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[Gaffers]

I know a few people on here are audiophiles so I trust the views of people here more than perhaps an AV web forum.

I am in the process of setting a few things around the house on Raspberry PIs, one of them being a multiroom sound system using Logitech Media Centre with clients around the house to act as zones.  The entrire system is running off a bank of leisure batteries topped up with a solar panel.  The batteries have not been topped up for a while as i am in test mode and read 12.6V without load and 9.3V with load.

I have tested a setup with a Digital Audio Card (DAC) going through a Class D 2x20W amp out to two 40W (as written on the back) 8 ohms ceiling speakers.  The sound was ok but lacking a bit of bass and it needed cranking to 60% volume before it was a usable level and at 100% it was loud but not deafening.

I guess that my amp isn't beefy enough but I am having difficulty finding a 12v class D amp for 2x40W.  Should a just go for a bigger amp (even though it is not class D) or should I get some speakers rated at 20W?  Or is the fact my batteries slightly low affecting the output?  I prefer class D because of the efficency, I do not want to loose much precious battery power to wastefully producing heat

The speakers:  http://www.amazon.co.uk/gp/product/B000IUTOZ4?psc=1&redirect=true&ref_=oh_aui_detailpage_o04_s01
The DAC - http://iqaudio.com/?page_id=454
The amp:  http://www.maplin.co.uk/p/adafruit-stereo-20w-class-d-audio-amplifier-max9744-a54qn

The idea is to reproduce this setup in each room so I need something that is fairly cost effective too 

Not too much of an expert in this and I know how passionate you audiophiles can get, so go gently

[Taxi_Driver]

The entrire system is running off a bank of leisure batteries topped up with a solar panel.  The batteries have not been topped up for a while as i am in test mode and read 12.6V without load and 9.3V with load.

Ummm that's a flat battery, if its a 12v battery  And needs charging pronto....altho leisure batteries can take more abuse than a car batteries...

It would certainly be affecting the sound level....at full volume your asking the batt to supply 80+ watts , and that aint gonna happen with a battery in that state of charge...

Also, are you sure the leisure batts will be able to supply that amount of power, just being charged with a solar panel?? 

[Gaffers]

They are AGM  atteries so yes they can really take some abuse. But you confirmed my suspicions, i shall top them up this weekend.

As for handling the load. There are 2 in parallel with 64ah capacity and if i need more then i will just add some kore. Each of the PIs draw 0.5a and obviously the music wont be on all the time......honest.....

[tidla]

what capacity is the solar panel?

[aaronjb]

Charges electric car from the grid.
Runs home hifi from car batteries.


You're a strange one, Cap'n

[05omegav6]

Doubtless using Led Zepp at full blast to use the speakers as mini generators to feed power back to the house and charge the car... Genius

Misunderstood, but genius nonetheless 

[Kevin Wood]

You won't get much bass out of those because they aren't being loaded by a cabinet behind them.

The problem with running amplifiers from 12V is that, without first stepping up the voltage, you can't get much power from them, hence the decent in-car amplifiers have an inverter to get +/- 30-50 volts DC or more, before the amplifier, and they also normally drive 4 ohm speakers. I suppose there might be some definition of 20 watts that you can make from a 12V supply with that amplifier, but it's not RMS power into those speakers at 8 ohms, unfortunately. You'll get about 10 watts, I'm guessing, and the speakers might well not be that efficient.

The PiDAC is very well regarded, though.

If you're looking for an LMS client with a bit more of a user interface than a Pi, get a couple of O2 Jogglers. I'm flashing one with squeezeplay as I type.

I've got umpteen different types of amplifier, valve and solid state, languishing in the loft if you want to try some for size and see how much power you need.

[Gaffers]

Thanks, I might take you up on that. 

OK then, so if I went for a mains driven Amp that I can switch on/off via the GPIO what should I look for that is cost effective (bearing in mind that it will be replicated in several rooms)  This reduces the demand on the batteries which is only a good thing.

As or the client, it has to SBC based and thus I prefer the PI for this due to the huge following behind it.  The idea is to have a small touchscreen to a web interface which controls the house (lights, alarm, music, heating, etc) first stage is the alarm and music....I will add servers and modify the interface as required.

[Marks DTM Calib]

Yes 12V limits you to around 20W RMS tops in push pull into a 4 ohm, about 17-18 into an 8, without push pull it will be much less.

And as Kevin has said, ceiling speakers wont give bass as there is no tuned enclosure behind them (beware Bose stuff to as its designed to be tinny and un natural....tuned for a compromised US ear).

As an open frame amp, I really rate the OMPs, great clean sound, low distortion and an all in one package. 

http://www.bkelec.com/amplifiers.htm

They will need a simple anti pop circuit though (easy to do).

Having said that, your using Class D so clearly not to concerned about quality in general

[Kevin Wood]

Well, the joggler is pretty much a Pi with the display and touch screen already integrated in a nice case (although it's atom based, not ARM) and it also runs linux, so I'm struggling to see what it can't do that a Pi could. You can pick them up quite cheap if you bide your time.

