New (to me) amp: McCormack DNA-125

Clipdat

I tried to carefully listen to the amp again, in an attempt to figure out where the hum was originating from. It does not appear to be coming from the middle front center of the unit where the power transformer is located. It was directional in the sense it seemed to be coming from the left and right sides about midway back. Maybe these things circular things that have power cords running into and out of them that are mounted to the heat sinks? Not sure what they are.

11tsteve wrote: »

And even before the upgrades, it was a dead quiet amp.
I have an NAD 2150 I just had rebuilt with that transformer hum, and frankly it drives me nuts. The tech insists he didn't hear it when he had the amp. I would like to know what the issue is and how to fix it.

Thanks for your thoughts and for having a civil discussion with me. Regarding this particular mixer, I chose it because I've used it several times hooked up to powered monitors and I know through my own personal experience that it does not appear to color the sound.

Still, you have a point about build quality, I'm sure it was built to a budget. I've personally tried 11 different DJ mixers and could comment about each of their sound qualities. In my opinion the Tascam is extremely neutral. It does seem to have some redeeming build qualities as described in the user manual:

"The oversized power supply of the XS-8 offers plenty of headroom at the inputs and outputs.Therefore a high dynamic range and output volume is achieved, without affecting audio quality. Let's compare: Normally, standard bipolar power supply outputs are 7.5 or 9 Volt (rarely 12 Volt). An input voltage of 9 Volt must be internally spitted into +/- 4.5 Volt. In contrast, The XS-8's internal power supply outputs +/- 18 Volt which means a total 36 Volt! This difference implies a much higher audio quality with a higher output level and better dynamics."

All that being said, I'm in no way tied to using this as a preamp, it was literally just to try to give a neutral preamp/frontend so I could attempt to judge the power amp.

I can certainly hook up the Schiit Saga or even my Rane MP2014 mixer that has "Line-input to Line-output dynamic range of 113 dB (A-weighted) with vanishingly low THD+N of 0.001%"

gmcman wrote: »

I don't know anything about the build quality of the Tascam. I have to assume for the sake of this discussion, that a DJ mixer is not a fair comparison to a NAD integrated preamp.

In theory, I see your point. But again, for the sake of this discussion, just because it's an "all analog" design...that doesn't necessarily mean it's doing the best job of trying to maintain sonic purity as it passes through it.

I personally don't feel that taking the clean sound from your Marantz, through a DJ mixer is going to aid you in assessing the SQ of your McCormack amp.

Cables currently in use is Kimber Kable Tonik from the Marantz to the preamp and Audioquest King Cobra from the preamp to the power amp.

Becoming slightly concerned that others have said that their McCormack amps run quiet and mine has this slight hum emanating from the chassis.

Thanks for the power related upgrades that could be done, certainly worth considering.

tonyb wrote: »

That can be a variety of things. You could have an impedance mismatch going on, a poor quality cable in the mix. That DJ mixer certainly isn't helpful.

Regarding the noise issue, something isn't right if the amp has a hum to it. These amps run quiet, and don't produce transformer hum or hiss in the tweeters. Either something is screwy with the circuit it's plugged into, or the amp itself.

A good non current limiting power conditioner could help as your in an apartment and limited to what you can do. You could also change the wall socket to a hospital grade at least, if that's possible.

Haha, I was actually thinking something similar to myself and felt like I was going crazy about not hearing the difference. I was like "Well I could save a lot of money, I'll just stick with the NAD. Might as well just sell all my fancy ICs and go back to Monoprice cables since I can't tell the difference!"

I agree that it's possible that the amp might need some upkeep. Thanks for the tip about leaving it on, I noticed it gets only slightly warm.

It's the stock power cord with a molded non-removable ground pin. I don't have access to one of those cool Pangea ones with the removable ground.

kharp1 wrote: »

I tend to agree with Tony here, there is considerable difference between the NAD sound and McCormack. No offense to anyone, but, sone people don't hear differences and you may be one of those people. I wish I was at times.

Hum could be related to a couple of things...transformer going bad, though I doubt it. I think, THINK, the McCormack uses a pretty good torroid, so I'd start looking elsewhere first, like grounding issues. Take the ground lug off the amp cord first and see if that eliminates all, or part, of the hum.

I'd just leave the McCormack on all the time, it'll draw practically nothing while idle and won't build up heat.

Hm, interesting, another experience that points to the fact that mine should be silent while powered on.

