The Ultimate AIO? Worklog.

Discussion in 'Modding Worklogs' started by Ratzz, Aug 8, 2018.

  1. Ratzz

    Ratzz Member

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    I need an amp. Basically, I plan to incorporate a pair of 4" car speakers (Probably these) into a cabinet, which will also contain my monitor (which has absolutely crap speakers) and the computer itself.

    I've looked at car amps, kits on ebay, shitty amps on ebay, etc but nothing really seems to fit the bill. They either all have bluetooth, which I don't want (I'll be using the computers bluetooth for headphones and the computers 3.5" output jack as a source) or are too cumbersome, too expensive, or too/not powerful enough.

    In a perfect world, I'd like something very compact, very reliable with relatively decent (think lowish end car amps) for 50 bucks or less. Maybe $100 if absolutely necessary, but under $50 would be much better :thumbup:

    2x30W RMS would be perfect, far better than the 2x2-3w usually built into monitors.

    No need for bluetooth, able to run on a 5-10A wall wart or even a computer PSU 12V rail. There will be a powerboard built into the cabinet, I plan on having basically a suitcase sized computer with a single IEC plug on the rear, no other inputs on the exterior. This means I also have no plans for a subwoofer, not that I actually want one.

    I'll be running the amp either full time (computer power on, but not necessarily with amp in use) or with a soft power-on switch, obviously preferable so that the amp only comes on when I turn the sound on for the PC, which is rarely. I mostly just use bluetooth headphones via the PC's onboard bluetooth, hence the lack of need for bluetooth.

    I would however like, and this is a want, not a need, to have a remote 3.5" headphone jack I can mount on the front of the case in case I need to use different headphones if desired.

    Of course people will suggest I just buy some powered computer speakers or a soundbar. I don't want these, I want half decent, very compact built in speakers such as the ones I linked above.

    They'll be loud enough, and in the 5L or so rear area I will have available to fit each speaker, I should have sufficient room to create a decent enclosure for each of them, providing me with sufficient bass and sound for my needs. I won't have the frontal area available for a pair of standard speakers though, due to some other stuff on the cabinet, hence the 4" speakers.

    I also do not want a subwoofer, so it is my opinion that any 2.0 computer speakers small enough to fit the space will not cut the mustard bass wise. I'm no audiophile, and they are to be computer speakers, not a home theatre.

    I don't wish the speakers to have a separate volume control. I might perhaps be persuaded to have a 'speaker on' button though, to switch the amp on and off as desired instead of full time power or 'soft on' auto switching.

    I'm sure there are heaps of kits out there which cost bugger all that can do all this. I don't have the skills to play with them. If anyone is able to find and adapt a kit to suit my needs, within my $50-100 budget, I'm all ears :)

    The nearest 'off the shelf' solution I have found is THIS ONE, but reviews are wildly varying. It would seem that the REAL output of these amps is probably about 2x25W, which is fine, but quality appears to be haphazard.

    Any ideas, or even better, anyone who can build or modify something cheaply to suit my needs?
     
    Last edited: Aug 8, 2018
  2. aXis

    aXis Member

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    It was a few years ago now but I was quite keen on the Class D amplifiers that were going around. Around 50W per channel and minimal heat generation. Could be run from switch mode power supplies OK.

    Ebay says they are still around:
    https://www.ebay.com.au/itm/Mini-TP...ier-Board-Case-2x50W-100W-AMP-AU/312186349767
    https://www.ebay.com.au/itm/SMSL-Di...-D-Amp-Heavy-Bass-50W-RCA-12V-AU/122719683904

    Or just a module without volume control:
    https://www.ebay.com.au/itm/TDA7492...Board-2-x-50W-AMP-Board-Radiator/282615269835
    AU supplier: https://www.ebay.com.au/itm/TDA7492...Board-AMP-Board-with-Radiator-AU/163141354520
     
  3. paulvk

    paulvk Member

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  4. Hater

    Hater Member

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    Wouldn't you be way better off buying a proper amp and a pair of proper speakers rather than using speakers designed for use in a car which have sound quality trade-offs due to being designed for use in a car?
     
    ruffdayz and ArmoureD like this.
  5. OP
    OP
    Ratzz

    Ratzz Member

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    I've looked at those, interested in opinions about their quality and possible downsides. The second one in particular seems interesting. Is the output quality as bad as one might think it would be due to its simplicity? Thanks :thumbup:

    I've also looked at those. Your opinion of them is high?

    Of course, but there is cost and convenience to take into account. I'm not after audiophile stuff, just something a bit better than a pair of $25 computer speakers that doesn't take a lot of space. I'd use the built in monitor speakers if they weren't utter rubbish.

    The entire computer will be within a single case, about the size of a thin suitcase, including the 27" monitor. I actually even intend including a handle :lol:

    A set of 4" speakers can sound pretty decent in a properly designed enclosure, and I have about 5 litres available to create an enclosure in behind the speaker (for each speaker) but only a 120mm square frontal area to fit the actual speaker into. I don't have room for a proper amp, nor do I really need one.. it just needs to provide a reasonably clean and reliable wattage sufficient to drive the speakers well enough. Even 2x20w RMS would probably be ample, although since the full range speakers I am looking at (reviews say they do bass reasonably well for their size) are 30w RMS that would be even better. More than that would be completely unnecessary for my purposes.

