Isaac_Blanc

Advise needed on compact HiFi componentary for school project

34 posts in this topic

Hello!

About me:

Before I start, may I just explain that my understanding of audio technology is pretty limited. I’ve taught myself the basics but, as this is for a one-off project rather than the beginnings of a hobby, I don’t know much more.

About my project:

For my school resistant-materials project, I’ve decided to build an iPod dock. It will need to amplify and play music. Rather than rely on battery power, it will plug into the wall and the audio input will be a 3.5mm jack. The exterior dimensions will be 400mm x 200mm x 200mm whilst the interior dimensions of the speaker enclosure (a simple non-ported design) will be 350mm x 150mm x 120mm. These dimensions are however not final – I can change my designs if need be. The whole product will be made from Baltic Birch Plywood. The final product needn’t be incredibly loud but I would like the sound quality to be quite good. I have a budget of £100 for audio componentry.

Question:

What audio componentry would you recommend I use in this project? As I understand it, I need the following:

A compact amplifier that will accept a 3.5mm audio jack as an input

A pair of full range 4” coaxial drivers

OR:

A compact amplifier that will accept a 3.5mm audio jack as an input

A compact crossover

A pair of 4” woofers

A pair of 1” tweeters

Are these the components I’ll need? If so then what specific parts would you recommend? Any other advice on the project would be greatly appreciated!

Thank you all in advance,

Isaac :-)

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Hello Isaac, welcome to the forum and good luck with your project. That's an ambitious cost target but I can recommend these speakers http://www.ebay.co.uk/itm/2pcs-HiEND-4inch-full-range-speaker-defy-lowther-fostex-new-NEO-version-/221391579717 after using them in a Frugal Horn Mk3 design - full range but not coaxial.

For the amp I would try a gainclone module or kit like this http://www.ebay.co.uk/itm/251603657715?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT. If you don't want to solder then there are soldered modules available like this one http://www.ebay.co.uk/itm/LM3886TF-Amplifier-AMP-Power-Supply-Rectifier-Filter-Completed-AUDIO-Board-Kit-/271041487070?hash=item3f1b54e0de. The latter has the advantage of including a power supply rectifier so you just need to add a transformer. If you're going to do this then please read this about mains safety http://www.decdun.me.uk/gainclone_psu.html. In fact, read it anyway. That site is a mine of information.

An alternative would be a 'chip amp' like this http://www.ebay.co.uk/itm/Dual-TDA7294-Channel-Amplifier-Board-with-Speaker-Protection/371161594989?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D32694%26meid%3D6691f38cf6a646f888dd3edb2ee140bc%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D251603657715. For either of these types of amp modules you could simply use a SMPS supply like these http://www.ebay.co.uk/itm/UK-Stock-DC-12-24V-Universal-Regulated-Switching-Power-Supply-for-LED-Strip-CCTV/151123354933?_trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D33433%26meid%3D668b61eef23d48a7acee8e75153fd7bc%26pid%3D100033%26rk%3D2%26rkt%3D4%26mehot%3Dpp%26sd%3D221391579717 or a laptop supply - the voltage will depend on what amp module you choose. I haven't made or heard either of the suggestions above, it should just give you an idea of what to look for.

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Don't forget that second-hand stuff can be a good deal cheaper than new or, to put it another way, your pounds may well buy you better kit if you can live with second-hand. You do need to be reasonably confident of its reliability of course. And you may have more choice if you look at amps with two phono inputs. A lead like this http://www.maplin.co.uk/p/35mm-twin-phono-to-stereo-jack-cable-15m-l32ba will let you connect them to anything with a 3.5mm output socket.

Best of luck :^.

VB

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That's an ambitious cost target

Thank you very much Steve for both the extensive advise and kind words on my project. Before I talk about your suggestions, may I just ask how much budget you would consider less ambitious? Would £200 be a more reasonable amount to spend on a project like this? This isn't to say I can increase my budget, I'm just interested :-)

Right, your suggestions:

The drivers seem great! I can't say I love the look of them but, superficial things like aesthetics aside, their specs are more than good enough for me. Considering that they're 4" full-range drivers costing less the £50, I think a frequency response that goes as low as 65Hz is also wonderful. They look fairly well built, very easy to mount and wire. All in all - one happy guy over here. Thank you very much for finding these!

May I ask what amp you used with those drivers when you put them in your Frugal Horn design? That way, I can make sure to buy an amp with similar specs so as not to damage to the drivers.

All three amp suggestions are definitely possibilities. I am fairly good at soldering in that I'm very neat and my welds are always well-sized. Therefore, I'm confident that I could solder an amp if I needed to. That said, in the interest of leaving plenty of time to perfect the wood-working aspects of my project I might opt for the pre-soldered one instead. Thank you for the link about building PSUs. Whether I use that info or not, I've found reading it very interesting and quite enjoyable. Again, I think I could probably build a PCU, but in the interest of time-management I reckon I'll buy the chip amp.

My one question then is, is there much difference in sound quality between a chip amp and a gainclone amp? You did say that you've never made any of the suggestions you gave me so its fine if you don't know :-)

Thank you very very much for your help. I've probably learned more from you than from a few days' research!

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Don't forget that second-hand stuff can be a good deal cheaper than new

Thanks for the advice Graeme! Please correct me if I'm wrong, but won't vintage componentry be a lot larger and less compact than modern equivalents? My worry here is that I have to fit everything inside of my product. :-)

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One other question: would it be worth lining my enclosure with convoluted foam?

