The Ultimate AIO Case? Worklog.

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

  1. OP
    OP
    Ratzz

    Ratzz Member

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    Thanks !! Unfortunately I just popped one of the 100uF 35V capacitors. Gotta love that magic smoke !! I'm hoping thats the only damage I've done, but hey, each component is worth bugger all so if thats all I've done its not an issue.

    I am confused by the power in connector. v-, G and v+. It would seem that I should have used v+ and G, but not paying any attention, I used v- and G (12v out from a computer PSU). Magic smoke ensued and no sound comes out. The left of the two caps as seen in the photo has bulged, and that's the general area the smoke came out so I can only hope that replacing that cap will solve the issue. To what should I connect the v- connector to though.. I assume its a remote power on signal?

    I'm over it tonight, but in the morning I'll go down to Jaycar and buy a handle of everything. One of the videos I watched regarding this kit suggested that a 220uF cap would have been more suitable, and thats certainly what it says on the circuit diagram, but he also said it shouldnt be a problem. He used the 100uF cap and the amp worked well.

    The video I've been watching is below. In his setup, he has 3 wires on the power input. A red, a white, and a blue. The red and white I am assuming are 12v and ground from the PSU? Where does the blue wire go?

     
    Last edited: Aug 27, 2018
  2. grrrr

    grrrr Member

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    You need to go back and read my post where I talk about single rail supplies (only +12V) making a virtual ground with larger capacitors and 2 extra resistors.


    Click to view full size!


    +12VDC connects to +V
    0VDC connects to -V
    Resistor to connect +V to G
    Resistor to connect -V to G
    Bigger capacitors to help maintain G.

    Please add a heat sink before you run it again.

    If you are using a computer PSU, it should have +12VDC, G, and -12VDC.
    http://www.smpspowersupply.com/connectors-pinouts.html
     
  3. OP
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    Ratzz

    Ratzz Member

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    Thanks, I'll use your instructions and parts exactly as described (sorry, I'd forgotten that post in my excitement today :lol: , I've just reread it thoroughly) and have a go tomorrow. I'll also take the opportunity to pick up that 1M resistor I was missing while I'm at Jaycar.

    Checking the pinouts, yep I could use -12v too, but I think I'll just go with your method for -6,G,+6 effect, as I'd like to just run it from a 12V molex rather than patching into the ATX pinouts.

    Getting to understand this a bit better now. One of the great advantages of low cost stuff.. if it blows up you just keep trying !!
     
  4. mAJORD

    mAJORD Member

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    I think you should just feed it a proper split rail supply . You're down to ~5w / channel now - possibly less - and possibly full of distortion as I believe 12v (or +-6v in this case) is below minimum supply voltage for that chip. resistor based rail splitting isn't all that great either. (though will 'do the job')


    either hack into your -12v on ATX , or for a noise free solution - grab an AC wall adapter (better still, find one in your pile of plugpacks - everyone has a pile of plugpacks) and wire into one of these.

    https://www.altronics.com.au/p/k5117-power-supply-kit-to-suit-k5116-amplifier/
     
  5. OP
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    Ratzz

    Ratzz Member

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    I'll look into the wall wart + power booster situation, but I might try this setup first as by all accounts it should at least work with the -12v,G,+12v arrangement. If I'm not happy with it, I can always upgrade later.

    So just to see if I've done any other damage other than the obviously popped cap in the region where the magic smoke came from, I replaced the cap with one from one of the other kits and tapped into the atx -12v for the 3rd wire. Multimeter reads +12v on the +v connector, and -11v on the -v connector. -11v? Probably just a dodgy connection or maybe the old PSU is getting a bit too old :lol: but I would have thought it was enough to get at least some sound?

    Speaker is just a 3W 2" speaker from an Edifier 2.0 set in which the controller recently shit itself, so it wouldn't need much grunt to move, but did nothing at all.. nothing to make it explode either. Input is via the speaker output on the motherboard, with ground and one of the channel wires spliced onto the other end. Same connector powers the speaker on its own, albeit at extremely low volume since its only the preamp signal.

    Not getting any heat from either the heatsink or the amp itself. In fact every component on the board is cool to touch.