MrBuhl wrote: »

Have to agree with others here, I have two McCormack's (one is 11Steve's formerly) and both are silent running

Tony, I got it here: http://tmraudio.com/components/power-amplifiers/mccormack-dna-125-stereo-power-amplifier/

tonyb wrote: »

Where did you buy the amp from ?

DaveHo

Thermal Protection relay?

tonyb

Don't take my comments as offensive pal, but those Kimber Tonics are the worst sounding IC's I ever had the displeasure of hearing. Put the monoprice ones back in it's place....and we all know how I feel about monoprice to say that.

Start eliminating causes, use the amp with one other source if possible, and your best cables.

Your going to need a dedicated pre amp sooner or later, hopefully sooner. Some sort of power conditioning would help also. If the Marantz has a digital volume control, use that hooked up to the amp alone with the AQ cables. Make sure all your connections are solid. If using bare wire speaker cable ends, make sure none of the plastic coating is stuck inside a post or stray strands touching another post. If possible try another wall outlet.

If using one source and the amp fail to relieve the symptoms, chances are your amp may have incurred some damage during shipping. Even though it looked to be well packed, just the jarring around could have caused something to become loose. Contact the seller if that's the case and see what arrangements can be done to solve the issue.

Clipdat

I was also testing music yesterday via the Sony SACD player which is ironically currently connected with Monoprice RCAs lol.

I have the Schiit Saga pre ready to go, just a matter of hooking it up.

As mentioned above, the Marantz has fixed outputs, not variable.

Speaker cable is Audioquest Bedrock with BFA bananas on both ends.

If I unhook everything and move it I can see if it hums from a different wall outlet, or bring it to work and try it on the power here.

I've already emailed tmraudio to ask them if they can bring up the test notes of when they verified it's functionality before selling it, to see if they noted that the unit had any hum. I'll report back here with what they say.

I suppose it's possible FedEx can destroy something in transit even though the boxes weren't dented.

tonyb wrote: »

Don't take my comments as offensive pal, but those Kimber Tonics are the worst sounding IC's I ever had the displeasure of hearing. Put the monoprice ones back in it's place....and we all know how I feel about monoprice to say that.

Start eliminating causes, use the amp with one other source if possible, and your best cables.

Your going to need a dedicated pre amp sooner or later, hopefully sooner. Some sort of power conditioning would help also. If the Marantz has a digital volume control, use that hooked up to the amp alone with the AQ cables. Make sure all your connections are solid. If using bare wire speaker cable ends, make sure none of the plastic coating is stuck inside a post or stray strands touching another post. If possible try another wall outlet.

If using one source and the amp fail to relieve the symptoms, chances are your amp may have incurred some damage during shipping. Even though it looked to be well packed, just the jarring around could have caused something to become loose. Contact the seller if that's the case and see what arrangements can be done to solve the issue.

Viking64

Is it possible that the way the heat-sinks are fitting tightly in the rack is causing something to hum? That seems like it might have an impact on those 2 items you circled.

Clipdat

It's a close fit, but the heatsinks aren't actually in contact with the rack.

I'm not sure what those items are that I circled, because I don't know about amplifier design.

Viking64 wrote: »

Is it possible that the way the heat-sinks are fitting tightly in the rack is causing something to hum? That seems like it might have an impact on those 2 items you circled.

Viking64

Clipdat wrote: »

It's a close fit, but the heatsinks aren't actually in contact with the rack.

I'm not sure what those items are that I circled, because I don't know about amplifier design.

I took a closer look at the image and I can see there is a space between the heat-sinks and the rack. At first it looked as if they were pressed tightly together.

A few posts above, DaveHo suggested those might be "thermal protection relays". They do seem to resemble some sort of temperature sensor.

kharp1

Not 100% but I'd say they are temp sensors. My McCormack was dead quiet. Spring for a power cord with detachable ground prong. PS Audio AC3 is a good one that can usually be found for about $100. Good quality entry level cable. I'd stay away from the Pangea, not that they're bad quality, but, it'd be easier to twist a steel belted radial than their power cords. If you're dead set on a Pangea I have one I'll sell cheap, but, I'd look elsewhere first. Douglas Connection may have something reasonable and he offers Forum members a discount.

Get a cheap cord (Walmart or similar, )and take linesman pliers and twist the ground prong out. That's a cheap way to see if you have a grounding issue. No reason running down roads that you don't need to. Heck, buy a grounded to ungrounded adapter for a few bucks and see what happens. Since you got your Schitt together put it in and see what happens.

