Man cave amp?

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I have a small portable speaker at the moment which I use with spotyfi on my phone in the garden shed. I also have two oldish speakers in the shed and I was wondering if there is something like an amp I could buy that I could plug the speaker into? and then I could use with spotyfi with if that makes sense.
 
If you don't have the Internet (and WiFi) in your shed, your best option is to get a bluetooth enabled amp, or a bluetooth receiver to plug into the amplifier, then let your phone transmit sound to the amplifier that way.

If you do have WiFi out there then a much better option is to use that with the below:

The simplest option is to get a normal amp and a Chrome Cast Audio, then cast from whatever app on your phone to Chromecast that then plays to the amplifier.

On top of that you could look on eBay for a Google Home Mini that someone has got bored with. You can set this up to cast to the Chrome Cast Audio by default and it works with SPotify so you can just talk to your shed to play whatever you like to your speakers. Handy in a shed where you might be too greasy to touch your phone. You can still cast directly from the phone to the Chrome Cast Audio. I have a few, didn't pay more than £25 for them, but they're usually on Google Store at £49.

That all said, if you're buying an Amp in the first place you might be better with just the Google Home Mini in a small shed - the sound is pretty decent, or the larger Google Home which has a much better speaker. Stand-alone both can be Cast to and will both do voice control Spotify.

If you're working out there, maybe you need a PC to run Youtube and Sketchup anyway, which would then remove the need for all of the above, so if you've space and have a budget, a second-hand PC might be an option.
 
You cany buy micro amplifiers, class-D stuff on ebay with a built in tuner and aux inputs. I have two, it's not bad. Finding a decent enough power supply (that doesn't hum) is your biggest problem.

Nozzle
 
Thanks for the replies I'm not sure if I have wi'fi in the shed so i'm going to take my lap top down there and see if it still works?
 
Ahh well not quite it cuts out a few metres short of the shed which is probably 20m from the back of the house.
I'm not sure Paul what the difference is between having the internet and wifi I thought they were the same thing!
I have a pair of B&O Bevox 3800 speakers in the shed doing nothing so I thought I may as well try and make use of them. I believe you can get extenders for wifi and I have a spare socket half way down the garden so that might be an option. I'm going to look into the crome cast stuff and the micro amp's Nozzle not sure what you mean by humming?
 
Your options for a signal connection are a physical cable (phone to amp), Bluetooth or WiFi.

Physical is easy to understand, but obviously ties the phone to the stereo system while plying music. You're using Bluetooth right now, so you've already got a handle on the distance limits and understand that the phone is using your mobile data allowance for 3G/4G if it cn't reach the house Wi-Fi for an internet connection. Wi-Fi is a bit like Bluetooth except the range you can move with the phone in your pocket is much greater, and the music is streamed via your house broadband connection.

Related to this then is which of the features are supported (and how) by any amps you might look at.

Again, physical is easy. Most amps have a Line Input of some description. Bluetooth could be built in to an amp, or available as an add-on adapter that connects to a Line Input on an older/non-Bluetooth (BT) amp. BT is a low cost technology. It's possible to pick up a BT plug-in adapter for under £25. You'd then be able to choose any amp you wish.

Wi-Fi is more expensive but more flexible too. Audio devices that support Wi-Fi generally have the ability to stream audio directly from the net.


Matching the amp to your speakers

Your B&O speakers are a nominal 4 Ohm load (impedance). They're also fairly large and fitted with a 12" bass driver. The consequences of the impedance and the bass driver size is that they'll need an amp capable to delivering some real wattage. What this means is that the cheap Chinese Class-T and Class-D amps might not be up to the task despite what the spec sheets and sales blurb claims.

You see, the adverts make some claims about power that look really enticing for the price, and unless you happen to be a bit of an electronics buff then it's very hard for you to verify or disprove those claims. Fortunately, some of us here have been there, done it and bought the tee-shirt, so if you want, you can learn from our experience rather than waste your own money.

Prompted by your enquiry, I've just been looking at Ebay and the sales page for a "600W" amp with BT and USB and FM, all for £25 delivered from China. 600W!?!.... my left buttock.

The spec is almost non-existent, so a quick look at the pictures reveals the power rating for the DC input. It shows 12V/5A, and since Wattage = V x A, and 12 x 5 = 60, then our '600W' amp can draw at most 60W. What we're looking at then is the first lie. The amp can't generate extra power. That would break the laws of physics. All it can work with as continuous power is what it draws from the mains. In this case it's 10% of the claimed power output. However, that's not the end of the story.

60W is the total maximum power consumption with all the features running. The tuner takes a bit of power, and so does the USB socket and the vacuum fluorescent display and the pre-amp and not to mention a bit of energy lost as heat too, so there's an overhead to running the product. Let's be generous and say that it's only 10%. This leaves us 54W maximum.

It's also well-known in electrical circles that the sort of digital amps found in these products are, at best, 70% efficient. The very best digital amps achieve 90%, but they cost hundreds and thousands of Pounds, not £25 delivered. That means at least 30% of the power is lost in the amplifier stage, so we have, at best, 38W in total.

The final nail in the coffin is distortion.

The maximum power available is with the amp running flat out, and that means a lot of distortion in the signal too. Distortion is bad for speakers. More tweeters are killed because of distortion than are killed because an amp is too powerful. With these small digital amps, they go in to distortion quite early. You might get to half or 2/3rds of the available power before distortion becomes noticeable, at which point the amp is already throwing out 10% distortion. Let's be generous and say it's 2/3rds the power. Our 38W then drops to 25W, and you have to divide that by two because you have two speakers. A whopping 13W per channel then of useable power, and even then it's at the sort of distortion levels that no self-respecting Japanese or European amp manufacturer would consider acceptable in a music product.

