canada
You may consider using an external power supply - that's what I do with my builds.
That's not such a hot idea, actually. The umbilical cord connecting the two chassis adds impedance in series with the power supply and you will often find that such builds have higher distortion than the same build with the power supply in the same chassis as the amp. This is especially true for Class AB and Class D amps as they draw current in pulses from each supply rail. In many two-chassis builds, builders use the same chassis for the power supply as for the amp, which causes folks to stack them. That usually puts the transformer and rectifier closer to sensitive circuits than they would have been had the supply been in the same chassis as the amp.

Now for OP's original question: More distance is better. But the key is that you keep the amplifier inputs away from sources of interference in the SMPS. The primary interference source in an SMPS is the rectifier. I've marked it for you in the attached image. Place the rectifier away from the inputs to the amp.

Tom
 

Attachments

  • Screen Shot 2021-01-28 at 04.28.42.jpg
    Screen Shot 2021-01-28 at 04.28.42.jpg
    252 KB · Views: 100

howard416

Active Member
Joined
Sep 12, 2019
Messages
246
Likes
143
That's not such a hot idea, actually. The umbilical cord connecting the two chassis adds impedance in series with the power supply and you will often find that such builds have higher distortion than the same build with the power supply in the same chassis as the amp. This is especially true for Class AB and Class D amps as they draw current in pulses from each supply rail.
What if there is local bulk capacitance on the amp modules?
In many two-chassis builds, builders use the same chassis for the power supply as for the amp, which causes folks to stack them. That usually puts the transformer and rectifier closer to sensitive circuits than they would have been had the supply been in the same chassis as the amp.
A grounded steel sheet as a shield will solve that.
 

tomchr

Addicted to Fun and Learning
Audio Company
Forum Donor
Joined
Nov 5, 2018
Messages
984
Likes
2,607
Location
Calgary, Canada
What if there is local bulk capacitance on the amp modules?
You're still moving large currents through long loops -> high inductive coupling.

A grounded steel sheet as a shield will solve that.
Only for capacitive coupling. A grounded sheet does very little for inductive coupling. It'll have some effect but you need several mm of steel to get any significant attenuation. You could get some mu metal, though. You can buy it on eBay in sheets with adhesive backing.

Tom
 
OP
D

datrumole

Active Member
Joined
Mar 26, 2020
Messages
156
Likes
64
Now for OP's original question: More distance is better. But the key is that you keep the amplifier inputs away from sources of interference in the SMPS. The primary interference source in an SMPS is the rectifier. I've marked it for you in the attached image. Place the rectifier away from the inputs to the amp.

Tom

thanks tom! i'll keep that in mind, but so far the general concensus is that there doesnt need to be much distance between teh amp and these smps
The Ebay link you posted does not specify voltage, is that the exact link you purchased from?

I am looking for that exact spec power supply, but I only see similar ones in 220v.

https://www.aliexpress.com/item/4000461356351.html

Thank you,

David.

yeah, it's only offered in 220, but if you email them, they will mod it for 110 (just a wire jumper after the voltage doubler circuit)
 

tomchr

Addicted to Fun and Learning
Audio Company
Forum Donor
Joined
Nov 5, 2018
Messages
984
Likes
2,607
Location
Calgary, Canada
I used to offer a Modulus-286 Kit which had an SMPS in it. As you can see from the image below, I fit a lot of sardines in a very small can. I had to have design spin of the mezzanine plate as I found I needed to rotate the SMPS such that the rectifier was away from the input of the amp module below it. The difference in mains hum was easily measurable. Even after I rotated the supply, you could still measure a difference in mains hum between the two channels.

index.php


Tom
 
Top Bottom