MiniDSP SHD - Possible benefits, or risks, to gluing PSU coils?

[tmtomh]

I recently got a MiniDSP SHD, and I had the common problem where it makes a hiss/noise when in standby - silent when on and operating, and of course silent when fully switched off. The hiss and noise happen only when the rear power switch is On, but the unit is turned Off aka put into standby mode using the remote.

After confirming that the sound was mechanical, coming from the PSU, and not caused by a ground loop or DC in the AC line, I contacted MiniDSP support and asked them to send me a new PSU, which they did.

I installed the new one and it still makes a noise, but it is greatly reduced, like 90%. Before it was low-level but audible from across the room if my ear was anywhere near level with the SHD's location in my audio rack. Now I have to get about 1-1/2 feet away and bend down to align my ear with the SHD in order to hear it.

I noticed that the new PSU has the same design and layout as the old one - but there are at least a couple of different components, including the largest capacitor (forget the brands but one is black with silver stripe while one is brown with silver stripe). And I noticed that there are two exposed copper coils, right next to each other, and that on each PSU there appears to be a very thin layer of dried yellow stuff across the tops of them, that looks like some kind of glue or adhesive. The new PSU seems to have slightly more of this adhesive applied than the old one, though the difference looks like normal variation rather than a conscious change in the amount.

Here is a photo of the old one (the new one is in the SHD now and I didn't think to photograph it before closing up the unit), with the two coils circled in red.

I am convinced the sound is coil whine, not transformer vibration. My question is, would it be worth trying to apply some kind of glue more thoroughly around the exposed coils of the original PSU, to see if that addresses the problem?

Would anyone have recommendations for adhesive? I assume something not too thick and heavy, and perhaps something that dries with some elasticity in it so it won't crack over time or overly stress the coils. Would there be any electrical or thermal risk to doing this?

I'm open to trying with this PSU since it's now an extra and the new one works so much better. But I would not want to try this if putting the modified PSU back into the SHD to test it would pose any risk to the SHD itself.

Thanks!

 

[Anthony LoFi]

Could I kindly suggest trying the "glue" fix on your old PS (if you still have it) and just power it up on its own supply not installed.
This would at least ensure you have a correct method to silence the sound.
Its seems the solution is to stop the component physically vibrating at high frequencies or abosorb the sound from getting out!
Another suggestion could be to use small polystyrene blocks to cover individual components to try and identify the sound source exactly.

When selecting the appropriate "glue/silicone" check the manufacturer does not have warnings on the corrosive nature that could damage the coils over time? I used a solvent silicone to fix a small leak on a steel roof which rusted pretty quickly.

I wonder if your problem is a manufacturing batch that is prone to this, or could it be over/under supply voltage.

So where other members who have this problem, maybe we could share serial numbers to see if its batch related as not every owner has this problem.
Also other members with the same problem could indicate the version (Nero2 or 3) Supply voltage used (230/110) and possibly an actual voltage measurement.

Using others environments data we could understand the problem where some users are fine and others not!
miniDSP should be aware by now what this effect is and has a solution but may yest filter down to customer.
Sometime the users may need to start the ball rolling especially if there are a number of use on a forum trying to sort it out.
Just saying.

 

[droid2000]

I'd stay away from chinese junk. You're already into a lot of wasted time. Do the math and it doesn't work out.

 

[restorer-john]

Your hiss/noise won't be coming from the common mode filter you have highlighted because it really is only in line with the 50/60Hz.

The main transformer is the likely culprit (the one covered in yellow tape), or the output filter/caps. I've even had small ceramic capacitors make noise in certain situations. You can't really mess with it as heat disipation may be affected.

Alternatively, you could invest in a suitable linear supply as they are pretty much dead silent. How many rails does it have and what are the voltages/currents required?