    No sound at all. I'm assuming I've done more damage than just the one cap, I might assemble a whole new kit later and try again.

    [​IMG]
     
  6. mAJORD

    mAJORD Member

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    Bugger. Most probably fried the chip

    Id solder the one in from other kit and see Can buy 1875s from jaycar for price of a burger
     
  7. grrrr

    grrrr Member

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    [QUOT"mAJORD, post: 17971602, member: 16009"]I think you should just feed it a proper split rail supply . You're down to ~5w / channel now - possibly less - and possibly full of distortion as I believe 12v (or +-6v in this case) is below minimum supply voltage for that chip. resistor based rail splitting isn't all that great either. (though will 'do the job')


    either hack into your -12v on ATX , or for a noise free solution - grab an AC wall adapter (better still, find one in your pile of plugpacks - everyone has a pile of plugpacks) and wire into one of these.

    https://www.altronics.com.au/p/k5117-power-supply-kit-to-suit-k5116-amplifier/[/QUOTE]

    Whoa !
    Please check the manual on what the mid rail is used for before speculating if rail splitting is a good fit or not. Have a look at page 3, it is pretty obvious that power is drawn from +V and -V and the mid rail is only used as a reference. Page 5 confirms it. Splitting the rail is fine, you just have to keep the speaker wires isolated from the power supply. With a 12VDC supply, when no music is being played the speaker + and - terminals will be siting at 6V, and at max volume it will swing from +12Vish to 0Vish (close enough).

    The altronics kit K5117 you linked needs to be paired with a transformer that needs to be plugged into the mains. No offense intended for Ratzz, but after getting too excited and blowing up his little amp, I don't think he is ready (or licenced) to play with 240VAC like that, nor is he ready to pay over $60 for the amps power.

    You are 1/2 right about the clean power on a 12V supply. This is from Johns Testing on youtube with a 4ohm speaker:
    12VDC (+6 to -6) the amp puts out 2WRMS of clean power - and the board draws a total of 4W
    24VDC (+12 to -12) the amp puts out 11.56WRMS of clean power - and the board draws a total of 18.48W.

    Thus for a for a 24VDC wallwart: Left + right channel, 37W, a 24VDC 2A supply would be good.
    Whoa! Jaycars wall wart is not the cheapest. Consider this PSU on Ebay with click and collect, or the 24V 5A from the same vendor, and a one of these to power the RPi or OPi or whatever your run with.
     
  8. OP
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    Ratzz

    Ratzz Member

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    Thanks again guys for your continued assistance. I am not totally comfortable with Majords solution, it just adds an extra (quite expensive) board and what appears to be an expensive wall wart. I do like the look of grrr's transformer, although I note that it provides a -v and +v, clearly marked except the -v according to the wiring instructions at the bottom show that the G is actually the -v. Am I to assume that any of the COM connections will provide the G connector to the amp, giving me the required 3 wire solution?

    Also, what is the purpose of the buck converter? It appears to have either input or output, not sure which, but not both? What is RPi or OPi? Is it for powering additional 5v devices, such as USB chargers, or not required at all if I don't need those functions? I had considered adding a tablet or Pi to the wasted area under the monitor, but I've decided against that, so I won't be needing a USB power supply.

    I am certainly not comfortable with 240v generally, no offense taken, but I can at least hook up the AC wires to supply the PSU with total confidence.

    Having looked at the 'you may also be interested in' section at the bottom of the page, I found myself drawn to the PSU HERE, the 24v 17A option. At 17A, perhaps its a little overkill, but the price is still good and it seems to provide multiple +v and -v connections, with a common ground, 2 AC wire inputs, and a voltage pot. That would be nice for powering both amps? Or is that ground something to do with the AC input? I'm assuming no unless you believe otherwise. Its size, at 215L 115W and 49H is no problem.

    However, in the 'connection instructions' it offers only the 12v version, with -12v = ground and no instructions for the 3rd 'G' connection on the amp, which again I assume I would use 'com' for 'G' on the amp?

    Your opinions?

    I'm sorry for all the noob questions, but better to do it right the first time I think... :D:
     
  9. mAJORD

    mAJORD Member

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    Settle. I did say it would do the job did I not? Point is you should either just configure it exactly as per datasheet for single ended operation , or since the -12v rail is there, get the full + -12v , since as I said, 12v pp is too low .

