Amplifier Over-Current Condition Detected

very helpful! thanks!

HL, I guess that would be up to Naim. However, as far as I’m concerned (and I would guess also from Naim’s point of view), the basic recommendation from the FAQ stands for any Naim amplifier - use the supplied plugs at the Naim amp end, avoid any cable of high capacitance and low inductance, and if still in any doubt, go for NACA5 and you won’t be disappointed…

I’ve been using “Go 4” with my Nova and PMC Twenty5.21 for about 2.5 years now with no issues, though they are much longer than yours. The Go4 is basically the Type 4 with Audioquest’s little black box attached (Sorry, I cant remember what magic is claimed of it, but it sounded better than Type 4 on demo) so it’s doubtful that your cable is the issue.

As an aside, I did compare with NACA5 and both AQ cables sounded better to my ears. I had intended to but NACA5, but the dealer said “have a listen to this” and put Type 4 on - he just left me to play music - left me as in left the room - he did no talk up of the AQ or talk down of the Naim product. So I chose the AQ despite knowing I wanted the NACA5 when I walked in.

Do you mean that you are biwiring? In other words, do you have the links between the two sets of sockets on the speakers removed, with two pairs of banana plugs in each speaker?

oh man, i dont even know that that means! the only reason i knew what kind of cables they were was because i asked the gent who installed the system. But there are 4 connections to each speaker, if that is what you mean. Here is a photo.

I have a feeling this method of wiring (called bi-wiring) doesn’t suit the Atom and bi-wiring isn’t recommended for Naim’s amp’s.

Further questions, to get to the bottom of this:

1- How does the speaker cable attach to the Atom - I assume both blacks to black and reds to red?

2- Can you advise the precise model of the B&Ws … and are you aware if they’ve been modified in any way?

3- Have you link plates (or jumpers) which can be used to slide between the speaker terminals, so as to join and respective red & black terminals together (not red & black joined together of course).

4- Did an authorised Naim dealer install this?

See the guidance at the bottom of the Forum FAQ page:

Judging by his nick, I would guess 604, but which series?

Is it really bi-wiring if it’s the same terminals on the amp side, the atom only having one set?
I thought for bi-wiring you had to use different sets of terminals. This way the original jumper has effectively been replaced by the speaker wire, nothing more than that.

Hence the Q’s - as:

1- I know some legacy B&Ws are real current eaters
2- I’m not au fait with how B&W’s 4 speaker terminals work e.g. I assume whatever X-over is inside is bypassed?

The confusing bit to me is that (assuming the amp end only has 2 terminals, with 4 core cabling), is how the Atom is feeding the drivers - independently?

It seems the OP has a hybrid bi-wiring set-up - the Atom only has 2 pairs of speaker terminals.

I know bi-amping B&W’s was a solution for many, given how power hungry many legacy models were* - I think newer models are easier to drive.

*rumour has it B&W used large current pumping amps in their design workings at Worthing.

Hi all. Again, i am pretty ignorant of technical stuff. But let me do my best: 1) this one i dont know, but will get an answer. 2)I just looked at B&W website, and i think they are maybe 607s? they are small bookshelf speakers. 3)No idea. Will find out 4) yes, i have been buy from them for years, and they are the only authorized dealer in my vicinity. I’ll come back with proper answers. Thanks.

haha. No, 604 is the area code for Vancouver, Canada, which is where i live. also the name of my company. the rest of your note is way over my head! thanks.

i have an answer re speakers. B&W CM1 S2

All noted - thanks.

To explain a little:

An amplifier is like an engine, and the engine’s gearbox (output stage) provides power to whatever is connected to it. In hi-fi terms, this is a combination of the electrical qualities of both the cabling and speaker (and any joints in play).

I’m not sure what the electrical qualities of your AQ speaker cable are but it seems to be 4-core (2 red & 2 black), which are connected to the respective channels on the Atom i.e. each terminal at the Atom has 2 cables attached to it (that’s OK perhaps).

Now, the B&W’s appear to be quite demanding in efficiency terms (in converting electrical current in to sound level) - they appear to be rated at around 84db - although I see a review test suggested lower (~81db). This means the Atom has to work hard(er) to make them work which, in general terms, isn’t the best.

