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> Regulated Power Supply, Adapter., 12V DC, no hum

santik
post Oct 20 2010, 01:50 PM


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Does anyone knows where to get a 12V DC regulated power supply that will have no AC hum? It is to be used on an headamp...

and how much does it costs? anyone has it here?

Thanks... smile.gif
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jazzy939
post Oct 20 2010, 01:56 PM


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There are of course commercial units, the better ones going to cost a lot of $$$ on your part. Other than Jalan Pasar, KL, I can't think of anywhere else.
If you are good, there are power supply kits available. With a good transformer and casing, it can be built cheaper with better parts, equal or better performance with equivalent commercial units.
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LittleGhost
post Oct 20 2010, 03:55 PM


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Hum is usually EMI induced. Make sure transformer is well shielded.
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santik
post Oct 20 2010, 11:41 PM


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but does anyone sells it here?
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LittleGhost
post Oct 21 2010, 12:27 AM


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just go to a shop
and ask for a linear regulated 12VDC adaptor.

Teletron Malaysia makes decent wallwarts, been using them for my designs since long ago.


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jazzy939
post Oct 21 2010, 10:06 AM


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Take a look here under AC-DC Regulated.

http://www.teletron.com.my/products/adapters/adapters_1.html


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bsl555
post Oct 21 2010, 10:25 AM


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Seen Teletron stuff for so long, which I feel this company really need to revamp their quality and looks. Its not really cheap but they should at least improve to a more upmarket look. It still feels like some backyard cottage industry product. Sad!.
A good PSU would be based on low noise LM317/LM337 DC regulation and neccessary AC filtering on the primary side. I think I saw some DIY kits on this on Ebay. I was thinking of building one for my phono stage.
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jazzy939
post Oct 21 2010, 10:55 AM


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Now that you've mentioned it, yeah their products certainly looks the same since I frequent Jalan Pasar when I was still a school boy! laugh.gif

Yes good power supply starts with a good AC filtering.. any hint/clue with regards to ebay kits?

Something like this?

http://cgi.ebay.com/DIY-LM317-Variable-DC-...=item27b273616c

http://cgi.ebay.com/DC-Power-Supply-0-30V-...=item4aa55c2a82



This post has been edited by jazzy939: Oct 21 2010, 11:01 AM
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santik
post Oct 21 2010, 10:30 PM


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ok, you guys suggest to get a AC-DC Teletron, Linear Regulator...

so, how is it? good enough? got hum?

price range? wanna get around 12V-12.5V 1A-1.5A...
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jazzy939
post Oct 22 2010, 06:54 AM


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You go and survey lah what they have on the shelves.. Little Ghost use them, so I guess they're 'good enough'. I don't as I build all my PSUs.
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LittleGhost
post Oct 22 2010, 09:08 AM


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QUOTE(santik @ Oct 21 2010, 10:30 PM)
ok, you guys suggest to get a AC-DC Teletron, Linear Regulator...

so, how is it? good enough? got hum?

price range? wanna get around 12V-12.5V  1A-1.5A...
*
as i've previously said, HUM is usually caused by unshielded transformer. It has very little to do with the next stage regulation.
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santik
post Oct 22 2010, 09:49 PM


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so, it's about the transformer... ok... so, what can I do about it?
how to shield it?

I got myself EKK brand regulated 12V AC-DC adapter... it has some faint hum... what can I go around it?
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jazzy939
post Oct 22 2010, 09:50 PM


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Little Ghost, its your call! tongue.gif
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LittleGhost
post Oct 22 2010, 10:38 PM


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QUOTE(santik @ Oct 22 2010, 09:49 PM)
so, it's about the transformer... ok... so, what can I do about it?
how to shield it?

I got myself EKK brand regulated 12V AC-DC adapter... it has some faint hum... what can I go around it?
*
try separating both the devices as far as possible, see if the problem goes away.



What is the headamp used?
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santik
post Oct 22 2010, 10:47 PM


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it's Audio Technica M35.

separate both devices? you mean the amp and the headphones?

I got it from Maplin. Normally i get my stuff from nixie but they can't find it... I went to the shop beside Nixie... they don't have it and don't really understand what is it... they showed me a 12VDC switching power supply...


