NPC Phono NuWave buzz

Hello. I have a brand new NPC that produces an audible buzz when the volume is turned up to 50% or more. Couple things to note:

a. It’s not the NPC. This is the second brand new unit supplied by the nice folks at PSA. Both units buzz/hum in exactly the same way.

b. My previous GCPH had the same buzz.

c. The buzz goes up and down with volume.

d. I’ve spend hours tracking down a possible ground loop–no success. Took everything out of the system and started from scratch. Buzz starts when I add the NPC. Even tried a cheater plug. Tried grounding the chassis to other components. Tried running a ground from the NPC to a ground by wiring a plug with just the ground wire connected to the ground pole. No change.

e. The unit still buzzes with the LP12 and Lingo 3 power supply taken completely out of the system.

f. No buzz from cd player or DAC.

g. Tried numerous cables from cheapos to Chord interconnects.

h. Analog system is Linn LP12/lingo3;Rega RB300/Clearaudio Concept LOMC. Impedance is set at 100 on the npc.

i. Rest of system is Naim Nac 42 modified with Teddy regulators/Naim Hi-Cap/Naim 110 monos modified with Les Avondale type Minccap6. Naim Nac A5 speaker cable and old Aegis 3 speakers.

Everyone is stumped, including my dealer who has 40 plus years dealing with Naim, Linn and other analog systems.

Here’s what I’m thinking–could my gain be way too high? I initially tried it 57db. I recently read an article suggesting that the NPC’s gain values are set up way too high–meaning that it has so much gain authority, it can be noisy if now moderated. Who knows, maybe the guy is a wack but I’ve lowered the gain to 47db and the buzz is less pronounced but still there. Can anyone give me some insight on the gain settings? Any other thoughts on the buzz/hum?


Hi Steve-

If the gain on the NPC is too high, you’ll get clipping. The display will say something like, “clipping” and the sound will cut out. I think I’ve got mine just backed off a bit from that point and there’s no hum. The impedance setting shouldn’t cause a hum unless one of the dip switches is stuck between two positions.

Since the hum is present without the TT connected, either try moving the system to another outlet in the house or run an extension cord from another outlet to the NPC and see if that makes a difference.

You say the hum starts when you add the NPC, but what other components are in the system at that point?

Turn off and disconnect any other A/V equipment in the system, especially if you have cable TV. Check for any cables draped over each other or coming into close proximity to the phono cables or the NPC. Turn off any appliances that may be on that circuit. Turn off any lights that are on dimmer switches. Try swapping out power cords in the system.

Good luck.


Have you tried running an analog source through the other input? That might rule out the NPC if there is no buzz. You might also try changing cables and power chords in the off chance one of them is bad.

Thanks guys. I’ve tried three different interconnects and two different power cables. I’ve also dragged an extension cord through my house to try different outlets and circuits. No change.

I’ve done all the cable dressing. No power cables are in close proximity to the NPC or the interconnects as far as I can tell. I took the NPC off the rack and hooked it up away from all the other equipment. Still no change.

I’m at a loss. I’ll try running another analog source through the NPC. However, I don’t think the NPC is to blame. I can’t be that unlucky to get two defective components in a matter of three weeks.

I’ve had this problem before with Naim equipment. However, that problem was solved by grounding new component chassis to the Naim preamp. Something about Naim’s grounding scheme…way above my head.

Good news is that the music from the NPC is top notch. I just hear the buzz from my seating position when the record side is over. With the lower gain, I don’t hear the buzz on quiet passages as I did previously.

I’m thinking it’s the mix between old Naim equipment and new 21st century stuff.

Any other thoughts?

Well, you could run a USB cable from the NPC to your computer and monitor the signal there. If there’s still hum without anything else connected, that would narrow the list of possible culprits down a bit.

If the hum only occurred when your TT is connected, I’d try checking the connections on the leads from the cartridge and check the phono cables coming out of the RB300.

If it is a buzz rather than a hum, and you’ve described it as such, it’s likely a ground loop or the cartridge not being grounded somehow. As you suggest, it’s likely not the NPC.

I have seen turntable setups that were poorly grounded before. In one case, I had to run a separate ground wire to the head shell to fix it. I figured that out by attaching a wire to the ground terminal on the back of the phono preamp (your NPC has one). I then turned the volume up high enough to hear the buzz and started poking around with the ground wire on the turntable to see what might work. Nothing did until I touched the ground wire to the head shell and then…Bingo! Buzz gone.

You might experiment with something similar.

Thanks Paul. Just tried your suggestion. No change.

By the way, nice neeting you last week.

Does it buzz at that gain setting with the inputs not connected, just sitting empty?

I assume we met in LA?