But (and here I think is the crux), the way the speaker is wired could be exacerbating issues.

When run in ‘passive’ mode, the rear speaker terminal pairs should have a gold plate between them, so an amplifier is driving in to both drive units at the same time. Inside the speaker is a crossover unit which splits the incoming signal to the drive units (tweeter high frequency and woofer/bass unit low frequency).

Intuitively, by splitting the AQ pairs and without the rear links, the Atom is being asked to drive the respective driver units separately (I will admit I don’t know if/how the speakers X-over network is them employed, or not). I suspect (and not knowing the electrical qualities of the cabling), as a relatively low-powered amp (in the world of amps it is), the Atom often really struggles with the current demand which it is ‘seeing’.

When I say ‘seeing’, this is also a reflection of the efficiency and specs of the speaker. The B&Ws, as well as being inefficient (in relative terms), are rated at 8ohms resistance (nominal) but reviewers note this can dip down to close to 2 ohms.

This latter trait is nasty for amps. An analogy is like driving on a road when you encounter ice, the engine revs increase suddenly as the rolling resistance from the road reduces and the tyres lose traction - a side effect can be that the engine can over-rev and it becomes less responsive, and the amp’s grip & control of the speaker cones is compromised. And if you play music loud-ish, the amp can really struggle. It’s working its heart out just trying to keep up and the rev-range (headroom) of the amp is grossly diminished - the usual sign is that the amp runs hot.

I wonder if the way it is currently wired, the resistance of the speakers is reduced as the drive units are (in concept) being run in parallel.


If you have the gold link plates, re-install them and wire up to only one set of rear terminals on each speaker - you may be able to get away with splitting top & bottom (as it looks now). The key thing is that the speakers’ cross-overs are fully engaged.

FYI, the rule with amps & speakers is to have a far higher rated/better quality amp driving in to more modest quality speakers - a bit like the car analogy, the bigger the amp engine, the lazier it can work and when the music peaks come, it has the power to handle the signal needs and the traits of the speakers.

In the land of hi-fi, damage can be done to amps & speakers if, for example, a lower quality amp is asked to drive a set of demanding speakers as:

1- the amp may be being asked to operate > its performance envelope - shut-down (over-current) protections are often there to protect this from happening.
2- the signal the amp feeds to the speakers could, in extremis, be > the operating envelope of the speakers and could blow-up a drive unit/even damage a cross-over.

thank you. so much great information there. Much appreciated!

Maybe at first sight it appears that way, but it’s not. As the Atom has only one set of speaker terminals, the cables must by definition be joined there.
The effect of that would be that even though the jumpers have been removed the speaker terminals are still directly connected to each other by the speaker cable. There’s no need to got through any of the amp’s circuitry.

But even if better constructed, the lenght of “jumper” is now a lot longer and will have plenty more resistance.

I don’t know if it will help with the actual issue discussed, but my advise to the OP would be the following:

  • Put the jumpers back in place
  • Connect all black wires to a single black terminal, all red ones to a red one. (I’m not sure this is necessary, with the above in place, but as it’s the standard way of doing things let’s err on the side of caution)


  • If the length of speaker wire allows, cut a 15-20cm piece off of it, and use that to bridge the terminals instead of the original jumpers.

FYI (& @n-lot) , I’ve now managed to find copies of B&W’s CM1 manual & info sheet on line, and managed to have a look at AQ’s site re the features of the AQ Type 4 cable. I cannot post links here as not allowed.

Some further points and, in part, an apology perhaps(?), as:

1- The B&W Manual suggests the links can be removed to run in bi-wire mode (as you have currently?) BUT…the picture in the manual suggests this requires 2 separate cables to join to the 2 sets of terminals, with these cables only be joined (in physical terms) at the amplifier i.e. they share one output terminal (see on as to why this may be important).

2- If running with links installed, the B&W Manual suggests connection to the top set of terminals only. However, you can experiment to see what generates the best sound - some people go diagonal and others use only the bottom sets - remembering that the amp must be turned off when changing speaker connections.

3- now (and here could be a material issue), the AQ 'site suggests the Type 4 cables are ‘low inductance’ (and this marries to the guidance for cabling by B&W for the speaker).

