WTD 12v linear PSU

[Lawrence001]

I've just picked up a new dac with a wal wart power supply and fancy seeing what effect a better psu will have, has anyone got anything? It needs the standard common 12v plug with centre positive.

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[Firebottle]

Best to specify what current you need, plus the common power plug comes with 2.1 and 2.5mm centre pins, just to confuse the issue.
:)

[dennis]

I have one of these that I no longer use;
https://m.ebay.co.uk/itm/Finished-65VA-Ultra-Low-Noise-linear-Power-supply-5V-9V-12V-15V-18V-etc/221873423925?hash=item33a8afc635:g:JkYAAOSwTapV6S-S
It’s the 12v version

£60 inc postage

[lilolee]

Get one of these https://www.maplin.co.uk/p/maplin-41w-dc-fixed-voltage-bench-power-supply-xm20w on offer ATM for £15
https://i1.adis.ws/i/maplin/XM20W_1?w=365&qlt=80&img404=XM20W_set&v=1&locale=en-gb

They are internally adjustable and I have one set to 12v and another for 15v.

[Lawrence001]

"Best to specify what current you need, plus the common power plug comes with 2.1 and 2.5mm centre pins, just to confuse the issue.

[emoji4]"

I thought you could use an overspecified supply safely but not an under as the current drawn would just be what's required, is that correct? But yes I need to say the minimum current. The one it came with is 3a but I've tried a 2.1a one with good results. I'm not sure about the pin, it's the same as a supply I bought without having to add any adaptors, which I assumed meant it's the default on a generic supply.

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[Lawrence001]

I have one of these that I no longer use;
https://m.ebay.co.uk/itm/Finished-65VA-Ultra-Low-Noise-linear-Power-supply-5V-9V-12V-15V-18V-etc/221873423925?hash=item33a8afc635:g:JkYAAOSwTapV6S-S
It’s the 12v version

£60 inc postageThanks I was hoping for something a bit cheaper but it's a good fall back. Oh I should say a silver front is preferred.

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[Lawrence001]

Get one of these https://www.maplin.co.uk/p/maplin-41w-dc-fixed-voltage-bench-power-supply-xm20w on offer ATM for £15
https://i1.adis.ws/i/maplin/XM20W_1?w=365&qlt=80&img404=XM20W_set&v=1&locale=en-gb

They are internally adjustable and I have one set to 12v and another for 15v.Now that looks good, what do I.need to adjust the supply, a digital voltmeter and screwdriver? Why does it say fixed voltage in the spec?

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[lilolee]

I have the previous version which is adjustable. I would be very surprised if this wasn't. Yes screwdriver and MM is all you need.

If you are worried I'll sell you mine for £15 + P&P, which is adjusted to 12v.

[Lawrence001]

Was it marketed at 13.8 volts or whatever? Was the potentiometer external on yours?

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[Lawrence001]

This looks similar, 13.8v but walmart, those well known electronics experts, say it's suitable for 12v devices.

https://www.walmart.com/ip/Pyramid-2-5-Amp-Power-Supply/22866715


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[lilolee]

Was it marketed at 13.8 volts or whatever? Was the potentiometer external on yours?

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Yes marketed as 13.8v. Internal pot allows change of voltage. IIRC 10v to 18v

[Lawrence001]

Yes marketed as 13.8v. Internal pot allows change of voltage. IIRC 10v to 18vGreat, hopefully this is the same. I've ordered a couple from stores (last ones) will see if they actually have them

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[Lawrence001]

Forgot to ask, where do I get the cable from to connect it to the dac??

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[lilolee]

I just went through my old chargers draw and found one that fitted. Maplin sell them as well though. Make sure you get the polarity the right way around.

[Lawrence001]

I just went through my old chargers draw and found one that fitted. Maplin sell them as well though. Make sure you get the polarity the right way around.

Yes indeed! You mean you cut them off redundant chargers? Not a fan of those nasty thin cables, what's the chance of RFI etc affecting a low voltage? May be a gap in the market for these!