Thanks Paul. Yup, it buzzes even with the LP12 and power supply taken completely out of the loop. I’m going to run some electrical from a dedicated circuit down to my basement this evening. I’m hoping this will lessen or eliminate the buzz. Over the weekend, it dawned on me that I have numerous dimmer switches in my basement. Even though they’re off, they may produce some noise…

I met you at your office on Friday. Scott introduced us briefly while I was there picking up the new NPC.


Ahh, yes, I remember! Thanks, it was a pleasure.

This puts a whole different light on things. You suggest in your original post that the DAC connected to the power amp does not buzz. Add the NPC and then buzz?

Please reply back with exactly what your setup is - every component in the simple system where it does not buzz.

Thanks Paul. That’s correct. The system only buzzes when the NPC is added.

System from speakers:

a. Aegis 3 speakers

b. Nac A5 speaker cable (Naim)

c. Naim Nap 110s that have been modified by Neil James to convert them into mono amps with Avondale Minicap6, etc.

d. Naim Hicap power supply which powers Naim Nac 42 preamp which has also been modified by Neil James with Teddy Pardo type regulators. The hicap and the 42 are tethered via a Naim 4 pin din SNAIC. The 42 is connected to the mono 110’s via a Chord 4 pin din to rca interconnect.

e. Sources: Rega Planet CD player > Bryston BDA-2 Dac via spdiff; Linn LP12 with Lingo 3 power supply; Rega RB300 arm and ClearAudio Concept MC cartridge.

f. The Rega tonearm uses the left rca plug as the ground mechanism.

g. The 42 and the NPC are connected with a Chord 5 pin din to rca interconnect as is the Bryston BDA-2.

Thanks Paul.

The system is dead quite with everything plugged in minus the NPC.

Question: Could this be the multiple dimmer switches in my basement? They’re all in the off position, but I’m wondering if they can produce noise anyway and the sensitive NPC is picking it up.

I am still a little confused - not uncommon. Let’s keep it simple. I don’t need to know about everything just the electronic chain.

Sounds like you have a pair of mono amps, a preamp, a CD player. Right?

The system is quiet. You use this 5-pin DIN to RCA adapter to connect the NPC analog outputs to the preamp. Right?

When you do that, there’s hum.

And this is with nothing else plugged into the NPC except the preamp inputs. And it hums.

Have I got it?

If the answer’s yes, then here’s a few questions (no, I don’t think it’s your dimmers).

Does the hum go away when you switch inputs on your preamp to something else? If yes, then that’s very telling. If no, that is also telling.

And, you say the hum goes up and down with the volume?

Let me know.

Sorry for my verbosity. Job hazard. Here are your questions with my responses:

“Sounds like you have a pair of mono amps, a preamp, a CD player. Right?” Yes. With a DAC hooked to the CD player.

“The system is quiet. You use this 5-pin DIN to RCA adapter to connect the NPC analog outputs to the preamp. Right?” Correct.

“When you do that, there’s hum.” Correct.

“And this is with nothing else plugged into the NPC except the preamp inputs. And it hums.” Correct.

“Have I got it?” Yup.

“If the answer’s yes, then here’s a few questions (no, I don’t think it’s your dimmers).”

“Does the hum go away when you switch inputs on your preamp to something else?” Yes. If I switch the preamp to each of the other two inputs the hum goes away. “If yes, then that’s very telling. If no, that is also telling.”

“And, you say the hum goes up and down with the volume?” Correct.

Thanks Paul.

Ok, that means the NPC itself is buzzing and there’s no ground loop. My guess is the 5-pin DIN connector is somewhoe mucking things up.

Can you swap that cable for one that’s working and see? If swapping doesn’t solve it, send me a link to how it’s wired.

I’ve tried three different 5 pin DIN to RCA interconnects. No change.

Here is a description of how the wiring is on the back of the preamp from the Naim forum:

Not sure this is what you need–but I’m looking for more detailed info.

Steve, have you tried running the NPC’s S/PDIF output into your Bryston? That might be an easy way around this.

I have not. Not sure I completely understand how that works. I’ll take a look at it.


PB–I ran the S/PDIF from the NPC to the Bryston and the Bryston running the analog signal to my preamp. Same buzz. Weird, right?

Yeah, weird. What is your cartridge loading? Could one of the dip switches be stuck between on or off? Try moving all the dip switches and try a standard setting like 47 or 100.

Also, verify the the USB output is disabled using the front panel in case that is doing something.

What firmware version do you have installed? The display for the current version will read: main 00.54; CLPD: 01.08; USB: 00.17; Boot 01.10

Cartridge loading is 100. I’ll check the dip switches and verify they’re properly up. (9 and 10 are in the up position.) I’ll also check the USB and the firmware. Thanks!