My Nuforce DDA100 integrated amplifier started to have some issues recently and I traced the problem to the (Skynet SNP-G series) 28V 120W SMPS which is buzzing/hissing quite loudly and has a faint burning smell. The amp works perfectly fine running off my bench power supply so I’d like to replace the power supply. Im looking at these two power supplies, the Meanwell EPS-120-27 no PFC or EPP150-27 with PFC. Any opinions or other options? Thanks
https://www.mouser.com/ProductDetail/MEAN-WELL/EPS-120-27?qs=Kh9WxvXxjWm29iR9914aXg==
https://www.mouser.com/ProductDetail/MEAN-WELL/EPP-150-27?qs=Uzd/wh%2BZzhAREbslZUMOsQ==
https://www.mouser.com/ProductDetail/MEAN-WELL/EPS-120-27?qs=Kh9WxvXxjWm29iR9914aXg==
https://www.mouser.com/ProductDetail/MEAN-WELL/EPP-150-27?qs=Uzd/wh%2BZzhAREbslZUMOsQ==
The only thing I would want to know would be what the switching frequencies are of both what you have, and the meanwell ones, just to make sure there isn’t a huge difference between them. Any measures to quell potential noise in the rest of the amp may have been tuned to a specific frequency possibly. With any luck the frequencies are both way up high, and any noise filtering is also way high…
I couldn’t find that information when I looked however.
I was trying out an industrial ultrasonic noise detector a while back, and it went nuts whenever I got near a Marantz integrated amp I had playing that had a switching supply.
If/when you do get a replacement, you may consider leaving the amp turned on, if you didn’t already, since switching supplies tend to last a lot longer if they aren’t cycled on/off. The diodes can’t handle the inrush so many times.
I couldn’t find that information when I looked however.
I was trying out an industrial ultrasonic noise detector a while back, and it went nuts whenever I got near a Marantz integrated amp I had playing that had a switching supply.
If/when you do get a replacement, you may consider leaving the amp turned on, if you didn’t already, since switching supplies tend to last a lot longer if they aren’t cycled on/off. The diodes can’t handle the inrush so many times.
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Thanks Phase. If I’m reading the Meanwell data sheet correctly it looks like the switching frequency is 65KHz but the Skynet data sheet doesn’t mention it. I think I’m going to give the $25 Meanwell EPS120-27 a try and if it doesn’t work out at least It wasn’t expensive!
Meanwell is good, and if you get a metal cased one with earthing terminal, do use it.
Or else get hold of a linear supply, though $25 will be low, you could check out surplus sellers.
Or else get hold of a linear supply, though $25 will be low, you could check out surplus sellers.
I ordered the $25 Meanwell it should be here in a few days. If it doesn’t work out maybe I’ll build a little external linear power supply for the amp. I have plenty of suitable capacitors and rectifiers bridges in my parts bin and Antek has a 100VA 20V toroid for $24 so it wouldn’t cost me much to try.
I installed the new Meanwell power supply and I’m happy cuz the amp is working fine again and sounds great but also a little disappointed with how noisy the Meanwell is at low loads.
Among the reasons I told you to find a linear supply.
Now search thee forum for SMPS noise.
Practically, a ladder like circuit with assorted small capacitors for various frequencies will work as a filter in the supply.
You will have to look around for other posters' experiences.
Now search thee forum for SMPS noise.
Practically, a ladder like circuit with assorted small capacitors for various frequencies will work as a filter in the supply.
You will have to look around for other posters' experiences.
It’s not a noise coming through the speakers,, the amplifier is actually dead quiet with my ear next to the tweeters. It’s a sort of buzzing sound coming from the power supply itself. A linear supply would be nice and simple to build but unfortunately wouldn’t fit inside the small case.
Put some hot melt glue between ferrite and coil on the SMPS transformers, and tighten the transistors on their heat sinks.
You can try with an external power supply, some posters have used lap top bricks.
No harm in trying...if the voltage matches.
You can try with an external power supply, some posters have used lap top bricks.
No harm in trying...if the voltage matches.
That sounds like a great suggestion to stop the buzzing, however I would use some electrical potting material. RTV silicone might be tempting, but it has acetic acid, is corrosive.
Hot melt glue will absorb moisture from the air and release from surfaces, but is great for the disposable holiday decorations maybe.
https://www.newark.com/mg-chemicals...HOPPING-NewStructure-Tools-ProductionSupplies
Hot melt glue will absorb moisture from the air and release from surfaces, but is great for the disposable holiday decorations maybe.
https://www.newark.com/mg-chemicals...HOPPING-NewStructure-Tools-ProductionSupplies
Potting compound is harder than hot melt.
Some ferrite transformers are designed with an air gap or floating core, the potting compound might restrict that.
Hot melt is mostly LDPE, practically inert.
I mean the kind that is sold in sticks and a pistol like gun is used to melt and dose the stuff.
Neutral cure RTV silicone does not have acetic acid, that is usable here also.
Some ferrite transformers are designed with an air gap or floating core, the potting compound might restrict that.
Hot melt is mostly LDPE, practically inert.
I mean the kind that is sold in sticks and a pistol like gun is used to melt and dose the stuff.
Neutral cure RTV silicone does not have acetic acid, that is usable here also.
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Agreed that a semi-flexible compound is likely what you’d want, even if it meant sacrificing some of the better thermal properties of the epoxy products. I hadn’t realized that was a rigid compound. Complete encapsulation isn’t necessary, just enough to keep the parts from buzzing. Noise is probably coming from the large inductors, but could isolate it using a drinking straw or section of flexible tubing.
The commonly available Loctite PL sealant is a flexible urethane product that is a moisture-cure, rated up to 180F, would be a pretty simple solution since it’s stocked at home improvement stores here in the us. Would need to have some mineral spirits or just WD40 around since it’s a solvent based compound and won’t wash off with soap and water.
The commonly available Loctite PL sealant is a flexible urethane product that is a moisture-cure, rated up to 180F, would be a pretty simple solution since it’s stocked at home improvement stores here in the us. Would need to have some mineral spirits or just WD40 around since it’s a solvent based compound and won’t wash off with soap and water.
I didn’t even think of using PL sealant that’s a great idea and I have free access to it at my job. I’ll give it a try on Monday and see if it helps. I do kind of like the idea of an external linear power supply I’m just not sure if I’d need to go regulated. The amp is a full digital “power dac “ using Infineon SAB2403 which I haven’t been able to get a data sheet for but according to the info I found on this old Infineon PDF the max voltage on these chips is 27v. It looks like Nuforce is running them close to 27v.
https://www.infineon.com/dgdl/Infin...94894&fileId=db3a30432e5d3808012e70bab2006003
https://www.infineon.com/dgdl/Infin...94894&fileId=db3a30432e5d3808012e70bab2006003
Running a 27 V chip at full 27V is a bit too close for comfort in a linear supply.
Use a 24V zener controlled linear supply, with some arrangement that it does not go above 27 V.
Provided the chip works at 24V, of course.
Use a 24V zener controlled linear supply, with some arrangement that it does not go above 27 V.
Provided the chip works at 24V, of course.
I think I’m going to hold off on the linear supply. The Meanwell is noisy with the case open and my ear within a few feet, with the case on it’s not audible and the amp is dead quiet through the speakers. Im actually thinking of giving this amplifier away along with a pair of speakers to a less fortunate friend of mine that is interested in good sound. I think the Meanwell will be reliable and work well for him.