Keces DC-116 Linear PSU Quick Review

[JLVenter]

I hate these lights. I take a black marker/whiteboard pen/whatever and cloud it in. Much better.

[tboooe]

I hate these lights. I take a black marker/whiteboard pen/whatever and cloud it in. Much better.

 

Agreed! I put electrical tape over them! So bright is blinding especially since I like to listen at low light levels too!

[Yuh]

I ordered and received a DC-116 today to try out in my 2nd system. It is a 230V input, dual 5V and 12V output version, powering a small CAPS build.

 

It works fine, however it makes quite a loud hum/buzz. Easily audible at night around 3m away. Also very gentle vibration when touching it. I'm noticing that most others have mentioned that theirs is virtually silent. Any thoughts? Could this have anything to do with mine being 230V?

 

Temperature-wise, mine only gets mildly warm.

[jtm]

Hi Yuh, pls let me know if the humming will disappear or not.

I am interested in the Keces as well and received feedback from them that return and refund won't be possible, so I need to rely on their statement that with 230V here in Germany all will work fine ...

After reading your post now I think I will put this project on hold for now ...

[tranz]

I ordered and received a DC-116 today to try out in my 2nd system. It is a 230V input, dual 5V and 12V output version, powering a small CAPS build.

 

It works fine, however it makes quite a loud hum/buzz. Easily audible at night around 3m away. Also very gentle vibration when touching it. I'm noticing that most others have mentioned that theirs is virtually silent. Any thoughts? Could this have anything to do with mine being 230V?

 

Temperature-wise, mine only gets mildly warm.

 

Mine also hums. Most things with toroidals in them will have this sadly. I get so irritated with hums that everything is in a closet.

 

You can get noise damping rubber from a pro-audio store and try to tighten down any bolts inside as well.

[tgb]

hi,

don't worry about the hum.

i bought recently a second hand one, 9v+12v.

Strictly no hum, nothing.

The point is that the previous owner noticed that hum when he bought it from Keces. He just changed the rings that hold the toroidal with thicker ones. Since then the Keces is dead silent.

Before i bought it that was a major issue for me as well, but finally this little change is perfect, and cost nearly nothing.

Anyway that's a good product at very competitive price, but you need to do this little change.

Rgds

[sandyk]

Mine also hums. Most things with toroidals in them will have this sadly. I get so irritated with hums that everything is in a closet.

 

You can get noise damping rubber from a pro-audio store and try to tighten down any bolts inside as well.

 

Other than the toroidals with an epoxy centre, don't yours get supplied with 2 big rubber mounting washers ?

 

Humming can also be a sign of a DC component in the mains supply.

 

Regards

Alex

[elcorso]

Mine also hums. Most things with toroidals in them will have this sadly. I get so irritated with hums that everything is in a closet.

 

You can get noise damping rubber from a pro-audio store and try to tighten down any bolts inside as well.

 

Please try to bypass the ground with a cheater plug and see if the hum (vibration & noise) goes.

 

Roch

[tranz]

Hi elcorso and Alex,

 

Thanks for the suggestions. I will try them all. I have not had the balls to stick a scope on the A/C line yet, but DC noise could well be another culprit. My Furman balanced power beast hums like its mad too.

 

And whilst I have the Keces open I will see if there is a simple way to unplug the LED power.

[One and a half]

Hi elcorso and Alex,

 

Thanks for the suggestions. I will try them all. I have not had the balls to stick a scope on the A/C line yet, but DC noise could well be another culprit. My Furman balanced power beast hums like its mad too.

 

And whilst I have the Keces open I will see if there is a simple way to unplug the LED power.

 

The Furman balanced beast, which model P-2400 IT ? Depending on how much crud the balanced transformer is taking out of the system, the primary of the Furman will draw current in pulses, rather than waves as found in linear loads like a lamp. These pulses are harmonics of the crud, and they are audible and present in the transformer, and they are more of a growl. If you play music loud and draw load, the sound from the transformer should change.