 

[Anthony LoFi]

John's correct, but really the problem is still with the manufacturer.
Any manufacturer could argue that a certain amount of noise is acceptable i.e. fan noise where installed.
With SMPS there is always the side effect due to design and component layout for the ability to produce audible noise.
The problem is the audio industry has been designing silent electronics for a long time. They know what causes noise and design around it.
In your case, there seems to be a problem along with a number of other owners that although few have not been enough in quantity to force miniDSP to solve the problem by a general recall of affected products.

You shouldn't have to buy and install (negate your statuary warranty) another power supply.
I hope other owners here on ASR with this problem could combine together with the serial numbers to as a group directly enguage with miniDSP for an acceptable outcome.
miniDSP are well aware of the readership and forum numbers to take any combined problematic models seriously.

Have you advised miniDSP that the replacement has also a noise issue?
And if so what have they suggested?

 

[tmtomh]

John's correct, but really the problem is still with the manufacturer.
Any manufacturer could argue that a certain amount of noise is acceptable i.e. fan noise where installed.
With SMPS there is always the side effect due to design and component layout for the ability to produce audible noise.
The problem is the audio industry has been designing silent electronics for a long time. They know what causes noise and design around it.
In your case, there seems to be a problem along with a number of other owners that although few have not been enough in quantity to force miniDSP to solve the problem by a general recall of affected products.

You shouldn't have to buy and install (negate your statuary warranty) another power supply.
I hope other owners here on ASR with this problem could combine together with the serial numbers to as a group directly enguage with miniDSP for an acceptable outcome.
miniDSP are well aware of the readership and forum numbers to take any combined problematic models seriously.

Have you advised miniDSP that the replacement has also a noise issue?
And if so what have they suggested?

Thanks for this, your prior comment, and @restorer-john for your comment as well. To address a few of your points:

RE likely source of the noise - thanks John! It doesn't sound like transformer hum to me, so perhaps as you say it could be a capacitor. The largest capacitor is different on the two PSUs - same size and if memory serves same capacity, but clearly a different brand or rating.

RE which MiniDSP: it's a "Neo 3" model, not the older "Neo 2." I learned about this distinction after the fact, when I searched for and posted about my issue on the MiniDSP forums. Apparently the problem began with the switch to the Neo 3 version, when one of the USB input boards was changed. The story, as told on the MiniDSP forums, is that the earliest batch of Neo 3's had this PSU noise problem, and MiniDSP quickly changed to a new PSU and sent replacement PSUs to the affected customers who wanted them and felt able to install them. (It's really easy - four screws and two internal plastic plugs).

However, it is overwhelmingly obvious that the PSU noise was not limited to just that first production run of Neo 3 models - it continues to be a problem, for many users. Based on my online interactions in threads at the MiniDSP forums and elsewhere, it appears most people who have the issue - including a MiniDSP forum moderator wh replied in the thread there - just live with it, which I find incomprehensible.

I also learned that MiniDSP updated the firmware of the SHD to make it consume more power when in standby mode. The theory is that the PSU noise is related to the voltage drop that occurs when the unit is put into standby, and by increasing standby power consumption via a firmware update, they tried to minimize that voltage drop and therefore reduce the triggering of the PSU noise (which is another reason it seems like it could be coil whine).

RE MiniDSP's response: when I wrote them about the problem - and when I finally got a response after my 3rd message about it - they were very polite and did not question the truth of my claim, but they mentioned they were surprised to hear that I had this particular problem since they test for it in QC.

After I had received and installed the replacement PSU they sent me, I wrote them back and told them that it still made a noise but was about 90% quieter, which is a major improvement. I also told them that a lot of people are still having this issue. I noted that the replacement PSU had the same circuit layout and design, but several individual components on the new one were slightly different than the old one. I politely suggested that at the very least they need to standardize their PSU components because clearly the variation is producing tremendous variation in the quality and amplitude of the mechanical standby noise.

Their reply was again very polite, totally ignored my comment about standardizing the PSUs, and said they couldn't be aware of other customers having this issue if those customers are not contacting them.

