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Once and far all How does my 71 superlead differ from a 68/69 plexi?

10/13/2000 2:52 AM
Dave	Once and far all How does my 71 superlead differ from a 68/69 plexi? It is very difficult to get any consistent thoughts on the what separates my 71 SL from a late 60s Plexi. I am told be some that the transformers are the major difference but My amp tech told me it has the same transformers as a late 60s plexi.Others have said its a matter of changing One cap and disconnecting something with the presence control. I have others that say their are a lot of differences and still others advice me that the differences are minimal and not to bother changing it to plexi specs. What say you? Thanks Dave

10/13/2000 2:52 AM

Dave

Once and far all How does my 71 superlead differ from a 68/69 plexi?

It is very difficult to get any consistent thoughts on the what separates my 71 SL from a late 60s Plexi. I am told be some that the transformers are the major difference but My amp tech told me it has the same transformers as a late 60s plexi.Others have said its a matter of changing One cap and disconnecting something with the presence control. I have others that say their are a lot of differences and still others advice me that the differences are minimal and not to bother changing it to plexi specs.

What say you?

Thanks

Dave

10/13/2000 2:56 AM
Dave	Also, For the people that have heard the difference between a metal and plexi. What are the diffences?And what are your personal opinions on whether converting to plexi specs will be an improvement in tone? (of coarse tone is subjective and yada yada yada but I want your opinions)

10/13/2000 4:22 PM
Peter S	Dave, There really isn't any significant difference other than the OT and on the early Plexi's you'll find 32uf power supply caps, which by itself won't really make much of a difference in tone. I see alot of people recommending the .68uf bypass cap on the second gain stage, but I honestly can't remember ever seeing one on an amp built before '69. Splitting the cathodes doesn't make a whole lot of difference. The volume pot on alot of '72 amps and later was almost a linera tapre which causes the amp to go from no volume to raging distortion very early in the knob rotation. If you want early Plexi-Specs....put the cathodes in the first stage together with an 820 ohm resistor and a 250uf cap......change the tone stacke to 56K slope and a 250pf treble cap. Change the output coupling to .1uf. Remove the .68uf bypass cap on the second gain stage. Use a 500pf bypass cap on the bright channel summing resistor and a 500pf bright cap on the volume pot and change the power supply caps to 32uf. Power supply caps are definately optional because it really won't make much tonal difference.....mostly a difference in feel with the bottom being a little squishier with the 32uf caps. For later Plex.....'69......keep the early seventies setup. If you want the amp to sound as good as a Plexi......replace the OT. OEI will have a 100 watter out soon and I'd recommend waiting for it to come out. That's all there is and there isn't anymore.......the really big difference is going to be in replacing the OT. Peter

10/13/2000 4:22 PM

Peter S

Dave,

There really isn't any significant difference other than the OT and on the early Plexi's you'll find 32uf power supply caps, which by itself won't really make much of a difference in tone. I see alot of people recommending the .68uf bypass cap on the second gain stage, but I honestly can't remember ever seeing one on an amp built before '69. Splitting the cathodes doesn't make a whole lot of difference. The volume pot on alot of '72 amps and later was almost a linera tapre which causes the amp to go from no volume to raging distortion very early in the knob rotation. If you want early Plexi-Specs....put the cathodes in the first stage together with an 820 ohm resistor and a 250uf cap......change the tone stacke to 56K slope and a 250pf treble cap. Change the output coupling to .1uf. Remove the .68uf bypass cap on the second gain stage. Use a 500pf bypass cap on the bright channel summing resistor and a 500pf bright cap on the volume pot and change the power supply caps to 32uf. Power supply caps are definately optional because it really won't make much tonal difference.....mostly a difference in feel with the bottom being a little squishier with the 32uf caps. For later Plex.....'69......keep the early seventies setup. If you want the amp to sound as good as a Plexi......replace the OT. OEI will have a 100 watter out soon and I'd recommend waiting for it to come out. That's all there is and there isn't anymore.......the really big difference is going to be in replacing the OT.

Peter

10/13/2000 6:38 PM
Dave	Thanks Pete, I acually owned a 1959 RI and sold it to get the 71 but I prefereed the Reissue, It just sounded better to my ears. Thanks again.

10/13/2000 7:26 PM
Trace	Peter is pretty much dead on Dave. The 68-69's did have the .68uF cap across V2A's cathode and so do all the point to point Marshalls up to 73. In 73 they converted to PCB's and removed the .68uF bypass from V2A. The 32uF caps do make a difference and while the 50uF caps give a bit more low-end I think the 32uF's sound a little more "open" over all. It's hard to explain but if you try it you'll hear what Peter and I are talking about. The output transformer is where A LOT of the mystery, myth, and legend comes into play. The whole Aluminum verses steel chassis debate is not as relevant (in my humble opinion) as opposed to the differences in OT's. OEI's is the best plexi replacement OT out there HANDS DOWN!! (no I don't own stock in OEI..not yet!!! ha, ha) Trace

10/13/2000 7:26 PM

Trace

Peter is pretty much dead on Dave. The 68-69's did have the .68uF cap across V2A's cathode and so do all the point to point Marshalls up to 73. In 73 they converted to PCB's and removed the .68uF bypass from V2A.

The 32uF caps do make a difference and while the 50uF caps give a bit more low-end I think the 32uF's sound a little more "open" over all. It's hard to explain but if you try it you'll hear what Peter and I are talking about.

The output transformer is where A LOT of the mystery, myth, and legend comes into play. The whole Aluminum verses steel chassis debate is not as relevant (in my humble opinion) as opposed to the differences in OT's. OEI's is the best plexi replacement OT out there HANDS DOWN!! (no I don't own stock in OEI..not yet!!! ha, ha)

Trace

10/13/2000 8:42 PM
Dave	"OEI's is the best plexi replacement OT out there HANDS DOWN" Trace, Where can I get an OEI tranformer? Plexipalace is always talking about the Mecury transformer,Any opinons on that one? So If I'm hearing you guys correctly, Your saying keep everything as is and upgrade the tranny.

10/14/2000 5:02 AM

Trace

[QUOTE]Trace,

Where can I get an OEI tranformer?[/QUOTE]

Speedracer is a frequent poster here and you can email him at Joe@ObsoleteElectronics.Com or visit his website.

quote:
"Plexipalace is always talking about the Mecury transformer,Any opinons on that one?"

Ohhhh boy!! (ha, ha) "Yes" I have opinions on that one!!

...but I'm not sure I should go into all there on here (ha, ha) Basically, the Mercury Magnet's OT's are "OK" but in my humble opinion they are wayyy over priced for how they sound.

They sound more like a metal faced Marshall OT than a plexi OT, meaning they "mush" up and sound "cloudy" compared to a plexi OT. OEI's OT does sound exactly like the original. With an OEI you can pretty much set the EQ anywhere and it will still sound good!

quote:
"So If I'm hearing you guys correctly, Your saying keep everything as is and upgrade the tranny."

Bingo matey!

Run with it and you should be all set.

Hope it helps

Trace

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