Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems One of my DSP33s is broken (in a very strange way)

I almost made this the Meridian Geek 2008 thread because I don't think many people would get the answer, but I didn't... It's a weird one though.

Basically, I have a G68 with 5x DSP33 and a completely kosher 511-based comms set-up (1 master + 5 slaves). On several occasions, one of the 33s would go completely wacko on a non-reproducible basis: Think listening to a 56k modem at high volume.

So I sent the speaker off to M who played with it, soak tested it, and could find nothing wrong with it.

Plugging it back in, it's going wacko on SkyHD, but only on SD channels. [censored]???? Swapping cables makes no difference. Swapping speaker positions makes no difference. Flipping the L/R channel switch makes no difference. This essentially rules out my G68.

So I investigate further. Amazingly, Dolby Digital 5.1 and 2.0 from SkyHD are fine, but stereo PCM triggers the problem *every time*. I now try a CD - stereo PCM - and it is fine! [censored]????

Have you got it yet?

I'm now completely mystified and am wondering if there's something wrong with the comms receiver in the speaker. Could the fault be triggering on one particular source (of the twelve)? So I plug the SkyHD optical into the input usually used by my PS3 and the fault rears its ugly head again. I guess I was clutching at straws...

So now I'm thinking: What is different about DD, SkyHD PCM and CD PCM? And it hits me!

- DD is decoded in the G68, but is not upsampled: 48kHz is output to the speakers.

- CD PCM is upsampled by the G68 and 88.2kHz is output to the speakers.

- SkyHD PCM is upsampled by the G68 and 96kHz is output to the speakers.

My conclusion: My dodgy speaker barfs on 96kHz signals. Whether or not this is MHR related or not is incidental; when I turn off upsampling in the G68, SkyHD PCM is fine...

So now I have to see how much "new M" is going to charge me to fix it...

I had a similar problem once and it turned out to be the CABLE. The cable could do 48k but it could not do 96k. But it sounds like you rules that out.

Good detective work (maybe they will give you a break for debugging it).

Thanks George. I will try one more cable swap before I return it to Mother, but I suspect there's a bad joint on one of the boards that can't handle the highest frequency input.

Have you tried a 2-Ch DTS Disc or even a DVD / Bluray Output from your PS3 in 2-Ch PCM Mode to confirm your diagnosis???

Seems strange that your speaker would be ok with 88k but not with 96k

Edit: Just to clarify

* A DVD of an Older Movie with a DD 2.0 soundtrack (Bullitt perhaps!!)

* Bluray Soundtrack Uncompressed PCM or DTS-MA over LPCM from the PS3

Your cables may be picking up RF interference form some local source.
Often this will cause the symptoms you describe and it's very difficult to trace, as the interference will vary with weather conditions and local RF signal level.
Interestingly, one cable can cause the problem when to connected different components.
Are your cables original Meridian or some custom cable?

VK:

Have you considered the possibility that the issue is with the Sky signal flagging DD2.0 as PCM instead of outputting PCM as PCM 2.0?

Also, you can try a concert DVD -they often have a stereo PCM track at 48K you can check with.

I'm not sure we're to the point where we know conclusively that PCM @ 48K is the issue.

Not yet, but I'll try tonight.

You're right that the two frequencies are pretty close together. My other thought is the G68 might be MHR encrypying based on whether or not the source is flagged as copy protected. i.e. It's an MHR problem in the speaker. I reverse engineered the G68 diagnostics from the 568 ones, so I'll take a look to see what the MHR output status is:

DSP VEAC 6/0/NE/0102.
- VEAC as per 568
- 6 is probably the sampling frequency
- 0 is ?
- N is MHR input status (N=not enabled, E=enabled)
- E is MHR output status (N=not enabled, E=enabled)
- 0102 - looks like it could be input stream status and output stream status

Cables are original Meridian. I'll swap the speaker once more, but I'm pretty convinced it's not a cable problem.

How would this affect one speaker and not the other four?

I'll do this.

I think you're right - see my comment about MHR above.

Re: Sky outputting odd things....

Last week on returning from a trip away, I switched all the gear on from a cold start and tried to watch the Olympics (a past-time we Brits can now admit to doing).

I was watching Sky/BBC HD ch 143. No sound from the centre channel. Only ambiance out of the L/R. I immediately and incorrectly assumed the G68 had lost some settings as even the SB+ seemed very very quiet (75+ on the scale just to get a volume I'd normally associate with ~55).

I went to bed and ignored it. 1st thing in the morning I reloaded the config file and all was back to normal....except for BBC HD 143. No centre channel. It was like it all week and was only a problem on that channel.

Relevance of the story is that odd things can happen for single channels.

Rebbot your sat receiver while you're at it.

I noticed that too...

Surely not for a back right channel derived from a two channel source!

Nick,

It's a bit concerning when, just switching on your gear after a few days, you immediately suspect that G68 has gone belly up and you reload the config files. It's supposed to be a bit of consumer electronics used by less than savvy members of the public. It's this mindset that Meridian have instilled in even us ardent fans. "If it suddenly doesn't work it will be the Meridian gear."

Agreed. I'm so paranoid, I always check that my two rear speakers have actually come on... Whilst I love playing, it would be nice to just run the damn system for a change!

Guys, I agree. I'd be a bit more vocal about it if I hadn't been so frazzled after a fairly tiring trip home. I can't rule out user error.
The centre ch was defo not user error.