Clipdat

Grounded vs ungrounded cable could cause a hum to originate from the unit itself?

kharp1 wrote: »

Not 100% but I'd say they are temp sensors. My McCormack was dead quiet. Spring for a power cord with detachable ground prong. PS Audio AC3 is a good one that can usually be found for about $100. Good quality entry level cable. I'd stay away from the Pangea, not that they're bad quality, but, it'd be easier to twist a steel belted radial than their power cords. If you're dead set on a Pangea I have one I'll sell cheap, but, I'd look elsewhere first. Douglas Connection may have something reasonable and he offers Forum members a discount.

Get a cheap cord (Walmart or similar, )and take linesman pliers and twist the ground prong out. That's a cheap way to see if you have a grounding issue. No reason running down roads that you don't need to. Heck, buy a grounded to ungrounded adapter for a few bucks and see what happens. Since you got your Schitt together put it in and see what happens.

Clipdat

Response from TMR where I bought it:

"I don't have any notes that this particular amp was having any issues with that when we tested it. I will say that having a transformer hum be noticeable from only a few feet away isn't outside of the normal but I don't know for sure on this particular amp.

Additionally, one cause of this often times is the AC power that is being fed to the unit. Why some level of noise from the transformer is inevitable it can be increased by DC offset on incoming AC power. This can be caused by a number of modern electrical devices including dimmers, led lights, heaters, ect. It can be a bit of a rabbit hole to go down but solutions do exist including the Emotiva CMX-2 power conditioner, PS Audio regenerators or sometimes even upgraded power cords. It always depends on the individual conditions but there are solutions to reduce the transformer humming to almost inaudible levels.

https://www.google.com/search?q=dc+offset+transformer+hum&oq=dc+offset+trans&aqs=chrome.3.0j69i57j0l4.11159j0j1&sourceid=chrome&ie=UTF-8

I hope that helps."

tonyb

That CMX-2 for 99 bucks looks like it's worth a shot, plus you can return it if there is no difference.

DC can also be adjusted within the amp itself, how though you'd have to consult the guys at SMC. Probably only a trained repair guy would be able to do that.

Tony M

Drew.

I've used those .50 plug adapters to successfully eliminate hum in Subwoofers for years.

The cheapest audio fix in home audio hum problems. I hope it works for you.

I also have a NAD Int. c372 and it's awesome to my ears and many others too.

You having 3 CD players does not make you a weirdo in the least. Maybe to some, but you haven't seen my man-cave in all it's glory yet.

You're not even close to my eccentric system set-ups. I can play 5 or 6 cd's at once on all my systems, but only one gets played at a time of course. I have been known to tune all of the systems to one radio station and see how life-like I could make the music sound. Now that's an interesting experience to say the least.

I planned on posting photos this year before I start liquidating most of my hoard...um... collection. I hope to be able to go out and really, really relax out there again .

Good luck finding the reason for the hums and hisses. May it be a .50 fix !

kharp1

Clipdat wrote: »

Grounded vs ungrounded cable could cause a hum to originate from the unit itself?

Yes, well maybe. it being the cause is unlikely, but, removing the ground prong often eliminates the hum. The hum happens when there is a grounding issue somewhere in the circuit. They get out of "phase" and that's when offset cycles become noticeable. Unground the plug at the amp and see what happens.

Clipdat

I have this thing I could try on it tonight: https://www.amazon.com/Ebtech-Hum-Voltage-Filter/dp/B0002E4YI8/ref=sr_1_3?ie=UTF8&qid=1514933402&sr=8-3

kharp1 wrote: »

Clipdat wrote: »

Grounded vs ungrounded cable could cause a hum to originate from the unit itself?

Yes, well maybe. it being the cause is unlikely, but, removing the ground prong often eliminates the hum. The hum happens when there is a grounding issue somewhere in the circuit. They get out of "phase" and that's when offset cycles become noticeable. Unground the plug at the amp and see what happens.

tonyb

or he can just buy a cheater plug at the hardware store for like 2 bucks. A cheater plug, is a 3 prong plug going in and a 2 prong going out, so it lifts the ground without having to rip apart power cables. That's the cheapest easiest way to start with.

