Need Dan Alexander Class A Dual Channel Mic Preamp Schematic

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fnps90
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Need Dan Alexander Class A Dual Channel Mic Preamp Schematic

Post by fnps90 » Fri Sep 27, 2013 11:29 am

Hi,

I just bought a Dan Alexander Class A Dual Channel Mic Preamp and the Phantom Power is not working on the unit. I need a Schematic for it to get it fixed. Here is a Picture of the unit. If anyone has one, I would really appreciate it.

Image

Thanks!
Steve

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Post by digitaldrummer » Fri Sep 27, 2013 3:01 pm

not sure what the power supply looks like on that unit, but here's a picture on the DAA site showing an external power supply that might help...

http://www.danalexanderaudio.com/pastprojects.html

I would suspect it's probably sending +24 and +48 separately. Bad cable or connector? fuse blown? actually in this photo it looks like they have a separate board/transformer stepping up the +24 to +48 for the phantom. so I'd make sure you are getting +48 out of there first.

Mike

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Post by Marlowe » Sun Sep 29, 2013 5:15 am

If you bought that one on eBay, it seems as if all it needs is a proper power supply. The one in the photo is absolutely the wrong one.

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The Power is Supply IS Correct, Straight from Dan!

Post by fnps90 » Sun Sep 29, 2013 6:34 am

Straight from Dan Alexander himself. The Early ones had a Black Power Supply "Box" say like a Brent Averill.The Later Units had a "Harman Kardon" power supply. I thought the same as you, but Dan said 1/2 of these preamps that they made indeed has a wall wart. Also, the Cord to the earlier ones are Multi-Pin like most External Power Supplys. On the back of this Unit is the from the factory input jack for a Wall Wart. I got a screamin' price on this unit and it's because the whole "that's the wrong power supply deal" scared alot of bidders off, thinking they would have to spend $250 or more. I talked to Dan and was no longer worried, so I bid and here we are.

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Post by rhythm ranch » Sun Sep 29, 2013 8:09 am

Yep, I've got one and it's got the 24V line lump power supply.

If you've spoken with Dan already, give a him a holler back and ask him for help with the phantom power or at least a schematic. :^:

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Post by fnps90 » Sun Sep 29, 2013 8:13 am

That's the thing, he doesn't have the schematic, I called him. Somebody on either here or GS has to have a copy. I am having a guy look at it when it gets here. Just would be so much clearer and easier about what is going on if we had the schematic.

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Re: The Power is Supply IS Correct, Straight from Dan!

Post by Marlowe » Sun Sep 29, 2013 8:27 am

I stand corrected. Great score!
fnps90 wrote:Straight from Dan Alexander himself. The Early ones had a Black Power Supply "Box" say like a Brent Averill.The Later Units had a "Harman Kardon" power supply. I thought the same as you, but Dan said 1/2 of these preamps that they made indeed has a wall wart. Also, the Cord to the earlier ones are Multi-Pin like most External Power Supplys. On the back of this Unit is the from the factory input jack for a Wall Wart. I got a screamin' price on this unit and it's because the whole "that's the wrong power supply deal" scared alot of bidders off, thinking they would have to spend $250 or more. I talked to Dan and was no longer worried, so I bid and here we are.

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Post by digitaldrummer » Sun Sep 29, 2013 12:14 pm

I agree a schematic would be best, but if nobody has one, maybe post a picture of the insides and maybe someone can suggest where to start looking. If its a 24V AC line lump then there has to be some kind of conversion to take it up to +48Vdc.

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Inside of the preamp

Post by fnps90 » Sun Sep 29, 2013 12:19 pm

Image

So, it is most likely the circuit board in back left corner. Any thoughts. feel to contribute.

Steve

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Post by The Scum » Sun Sep 29, 2013 1:41 pm

Can you post a close up of that boart at the top right? Preferably wih angles that let us read the markings on the caps and the two to220 dudes.

I'd guess 24VAC transformer, using a diode-cap doubler circuit. But a close up that would let us see what's a resistor and what's a diode on that board would help.

Nice of them to use color coded wire that would allow us to trace the hookup.
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Post by digitaldrummer » Tue Oct 01, 2013 12:01 pm

I would remove the tie-wraps, then follow the wires from that small board. It should go to both of the preamp boards. either at the small board or at the other end, see if you are getting +24 and +48. if no +48, then it's likely the smaller power board and then (like The Scum said) you gotta start looking at those components close up... this would at least start to narrow it down.

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Post by The Scum » Tue Oct 01, 2013 1:50 pm

Or if we could read the silkscreen on the boards, it might be perfectly apparent...
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