Added on October 22, 2010, 11:04 pmoh yeah, there is not ground on the adapter... only a plastic ground pin for ease of plugging in... live and neutral is metal only...


Added on October 22, 2010, 11:20 pmis not really a hum... but somewhat hissing... 'ssssssss' very faintly...

This post has been edited by santik: Oct 22 2010, 11:20 PM
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LittleGhost
post Oct 22 2010, 11:27 PM


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If it's not a hum, then it's not a transformer induced noise.


You mentioned "SWITCHING" PSU. These type of PSUs only do well in terms of efficiency and they are not meant for low noise applications. They are noisy.

You need a "LINEAR" regulated PSU.

You also need to double check which type of PSU you're using, I suspect the one you're having is either NON-regulated or SWITCHING PSU.


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santik
post Oct 23 2010, 01:01 AM


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the one I am using is regulated PSU.
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chchyong89
post Oct 23 2010, 02:25 AM


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QUOTE(santik @ Oct 23 2010, 01:01 AM)
the one I am using is regulated PSU.
*
1. Both channel hissing?

2. Try open up the casing, check if
the signal wires and signal ground wires was separate
too far? if yes, twist both the wires together will solved it.
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santik
post Oct 23 2010, 04:07 AM


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ok, but cable tying method can be done now... cables too short... but anyway... I have done tying on signal cable...

I have connected a 680uf 16V capacitor to the power. + to +, - to - ... but I wonder is that good enough... capacity enough?

hissing gone... but there is still very very faint hissing... so, now I think using capacitors to smooth it out... higher capacitance? put in series? how?
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LittleGhost
post Oct 23 2010, 08:58 AM


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QUOTE(santik @ Oct 23 2010, 01:01 AM)
the one I am using is regulated PSU.
*
re-read my previous reply again.

There are in general two types of regulation, one is noisy, another is not.

I'm fairly sure you've bought the wrong adapter.


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jazzy939
post Oct 23 2010, 09:48 AM


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Show us some pix of the said regulator.
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santik
post Oct 23 2010, 09:44 PM


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from what I see and remember now... it is using isolated transformer...

pics will come later...
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jazzy939
post Oct 23 2010, 09:49 PM


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Isolated transformer? Oh really? hmm.gif
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santik
post Oct 23 2010, 09:59 PM


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from the symbols la...

but anyway... I put capacitor at the power and it cleaned most of it... but there is still a little bit more, hissing... but very very faint... you need to listen to it carefully... so I believe capacitors does help...

is not hum ah... is hissing...
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jazzy939
post Oct 23 2010, 10:05 PM


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I'd say hissing normally does not come from PSU, its more related to your head amp circuits.. could be related to your impedance mismatched..

This post has been edited by jazzy939: Oct 23 2010, 10:08 PM
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santik
post Oct 23 2010, 10:08 PM


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headamp?

previously... I was using lantern batteries... 6+6...
it is so clean... that there is no hissing at all.

I wanted to use adapter cos battery died in 2 days of 4-5 hours listening per day... =P
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jazzy939
post Oct 23 2010, 10:11 PM


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Here's a good read I picked up:

Some headphones have limited frequency which can limit the amount of hiss you can hear. Few common causes of the hiss/pops are
1) Unregulatered/unfiltered/noisy power to CD player/DAC/amp,
2) unmatched impedance of headphone and inadequate amp (amp can't handle low impedance cans),
3) picking up interference/noise from unshielded or inadequately shiedded interconnect/power cable/headphone cable, just to name a few.

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santik
post Oct 23 2010, 10:34 PM


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here are the pics of the PSU...

