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transformer-related questions

post #1 of 8
7/28/11 at 3:51pm
Thread Starter 

I just picked up a  24v 450ma transformer from radioshack to use with a cheap desktop cmoy.  

the schematic i'm going off of http://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf

1.  I have a wire with ground to the wall jack(three prong) would this make anything easier or change anything for the better in the cmoy's circuit or should i just leave the ground connection alone?

2.  The transformer has two yellow (12v?) wires and one black wire.  As far as positive/negative goes which are which. The schematic calls for one positive, one negative; will i have to do anything to get this?

3.  Will changing input voltages affect output volumes?  I have a mono 100k potentiometer so i am hoping i can change the output volume by have the input of the transformer run through a potentiometer before getting to the proto-board thus adjusting the input voltage to the chip (reducing the volume?).  

            3a.  If i do run it through the pot should i run one of the 12v through and it meet the other 12v for a constant 12 + (whatever i have the pot set to) or both of the lines for a 0-24v volt             connection? 

 

Sorry for the laundry list of dumb questions, just wanted to make sure that i was doing everything right.

Thanks in advance.

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post #2 of 8
7/28/11 at 6:09pm

I think you need an ac adapter. Transformers usually output AC rather than DC.

You could build a TREAD(see tangetsoft, oops sorry tangentsoft doesn't seem to have a page for their TREAD design anymore) to accompany your Transformer.

 

Remember you'll need a regulated dc power supply.

 

 

WARNING do not connect your transformer to the cmoy. You will fry it.


Edited by Nagasaki_Kid - 7/28/11 at 6:47pm
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post #3 of 8
7/28/11 at 6:46pm
Thread Starter 

Oh wow thanks, i kinda thought the main point of a transformer was to "transform" AC to DC.  Well now some things make more sense...

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post #4 of 8
7/28/11 at 7:28pm
Thread Starter 

Hmmm it seems TREAD's page is broken.  Know of any other ways to see it, steps to make it or schematics?

Also i ran yellow to black with a rectifier in between and im getting 6v on my multimeter and when i run yellow to yellow i get 12v.  The transformer is rated for 2 12 volt rails.  Sorry for my lack of knowledge but could you tell me where my rectifiers should go and where im getting the 12v from?

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post #5 of 8
7/28/11 at 7:34pm

http://tangentsoft.net/audio/opamp-ps.html

 

this might help

 

 

I think you can buy a power supply regulator kit on ebay

 

somthing like this which kinda looks almost exactly like Tangetsoft's TREAD(from memory)

 

They also have it preassembled

 http://cgi.ebay.com/1-5-27V-DC-Adjustable-Voltage-Regulator-Module-LM317-/200615222080?pt=LH_DefaultDomain_0&hash=item2eb5995b40

 

The board accepts either ac or dc input and outputs a regulated dc.

 

A rectifier alone would leave it still unregulared

 

 


Edited by Nagasaki_Kid - 7/28/11 at 7:58pm
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post #6 of 8
7/28/11 at 8:27pm
Thread Starter 

Wow thanks for that looks like i have to order a few more parts then i thought.  

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post #7 of 8
7/28/11 at 8:45pm

if you already have a rectifier you might be able to get away with something cheaper after patching the transformer throught the rectifier

 

 

 

 

 

http://cgi.ebay.com/LM317-DC-5-24V-Out-2-5-12V-Volt-Regulator-Converter-/350480050084?pt=LH_DefaultDomain_0&hash=item519a3d27a4#ht_3669wt_957

 

might want to add a diy heatsink if you have one lying around but might not be nessary since the cmoy doesn't draw that much


Edited by Nagasaki_Kid - 7/28/11 at 8:48pm
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post #8 of 8
7/28/11 at 8:52pm
Thread Starter 

Do you think a 2500uf cap will smooth enough to be suitable for the amp? Should i add a resistor at the end to lessen the draw on the cap giving the cap more time to charge?

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