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

jbeckva

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So for this one (and the other one seemed somewhat modified in this area too) I first upped the voltage to 17 as K13 (main time relay/output) wouldn't kick over. I ended up replacing it's switch transistor with a 2n5088 and taking the emitter right to ground instead of up .7volts with that diode. Scared crap outta me.. NO output whatsover after the voltage was dropped from 20.

All good now.. well maybe.. gotta look at the phono section (dayum.. one relay left, spend it wisely gamgee!!)
 
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Gepetto said:
Why don't you fix it with the gold crosspoint relays Jer? Put something reliable in there...those original relays were not all that reliable.
Click to expand...
I'm thinking 'bout it...

Here's the result... mic just doesn't do it justice, but good nuff!

<iframe width="640" height="360" src="//www.youtube.com/embed/qBbtgnDceVQ?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>
 
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So, while we're waiting for relays, responses, that sort of thing...

Another oddball IC I noticed... those RC4739's.. not to be confused with the RC4136's (for which I have two BD's already made up, to the horror of realizing I don't have these in the 3000's.. )...

These here appear to be dual amps, but in a quad amp sized 14 pin DIP. Observe...

rc4739_s.png

I believe 7 and 14 are the supply lines.. anywhoo... What I am thinking there is to perhaps get some LME49720's (dual version of the 49740's), and in the TO-99 variety. Then just move this lead "here".. that lead "there".. yeah, has it's possibilities.

but on the 7th day, rest was called for and observed... :glasses8::mrgreen:
 
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There are some other attributes the 4739's have that don't lend them for replacement either Jer. Joe explained them in a 2000 thread sometime and it became obvious ( to him) that some circuit modification was necessary to keep things from oscillating....
 
kevin

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jbeckva said:
Man, then another relay..

Kev I might want to just hardline it with one line and one phono input, maybe two line. What you figure you are going to hook in with it?
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Like I said before Jer ! You just fix it like yours and tell me what I got !.. I really dont ever see me using a TT... I'd say two inputs would do me just fine !!! Now... I know I ask you this question in a PM but Im going to ask it again here...... What can be done to that Pre to put a sub out on it ???? I KNOW I DONT NEED NO SUB WITH K'S LEE.... LOL... BUT... I was just wondering where do they get the sub out they put on all the new stuff.... Bout all pre amps now have a sub out... DONT THEY ???
 
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kevin said:
Like I said before Jer ! You just fix it like yours and tell me what I got !.. I really dont ever see me using a TT... I'd say two inputs would do me just fine !!! Now... I know I ask you this question in a PM but Im going to ask it again here...... What can be done to that Pre to put a sub out on it ???? I KNOW I DONT NEED NO SUB WITH K'S LEE.... LOL... BUT... I was just wondering where do they get the sub out they put on all the new stuff.... Bout all pre amps now have a sub out... DONT THEY ???
Click to expand...
Well for a sub, two choices. The hard way would be to create a low pass filter circuit and tie the output to the set of unused RCA preamp outputs. That would also require a circuit that would allow the two channels to blend, but not affecting the stereo separation on the other two main L and R channels.

The easy way perhaps would be to use these here, low pass in-line RCA filters that would go between the 2nd set of outputs on the pre and your sub amp(s). As long as the left and right are combined somewhere along the path.. perhaps with a dual VC subwoofer.

Two inputs.. ok... we can do that. Let's wait for the "good" relays tho... whatever ones I leave in your pre should be 100 percent trouble free for a few years...
 
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jbeckva said:
Well for a sub, two choices. The hard way would be to create a low pass filter circuit and tie the output to the set of unused RCA preamp outputs. That would also require a circuit that would allow the two channels to blend, but not affecting the stereo separation on the other two main L and R channels.

The easy way perhaps would be to use these here, low pass in-line RCA filters that would go between the 2nd set of outputs on the pre and your sub amp(s). As long as the left and right are combined somewhere along the path.. perhaps with a dual VC subwoofer.

Two inputs.. ok... we can do that. Let's wait for the "good" relays tho... whatever ones I leave in your pre should be 100 percent trouble free for a few years...
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Heh.. forgot link

http://www.parts-express.com/harris...source=google&utm_medium=cpc&utm_campaign=pla
 
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Yea Jerry.. that looks good to me... Never seen anything like those before... Works for me !!! :happy7:
 
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