DChristie's PL 2000

[Gepetto]

Joe, are those back-to-back 2.2/35V electrolytic capacitors (C47-C50) there to block DC from leaving the preamplifier?

Yes that is what they are for, you would also benefit from making them larger and non-polar. You can easily get a 4.7uF or larger polypropylene to fit in that area and get rid of those crappy electrolytics. You only need one cap to replace the 2 in series.

 

[laatsch55]

The center tap is just the easiest Lee, either works. When you put them in the 12V legs, you have to double the value (200) to get the result I was looking for in the center tap with 100.

I have some 220's....

 

[Gepetto]

I have some 220's....

close enough
That should take you down to around 15V +/-

 

[laatsch55]

Yes that is what they are for, you would also benefit from making them larger and non-polar. You can easily get a 4.7uF or larger polypropylene to fit in that area and get rid of those crappy electrolytics. You only need one cap to replace the 2 in series.

That would make for some long leads where they're at...

 

[laatsch55]

13.7 on the secondaries, 16.2DC +,-

 

[Gepetto]

13.7 on the secondaries, 16.2DC +,-

Poifect!!

 

[Gepetto]

That would make for some long leads where they're at...

Not sure I know what you mean Lee

 

[laatsch55]

Putting poly's where those 4 electro's are...

 

[Gepetto]

 

[laatsch55]

You have to go from the minus to minus holes, but it'd work....what voltage?

 

[laatsch55]

3.3uf/250 is all i have, nothing in the 4 range...

 

[Gepetto]

3.3uf/250 is all i have, nothing in the 4 range...

That is 3x better than what is in there now. 2.2uF in series with 2.2uF = 1.1uF

I call that a big win

 

[laatsch55]

Hookay, I'll put em in...

Gotta do Old Chicago with Jani for a bit. Date night..

 

[Gepetto]

Hookay, I'll put em in...

Gotta do Old Chicago with Jani for a bit. Date night..

Have fun! Post a pic once you get them in to keep George in the loop.

 

[laatsch55]

Will do, thanks Joe!

 

[Gepetto]

You have to go from the minus to minus holes, but it'd work....what voltage?

You can put the cap in place of one of the 2 caps and then just put a jumper in the other cap location. Will look neater that way.

 

[laatsch55]

Will do.

 

[mlucitt]

That is 3x better than what is in there now. 2.2uF in series with 2.2uF = 1.1uF

I call that a big win

We don't have DC blocking caps on the outputs of the OPAMPs in the Rev E or Rev G1 Control Boards, right? Why are these caps necessary in the PL2000? Do OPAMPs typically contain DC levels on the output, or is it just a failure mode that we are trying to prevent? Just curious.

 

[laatsch55]

Yeah, when something goes south in a pre.....that is hooked to a WOPL 700....without caps in line.....shit can get intense..,.

 

[Gepetto]

We don't have DC blocking caps on the outputs of the OPAMPs in the Rev E or Rev G1 Control Boards, right? Why are these caps necessary in the PL2000? Do OPAMPs typically contain DC levels on the output, or is it just a failure mode that we are trying to prevent? Just curious.

They aren't necessary in an extremely well behaved preamp where the output offset is sub millivolt. They are there...