    I believe I can get a better sound from a 4" car speaker (properly enclosed) than I can with a set of $100 2.0 computer speakers that won't fit into the space the way I'd like anyway. My problem is getting a cleanish reliable amp into a smallish space elsewhere in the box.

    I'll get around to posting a render so you can see what I'm talking about.
     
    Last edited: Aug 8, 2018
  6. Hater

    Hater Member

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  7. paulvk

    paulvk Member

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    I have 3 myself also Installed two in friends restaurant one in kitchen the other powers 8 sets of speakers where the customers are, another provides music/radio in a shop , in another friends cafe one runs two speakers for music/radio. Sound quality is good (Note I have built my own amplifiers and speakers in the past) they need a 5amp or more power supply if you want to turn up the volume. I put my CDs on to mini sd card and just let it play.
    I have tested the blue tooth version with computer, tablet and phone it has rca input on back and aux plug on front , usb charge point on back with usb memory stick input on front also has infrared remote.
     
  8. grrrr

    grrrr Member

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    I dont recommend the really cheap D class amplifiers off ebay unless you can live with a 'hiss' when the volume is low or there is no input. I have bought several of these TPA3116D2 amps and can't believe how loud they get, but the hiss is real let down. If using D Class amps, I also recommend a 5A or greater PSU for the D class amp. This amplifier switches the 24V on and off really fast (PWM) and kind of uses output filters and the speaker to filter the high frequency signal back into the audible signal. Every time the PWM signal turns 'on', it tries to drive full current (for a very short amount of time). So even at low volumes, a large PSU is beneficial.

    To improve audio quality (get rid of the hiss) I then moved back to the LM1875 which is great but needs a decent heat sink to achieve 20W for any length of time. Youtube JohnAudio

    Edit - Still the last post.

    If you don't want to make your own or get a PSU etc. Consider the Jaycar Amps:
    https://www.jaycar.com.au/low-cost-mains-powered-stereo-amplifier/p/AA0472
    https://www.jaycar.com.au/2-x-15-watt-rms-portable-stereo-amplifier/p/AA0487
     
    Last edited: Aug 8, 2018
  9. mAJORD

    mAJORD Member

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    Good layout and component choice is important on these Class D's.. so probably lacking there on some of the really cheap ones.

    These are quit nice, and well priced considering it's Element14:

    http://au.element14.com/sure-electr...4Xsm0PMkmyHfiaBoCfugQAvD_BwE&gross_price=true


    This and some of the other module's listed don't have volume pot's included, you'd have to get a bit handy there.. Above one does have adjustable fixed gain though, so you can get a good 'maximum' gain level to suit the input type.
     
  10. grrrr

    grrrr Member

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    Yeah I set the amplifier gain then just vary the volume of the input.
     
  11. OP
    OP
    Ratzz

    Ratzz Member

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    Yep, I considered the Jaycar version of that too. They look good, the downside being the price of a single speaker is close to the price of a pair of the Sony ones I linked. I suspect sound would be far superior on either the one you linked or the Jaycar one, but again, without trying to be too much of a tightarse, I'd like to keep costs down as much as I can without ending up with a total piece of crap. Definitely another option to be added to the mix.

    Sounds good. I (currently) intend having a 240v power board within the box to power everything, with an IEC input adapted to it so I can remove the external cord. One cord powers all... this may change of course. The USB charge point I assume is for powering USB devices? Potentially useful.

    I assume I'd use a 3.5mm to RCA adapter to get my input from the PC? Can the bluetooth be disabled or omitted altogether? A preset gain would be fine, assuming its within an appropriate range.

    I've looked at the Jaycar ones, both of those. Although I haven't discounted them altogether, cost is a little high and they are a little larger than I would prefer. They do of course have the advantage of being ready to go, and easily returned to the Jaycar 500m from my place !!

    Some of the cheap ready made ones, such as the Boss amp I originally linked, I've noted in reviews tend to activate with a bit of a 'pop' according to some people. This wouldn't be ideal of course, which is why I am asking for peoples advice. My skills are limited, but your linked LM1875 looks like it might be within reach. I don't suppose you'd consider putting one together for me, with the better heatsink added? I've no doubt that some slightly better components could be added easily by someone with the knowhow too.. ;)

    I'd definitely not want to live with any hiss. Hard to know via ebay ads whether this is likely to happen. This is where you guys come in :)

    I wouldn't mind a simple pushbutton switch on the front of the computer to enable or disable power supply to the amp, given that I mostly use bluetooth headphones anyway. The speakers are for occasional use, so don't need the amp to work most of the time anyway. I'd just like those occasional uses to be a reasonable experience.

    Thats kinda what I want. Set and forget, use the computer to vary the input.

    On a further note, I would prefer to source my components within Australia if at all possible, although to save such a substantial amount of money, I'd be willing to import if required. Its assembly of these small boards that scares me, again, my skills are limited, but the price and size of these little amps is attractive.
     
