Shared cathode convert? Maybe

[Joshabr1]

Well I been tinkering with my 74 superlead. Neg feedback,tubes.......so today I changed it to shared cathode left everything thing else in place. I really really like it. Kinda maybe took it from a screamer to a screamin singer??? Not much gain difference just maybe the gain is a little more in the mid mid lows. Left the neg feed at 100k to 4ohms. Thinkin of adding a .68 to v2 and changing the feedback to 47k on the speaker jack. Would this keep the gain in the same ballpark and maybe add a touch more mid highs??? Lookin for the Koss thing.

[neikeel]

The changes you suggest sound reasonable, easy to do and easy to reverse on a turret board amp but can be tricky to do neatly on those early Marshall PCBs without wrecking them. Once you have done that you potentially slash their resale value.

Shared cathode gives a thicker sound for sure, if the rest is stock SL (0.0022uF coupler and 5000pF bright cap etc) you will keep the ability to cut it in a mix. I find the 100k/ohm NFB a bit whoolly (I have an NFB pot on my Hotrod that goes from 200k on 16ohm which is equivalent to 100/4, through to 27k on 16ohm and I find that I like the higher NFB best - somewhere between 47k and 27k. The amp is louder with higher NFB too.

The 0.68uF on V2a adds more upper mids in a focussed way on a split cathode amp, confess that I have never tried that value in that circumstance, I know a few here have. The big 330uF cap there does nothing for me - always seems a bit messy with too wide a boost on that stage.

Hope that helps (sounds like you need to make a Metro/Valvestorm amp as a test mule!)

[Joshabr1]

Yea Neil. That is the next step. A build of my own. I think I could handle it. With a little more study. I am keeping the 74 the way it is now. I really like it. Like u said the girth of the shared and the cut of the lead still. I think it a good Combo for what I like.