Kev's "Cobble Together a Good 3000 PL Preamp" thread...

Gepetto

Gepetto

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jbeckva said:
What size and wattage do you recommend? Heck tho I already put in the order for four TO-220 mounting kits (note four.. I am going to build another for my own 3000! - Ordered another batch of parts to build one more)

Sounds reallly good
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Hard to tell you Jer without knowing two things, the raw, unregulated DC voltage going into the regulator and the approximate load current. You can stick a temporary 10 ohm 2W resistor in the path to the regulator input and measure the voltage across it to determine the load current.
 
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laatsch55 said:
So, heatsink it where it sits?
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Along the inside wall of the ps cage, yup.

All done... voltage exactly where it was last. Yes Joe... about 3 inches max that wraps around the edge and terminates about a quarter of an inch from the hole all three pass thru on the board.

No heat no mo... Only did the positive regulator as the negative one is not breaking a sweat.
 
kevin

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jbeckva said:
Evaluating it now... Bumped the volts back up to 17 - gives a slightly better sound, but that ambient hiss is a little higher. I think I am going to go forward with Joe's suggestions on the input impedance changes.

Yeah I'm a stickler... heheh
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I know it will be PERFECT when I hook it up Jer !!!! Thats just how you roll !!!!! :happy7:
 
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Gepetto said:
Well then:

C242 from 0.22uF to 0.33uF or greater, non polar
R260 from 1M to 100K
R257 from 100 to 0
C241 from 33p to 180p
R250 from 20K to 100
R258 from 20K to 16.5K

All resistors from carbon film to metal film

The same applies for the 100 series of parts too Jer. I just listed the 200 series channel.
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All done Joe!! (yeah took me awhile to get started.. hehe)

It sounds really really good. A lil residual but not bad at all. Thing is - the gain is too high.. had to throttle back the input or each successive step of the volume is way louder than it should be. What if I increased R250/150? I predict a good -6db needed to bring it in line.

Or .. KEV... Do you have a output volume control on the sources you'll be plugging in? If you do, set them initially at 1/4.. take the pre to about 9 o'clock then adjust on the source to medium to med loud.. thereabouts, anyway...

Gonna let this guy cook for a few days, then here she comes Kev! (really really really )
 
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