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Old 19th June 2010, 12:36 AM   #1531
Salas is offline Salas  Greece
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Quote:
Originally Posted by ClaveFremen View Post
Hello,

in BOM a 2x12V 50VA transformer is indicated.

Can a 2x12V 30VA R-Core one be suitable?

Thanks in advance
Yes, suitable. Remember to connect its screen wire (if your make will have one) to the mains ground. It helps.
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Old 19th June 2010, 08:36 AM   #1532
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Yes, suitable. Remember to connect its screen wire (if your make will have one) to the mains ground. It helps.
Thanks
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Old 19th June 2010, 12:38 PM   #1533
Malka07 is offline Malka07  England
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So my ldr's arrived yesterday, and i managed to get my preamp up and running. I measured the dc-offsets...left channel=0.02mv and right channel=0.03mv so all very good there. i hooked it up to some cheap speakers and switched on, and was greeted by HUM!!! and it was quite loud, didnt change with the volume...thought i might have a ground loop, so i tried disconecting the ground wire on the preamp...and the hum disapeared...well almost...i can still hear a tiny amount of hum when i stand near the speaker, but not like it was before. I obviously dont want to keep the preamp chassis un-grounded, so was wondering if anyone had a suggestion as to what i could do??? As for the sound of the dcb1 with ldr volume...lets just say that im very happy...much more emotion in music, detail is amazing...and yet it portrays the music so calmly and with ease...never sounds like its struggling...but still early days, will give a more in depth review of my thoughts on the sound as i get more acquainted with it.

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Old 19th June 2010, 12:52 PM   #1534
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Search deeply for how the ground wires might form a circle...
I take all grounds and solder them to the ground jumper wire on the 'signal' part of the board. If you do this, then run a clip lead to chassis. If you still get hum, then run a CL60 Thermistor from chassis and IEC ground to star ground point. This should stop it, assuming there is a loop no place else.
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Old 20th June 2010, 08:10 AM   #1535
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Ok, so I am thinking at some point I will make an 'integrated' amp w/ my dc b1. But I've never had multiple transformers in a single unit before. How do would I connect the amp toroid and b1 transformer to my mains IEC? Do I need something in between or can I just wire both directly to the Line, Neutral etc on the IEC?
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Old 20th June 2010, 08:38 AM   #1536
AndrewT is offline AndrewT  Scotland
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I would fuse each transformer separately.

You may want the "control" transformer always on.
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Old 20th June 2010, 02:00 PM   #1537
udailey is offline udailey  United States
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I would take the AC lines from IEC to a terminal block. Screw the terminal block to your chassis. Then connect each transformer to the terminal block. I agree with Andrew on separate fusing. Something we might not all immediately think about but it makes a lot of sense.
Uriah
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Old 20th June 2010, 04:41 PM   #1538
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Hey Uriah,
Dunno about your electrical systems but with most of the 240 volt ones, you can only connect that green and yellow fellow to the chassis via a direct connector, screw or bolt - terminal blocks are "verboten" for the earth wire.

I'll tell you a story, and it's true, unfortunately!
I got one of those Bobcat Computer Dac things (absolute rubbish product!)from Levinson in NewYork just a few years back and it used the USB wire as the earth connection!! - it blew up 1st day (and the computer too!) and on return to the States for repair, they just totally refused to add any sort of a safety earth wire to the dac's metal case - unbelievable attitude - according to Levinson, even with a 240 volt mains supply, a direct chassis earth wire isn't required - ie. pull the USB plug outa the computer and maybe die - too bad!

A brand new (and bloody expensive) Yankie Doodle HiFi crap product and an Ozzie "super credible" sucker had to rebuild it for safe use!

How about that one, eh!!
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Old 20th June 2010, 04:47 PM   #1539
udailey is offline udailey  United States
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Hi James.
No, I meant to wire everything to the terminal block. One of those big plastic things with about 6-8 screws in it.
Then attach the terminal block (plastic) to the chassis.
Uriah
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Old 20th June 2010, 05:04 PM   #1540
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Quote:
Originally Posted by AndrewT View Post
I would fuse each transformer separately.

You may want the "control" transformer always on.
What do you mean by the 'control' transformer...
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