    I had a quick look back at exactly what you proposed - where is the output capacitor as per the single supply schematic?

    you're right about the supply i linked. had a slight brainfart there, would need center tapped transformer to feed it, so scratch the idea of using a simple plugpack.. no biggie though, not sure why you're concerned with this idea of having to wire these since you went ahead and linked a psu with open screw terminals for 240v anyway?

    moving back to the idea of using the atx supply - the issue there is current capacity of -12. Some PSU's only have fractions of an AMP capacity on these.

    my final recommendations are:

    1. Commit to using these modules - and either confirm the -12v rail on your atx is sufficient, if not make a proper (but simple) dual rail power supply for it using the kit i linked, and a transformer - (a 30-40va 9+9 vac would do, as opposed to the big one suggested in the altronics link).

    yes it's oldschool, linear. but on a budget this is the best way to get good clean power.

    2. Cut your losses, and buy a class D module like those linked earlier - one of which was 2 channel in the one board, as you'll get far more output from a simple single supply +12v which you can pull off your PSU.

    Then use your LM1875 to make a nice little amp for the living room or something. maybe some DIY hifi powered speaker they are nice chips. now im sure you have the diy audio bug
     
  10. grrrr

    grrrr Member

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    RPi OPi = Raspberry Pi or Orange Pi. If you dont need 5V dont worry about it.

    I love your enthusiasm with the 17A supply, which would be great for a 3D printer, but I would like to remind you that at low loads these things are not as efficient as when they are loaded (if you are just running the amps of it, it will waste more power than you will use), and a 17A PSU will weigh significantly more than a 3A which may effect your overall portability.

    Those 24V PSUs put out 24V. The +V will be 24V and the COM or -V will be 0V.
    These connect to the amp(s) as follows:
    PSU +V to the amp +V
    PSU -V or Com to the amp -V
    Resistor from +V to G
    Resistor from -V to G


    The multiple +V terminals on the PSU are not separate supplies. They are all connected together, it just makes it easy to run multiple cables to the PSU.

    The ground connection on the PSU is still part of where you connect the incomming power. Hypothetically speaking, if you chopped an extension lead in half, there would be 3 wires, Brown for Active or L, Blue for Neutral or N, and Green Yellow for Earth or Ground.

    The PSUs have a metal case and need to be grounded.

    IT is up to you if you want to connect the -V of the PSU to Ground. There is an EU wiring standard where that is required. In an industrial control panel, it is handy to connect all the PSU -V's to ground as then you can easily measure 24V anywhere in the panel. Also if a cable gets damaged and shorts to ground then that should trip a CB or fuse...
     
    Last edited: Aug 29, 2018
  11. grrrr

    grrrr Member

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    I indirectly explained that in my post that you quoted.

    I don't want to get in a personal argument, especially when you just want to help ratzz out, but if you don't understand what the purpose of the output cap is in the single ended typical use, then how can you comment if it is a actually required or not?
     
  12. mAJORD

    mAJORD Member

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    Rather than be rude, you could have easily answered that question. even better post a simple schematic.

    I think i'm clear now though - what's thrown me, and had me asking the question, is If you're proposal is simply making a virtual ground on the existing split rail layout, and hooking the speaker up to OP -> VG , then firstly,[again], voltage divider rail splitters used like this aren't a great idea on an amp. but critically so with a 2.2K resistors. That would work fine for op-amp signal levels, that's about all. the low load impedance will be pulling the VG 'up / down' to the rails with any attempted output swing from the amp.

    and secondly, if doing it this way the single ended input arrangement - the signal ground will be tied to your -VE unless you use an isolated power supply , i would see this as a potential problem?
     
  13. OP
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    Ratzz

    Ratzz Member

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    No offence to mAJORD, but I'm finding grrr's instructions easier, and that matters to me... :lol:

    As yet untested, but here is what I now have, after making the mods recommended by grrr. I used a new kit, which was also missing a couple of resistors.. FFS, none of the 3 kits have had all of the components included as described. I replaced the missing ones, like for like, and added grrr's mods. Also made a heatsink.