Per the link to the Naim FAQ page I posted earlier, Naim amps (in general) don’t marry well/like a low inductance cable. Further, I wonder if the use of 4 strands in each cable (per your photo) and not using 2 separate 2-core cables, is elevating the traits of the speaker cable. Where signal cables are wrapped-around each other, this can adversely affect the electrical properties of the cable (IIRC it increases capacitance - I stand to be corrected).

In summary - I think there could be a combination of factors in play here as to why the Atom is showing ‘over-current’ messages. The speakers aren’t the easiest to drive and, it could be, the speaker cabling and current wiring arrangement is adding to this.

One option would be to speak to your dealer (are you in UK?) and see if you can borrow some NACA5 cabling and see how this goes for you. I will admit that other cables can outperform NACA5 when it comes to detailing but these other cables (as you may be experiencing here) can generate other issues.

Alternatively, as I’ve already suggested (as has @n-lot), put the links in and only connect to one set of terminals (with 2 blacks and 2 reds looking at the 4-core cable?). This may remove some aspects. Worth a try first up.

I think you’re misunderstanding the layout of the Type 4 cable which is not twisted, but straight wires in a “star quad” layout. So you have 2 ‘live’ and two “negative” in parallel with each other. The cable is bought terminated by AQ so the two live are connected into one plug and the other two into the other plug. This is duplicated at the other end.

When you open the box you have what appears to be (and is) a standard speaker cable with two plugs at each end. You shouldn’t twist the cables as they aren’t designed to be a twisted pair (like, for example, Kimber cable is).

It is possible to use as a bi-wire by removing the AQ connectors and replacing with your own, but that’s not how it’s intended to be used.

Effectively the AQ cable is a solid core cable, but with two strands per core, rather than one. These are laid out as a “star” inside the single sheath - clockwise being red, black, red, black. AQs web site gives the “benefits” of this layout.

Electrically the measurements are nothing out of the ordinary I believe. My Nova has no issue with the related Go-4. If the cable is an issue it could be that the OP has only 4 feet per channel, which is according to Naim, for their separates, too low for NAC5, so probably for most others too. They don’t give a minimum for the all-in-ones so it’s hard to know if this is the issue.

Perhaps trying a cheap, but good, multi core cable such as Van Damme ofc would be of use determining if the cable is the issue - should cost less than £20 for 2 x 4 feet lengths so shouldn’t break the bank as a test.

From AQ’s web site for type four speaker cable.


High-Inductance geometry smears sound and reduces information. Star-Quad low-inductance geometry preserves time information, preserving dynamics and clarity.

Classic Naim amps require a certain inductance for stability, the Unitis are meant to be more tolerant and the Nova working fine with with go 4 supports this but you have PMCs and a nova, the OP has some low sensitivity B&Ws and an atom so is probably putting a few more demands on the amp. If there is a hint of oscillation but not too much it might just warm things up just enough to trip the thermal cutout on an amp already working hard. The DNM cable looks like a good match for Naim if solid core is your thing, reports are the bass is a bit lighter than A5.

Apologies for the late reply, but I see that others have stepped in! I think the short answer is to get regular single wire speaker cables (or the ones you already have, wired as such) and have them soldered with proper banana plugs. I can vouch for the fact that Naim’s NACA5 works very well with the Atom, although it’s rather stiff and unwieldy. There are decent alternatives from Chord and others that are known to work well with Naim gear.

It strikes me that this thread has drifted away from the problem the OP is reporting. His first post says it’s been fine for 2 years but has just started showing this over-current error message. That could be a speaker cable malfunction, like two wires shorting, but it is most unlikely to be caused by using the wrong type of cable, or the biwiring, because that would for sure have shown up more or less from the outset two years ago.

So if there are no short circuits or dodgy speaker connections, then this strikes me as an amplifier fault and no fiddling around with jumpers or changing biwiring to conventional wiring is going to help at all.




You have a point, David, but I can’t help thinking that very short lengths of biwired speaker cable are not ideal, and if it was my system, I would certainly look at changing it to a standard cable that fits with Naim’s recommendations. Also, one of those black cables in the photo has a tight kink in it that looks dodgy to me. When that Atom says “Amplifier over-current detected. Reduce volume and check loudspeaker connections,” it probably knows more than we do.