[Voyage-linux] Control amplifier volume control through MPD: solution

[Hannes Werner]

Thank you very much for sharing! Nice...


On Sun, Aug 18, 2013 at 4:00 PM, Muffinman <news at koster.tk> wrote:

> Hello all,
>
> A while back I asked on this mailinglist on how to control volume of an
> amplifier via MPD through a serial connection (rs232/ttl). Time passed
> without an answer, so I did some digging and learned C. While building
> the app I figured I might as well expand compatibility. While it doesn't
> support every amplifier (with a serial connection), it does have quit
> broad support and can in some cases be extended if needed. In addition,
> in combination with MPoD/MPaD it also give control over input, power,
> and whatever options the amp has. Last, but not least: it syncs data
> both ways, from computer to amp and back.
>
> In short, the inner workings: applications such as MPD, but also
> shairport (dev 1.0), have the option to use a different soundcard for
> mixer controls. Therefore, we set MPD etc. to send volume control data
> to a dummy soundcard. Alsa notifies the application volume has changed
> which in turn sends the appropriate serial command to the amplifier. For
> other options icm with MPoD/MPaD a small PHP script notifies the
> application what to do. The amplifier in turn notifies the application
> of any changes in volume, power, or input changes (if needed by explicit
> request of the application).
>
> Broad support is somewhat frustrated by strange decisions of
> manufacturers to have a bit of silly serial command structures:
> completely different commands & structures for incoming and outgoing
> commands (Parasound) or have a completely different volume range for
> incoming (-93, 14) and outgoing volume commands (-150, -50, Classe).
> Anyways, in such cases support is limited (for now at least).
>
> Initially I've created the app for Leema Acoustics, so that's 100%
> supported. The following brands (fully or partially) supported:
> Cambridge Audio, Classe, NAD, Parasound. Ayre should be supported, but I
> don't have enough documentation on that to be sure. Cyrus can have
> support if anyone cares. Other than Leema (and Classe to some extent) I
> have not done any testing yet. But looking at the relevant documentation
> and having hooked up my computer to Classe, NAD... it should work. Once
> I have gotten myself the required cables I will hook them up and do some
> real testing. Though anyone else willing to do some testing is very
> welcome.
>
> Enough introductory talk: after reading the few notes below, all files
> and instructions can be downloaded at the ftp address below.
> - I don't take any responsibility for anything that may or may not happen.
> - The app is still in beta and needs further testing.
> - Be very careful when installing and testing regardless of its beta
> state: unplug speakers when testing or disconnect any sources. If
> something goes wrong, either faulty configuration or a bug, volume could
> go to unwanted heights (though I've never experienced that result).
> - The application allows volume limits to be configured, use it. You
> don't need to go to 100% volume through MPD, more likely, you don't want
> that. So, don't configure it.
> - Be careful of security. Anyone with access to your computer can modify
> its configuration. Well, use your imagination, the results in potentia.
> - Any suggestions/improvements of the code are welcome: I'm a beginner
> and probably violate every rule in the book.
>
> ftp://muffins.diskstation.me (guest login).
>
> If any question, please do ask.
>
> Kind regards, Maarten
>
> _______________________________________________
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> Voyage-linux at list.voyage.hk
> http://list.voyage.hk/mailman/listinfo/voyage-linux
>
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