When I started looking at amps on Ebay for this reply, I came across a second-hand Yamaha AX300. It's on a Buy-it-Now at £39 delivered. It looks tidy. The only negatives are that it would need a BT adapter, and that the mains cable is short.

Specs for this type of product are widely available. I can see that the maximum power consumption is 180W, and yet Yamaha rate the amp at just 30W/ch. That's because they rate the power output very conservatively. The distortion figure is 0.05%, and measured with both channels driven continuously and using a real music signal (20Hz-20kHz). They've taken an RMS value for power which is another conservative step because it's 70% of what would be available as peak power. The bottom line is that this older Yamaha has a lot more real world power than any of the Chinese Class-T/Class-D amps under £150.

If this or any other reply was helpful to you, then please do the decent thing and click the T-H-A-N-K-S button. It appears when you hover the mouse pointer near the Quote Multi-quote buttons. This is the proper way to show your thanks for the time and help someone gave you.
 
Thanks Lucid for the time and effort you have taken to explain things.
I have an amp buried somewhere in the house, I will dig it out and let you know what make it is and hopefully it will be suitable.
 
I made a distinction between WiFi and the Internet because the stuff I mentioned is a faff to make work without WiFi, but you might have the internet out there via an ethernet cable or something like a Power Line adaptor. If you do, you'll need to turn that Internet connection into a WiFI network as well. You can get Powerline WiFi plugs, chances are this is the best way to get the internet out there, but it's a bit dependent on how you have power out there. Best bet may be to buy from Amazon and send back if that doesn't work.
 
You can get Powerline WiFi plugs, chances are this is the best way to get the internet out there

Powerline plugs are known to interfere with electronic equipment by the radio frequency energy radiated from the mains cable. No use to have a good qualtiy amplifier and music source if they are going to suffer interference from the mains cables in the man-cave,
 
That's completely wrong, they don't cause interference.

You would have a digital signal for the audio right up until the point it leaves the DAC in the amplifier, so you're only talking about interference being possible at the amplifier. You'll be doing really well to generate any interference given the amplitude of the encoding signal is tiny compared to the inherent change in amplitude of an AC powersupply. You'd also have to put the powerline plug inside the amplifier, which seem unlikely at best. If you're really worried, put the amplified at the opposite end of the workshop to powerline plug.
 
https://www.ban-plt.org.uk/what.php

quoting from HERE published in 2009

The study found that there will be a low likelihood of interference with other spectrum users, providing certain technology enhancements (smart notching and power control) are implemented. The study also found that these technology enhancements are on the product roadmaps of many of the PLT device manufacturers and suppliers and are expected to feature in products from Q2 2010.

and from THIS

Our results show that users of sensitive radio systems may increasingly suffer interference from PLT devices In this study we have taken a statistical approach to quantifying the probability of interference occurring as PLT devices become more commonplace. We have concluded that if uptake increases in line with our market forecasts, there will be a high probability of interference to some existing spectrum users at both HF and VHF by 2020 if PLT device features do not change from those currently implemented.

Squirting RF energy along parallel conductor mains cable does radiate RF energy. if PLT device features do not change..... There is evidence that features have not changed as much as was necessary
 
Ok so I've located my old amp! if this is suitable can I just buy a lead that will go from my phone to say the auxilary on the amp?
Amp.jpg
 
Yep. That'll do just fine.

Presumably, your phone has a standard headphone socket? If so, then a lead similar to this will work: 3.5mm to stereo RCA These sorts of cables come in various lengths, so just choose something appropriate for your needs.

The speakers could end up sucking a fair bit of current if you're enthusiastic with the volume knob. Buy some speaker cable that's all copper so it can take the power. Avoid anything listed as CCA (copper clad aluminium). No need to go mad, just a decent quality all-copper. I'd recommend something at 1.5mm2 thickness unless you plan to run the speaker cables more than 20m to each speaker. Something like this one will do just fine. There's a pinstripe down one of the two conductors so it helps keep a track of the terminal colours you're connecting to.

Hook up to the MAIN speaker terminals. Connect Black to Black, and Red to Red, from the amp to the speakers.

Bear in mind that the speaker and amp may not have run for a while, so remove the speaker grille covers and have a look at the drivers themselves. Check the suspension ring that attaches each of the speaker cones to the outer metal ring of the speaker. You're looking for cracks or tears in the foam or rubber.

With the amp, make sure the volume is turned all the way down before switching on.

For this first outing, use it at low volumes to begin with. You're listening for any distortion in one or both of the channels. Over the course of an hour as the amp warms up, gradually increase the volume until the dial's pointer is at 10 or 11 o'clock (3 to 4 on the dial). What you're doing is gently breaking the amp in again after months or years of no use. It's the same for the speakers. In old amps, the first thing to let go will be the big output capacitors that act as power reserves. What can happen is that they dry out due to heat and age. It doesn't happen all the time. I've had amps at 30 to 40 years old that run just fine, but others at under 10 years old that had poor ventilation, so they slowly cooked to death. Banging the amp on at half volume from cold could just tip the balance to a failure, so start gentle each time and let the amp and speakers wake gradually over a 10 minute period.


If this or any other reply was helpful to you, then please do the decent thing and click the T-H-A-N-K-S button. It appears when you hover the mouse pointer near the Quote Multi-quote buttons. This is the proper way to show your thanks for the time and help someone gave you.
 
Thanks Iron Man
You are right Those speakers have not been used for about five years or so, same with the amp. I will let you Know how I get on.
 
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