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Old 27th December 2011, 10:21 PM   #1
JoeDJ is offline JoeDJ  United States
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Default Installing a DC PS jack in Cmoy amp...

I ordered a Cmoy amp mainly to use to boost the output of my MP3 player when used with my home sys.
It's just a basic one with a single 9v battery.

However, I'm not one to leave well enought alone and if it works as expected, I was thinking about installing a DC jack for a 9v DC PS

So, if I install a "closed circuit" DC jack, would this be a good way to wire it as in my crude pic? I understand that 1&2 are shorted with no adaptor plugged in and the circuit is broken when the adaptor is plugged in disconnecting the battery. Is it OK to wire it like this with the Cmoy's V ground?

I realize that I should use a regulated PS but, is there anything else I should do? How about inserting something in line with it to prevent any voltage spikes from reaching the board?
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Last edited by JoeDJ; 27th December 2011 at 10:24 PM.
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Old 27th December 2011, 10:40 PM   #2
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Looks correct, but I always verify the jack pins with a datasheet and/or ohmmeter.
Have you considered just putting a battery snap on the ps output?
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Old 27th December 2011, 10:46 PM   #3
JoeDJ is offline JoeDJ  United States
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Quote:
Originally Posted by sofaspud View Post
Looks correct, but I always verify the jack pins with a datasheet and/or ohmmeter.
Have you considered just putting a battery snap on the ps output?
Yes, I plan on checking everything with a ohmmeter.

Do you mean install a battery snap that can plug into the PS jack?
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Old 27th December 2011, 11:11 PM   #4
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A 9V battery snap on the regulated supply that can be connected to the already-there battery snap.
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Old 27th December 2011, 11:18 PM   #5
JoeDJ is offline JoeDJ  United States
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OK ....... to be honest, if I install a DC jack, I might as well install a closed circuit one so I wont have to snap and unsnap connections.
I like the idea of just pluging in the DC PS without removing the battery.

However, it still may be an option.

Last edited by JoeDJ; 27th December 2011 at 11:30 PM.
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Old 28th December 2011, 03:52 PM   #6
JoeDJ is offline JoeDJ  United States
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The more I think about it, the more I like your suggestion of the battery snap with a staight DC jack.
For one thing, the switch on a closed circuit DC jack can be somewhat delicate and prone to malfunction. Also, battery snaps are easy to replace if needed.
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Old 4th January 2012, 02:43 AM   #7
dangus is offline dangus  Canada
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You may need to be selective when choosing the 9V adapter. Some are unregulated and will be several volts higher when lightly loaded. They'll also have plenty of ripple. I'd consider using a 3-terminal regulator and filter cap in the amp. Maybe a full-wave rectifier as well, since then you could use AC or DC wall-warts. Or just one rectifier in series; 1/2 wave rectification may be good enough, and it'll protect against reverse polarity.
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Old 4th January 2012, 03:41 AM   #8
JoeDJ is offline JoeDJ  United States
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Thanks......

I decided against using a DC PS. I thought I had a a suitable one packed away but, I don't

However, I have access to inexpensive AA batteries and 6xAA wiil be much cheaper than a single 9v and the 6xAA should last longer.
So, I ordered the jack, male plug, battery snap and a 6xAA battery box on Ebay (all from Chnia) for a grand total of about $5.
So I will be able to use a 9v or 6xAA, which ever is cheaper. The 9v batteries are usually just too expensive around here.

BTW,, the CMoy solved my problem, sounds great for the MP3s and it's getting a lot of use.

Last edited by JoeDJ; 4th January 2012 at 03:51 AM.
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Old 28th January 2012, 10:36 PM   #9
JoeDJ is offline JoeDJ  United States
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I installed the CD jack etc, including a battery snap. So, now I can use either a 9v or 6x AA batteries via a battery box.

One thing I discovered is that I had to completly insulate the female jack from the Altoids case. Is this normal with a CMoy amp due to its "V ground"?

Last edited by JoeDJ; 28th January 2012 at 10:48 PM.
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Old 29th January 2012, 02:02 AM   #10
wwenze is offline wwenze  Singapore
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Yes it's normal.
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