Shared/Split Cathode

Guest · Post by **Guest** » Tue Nov 02, 2004 4:29 pm

Hey all,

I just finished building the 68 PTP to replace the PCB in my SLP R/I this past weekend.

It looks like the PCB is using the split cathode arrangment whereas the PTP is using the shared cathode on V1. Do I just need to bridge pins 3 and 8 on V1?

And, what's the difference as far as tone is concerned. I never use Ch II anyway so would the shared cathode make any difference in my case?

white room · Post by **white room** » Tue Nov 02, 2004 4:34 pm

Anonymous wrote:Hey all,

I just finished building the 68 PTP to replace the PCB in my SLP R/I this past weekend.

It looks like the PCB is using the split cathode arrangment whereas the PTP is using the shared cathode on V1. Do I just need to bridge pins 3 and 8 on V1?

And, what's the difference as far as tone is concerned. I never use Ch II anyway so would the shared cathode make any difference in my case?

Still can't figure out why my post are coming out under "Guest" when I'm signed in as white room before I made the post.

Flames1950 · Post by **Flames1950** » Tue Nov 02, 2004 10:41 pm

The forum software is always a little funky about logging in. Make sure you've checked to remain logged in an your computer, and as long as you aren't deleting all your cookies/temp internet files to hide your porn sprees you're fine.

At any rate, yes, just jumper pin 3 to pin 8 of the first 12AX7 tube (V1.)
I find the shared cathodes creamier sounding, less "cutting" than a split cathode amp, a little more "rock" and less "metal" if you will.
Channel II would be much more usable for you if you get rid of the 500pF cap across the bright channel's 470K mixer resistor. That cap helps leak your high end off into the bright side when using channel II. But if you like channel I and mainly use that as is, you're set.

white room · Post by **white room** » Wed Nov 03, 2004 7:27 am

Flames1950 wrote:The forum software is always a little funky about logging in. Make sure you've checked to remain logged in an your computer, and as long as you aren't deleting all your cookies/temp internet files to hide your porn sprees you're fine.
At any rate, yes, just jumper pin 3 to pin 8 of the first 12AX7 tube (V1.)
I find the shared cathodes creamier sounding, less "cutting" than a split cathode amp, a little more "rock" and less "metal" if you will.
Channel II would be much more usable for you if you get rid of the 500pF cap across the bright channel's 470K mixer resistor. That cap helps leak your high end off into the bright side when using channel II. But if you like channel I and mainly use that as is, you're set.

That's good to hear ! I can can pretty much get that warm, creamy tone right now but still have some "cutting edge" riding on top that I can't seem to get rid of so, this is probably the answer to my problem with that

As for the login thing, I'm not clearing my history or cookies cache ( as often as I should) so I don't think that's a problem. It's no big deal though.

Thanks for the help.

Flames1950 · Post by **Flames1950** » Wed Nov 03, 2004 8:31 am

Yeah, shared cathode should help if you're still getting too much cut.
What bright cap are you running across the volume control? If shared cathode on V1 still isn't enough the bright cap may come into the equation.

white room · Post by **white room** » Wed Nov 03, 2004 10:05 am

Right now, with the PCB, the cap is on the board and I can't quite make out what the value is going by the "skeez" but, I was thinking of not going with one at all after I drop the PTP in there just to see if that get's me where I want to be.

As it stands for now, I use a SD 59 in the bridge of a LP Special and just roll of the Presence and Treble on the amp to about mid point and roll of the guitars volume just a touch and it get's close but still does not hit the mark for me but I see that the PTP has a few changes from the PCB layout that look promising so I'm pretty jacked up about getting this board in place.

I'm definitly from the old school and like that "classic rock" Marshall tone

shawnpurcell · Post by **shawnpurcell** » Wed Nov 03, 2004 2:28 pm

Hey Flames,

I have my kit running to nearly exact specs as '69 board. The only change is that I didn't put the bright cap across the lead channel volume.

Are you saying that if I jumper pins 3 and 8 of V1 with this setup I will get a creamier sound??

I usually use the normal channel jumpered to lead channel leaked in to give me some high end sparkle...

Shawn

Flames1950 · Post by **Flames1950** » Wed Nov 03, 2004 11:41 pm

You'll get a creamier sound jumpering pins 3 and 8 of V1, assuming you disconnect the wire currently going to pin 8 (coming from the 2.7K/.68uF combo.)
You can tie the wire off to the board mounting post to try this, then you can switch back if you choose.

shawnpurcell · Post by **shawnpurcell** » Thu Nov 04, 2004 9:23 am

Hey,

thanks for the tip, I just may have to try this one

Shawn

Lou · Post by **Lou** » Sun Feb 06, 2005 9:24 pm

shawnpurcell wrote:Hey Flames,

I have my kit running to nearly exact specs as '69 board. The only change is that I didn't put the bright cap across the lead channel volume.

Are you saying that if I jumper pins 3 and 8 of V1 with this setup I will get a creamier sound??

I usually use the normal channel jumpered to lead channel leaked in to give me some high end sparkle...

Shawn

When you take out the bright cap across the lead channel volume what did that do to the tone?

Did it take some focus away from the hights?

Thanks

Lou

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Shared/Split Cathode

Shared/Split Cathode

Re: Shared/Split Cathode

shared cathode

Thanks Flames

Re: shared cathode