Amplifier

[George Sephton]

Hi All,
I'm looking to built a home multiroom sound system and was just wondering a few things,
firstly does anyone know where I can buy some small amplifier modules, only like 30W would do, I've seen you can get a decent 7W one from maplin and those Kemo ones, although the Kemo one produce really bad audio so preferably not those.
secondly, would my audio be alright if I put an input in one end of the house, that then goes to the base station at the other end of the house, is amplified and returns to the speakers, this'd be roughly 40ft max each way.
Thanks,
George.

 

[Dippy]

First thing Georgey Boy is your budget.
Do you want cheap Ch tat or quality Amps?

You don't fancy trying to make your own using one of the hundreds of chips available?
"Decent" and "Maplin" in the same sentence? Is that an oxymoron?

The second part of your question; I haven't got a clue what you are talking about, sorry. Draw us a picture.

Thirdly, where is the PICAXE involvement?

 

[Jeremy Leach]

Sorry George, but from your description I can imagine an input jack on the outside of your house . Or maybe that IS what you mean !

 

[john2051]

re:

Hi George,

I think that 40ft of low signal level is asking for trouble! Ignoring attenuation for a moment, I think you are going to have enormous problems with noise pickup. Have you considered wireless?

regards....John

 

[Dippy]

Oh, so is this 'input' at line/signal level then?
And "goes" is standard wiring? Not some fancy screened or balanced method?
And this "base station" is what exactly?
Sounds like a PASBAWQ.

I'm glad your C.Ball is working John - maybe you can take this one on?

 

[hippy]

would my audio be alright if I put an input in one end of the house, that then goes to the base station at the other end of the house, is amplified and returns to the speakers, this'd be roughly 40ft max each way.

Possibly okay if you don't get interference, use quality high-current, low-resistance cable from amp to speaker. You might need to run the audio signals using balanced line and have solid gold speaker cable Then again, cheap screened cable and mains cable for speakers may work. It's really a try it and see.

Most audiophiles probably wouldn't recommend such a setup but it's more common for stage gigs, though even there cables are usually kept as short as possible between amp and speakers.

 

[Rickharris]

Generally for audio cheap and quality are not two words you put together.

For the low cost - Maximum control build your own amp based round one of the audio ICs available - http://www.rapidonline.com should provide you with some ideas

Audio over 40 feet? Don't know so many variables - either go for the options above re wiring etc or try it and see what you get.

 

[George Sephton]

Hi everyone, thanks for all your replies. Looking at what you all said, especially about line level signals I have decided to do it differently.

Bascially to clarify what this is:
It's like a multiroom audio system, each room has speakers and a control panel that allows you to select inputs (iPod, DVD player, Aux In and MP3). This links to the base station via some sort of serial connection (I'll probably do it digitally) where there are inputs for DVD and Aux, an iPod dock and an MP3 player module that can be controlled from the control panels in each room. Returning from the base station (which has an amplifier for each room and takes an input depending on the users preference (using relays or possibly analogue switches) are the speaker wires which will connect directly to the speakers in that room. Originally I was going to take an Aux In from the room, send it the base station and then amplify it and return it but you said line level signals long distance aren't good so I wont.

Between each room and the base station are these wires (5V+ and GND, Audio Send + and - and Serial TX and RX).

For the amplifier I will probably use These as it seems good.

Basically how should I power this amp as there will probably be about 5 in the base station and what sort of wire should I use for the wires I mentioned above.

Thanks for everyone's help this has been really useful.
George.

 

[Jeremy Leach]

And the PICAXE is where?

 

[George Sephton]

in the control panels, connect to the LCD and buttons, and in the base station connected to the MP3 module and iPod and controlling the relays.

 

[Jeremy Leach]

Ok, just checking . That could be quite a project.

So I guess there won't be any control over the mp3 track being played - it will just basically be selecting from a range of sound sources from the base station, with perhaps volume control of each amp too.

 

[Dippy]

On that supplied link are other links entitled "User Manual" and "Amplifier Power Supply General Advice".
They tell you what you need to know. Why not have a good read for yourself?
You should be able to spec and amp and any subsequent components easily.

So, either a PSU for each amp or a bigger one and power all amps off one.

How are you going to control volume levels?

Will each room have a display showing track played?

Do you want other people to design the switching/input stages too?