If so then what foam would you recommend?

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Thanks for the advice Graeme! Please correct me if I'm wrong, but won't vintage componentry be a lot larger and less compact than modern equivalents? My worry here is that I have to fit everything inside of my product. :-)

Vintage stuff might well be. But you can buy second-hand stuff which is only a year or two old but whose owners have either got bored with it or have upgraded to something more expensive. It could even be a decade or more old and not significantly bigger than current products.

VB

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Actually, I rather suspect, if this is a school project for a resistant materials course, the actual result is less important than the learning you achieve from the undertaking the project. So one of your learning outcomes might be that with a larger budget, better components and in particular, better speakers might deliver a better and more 'pleasing' sound.

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Hello Isaac, apologies, I've been a bit busy lately. The budget should be fine, it seemed tight because of the speakers which will always cost a fair bit more than amp modules at this level. With fairly decent speakers for the job (like those 4 inchers are) then I think upping the budget on the amp modules will reveal little extra benefit.

I've made a gainclone but it was from a 'boutique' kit (audiosector). I haven't made one of those chip amps although I have a module and a SMPS that I will put in an old valve radio with a raspberry pi to turn it into a streamer/internet radio. I've not got round to it yet.

A lot of people call gainclones chip amps, they're distinguished by the fact that they mimic to a greater or lesser extent the design layout of the Gaincard amp by 47 Laboratory - check that out, it's an interesting story and 47 Labs is an interesting company.

Have a look at ebay for amp modules, I'm afraid I can't personally recommend one but diyaudio.com is a good place to research some of them - people give their feed back on what they've bough and built. As it's a school project, look for ready made (and tested) modules and hook one up to a SMPS. One comment on your project is that a 'dock' would normally have the ipod sitting in it. Using the audio out is fine but when I briefly looked at a few amp modules quite a few seemed to have bluetooth receivers as part of the package.

If you have an iphone then you could play it through your amp and speakers whilst holding it, it seems a lot easier. If you're buying anything on ebay then try to research the particular unit in the sellers feedback - particularly to make sure that it will work - with bulk sellers set the page to review 250 items, hit <Ctrl F> and search for your item. I've received things (very rarely) from the far east on ebay that didn't work and the sellers have always refunded the cost because they don't want bad feedback - and you have a statutory right to cancel the transaction under the Distance Selling Regulations. The Paypal dispute procedure should help you out.

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Check this thread out for some inspiration http://www.hifiwigwam.com/showthread.php?122116-Roberts-raspberry-pi

Quite a few people seem to be 'upcycling' old kit in interesting ways so just think of your project box as an old radio chassis!

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No worries about the delay in communications!

Thanks for your explanation about budget - definitely good to hear.

Interesting to finally understand the name gainclone - I'd been wondering how those DIY amps earned such an odd name.

A few updates on my project:

I've decided to use these drivers instead. As I understand it, they're exactly the same as the ones you suggested, only a different colour (one that I much prefer). They have a "rated input" (I'm assuming that means RMS) of 10W and an impedance of 4 Ohms. As I understand it, I therefore need an amp that can provide a 15W, 4 Ohm output on both channels. As you suggested, I've had a look on eBay and diyaudio.com and found this. Whilst it may be more expensive than other amp options (ie: this), I really value its simplicity (all it needs is an ICE C14 plug). If need be, I can even remove the circuitry from the metal case and re-house the amp directly inside of my product. You may consider me buying this amp lazy, however, my final piece will be marked on quality of carpentry, not electronics and I urgently need to finalize my designs and start construction. I believe I'll be able to connect my iPod via a 3.5mm jack to phono cable like this. I agree that bluetooth or even an iPod dock would be lovely but I'm doubtful about having the time to include it into my design!

If you could run your eyes over the drivers and amp that I've chosen just to check that nothing jumps out at you as obviously wrong (ie: I've accidentally mismatched the two components and therefore they will explode), then I would be very grateful.

Thank you once again for your help :-)

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I loved that man's retro-speaker rasberry pi project by the way; impressively crafty and very authentic looking. :-)

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Yes, that all looks good :^ Tripath amps are highly regarded, have a look a this where it all started http://www.6moons.com/audioreviews/sonicimpact/t.html another interesting story!

I bought drivers from that fella and they arrived quickly. Don't worry too much about amp/speaker specifications - the speakers will only 'draw' the power they need, my similar drivers sounded best with a 100 watt per channel amp. Remember that power is pulled by the speakers not pushed out to them so you can't go wrong.

If you need or want to keep that amp intact then check out one of these http://www.hificollective.co.uk/potentiometer/extension_kit.html it will help you move the volume to the front and keep your RCA input sockets at the back. A picture when you're finished would be great.

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Yes, that all looks good

Thanks for the confirmation - very welcome news indeed! I'll order the parts ASAP.

I might include that snippet of HiFi history in my coursework. Perhaps the examiner would find it impressive or at least interesting to learn about the origin of my tripath amp.

That knob extender thingy (well that sounds a tad euphemistic) looks really really useful. I'll order one along with the drivers and amp.

So, that's me pretty much done. Componentry compared and decisions made. All I can say now is thank you very very much for all your help. It'll be quite a while before the product is finally finished but I'll be sure to send you some pictures when it is. In the meantime, feel free to have a look at this computer rendering of my design. Whilst the render quality is really nothing special and I have made a few alterations to my design since exporting this image, it does illustrate the main concept of the design fairly well.

Pill.jpg

Thank you once again!

Isaac :-)

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