That's where I left it. Since MiniDSP's return policy is "Absolutely not, and no exchanges either," and since I have approximately 0% confidence that a 3rd PSU would be silent in standby - and since the replacement PSU really is much, much quieter than the first one - I've decided there's no point in dealing with MiniDSP any further, except perhaps to send them one final message summarizing why I think their quality control is garbage and suggesting that they maybe read their own official user forums where they will see that this problem persists.

I should also note that one could solve this problem, in a way, by just leaving the SHD on 24/7. Its display turns off after a few minutes, and so it looks just like it does when it's on standby and stays entirely quiet since it's still on and not in standby. The problem, though, is that the SHD is only 2 inches thick and there's no venting on the top of the case, only a small vent on each side. So when you leave it on 24/7, even if it's not actively doing anything, it gets pretty warm inside and pretty warm on the top of the case. That warmth begins and is centered directly above the PSU, but after an hour or so it spreads across the entire top of the case. It's not burning hot, but after a while it's not just "barely warm" either. I would be concerned that the heat could shorten the life of one or more components inside the unit - not to mention you shouldn't have to keep a piece of gear on 24/7 to prevent it from making noise.

I have no interest in actively going after MiniDSP publicly, but I certainly will not be shy about relaying my experience here and on other forums whenever it's germane.

 

[DWPress]

The "polite" but slightly condescending replies from MiniDSP were incredibly frustrating to me as well - especially when it seemed they hadn't even correctly read the questions asked. I used a 4x10HD for years (still have it in a closet) and still admire the kit but dreaded anytime I had to deal with them on the forums or via a ticket. This was 15 years ago, sad that things haven't seemed to improve any for customer care....

 

[tmtomh]

The "polite" but slightly condescending replies from MiniDSP were incredibly frustrating to me as well - especially when it seemed they hadn't even correctly read the questions asked. I used a 4x10HD for years (still have it in a closet) and still admire the kit but dreaded anytime I had to deal with them on the forums or via a ticket. This was 15 years ago, sad that things haven't seemed to improve any for customer care....

Yes, that's basically it. They are fairly knowledgeable and fairly responsive (though sometimes they go MIA for a week), but it's clear that along with the substantive responses, you're also getting "handled."

I don't want to overstate the situation - in many ways they make some very good kit - but it definitely leaves a bad taste. I can't imagine ever buying another MiniDSP product again.

 

[Mnyb]

Thanks for this, your prior comment, and @restorer-john for your comment as well. To address a few of your points:

RE likely source of the noise - thanks John! It doesn't sound like transformer hum to me, so perhaps as you say it could be a capacitor. The largest capacitor is different on the two PSUs - same size and if memory serves same capacity, but clearly a different brand or rating.

RE which MiniDSP: it's a "Neo 3" model, not the older "Neo 2." I learned about this distinction after the fact, when I searched for and posted about my issue on the MiniDSP forums. Apparently the problem began with the switch to the Neo 3 version, when one of the USB input boards was changed. The story, as told on the MiniDSP forums, is that the earliest batch of Neo 3's had this PSU noise problem, and MiniDSP quickly changed to a new PSU and sent replacement PSUs to the affected customers who wanted them and felt able to install them. (It's really easy - four screws and two internal plastic plugs).

However, it is overwhelmingly obvious that the PSU noise was not limited to just that first production run of Neo 3 models - it continues to be a problem, for many users. Based on my online interactions in threads at the MiniDSP forums and elsewhere, it appears most people who have the issue - including a MiniDSP forum moderator wh replied in the thread there - just live with it, which I find incomprehensible.

I also learned that MiniDSP updated the firmware of the SHD to make it consume more power when in standby mode. The theory is that the PSU noise is related to the voltage drop that occurs when the unit is put into standby, and by increasing standby power consumption via a firmware update, they tried to minimize that voltage drop and therefore reduce the triggering of the PSU noise (which is another reason it seems like it could be coil whine).

