Last ditch attempt to save my B&W MM-1 - Would higher rated PSU help?

[Kendalbeefcake]

Hello,

I've been battling for a while with an issue with my Sonos ZP90->Gaterised Caiman-> B&W Speakers MM-1 with distortion. Having replaced every component, I'm now 99% sure it's some issue with the line-in stage on the MM-1 speakers.

Essentially, certain FLACs (Sia - Chandalier, Amelie' soundtrack to name a couple) reliably distort at certain points. It's not necessarily volume related, as even a "simple" piano track can flummox it, but "beepy-cleapy" Dance music such as 65DaysofStatic are fine.

The issue doesn't occur when I use the internal DAC on the speakers, however the sound is noticeably flatter. Whilst the DAC is probably fine in it's own right, even with the crackle I prefer the sound of the Sonos/Caiman. I've been putting up with it for ages, and now I've had enough.

On another forum I've noticed that some vendors have been uprating/making available a 6A 16v PSU as an upgrade over the "standard" 3.2A, the logic being (I guess) that a beefier PSU can better handle the extreme highs and prevent/reduce clipping.

The SMP on the MM-1 is 16v, but a relatively weedy 3.2A. Bearing in mind that I listen to music and >70% volume for hours on end, I wonder if that is the last weak link. I cannot find an "off the shelf" replacement PSU for the MM-1s, so I'm forced to go off-piste.

For about £30 I've found a 16V, 5A Laptop PSU that could easily be fitted, so I'm wondering if that would help. Whilst it may not be as "clean" or "audiograde" as purpose built device, it should prove whether my issue is power related or not.

So am I barking up the wrong tree, or could it be as simple as a dry joint on the analogue line-in? Unfortunately the speakers are out of warranty, and I'm not keen to start poking around as the sale of the MM-1 will have to fund whatever I replace them with.

So, help me Obi-Wan Kenobe(s) you are my only hope..

[Firebottle]

Obi-Wan here.

More detail required to help out.
You say the problem is not necessarily volume related but then say 'I listen to music and >70% volume'.

If you reduce the volume does the distortion reduce or disappear?

Does the distortion only happen with certain frequencies? May be difficult to ascertain if it's around the crossover frequency of the speakers. Or is it a specific bass note?

Can you describe the distortion, is it a rustling (could be loose voice coil - usually heard at low volumes), is it a very sharp crack type of noise (at high volume the speaker may be bottoming out, exceeding its design movement/output)?

:cool: Alan

[Arkless Electronics]

No a power supply won't help. Sounds more likely to be clipping of the analogue line inputs. try attenuator plugs on the line in.

[walpurgis]

No a power supply won't help. Sounds more likely to be clipping of the analogue line inputs. try attenuator plugs on the line in.

That crossed my mind too. Input overload on the B&W active stages.

[walpurgis]

Something like these. Assuming RCA/phono inputs are used and -10db is suitable.

http://www.ebay.co.uk/itm/Rothwell-Attenuators-/252013176276?pt=LH_DefaultDomain_3&hash=item3aad27e5d4

[Kendalbeefcake]

Hi Alan,
I'd say it's detectable @ 50% volume, but at higher volumes it becomes so pronounced it begins to ruin the experience on about 20% of tracks. Certain frequencies is probably a better explanation; it's always certain points in certain tracks; some albums are perfect.

Describing the distortion is tough; it's like the vocal is suddently being routed through some particularly tinny laptop speakers; the verse ends and it soars once again..It's not a bass issue as far as I can tell; if anything it's the reverse; it's treble that seems to be the victim... Does that shed any light?

[Kendalbeefcake]

Thanks Arkless(?); I think I've talked myself out of this; as yet another desperate experiment I pulled the second speaker (cutting the power draw in half?) and it was still detectable in the remaining speaker..

[Kendalbeefcake]

Thanks Walpurgis, I had wondered about those; I do have phono on the DAC side I can use, but i'd talked myself out of it as if I need to reduce the volume; I probably need something more powerful to drive it..Or I have missed the point completely about these things? At ~£40 its worth a gamble..

[walpurgis]

You have to use the attenuators at the input to the speaker amps. Anywhere else will not work.

If phonos are not suitable, you can probably get attenuators with other configurations or adaptors that will fit.

[Kendalbeefcake]

Thanks very much; I meant I can use the "Source" end to plug into the Line-out on the DAC. I'm using a QED Phono to 3.5mm to connect to the line-in on the MM-1s.

At this point, it's probably my best option. I'll order them on Monday..

[Firebottle]

Hi Alan,
I'd say it's detectable @ 50% volume, but at higher volumes it becomes so pronounced it begins to ruin the experience on about 20% of tracks. Certain frequencies is probably a better explanation; it's always certain points in certain tracks; some albums are perfect.

Describing the distortion is tough; it's like the vocal is suddently being routed through some particularly tinny laptop speakers; the verse ends and it soars once again..It's not a bass issue as far as I can tell; if anything it's the reverse; it's treble that seems to be the victim... Does that shed any light?

It sounds like a resonance within the speakers, being set off by the volume level.
Without looking inside the speakers/ enclosure it is difficult to pin down further.

:)

[weetabix]

Hi Kendal,

Have you tried contacting B&W service? They may be able to look at them properly for you, before attempting a non-standard power supply.

Here's their contact number: 0800 232 1513.

Cheers

[Kendalbeefcake]

Thanks for your assistance; I did briefly consider contacting B&W support, but at the last minute I re-ran one of my earlier tests on the Analogue line-in and couldn't reproduce the issue. So as was suggested I ordered the attenuator plugs..And it's much better. Certainly, 4/5 of my "worst offender" tracks are perfect, and only one is still has some "crackle", but is still much better than it was. I'm still not 100% happy, but spending £40 has stopped me from spending £600+ for the forseeable future. Thanks again for your help people :)