One thing you should check first, though, is that you are driving your amp with enough level to reach its' maximum output. You don't mention it distorting horribly, which leads me to believe there's more to come from it and you just don't have enough gain in the system. You probably need an oscilloscope to see what's happening at the output and how close you are to clipping the amplifier and yes, in my loft...

I have a Squeezebox touch, Squeezebox 3 and an original Squeezebox around the house in addition to a couple of jogglers streaming music from LMS server running on an x86 machine.

Oh, I've just done the controlling central heating with a Pi thing too, so have a PCB design for that if you are doing something along the same lines.

Regarding amplifiers, if you want something cheap that will knock out a reasonable amount of grunt and are happy to do bit of construction work, I'd look for a single chip amplifier. There are plenty of boards on Ebay based on chips like the LM3875 and LM3886 that will be adequate for your application and you'll just need to add a mains transformer and switch it via a relay driven from a GPIO.

[Gaffers]

Having said that, your using Class D so clearly not to concerned about quality in general

I was restricting to class D as it was to run off a battery, so I was more interested in getting the best sound for Ah.  But if I throw the towel in on that and go for mains powered amps then all bets are off

[Gaffers]

Well, the joggler is pretty much a Pi with the display and touch screen already integrated in a nice case (although it's atom based, not ARM) and it also runs linux, so I'm struggling to see what it can't do that a Pi could. You can pick them up quite cheap if you bide your time.

One thing you should check first, though, is that you are driving your amp with enough level to reach its' maximum output. You don't mention it distorting horribly, which leads me to believe there's more to come from it and you just don't have enough gain in the system. You probably need an oscilloscope to see what's happening at the output and how close you are to clipping the amplifier and yes, in my loft...

I have a Squeezebox touch, Squeezebox 3 and an original Squeezebox around the house in addition to a couple of jogglers streaming music from LMS server running on an x86 machine.

Oh, I've just done the controlling central heating with a Pi thing too, so have a PCB design for that if you are doing something along the same lines.

Regarding amplifiers, if you want something cheap that will knock out a reasonable amount of grunt and are happy to do bit of construction work, I'd look for a single chip amplifier. There are plenty of boards on Ebay based on chips like the LM3875 and LM3886 that will be adequate for your application and you'll just need to add a mains transformer and switch it via a relay driven from a GPIO.

Yeah they aren't cheap at full price, twice what PI and screen cost.  I will stick to what I know and if I can get my head around the API I can design my own custom web interface for it 

Thanks for the heads up on the Amps, I think I have found some possibilities on eBay...I need to dig around some more though.  As for distortion, at 100% there was a little but not enough to really notice but the louder I set the DAC the more tinny the sound.  I found that the DAC on 40-50% and LMS on 90% gave the best sound but still lacking in bass plus the LMS usable range was 50-100% anything less was very quiet indeed.  Not much lacking in bass mind you but just enough to make me want to better the solution

As for the heating I am in the early stages of researching that, but as I want to control the lights as well I thinking of a z-wave or lightwave solution for both.  Depends on cost/ease of implementation.

[minifreek]

My tuppence worth....

Buy an enclosed speaker set-up, and sound deaden everything behind the speaker/s to give more of a thump than loss of bass it will be reflected back down, BUT the ceiling speakers won't create lots of bass anyway as the frequency response isn't there for those speakers...

If you intend to run everything off 12V - buy a decent automotive amplifier, they are very very good at what they do as they are built to produce 'big' sounds more than the Class D that you are currently using, that will give a more general sound... The other way, if you intend to use ceiling speakers, use component speakers instead of an 'all in one'... Component speakers systems are readily available from most automotive outlets like Halfords etc.. for reasonable outlay... but you get what you pay for with speakers....

Im sure there will be others on here that will know a hell of a lot more and be able to explain better what you might need... Basically the speakers you are using need an enclosure behind them to get any real bass produced at relatively low volumes...

[Kevin Wood]

Yeah they aren't cheap at full price, twice what PI and screen cost. 

They weren't, but they are discontinued now and you can pick up mint examples on Ebay for around the £30 mark. I recently bought an ex-display one for a tenner that had some markings from being wall mounted, so pretty tough to beat. I'd be interested in what solution you had in mind for the PI+Screen option, though, because I wouldn't mind betting that would have much lower power consumption.

As for the heating I am in the early stages of researching that, but as I want to control the lights as well I thinking of a z-wave or lightwave solution for both.  Depends on cost/ease of implementation.

I've recently hacked the RF protocol for these, and they are controlling my fairy lights, etc. from an R-Pi:

http://www.maplin.co.uk/p/remote-controlled-mains-sockets-5-pack-n38hn

They are often on offer much cheaper than that, too!

The protocol is completely insecure, but for lights and so on, I don't see that as an issue. They are much cheaper than the z-wave / lightwave stuff, of course.

[Marks DTM Calib]

Having said that, your using Class D so clearly not to concerned about quality in general

I was restricting to class D as it was to run off a battery, so I was more interested in getting the best sound for Ah.  But if I throw the towel in on that and go for mains powered amps then all bets are off

Thing is you get significant quality drop for not much of a power saving, a decent class AB amp can be circa  65% efficient