    I'll be taking all 3 connections from the ATX connector (-12v,G,+12v). I'll post a video if and when it actually makes a noise :lol: but about to watch a movie right now.

    I've added a pair of 470uF 25VDC Low ESR caps (Jaycar RE3626), replacing the original 100uF caps. I've used 1.1k Ohm 0.5w resistors (Jaycar RR0573) to create bridges on the back of the board. Hopefully I've done it right?

    I'm actually pretty pleased with the neatness of my soldering, its definitely improving :thumbup:

    I took a couple of heatsinks I had lying around, and modified one to suit the setup. I'm hoping this is enough heatsink for the job? (Jaycar 8522, 11C/W)

    Some pix. Excuse poor quality of the PCB rear pic, it doesn't show as well as I'd like but hopefully is good enough to demonstrate.

    [​IMG]

    Heatsink, before and after. I had to cut the heatsink for clearance. This is the upside down view, the LM1875T chip is bolted through the original heatsink hole.

    [​IMG]

    Final assembly. Total assembly is about 45mm high including 5mm clearance under the board. Heatsink is attached with an allen keyed 6mm long M4 bolt, with NTH1 and an M4 tap through the original heatsink hole.

    [​IMG]
     
    Last edited: Aug 31, 2018
  14. OP
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    Ratzz

    Ratzz Member

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    OK so no video :(

    It works. It would be great as a headphone amp.. maybe :lol:
    Connecting it to the little 3W speaker you saw a couple posts back, it is barely audible at 50% volume. Push it up to 60% and the heatsink is pretty hot, I wouldn't actually be game to touch the amp cause I hate blisters. Go to 70% and the PSU trips out....

    I'll have to go back through and check my soldering I suppose.. unless you guys can see something obvious I've done wrong?
     
  15. mAJORD

    mAJORD Member

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    Try cleaning up the solder, make sure it's not bridging through the solder mask (which is the coloured insulating laqure on the board) - i can see you've got some dags going across from ground to one of your + or- power rails there -only the layer of mask is stopping that from shorting (bottom left - big joint)

    It may also be oscillating - this will cause overheating with no apparent audio output. This the electrical equivilent of , say a bridge developing an uncontrolled From memory these things are prone to it - check the datasheet for tips - capacitor across input, keeping gain high enough. does the kit specifiy what gain the amp is 'as constructed' ? determined by feedback resistor values) . I'd make sure everything else was spot on first before assuming this is the cause

    Power cutting out - as I said before, check your -12v rating . I have several PSU's sitting next to me that say between 0.3 and 0.5amps - that's not enough , particuarly it has OCP

    PS no offense taken, i was just smashing out my suggestions during work break, as opposed to giving any step by step instructions :p
    PPS, the mods grrr has suggested are for operating in single rail operation - since you've installed them, for now you could try hooking it up single rail to elliminate the issues with the -12v on your psu : to quote him:

    PSU +V to the amp +V
    PSU Com to the amp -V

    G not connected
     
  16. grrrr

    grrrr Member

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    Is the 3W speaker 8 ohms or 4 ohms?
    What did you use as an audio source?
    What were you using as a power supply?
    I'm using much bigger heatsinks.

    I was surprised you said it wasn't very loud so I did some tests this morning using:
    1. my phone as the audio source
    2. a 4 ohm 6x9 speaker mounted in a carboard box for testing. The speaker is rated for 500W in big text and small text it says 70WRMS . JVC CS DR693
    3. 12VDC 6A power brick, intended for powering led strip lighting, it is pretty light, I doubt it would maintain 6A for very long.
    4. 24VDC 6A PSU.

    I found the 12VDC supply was not too bad, but definitely not crazy loud for a single speaker and for computer use and thought it would be pretty close to OK with 2 speakers.
    I tried the 24VDC supply and found it was louder but not much.
    I tried the 24VDC supply on new and 'unmodified' D class amp and it was louder again than the LM1875 but not crazy loud. This one hiss'es as well.

    The D class not being crazy loud set off little alarm bells because the last time I tested that D class amp on 24VDC it was 'neighbours will call the cops' loud...