Speaker wires? Fattish ones. Lowish Ohms per metre without going OTT and don't fall for salesman crap.
You can do the volts/amps calcs. No need to get carried away and pay a fortune. If you were going for mega-amps and real Hi-Fi thats one things but for this app something a little more economical is fine.

 

[George Sephton]

Oh no, the intention is for the control panel to allow you to completely control the iPod and browse through an SD card with MP3s on it.

I think one big PSU for the whole system would be easier and I'll be sure to look at those manuals, I didnt see that before.

As for volume levels, with either be done with a simple potentiometer at the control panel which are wired into the speakers wires, or I may use a digital potentiometer at the amp which is controlled from the control panels as I have quite a few audio i2c potentiometers lying around.

Do you want other people to design the switching/input stages too?

What do you mean by this?

 

[hippy]

Basically how should I power this amp as there will probably be about 5 in the base station

Not sure how you count five amps as they are mono; if five rooms you'll need ten for stereo. Each needs 25V, positive and negative, at 4A. The power supply would depend on what you actually have; can all rooms be on at the same time or are you switching outputs between rooms ? I think a block diagram of exactly what you envisage would help.

Given the cost of mono amp modules, having to build good power supplies, it may be easier and no more expensive to just grab Hi-Fi amps off the shelves from Richer Sounds or wherever. You can often pick up very credible Cambridge Audio and NAD amps for around £50 and have one per room. Can't say they will be better than DIY modules but I know which I'd choose as first choice. Plus they come with tone controls and connecting graphic equalisers and whatnot is far easier. Then it's just a question of routing an audio source into them, separately sending docking station audio back to the base station.

It's really a topographical issue than anything else; work out what you want and it will be the same no matter where things are placed, centrally or distributed. The only thing with 'stretching cables' is keeping noise down and quality up. There are three main options for audio line signals; do nothing, upping line voltages and using balanced lines with suitable interfaces each end, and digitising and un-digitising.

I've run audio up screened pair and even over Cat 5 over long distances and it 'works fine' but then I haven't judged it in terms of quality. What's okay in a field may not be acceptable in the home for Hi-Fi enjoyment and ultimately only you can judge that.

What we used there were under-dash equalisers / amps for cars. Really small, really cheap. Possibly an option to consider but probably not Hi-Fi.. You'll probably not want a car battery in a bin bag as a power supply though

 

[George Sephton]

I decided not to bother with stereo speakers as the rooms with have them in the ceiling and ultimately once person on a sofa will hear left and right but another would end up hearing left in front of them and right behind, and although thats cool I'm just gonna do it in mono.

Ultimately I think they'd be rooms where I could just use a cambridge audio amp but that'd probably be one out of the 5 rooms so I still need a good amp. I was thinking about using a 12V car amp but wasn't sure what people would make of it, whether the kits would be a better option or not.

And also I think i'd be best if I designed the system to be able to work with all amps being powered as this is the idea, that the kitchen can be listening to the DVD player whilst 2 rooms listen to MP3 and another rooms listens to iPod.

I was considering cat5 cables but many people were talking about braiding and the point of, cat5's are used for low voltage etc so aren't recommended.

 

[hippy]

I think it's becoming clearer now ... a Lo-Fi, ambient system. Five rooms, five amps, big box somewhere powering and controlling it all.

I'd question the need for 30W but probably good to have some overhead and depends how those watts are meant. Central amps would seem fine, big hefty power supply with some big caps, 6A or 13A mains cable from amps to the speakers should do it.

Screened audio cable from all the sources up to the big box. Likewise Cat 5 cables from PICAXE controllers to big box.

Then all you need is to build the controller / router to switch the right source at the desired volume into the appropriate amps.

Some manufacturer (Bose?) demo'd a system like this with occupants having RFID tags so their selected music could follow them around the house but that's probably overkill though nice.

I'd really suggest you try it with a speaker connected to the Hi-Fi first, see if mono and a single speaker is good enough, doesn't simply create an annoying, or dead and lifeless, point source. Stereo will better fill the room even if not ideal for perfect listening. Consider putting speakers opposite sides of a room and facing each other rather than outwards or to the centre. Close to a back wall often fills the room with diffused sound so there aren't weird spatial effects, out-of-phase areas and dead-spots. Alternatively possibly have multiple ceiling speakers with some out of phase.