Salas hotrodded blue DCB1 build - Page 127 - diyAudio
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Old 22nd August 2011, 09:10 PM   #1261
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Quote:
Originally Posted by Salas View Post
Is the amp you gonna drive DC input? Or it has a capacitor? The goal is under 5mV offset in order not to be highly multiplied by a DC input amp. Last chance with the JFETS you got, mutually exchange positions in those two associated with the 6.9mV offset. Maybe you luck out and they will fall a bit more, or they simply go higher offset and you put them back as they were.
DCB1 will be on F5 ...

OK, Will try this swap, but - not tonight :-)

Thanx for your time and advices :-)
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Old 22nd August 2011, 09:15 PM   #1262
Salas is offline Salas  Greece
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You would need dead on matched FETS to near 0mV, but up to 5mV is OK for the F5 which will not multiply it much due to its a low gain amp. The general disclaimer that when mating a DC preamp/buffer to a DC amp without any output DC sensor protection, your speakers are in danger in case of any failures in the future still stands. Nobody cares and most mate an F5, but anyway.
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Old 23rd August 2011, 10:01 PM   #1263
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Quick question;
I'm building a balanced version DCB1, at what pad or point on the blue board should I take the ground from as a ref point for a ground loop breaker or such?
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Old 23rd August 2011, 11:05 PM   #1264
Salas is offline Salas  Greece
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There are two points reminding a power amp config. One is the middle Tx wire connecting point where the big caps recombine currents and its dirtier, and there is a ''tail'' point at the other end where the regulated outputs are closing to earth, marked G(round). Can take a connector as well. Don't know your loop breaking purposes or what happens when balanced, but those are two points convenient to try.
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Old 24th August 2011, 12:43 AM   #1265
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Thank you Salas.

Build is getting close now...
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Old 24th August 2011, 12:57 AM   #1266
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Quote:
Originally Posted by cersepn View Post
Before i mount my lvl 1 hot rodded dcb1 into the chassis, i was wondering if it would be better to use the bottom of my chassis (bottom alu sheet measures ~ 350mm x 430mm x 4mm thickness) as the heatsink instead of the heatsinks that i'm using right now. I realize with these heatsinks i can only rest my finger there for at most 5 seconds - it is really quite hot.

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I think you can do what I did...

Click the image to open in full size.

I bent my mosfets over and added heatsinks. Now I'm going to mount them to the case... I think I'll need to place spacers (or maybe just washers) and insulate them from the case. I'm not there yet, I'm ordering a case soon.

Last edited by merlin2069er; 24th August 2011 at 01:03 AM.
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Old 24th August 2011, 01:20 AM   #1267
Salas is offline Salas  Greece
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If the Mosfets are already insulated on their metal backs from each sink with thermal pads, no need to insulate again. The screw does not touch the metal part of the Mosfets, they are TO-247 package with a plastic covered mounting ''eye''. Simplest way is to use pads.
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Old 24th August 2011, 01:54 AM   #1268
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Thanks, I have insulating pads between my mosfet and sinks. So I'll just get a longer bolt to mount it right to the case (with a spacer).
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Old 24th August 2011, 08:30 AM   #1269
syklab is offline syklab  Hong Kong
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Quote:
Originally Posted by cersepn View Post
Before i mount my lvl 1 hot rodded dcb1 into the chassis, i was wondering if it would be better to use the bottom of my chassis (bottom alu sheet measures ~ 350mm x 430mm x 4mm thickness) as the heatsink instead of the heatsinks that i'm using right now. I realize with these heatsinks i can only rest my finger there for at most 5 seconds - it is really quite hot.

Click the image to open in full size.
Hi,
Was that a separate PS module for the DCB1on the right side of the photo? So, you are not using the on board reg?
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Old 24th August 2011, 06:02 PM   #1270
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Default lightspeed attenuator

Should I build a lightspeed attenuator into the input of the dcb1 buffer or just use the stand alone unit I have with the dcb1 buffer?

I'm not sure what makes more sense?
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