 

I found by chance and advice, that the current pulses can be tamed with a reactor, but to design one is problematical. The best results a hobbyist can do, and it worked for me, is to use an isolation transformer upstream of the Furman. This will slow the current pulses and stop the noise.

 

By it's nature a transformer cannot pass through DC. However if the distortion caused by switching devices on your network cause the zero of the sinewave to be offset, then the transformer will pass through this distortion, and affect other devices, like the Keces toroid.

 

You can check for distortion by measuring the voltage between neutral and earth. This value with all appliances turned off should be close to 0V. Once you start using devices with a rectifier, this voltage increases as a result of the distortion on the neutral. My house runs at 60mV but anything 2V and higher is a worry.

[sandyk]

Hi elcorso and Alex,

 

Thanks for the suggestions. I will try them all. I have not had the balls to stick a scope on the A/C line yet, but DC noise could well be another culprit. My Furman balanced power beast hums like its mad too.

 

And whilst I have the Keces open I will see if there is a simple way to unplug the LED power.

 

In a 240VAC world it may be safest to look via a step down transformer?

See also

http://imageshack.com/a/img843/2906/ums32.jpg

[Superdad]

In a 240VAC world it may be safest to look via a step down transformer?

See also

http://imageshack.com/a/img843/2906/ums32.jpg

 

Please don't fry yourself--or your o-scope Tranz! SandyK is correct. Use a 6V step-down transformer. Don't hook any test gear (except a voltmeter) directly to the mains.

 

BTW, properly spec'ed, good quality toroids do not hum. 50Hz countries are a little harder to get any transformers to stay quiet, but if the laminations are vacuum-impregnated and ovened with the epoxy/lacquer, they can be quiet. But if they a not well designed for the primary voltage, there is nothing you can do to get them to shut up.

Sorry, IME, the whole getting rid of DC on the mains line to cure transformer hum is bunk. Years ago, with the monster Hovland Stratos mono-blocks, we had a mechanical hum problem (only in certain countries, and generally with 50Hz), despite the extreme lengths we had designed in with full suspension of the trans (an expensive quasi-C-core). Shortly after one of our distributors first reported it I chatted about it with Paul McGowan at CES--we were exhibiting two doors down-- and he said, "Oh, that's easy. Just build them this circuit to put in line with the mains plug and get rid of the DC component." He drew me a detailed sketch which I excitedly too back to our engineers. After CES, we made up a couple of the devices (with male/female IECs on them) and FedExed them off to, IIRC, Netherlands. They didn't do squat to cure or change the mechanical hum, which as it turns out was only coming from one of his two 41kg mono blocks.

 

On a separate note, but still about transformers: R-cores don't seem to hum at all. Because of the way the cores themselves are wound, there is virtually no magnetic excitation. Check out this explanation of how the cores are made: :::ARROW TECHNOLOGY LIMITED:::...

 

Of course R-cores have all sorts of other advantages as well. But even at wholesale from China, they cost about twice what a decent toroid costs, and at least three times a cheap toroid. I know, because I have 25 custom 100VA R-cores en route from China right now. I compared it in my forthcoming JS-2--versus a good 100VA toroid. In fact, this comparison took place with John Swenson here at may place just this afternoon. We went back and forth between the toroid prototype and the R-core in a pre-production chassis I finished assembling last week.

 

We were hoping that my decision to spring for the R-core would prove worthwhile. Wow, did it ever! For my Mac mini it made the bass even more solid and detailed--R-core versus toroid. We were both surprised at how obvious it was (well my system does very good bass). But the knock our socks off moment came when doing the same switch with the JS-2 powering (at 5V) a pre-production BottleHead DAC board that John had brought along for tests. The effect on clarity and detail (oh, I'm a very unimaginative writer about what I hear) with the R-core was on much more than just the bass. It was a cymbal to vocal to piano to upright bass and horns attack improvement. I am REALLY happy about this as I now feel that the supply could find a even wider market that for computers, drives, and headphone amps. Not that there are that many top-flight DACs that take just a single-ended (+DC) supply.