  12. paulvk

    paulvk Member

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    The aux port on the front is 3.5mm the rca is on the back with the 1amp usb charger port, you can select the functions from the front panel buttons or the remote, my friends have been using the blue tooth to play music from their phones.
     
  13. Matthew kane

    Matthew kane Member

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    Class D or Class T icepower or gainclone inspired amplifiers will do.
     
  14. Straylight

    Straylight Member

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  15. OP
    OP
    Ratzz

    Ratzz Member

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    Checked out the JohnAudio link.. very informative. One question I do have though.. most of his testing appears to be at the max possible voltage supplies.

    I'm concerned that a 12V supply, which is all I will realistically have available without spending a lot of extra bucks, will not supply anywhere as much volume as 24V or 32V, thereby no longer providing the 30W/4Ω power stated. Have you found this to be an issue? If not, your specified combo may be the perfect solution for me. Would you think buying a version of this with included heatsink would be a better idea? The cabinet will in fact have plenty of space and airflow, it is specific depths and spacings that would be my issue rather than anything else.

    I'm a total newb at this stuff, but I am pretty confident I could actually assemble one of these kits.. nothing too difficult with the soldering etc and the boards look very easily laid out with plenty of room. I've looked at a few other versions using the LM1875 chip, some with heatsinks included which also appears to be a better idea.

    Another thing that has piqued my interest is his review of the Kinter MA-150. Although it appears that @ 12v I would only get about 2x10W, reducing my expectations and buying a lower rated, high db speaker this would work pretty well straight out of the box. Still a million times better than original speakers, but soooo simple and cheap to do. Even the speakers I would use would then be cheaper (though of course not as good.. like these https://www.jaycar.com.au/125mm-5-all-purpose-replacement-speaker/p/AS3007.. I'm thinking I may be able to squeeze a pair of these in with a minor redesign of the cabinet.

    Since I wouldn't use the USB charge function, the weakness of the cooling on that unit would not be an issue. Nor of course would be the total lack of bluetooth, not something of interest to me.
     
    Last edited: Aug 9, 2018
  16. mAJORD

    mAJORD Member

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    10 watts or so is ll you'll get from a 12v single supply on chips like LM1875 because of there topology essentially.

    also that jaycar speaker will be pretty horrible.
     
  17. Straylight

    Straylight Member

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    Well, the Bluetooth speakers I made run at 12V and produce a big sound with a very similar AMP to the one I linked. You just need to make sure that the cabinet you are putting speakers into is air-tight or the sound will be terrible. Ideally, each speaker needs its own dedicated enclosure of a large enough size to resonate properly.
     
  18. grrrr

    grrrr Member

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    The LM1875t kits are like $3 from china or $10 for 2 in Australia. Just buy one (or 2 for stereo) and see if 10W RMS is loud enough for your application. My educated guess is that it will be plenty loud enough. Lots of little blue tooth speakers are 3W, slightly bigger ones are 5 or 6W. 2 x 10WRMS is heaps for sitting in front of a computer.

    Just for testing purposes you can screw the chip into any heatsink, or length of aluminium angle you have kicking around.

    For speaker selection, the speaker needs to be able to handle the maximum power you are applying (10W or 30W or 50W etc) and then the higher the sensitivity the more 'loudness' you get per watt.
    Generally speaking, the more power a speaker can handle, the lower the sensitivity.

    Short version: You could use a speaker rated for 30W with 90db/W sensitivity or a speaker rated for 300W with 90db/W sensitivity and they would both generate the same SPL (volume or loudness) on a 10W RMS amplifier. However a xxxW (the wattage doesn't actually matter) speaker with 93db/W would be noticeably louder.

    Long version:
    https://www.lifewire.com/speaker-sensitivity-3134850

    That article also explains why john tests the amps like he does. Instead of getting exaggerated numbers as touted by the ebay sellers, or the absolute number from the chip manufacture, he tests for the maximum, 'clean' (no clipping) power the amps can put out.

    There are other factors as well in selecting speakers, like the frequency response but don't worry about that too much at this stage.

    For building your own stuff, check out Kirby meets Audio on youtube and his website here.
     
  19. grrrr

    grrrr Member

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    Oh and a few tips for soldering components onto boards

    Solder the 'lowest' components first and work up to to the tallest components.
    1. Put on all small resistors, solder those, trim the legs.
    2. Put on the 1W resistor, and the yellow ceramic capacitors, solder those, trim the legs.
    3. Put on the connectors, solder the middle leg, check that it is sitting flat and square, solder the other legs. Don't trim the connectors.

    Hold the soldering iron on the pad and the leg of the component for 2 or 3 seconds to allow it to heat up a bit before applying your solder to the joint.

    Use a solder that has a flux core (most do).

    Open a window and ensure you have plenty of ventilation.

    Heaps of youtube videos to help with soldering as well. And don't hold your soldering iron like this ;)
     
  20. grrrr

    grrrr Member

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    I feel bad for spamming... but it doesn't belong with the previous post..

    I had a search for arcade amplifiers and kiosk amplifiers and found this. I have no idea if it is any good but it seems to tick many of your requirements.
     

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