[Lawrence001]

Yes marketed as 13.8v. Internal pot allows change of voltage. IIRC 10v to 18vGot my first one today. I can see 2 pots (if that's what you call these flimsy things). Is yours like this? Do you know which one does what? I've got to say it's quite weighty and chunky.https://uploads.tapatalk-cdn.com/20180122/6bba39087be6489d7a79014d2e9e3dfa.jpghttps://uploads.tapatalk-cdn.com/20180122/d35fe482100f282a91ac90704d49fde5.jpg

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[lilolee]

Mine only has 1 variable resistor. I find it hard to work out but just from the number I suspect vr1 sets the input voltage before the regulating circuit and vr2 the final output voltage. BUT THIS IS GUESS WORK. I would connect a MM to the out put and vary vr2 until you get the 12v you require. BUT AGAIN THIS IS GUESS WORK.

[Lawrence001]

Thanks for that, would decreasing the input voltage also make the output voltage fall (which sounds like the wrong way to achieve it) or is the point of the regulator to stop that happening? In which case, why would the input voltage be variable?

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[lilolee]

Again this is supposition, but it can be like this to allow for voltage drop across the regulation circuit ie the voltage in needs to be higher, but within a certain tolerance, than the voltage out. Remember mains varies hence the ability to vary both input and output voltage. Try googling the transistors that are in circuit, this may lead you to a circuit diagram of their usage.

I hope somebody with better circuit knowledge will confirm/correct me if I am wrong.

[Lawrence001]

Thanks Lee I'll just experiment with small changes first to v2 then v1 and see the effect on output voltage. If my device is rated 12v, I'll probably aim for about 12.2v measured.

[Firebottle]

One of the pots is for the current limit setting, the other is for the output voltage setting.

Connect a meter to the output and turn one of the pots, if the voltage varies that is the correct one. If the voltage doesn't vary then set the pot as it was originally then adjust the other for voltage adjustment.

:)

[Lawrence001]

Thanks for that Alan, is it worth trying to tweak the current limit down a little as I am reducing the output voltage or is it best left alone?

Btw the new dac pre seems to have a very fine digital volume, I think it may be using the sabre dac's built in 256 step "bit perfect" volume control. As a result I get to fine tune my low listening level with no channel imbalance so the problem has been sorted :)

[Firebottle]

Just leave the other pot as is.

Great to hear your low level imbalance has been sorted :thumbsup:

[Lawrence001]

Got the second one today, they had run out of the 2A version and gave me a 3A one. It has a larger transformer and a big heatsink on the back with a big voltage regulator or something attached. As a result it weighs a lot more. Is this likely to be better? The problem is it buzzes very loudly, the first one is quiet. Pressing on the case makes it quite a bit quieter but not entirely. Is this easy to remedy or is it a lot of hassle, in which case I should return it. There's no chance of an exchange as they're all out across the country now.https://uploads.tapatalk-cdn.com/20180123/c7cbba4f01fc06712fba75110410dde9.jpghttps://uploads.tapatalk-cdn.com/20180123/934edb0c0a83f4940122e634d1ece696.jpghttps://uploads.tapatalk-cdn.com/20180123/33b5cf3eb9706ace0898d553e70673da.jpg

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[Firebottle]

They are made to a price and most I have come across have some buzz from the transformer, which also resonates through the case.

You can try damping the case, wedge some solid rubber between the transformer and top.

[Lawrence001]

Thanks might try that, I've also got dynamat, just worried about returning it.

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[Lawrence001]

I took the lid off again and switched on, no buzzing at all which was a good sign. Stuck dynamat all over it and screwed back on and the buzz is now very quiet so good result. I have to say the positive impact on bass tightness and level, smoothness/lack of grain in the treble, detail and soundstage is very noticeable, these chunky cheap PSUs are a total bargain.

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[lilolee]

Good result. Out of interest what is the DAC?

[Lawrence001]

Northern fidelity/Lead audio 32/394 dac. Got a good review in Hifiworld a few years ago. Have been struggling with finding a modern dac the last couple of years, finally settled on 2 I like.