 

Here are some pics to show what were were doing (click pics for larger version; also, my production R-cores will have the pretty copper electrostatic shield--and some fancy labels I am making):

 

Oh wow, DHL just delivered the first chassis from Japan! The printing came out perfectly--what a relief. I can start assembling. Exclusive first peek. Sorry if this is not the right thread. This has just been such an exciting day (except for blowing out two woofers with blocked DC pulses during some DSD DAC pro to tests; argh; I'm now down to my last spare…).

 

 

P.S. The differences heard between the toroid and the R-core were even with both supplies being fed through Hovland VoltAire 1:1 isolation transformers. And BTW, mains grounds on all gear is floated--at the wall in my system, not in the power supplies.

[tranz]

Thanks One and a half.

 

I will check the neutral-earth voltage as well. That is the beast, and it has a big isolation transformer in it. Sticking an iso transformer in front of an iso transformer would then just move the hum upstream? But I will check it out.

 

Cheers

[tranz]

Hi Superdad.

 

Thanks for a glimpse into the new PSU. I believe Audio Research and McIntosh also use R-Cores in many of their gear.

 

Would a step down transformer not influence the results of the scope by introducing its own noise to the picture?

 

Cheers

[Yuh]

Update: PSU has been on for a day, nil change to transformer hum. There is a lot of resonance from the top cover of the chassis. Tried tightening screws to case and toroidal but these made no difference. Found a suitable weight to put on top of the chassis and this cut out the noise by about two thirds. Much better than before, but still there... will update again after i have a night session to listen to.

 

Don't have a cheater plug to test lifting the ground. However none of my other components have any hum at all, so don't think that would make much of a difference. All components are on their own separate power circuit.

[sandyk]

There is a lot of resonance from the top cover of the chassis.

 

Is the top cover very close to the top of the transformer ? I had a problem due to that some time back.

[One and a half]

Thanks One and a half.

 

I will check the neutral-earth voltage as well. That is the beast, and it has a big isolation transformer in it. Sticking an iso transformer in front of an iso transformer would then just move the hum upstream? But I will check it out.

 

Cheers

 

Once you smooth out the pulses, the noise doesn't transfer upstream. I like the Furman, it uses a 60-0-60 output, very nice. I'm not sure what else they have on the front end, most likely overvolts protection, don't need much else. Heavy bugger to move around isn't it?

[Yuh]

Is the top cover very close to the top of the transformer ? I had a problem due to that some time back.

 

I suppose it is. Stock product image:

 

http://www.keces.com.tw/5_english/dc116_04.jpg

[Superdad]

Hi Superdad.

 

Thanks for a glimpse into the new PSU. I believe Audio Research and McIntosh also use R-Cores in many of their gear.

 

Well I guess I am in good company then.

 

Would a step down transformer not influence the results of the scope by introducing its own noise to the picture?

 

While the step-down trans should not introduce any distortion into the measurement (unless it is a total piece of garbage; but Swenson tells me he has used cheapies for this before), to some extent it will mask of eliminate some of the very noise and distortion you are wanting to see.

I too have longed to be able to easily put a scope or analyzer on the mains line at various places. It would be great to be able to directly see the waveform and nasties at both line frequencies and way above--straight from the wall, after different types of isolation/filtering devices, and also to see what other equipment and power supplies are kicking back into the line.

Wouldn't it be wonderful to have such a device that you could plug into any mains line (and/or have probe leads)--and have a USB output that plugged into your computer and worked with a s/w app to show you everything going on (and be able to take screen shots to share)? That would be fun and might allow folks around the world to quantify at least some aspects of AC quality and filtering. (Though such a device would not be capable of quantifying DC supply performance--measuring that is a whole other can of worms as I am learning as I push John to produce measurements of our supply.)