Clipdat

I found one at work, will try tonight.

tonyb wrote: »

or he can just buy a cheater plug at the hardware store for like 2 bucks. A cheater plug, is a 3 prong plug going in and a 2 prong going out, so it lifts the ground without having to rip apart power cables. That's the cheapest easiest way to start with.

Tony M

The suspense is killing me.

I pray it works !

kharp1

tonyb wrote: »

or he can just buy a cheater plug at the hardware store for like 2 bucks. A cheater plug, is a 3 prong plug going in and a 2 prong going out, so it lifts the ground without having to rip apart power cables. That's the cheapest easiest way to start with.

Absolutely, either way he just needs to remove the ground at the amp and see what happens. That will tell which way to go next.

Clipdat

Alright, so using the ground lift cheater plug resulted in a slight reduction of both the white noise/hiss that comes through the speakers as idle, as well as the physical hum that's coming from the amplifier itself.

So, I'm not sure what this means. I was optimistic that it would make the humming from the amp go away completely, but I guess a slight reduction is good?

kharp1 wrote: »

tonyb wrote: »

or he can just buy a cheater plug at the hardware store for like 2 bucks. A cheater plug, is a 3 prong plug going in and a 2 prong going out, so it lifts the ground without having to rip apart power cables. That's the cheapest easiest way to start with.

Absolutely, either way he just needs to remove the ground at the amp and see what happens. That will tell which way to go next.

Tony M

That's sort of good news.

Did you move that adaptor to other plug ends ? Maybe another elec. connected to your amp is a cause.

Or did you just unhook anything connected to your amp and test its internal hum that way also ?

Remember, this is the cheapest first step to investigate. Good luck .

Clipdat

I didn't try the cheater plug on other things, but I did completely unplug the three prong grounded cable that powers the preamp - no effect on the hum.

Tony M

Darn,
I was hoping for complete success tonight .

I'll check back in in the morning or if and when I get back up tonight to see if your investigation has a better outcome with a grounding solution answer.

Good Luck Drew.

Clipdat

I found out from SMc Audio that the red things I circled above are indeed thermal cutoffs, and that they would get removed if I were to send the amp in for upgrades.

I was also informed that for optimal performance, the amplifier should be left on at all times.

Regarding the hum, it could be normal transformer hum, or it could be another component. I will try some more things tonight like plugging it into the surge strip vs. directly into the wall like I had it. Another option is lugging it to work and trying it on the power at the office to see if it hums.

tonyb

Surge strips won't do anything, and may introduce more noise.

Clipdat

I figure at this point I have nothing to lose, and the surge strip claims to have "EMI/RFI noise filtration".

tonyb wrote: »

Surge strips won't do anything, and may introduce more noise.

daddyjt

If the noise is coming from the transformer (and I suspect it is), then it’s almost certainly from Magnetostriction, which is a completely normal phenomenon in higher powered transformers, and nothing to worry about.

https://en.m.wikipedia.org/wiki/Magnetostriction

Clipdat

Definitely a possibility, but the hum doesn't sound like the sample audio file that they link in the article.

Also it doesn't explain why others have stated their McCormacks run completely silent.

I can make a recording of the hum tonight with my handheld Sony recorder.

daddyjt wrote: »

If the noise is coming from the transformer (and I suspect it is), then it’s almost certainly from Magnetostriction, which is a completely normal phenomenon in higher powered transformers, and nothing to worry about.

https://en.m.wikipedia.org/wiki/Magnetostriction

motorhead43026

I have 4 different Amps and all have trans hum to some degree. None of which can be heard @ the listening position.

Clipdat

Interesting, thanks for sharing your experience.

I both can and can't hear it at the listening position even though that doesn't make much sense when I read it back. Certain areas of the room you can hear it and others not, its a strange frequency.

And certainly not while music is playing. It would probably only be an "issue" during quiet transitions in classical music.

motorhead43026 wrote: »

I have 4 different Amps and all have trans hum to some degree. None of which can be heard @ the listing position.

kharp1

Try the strip just for reference, but, keep in mind that many of them will restrict quality power and you're better off plugging directly in to the wall in most cases, especially with an amp. Not sure what else is plugged in to that outlet, but, I would start eliminating pieces one at a time. Unplug a piece and see if the hum goes away. Many electronics can interfere with each other. Also, is there a fluorescent light in the area? Is there a dimmer switch being used.

You could also go the reverse route and unplug everything from the system except the amp and see if there's hum, then start adding components back in one at a time.