RE MiniDSP's response: when I wrote them about the problem - and when I finally got a response after my 3rd message about it - they were very polite and did not question the truth of my claim, but they mentioned they were surprised to hear that I had this particular problem since they test for it in QC.

After I had received and installed the replacement PSU they sent me, I wrote them back and told them that it still made a noise but was about 90% quieter, which is a major improvement. I also told them that a lot of people are still having this issue. I noted that the replacement PSU had the same circuit layout and design, but several individual components on the new one were slightly different than the old one. I politely suggested that at the very least they need to standardize their PSU components because clearly the variation is producing tremendous variation in the quality and amplitude of the mechanical standby noise.

Their reply was again very polite, totally ignored my comment about standardizing the PSUs, and said they couldn't be aware of other customers having this issue if those customers are not contacting them.

That's where I left it. Since MiniDSP's return policy is "Absolutely not, and no exchanges either," and since I have approximately 0% confidence that a 3rd PSU would be silent in standby - and since the replacement PSU really is much, much quieter than the first one - I've decided there's no point in dealing with MiniDSP any further, except perhaps to send them one final message summarizing why I think their quality control is garbage and suggesting that they maybe read their own official user forums where they will see that this problem persists.

I should also note that one could solve this problem, in a way, by just leaving the SHD on 24/7. Its display turns off after a few minutes, and so it looks just like it does when it's on standby and stays entirely quiet since it's still on and not in standby. The problem, though, is that the SHD is only 2 inches thick and there's no venting on the top of the case, only a small vent on each side. So when you leave it on 24/7, even if it's not actively doing anything, it gets pretty warm inside and pretty warm on the top of the case. That warmth begins and is centered directly above the PSU, but after an hour or so it spreads across the entire top of the case. It's not burning hot, but after a while it's not just "barely warm" either. I would be concerned that the heat could shorten the life of one or more components inside the unit - not to mention you shouldn't have to keep a piece of gear on 24/7 to prevent it from making noise.

I have no interest in actively going after MiniDSP publicly, but I certainly will not be shy about relaying my experience here and on other forums whenever it's germane.

SMPS has transformer whine not hum , due to that they feed the transformer high frequency hence its small size for a power transformer , so Johns idea is solid .

 

[Trdat]

The "polite" but slightly condescending replies from MiniDSP were incredibly frustrating to me as well - especially when it seemed they hadn't even correctly read the questions asked. I used a 4x10HD for years (still have it in a closet) and still admire the kit but dreaded anytime I had to deal with them on the forums or via a ticket. This was 15 years ago, sad that things haven't seemed to improve any for customer care....

After 15 emails back and forth, I still didn't even understand the fundamental of routing the UDIO-8, it only took 3 posts in 1 thread for it to be explained in the Jriver forum. I get the slighlty condescending replies all the time, on product info or any tech support. And most importantly, they never answer the question directly, missing key parts of what needs to be responded to all the time, I wonder if it is a non native speaker behind the support system if so I might understand but I doubt it.

If you don't have it in you, explaining and customer care should not be part of your job description. Very frustrating engagements with minisp.

 

[CarbonMakerU]

After 15 emails back and forth, I still didn't even understand the fundamental of routing the UDIO-8, it only took 3 posts in 1 thread for it to be explained in the Jriver forum. I get the slighlty condescending replies all the time, on product info or any tech support. And most importantly, they never answer the question directly, missing key parts of what needs to be responded to all the time, I wonder if it is a non native speaker behind the support system if so I might understand but I doubt it.

If you don't have it in you, explaining and customer care should not be part of your job description. Very frustrating engagements with minisp.

I salute you for the tenacity to remain on path as long as you have, but honestly for me it would be lesson learned time to move on. I'll agree to now be my own checkout clerk at the grocery, but having to be my own warranty department crosses the line.