 

BTW Tranz, yesterday John and I worked out more of the details of the Mac mini linear fan controller board and its cabling/connectors. Prototype PCBs for the circuit testing arrive tomorrow. Now I just have to hope that the quote to have 3-inch cables made with those tiny motherboard connectors (too small for manual wire crimping for the pins) does not come in too high.

 

Have a good weekend. Back to painting our kitchen (first time in 21 years--filthy!).

 

--Alex C.

[The Computer Audiophile]

Hi Alex C - Your posts, while informative, are a bit too much about your own products. I know you're excited about the products but please hold back on weaving them into your comments.

[Superdad]

Hi Alex C - Your posts, while informative, are a bit too much about your own products. I know you're excited about the products but please hold back on weaving them into your comments.

 

Hi Chris:

Thanks for the warning, and for not just deleting the posts. I will be more carful.

You are are correct. I am excited. And I need an outlet for communicating about the progress of the project. Very soon I will need both my own web site and some forum with which to discuss and dialog with people about the products. I wish you would consider adding some sort of Manufacturers' Corner sub-forum, ala what AudioCircles has. I live here not there--and most of my prospective client base (and all the friends I have made) are here at CA.

 

Regards,

 

Alex

[Yuh]

With a weight (old computer cpu heatsink) on the keces PSU, it is definitely quieter. At night time, it is just barely audible at about 2m, but at 3m at my usual seating position, it is basically not able to be heard.

[elcorso]

With a weight (old computer cpu heatsink) on the keces PSU, it is definitely quieter. At night time, it is just barely audible at about 2m, but at 3m at my usual seating position, it is basically not able to be heard.

 

I'm afraid, when a PSU is humming, don't deliver a clean DC power to the unit it feeds (like a DAC).

 

I don't know the Keces, but with the KingRex Mark II I own start the hum, SQ deteriorates. I found two solutions: Feeding the AC to the PSU by an Hospital Grade ISO transformer, or using a cheater plug. The second one gave me a cheaper solution and zero hum (noise).

 

I remember I used several years ago a heavy cast iron piece to do the job (aka "Magic Block") and it works in some transformers.

 

I didn't pay the "Magic Block" price, but some weights used in weight lifting.

 

I'm on 120VAC country.

 

Roch

[tgb]

hi elcorso,

i bought a second hand Keces because I was septical about this "upgrade".

As said before, the first owner put thicker rings to hold the key toroidal leading to a dead quiet device.

So when I received it i was more within a "nocebo" mood than a "placebo" mood, i mean a negative more than a positive mood, and the result just stuck me. Within a few second I realised that all blabla about linear power supplies for digital source... well... It was true and I was wrong.

Now, I have in mind that when you play with digital sources you MUST take into account the DC power supply.

For instance I'm quite happy with my dac (Dangerous Source), well known to be a good one, but having a wall wart power supply. Just use the Keces to power it and SQ surges with a so nice detailed and smooth SQ. I don't think I would have that result with a dac without possibility to change the power supply.

Just look at Lumin network player and others, they pretty much take care about the power supply with external one, and even you can have a better result according to customers with higher quality PSU with a Kenneth Lau for instance.

To conclude, the Keces is a great deal... a pity that you have to pay 2$ to change 2 rings to make it quiet... but not a big deal finally ;-)

rgds

[tboooe]

hi elcorso,

i bought a second hand Keces because I was septical about this "upgrade".

As said before, the first owner put thicker rings to hold the key toroidal leading to a dead quiet device.

... a pity that you have to pay 2$ to change 2 rings to make it quiet... but not a big deal finally ;-)

rgds

 

Curious about this "upgrade". Can you please tell me more about it, what it does, and where I can purchase these $2 rings?

 

Thank you.