Attached Image
the Adapter label


Attached Image
embossed 'indoor use only' and 'L, N, E'




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jazzy939
post Oct 23 2010, 10:45 PM


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It certainly says 'regulated'!
Thanks for the pics.
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santik
post Oct 23 2010, 10:49 PM


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yeah loh... don't know why got that hiss also... maybe my house have bad grounding... or there's short around...

will try at other places and see...
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jazzy939
post Oct 23 2010, 11:25 PM


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IF you tried with batteries and there were no hiss, I guess it must be the EKK PSU then.. sad.gif
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overclockalbert
post Oct 24 2010, 05:14 AM


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get a better power supply will sure help
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santik
post Oct 24 2010, 12:06 PM


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any brand or type to recommend?
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wui223
post Oct 24 2010, 12:15 PM


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hack the adaptor , mod the circuit inside for a real regulated supply
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santik
post Oct 24 2010, 12:25 PM


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real regulated power supply?
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jazzy939
post Oct 24 2010, 12:27 PM


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The ABS plastic will be hard to hack open..
You need a hacksaw and cut around it.. put it in a good metal casing for proper grounding and 'improve' the regulating circuit.. Not that I have not done it before.. wink.gif
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wui223
post Oct 24 2010, 12:38 PM


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QUOTE(jazzy939 @ Oct 24 2010, 12:27 PM)
The ABS plastic will be hard to hack open..
You need a hacksaw and cut around it.. put it in a good metal casing for proper grounding and 'improve' the regulating circuit.. Not that I have not done it before.. wink.gif
*
Exactly the same thing i did smile.gif but i didn't use hacksaw, use even crude (stupid) way to hack up.
These adaptor if can get dirt cheap at junk store, it serves good as cheap transformer, everyone know how expensive it is now sad.gif
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jazzy939
post Oct 24 2010, 12:44 PM


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How true.. sad.gif
But I am curious on the EKK's regulator part of the circuit..
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wui223
post Oct 24 2010, 12:50 PM


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My guess is 78xx the most they can give.
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santik
post Oct 24 2010, 01:04 PM


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if I open it... what can I do to it?
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jazzy939
post Oct 24 2010, 01:08 PM


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See if there is a possibility to improve the regulating circuit?
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santik
post Oct 24 2010, 01:26 PM


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well, I don't think I need a saw or anything... after many hours of usage... its casing is loose dy... the glue is not heat resistant...

see how...
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jazzy939
post Oct 24 2010, 01:42 PM


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Lets see it! wink.gif
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santik
post Oct 24 2010, 01:47 PM


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well, the hissing will be gone totally after 3 hours of usage... probably absorbed by the power capacitor...

for now... It is just one 680uf 16V... I might add it in parallel to 680ufx2, 1360uf and see how... I hope it will be better...

we see how... =>


____
I also noticed the mica in the tube has moved... probably due to vibration in my bag while I moving... haiz...
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wui223
post Oct 24 2010, 01:48 PM


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maybe changed to high voltage caps. nowadays those caps get at jln pasar mostly under rating.
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jazzy939
post Oct 24 2010, 01:49 PM


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Thats good to know! thumbup.gif

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santik
post Oct 24 2010, 01:54 PM


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the amp is using Panasonic FM caps...

the power cap is using a Nicichon cap.

will try...
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wui223
post Oct 24 2010, 02:03 PM


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the brand is good. just that whether the caps is genuine or not.
report ur result here smile.gif
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santik
post Oct 25 2010, 04:15 PM


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QUOTE(wui223 @ Oct 24 2010, 01:48 PM)
maybe changed to high voltage caps. nowadays those caps get at jln pasar mostly under rating.
*
ok... but my supply voltage is 12VDC... 16V capacitor should be good enough, isn't it?
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jazzy939
post Oct 25 2010, 04:37 PM


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Anything more than the working voltage, in this case 12VDC is ok. So 16V, 25V are useable.

QUOTE(santik @ Oct 25 2010, 04:15 PM)
ok... but my supply voltage is 12VDC... 16V capacitor should be good enough, isn't it?
*
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LittleGhost
post Oct 25 2010, 08:15 PM


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What's the headphone amp?

I'm more inclined to believe that it's the amp circuit's problem rather than the PSU's problem at this point.


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santik
post Oct 26 2010, 11:59 AM


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I have made the amp myself, with battery it's clean!
with PSU some hissing... but added a 680uf 16V as power cap and it's clean dy... just some more very minor hissing which is not a big problem... I am wondering on how to remove that remaining hissing..

add another one in parallel?
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jazzy939
post Oct 26 2010, 01:03 PM


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Yup. See if that would helps.
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santik
post Oct 26 2010, 01:34 PM


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ok. will try add it =>
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