ckaudio

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I ended up with a 100pf in my JTM45, even with the shared cathode. I think the most common value for JTM45s was 500pf, but someone posted their all original JTM45 guts here a few years ago and it had 100pf. I think certain values were more common on certain models and during certain periods, but there was some variation, so there's not really correct values and incorrect values. The schematics I have examined didn't start specifying real high values until the 70's.
Good to know! That makes me feel a little better about being happier with the 100pF 😆 the higher values can definitely have their own sound, but that wasn’t the sound I was looking for with this amp!
 

ckaudio

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For anyone interested -

I recorded this little jam with my SV20 post bright cap mod.

Running it straight into my Torpedo Captor X with a Pre Rola Greenback cab sim. It’s my favorite way to record because I can save/recall my settings without having to setup mics, plus I can crank the amp any time if the day 😄 and it sounds better than when I mic my cabs 😂

Settings are all listed in the description for those interested.

 

blackeye-liner

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Just did this mod to my SV20, tried a couple of different values just for safety but yes, 100pF was sounding good - didn't try even lower values since I didn't have them on hand. Sounds very good right now, compared to stock cap it's so strange I could tolerate it for so long - that brightness was glaring.

Thank you for the instructions! That demo sounds awesome.

Did not expect that drop in gain though! With boost it's just fine, but without boost it's so much cleaner now!
 

vivanchenko

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I just roll off the volume and/or tone pots a bit. Tames any excessive brightness like magic and sounds fantastic. Leaves your high end on tap which you will likely need when playing in a band.
 

2203xman

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A really useful option is a bright cap selector switch where you can choose between two different bright caps or none with a 3 way mini toggle.Works great and one of my favorite mods on the Ceriatone plexi 51.
 

ckaudio

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Just did this mod to my SV20, tried a couple of different values just for safety but yes, 100pF was sounding good - didn't try even lower values since I didn't have them on hand. Sounds very good right now, compared to stock cap it's so strange I could tolerate it for so long - that brightness was glaring.

Thank you for the instructions! That demo sounds awesome.

Did not expect that drop in gain though! With boost it's just fine, but without boost it's so much cleaner now!

Nice! That’s exactly how I felt after doing it on my SV20, how did I tolerate it for so long! Night and day difference to me.

There is a drop in gain, I usually run my presence knob dimed which helps but the amount of gain that was left is exactly the classic crunch Marshall tone I wanted with my Les Paul, and with single coils I can get that clean/edge if breakup Hendrix kind of tone.
 

ckaudio

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I just roll off the volume and/or tone pots a bit. Tames any excessive brightness like magic and sounds fantastic. Leaves your high end on tap which you will likely need when playing in a band.
To each his own! That’s why it’s such a great value to be able to tweak. The stock bright cap was more than I could handle even adjusting the tone/volume pots I could never get the sound I wanted. The 100pF value leaves me plenty of highs to cut through in a mix with the way I’m running it.
 

ckaudio

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A really useful option is a bright cap selector switch where you can choose between two different bright caps or none with a 3 way mini toggle.Works great and one of my favorite mods on the Ceriatone plexi 51.
Yes! I almost did this but was hesitant to drill any holes. I liked the 100pf so much that I decided I didn’t need a switch, but at some point I may add a 3-way toggle to have more flexibility!
 

blackeye-liner

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A really useful option is a bright cap selector switch where you can choose between two different bright caps or none with a 3 way mini toggle.Works great and one of my favorite mods on the Ceriatone plexi 51.
That's what I was thinking, and I ordered a 3-way switch as well as multiple cap values. However, seems like the lowest value was the best one I've tried, and doing it with values higher than that made very little sense at the time. Now I'm thinking to try 2-3 even lower value options to see if that would work, and maybe that will go into the switch options.
 

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