    So I changed from using the phone as the audio source to using the google home mini and tried the LM1875 board powered by 24VDC, it was proper loud, and I didn't turn it up to max volume.
    And finally I tried the 12VDC supply on the LM1875 with the goolge home mini as the audio source and at 90%ish volume it was plenty loud in the next room and much too loud in the computer room.

    I don't have an oscilloscope at home to see what the mobile phone is putting out compared to the google home mini.

    I took some videos of my little tests using my cheap action cam but the mic / playback audio is dreadful. We normally just use the cam on the boat and don't care about audio cos all you can hear is V8. I haven't bothered uploading the vids but if you are keen then I can.
     
  17. grrrr

    grrrr Member

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    Being single channel amplifiers, how are you hooking up your audio source?
    For today's test I just cut a 3.5mm stereo cable and connected the tip (red) and ground. ... And was going to upload a pic but ocau pix is having issues...
     
  18. OP
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    Ratzz

    Ratzz Member

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    Audio source was the PC.. old 3.5mm jack with one end of the cable hacked up (soldered and heatshrinked) to provide ground + right channel.

    Speaker, not sure. No useful labelling, just some chinese script on the base of the magnet. Came from a non functioning pair of cheap Edifier 2.0 speakers. Lots of specs on the bottom of THIS PAGE.. turns out they are 2W, not 3, but no mention of Ohms. Gotta laugh at the frequency range of 30-20000 Hz :lol:

    Power came from a 650W Silverstone Gold PSU, -12v, G, +12v, all from the ATX header. Had it for years, its an oldie but a goody. Still works fine on computers. Multimeter gave the right readings on the terminal block on the board.

    Maybe I'll try buying a proper 3.5 to dual cables, see if that helps. I wasn't sure about the heatsink, but I had them lying around, thought I'd give it a go. I'm now considering chopping a stock Intel heatsink in half to make a big half flower instead. Or maybe even not chopping it and using the fan too :lol:


    Sorry you posted this while I was typing. Yep, that's exactly how I made my cable, source is PC speaker out.

    [​IMG]
     
    Last edited: Sep 1, 2018
  19. OP
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    Ratzz

    Ratzz Member

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    So I'll continue play with those amps later. Maybe learn a thing or too and hone my electronic skills :lol:

    In the meantime, I've given up on them. I bought one of these Accento Dynamica ADA30 class D amps. $74.90 posted.

    Only 15Wx2 RMS, but that's all I need. Compact, 2 sets of speaker wire clamps, 3.5 input, and a wall wart, assembled and ready to go.
     
    Last edited: Sep 2, 2018
  20. OP
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    Ratzz

    Ratzz Member

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    I was down at Supercheap earlier.. one of the advantages of a place like that is that you can compare various speakers all connected to the same HU, at the same settings of course, whereas the Jaycar speakers, all I can do is go by specs and hearsay..

    I listened to various speakers at Supercheap, and the ones I liked the most were actually 5.25", without going the whole hog and getting 6.5" speakers which are definitely too big, and expensive, for my purposes. They were noticeably louder and had better bass (being slightly larger of course). The display said the SPL was 90db which isn't too shabby either. Given I'll only be giving them 15Wx2 RMS, I figure a high SPL would be desirable. So I bought them ($45). I'll have to redesign the damn case now to suit the bigger speakers.

    I'm still going to go with 3L enclosures, but the case is going to have to be a smidgeon taller to accommodate the bigger speakers. I'm going to make the actual enclosures separately from 16mm MDF and incorporate them into the case, which will only be constructed of 7mm heavy duty construction ply.

    Now I get home and find a link for them and it seems the SPL is actually only 88db. Oh well, pretty decent anyway. They were running from a basic HU which would be lucky to have 20W RMS per channel at Supercheap, and had more than enough volume for my purposes, and pretty decent bass considering the crappy multispeaker enclosure those speaker displays use. I think they'll run well on the amp I've chosen above, in proper enclosures.

    So, the amp is bought, as above. Hoping it works well. The speakers are JVC CS-DR520's, which are larger than the original plan but shit all over the 4" speakers in the Supercheap display, including some that were much more expensive. It will be interesting to discover the result.
     
    Last edited: Sep 2, 2018

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