Plexi bright cap

Emiel

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I will test the cab more when i get the other speaker. I guess what im looking for is that classic AC/DC tone through greenbacks. I dont know the science behind closed vs open cab, my guess was that closed back would give me a bassier sound....

I guess you have seen this video already. I get really close if I try his settings on my 1987. Presence 1, bass 3, middle 3, treble 3, bright channel 8. Don't forget a nice SG with a low wind bright humbucker.
 

Marcomel79

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I guess you have seen this video already. I get really close if I try his settings on my 1987. Presence 1, bass 3, middle 3, treble 3, bright channel 8. Don't forget a nice SG with a low wind bright humbucker.

Yeah i did! Not sure you read my update but i ended up taking off the bright cap completely. Still lots of edge and aggression... well see when i fit the other speaker if i need to put back the 100pf or not... actually im also setting my presence very low, 2/3 on the dial...im playing an epiphone sg with Gibson 498T on bridge on 6. Gets pretty close. Otherwise on both my les pauls i have low wind humbuckers i wound on 7.5/7.8K...running the amp on 6 now with just one speaker. Will do 10 when i get the other one on monday:headbanger::jam::shred2:
 

Derrick111

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I will test the cab more when i get the other speaker. I guess what im looking for is that classic AC/DC tone through greenbacks. I dont know the science behind closed vs open cab, my guess was that closed back would give me a bassier sound....
A "tighter" sound with less boxy mids is a more accurate description between open/closed back cabs.
 

Marcomel79

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Would it be an option to use a 500k pot instead of the 1meg one for the high treble volume to tame the high frequencies? That way i could use a bright cap and get some edge without the over brightness... or, would it be the same by just lowering the bright cap? I had the 4n7 stock cap.
 
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gregr

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Use a 220pF or 330pF bright cap and throw a master volume in there (Fletcher-Munson).

Using 22nF coupling caps to the PI isn’t going to make it less bright.
 
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Marcomel79

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UPDATE: so in the kit instructions for my amp it said to bias both tubes (combined) at around 60mA. I had biased at 50mA and that was the reason my amp sounded so trebly. Today i rebiased the amp at 60mA and resoldered the 4n7 bright cap and now it sounds glorious!! I even lifted a leg of the mixers bypass cap for extra warmth but i didnt need to. I resoldered it in, and i think im officially done tweaking this amp. I need a few more hours to break in my speakers but i love the amp now.

Thanks everybody who chimed in to help.
Case closed.
 

gregr

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I upped the bright cap on the crunch mode on a JCM2k DSL50 from 1n to 1.5n. I might even go higher. I’ve been plan on doing the same thing with my JVM.
 

Marcomel79

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I upped the bright cap on the crunch mode on a JCM2k DSL50 from 1n to 1.5n. I might even go higher. I’ve been plan on doing the same thing with my JVM.
I wish i had tried no bright cap with new bias to see how much warmer it would have been. But definitely no bright cap mellowed the amp too much. Sounds so good now. Never played any of those amps... the jvm looks intimidating
 

tschrama

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Nobody ever mentions a plain short instead of a cap, like Peter Diezel does. Works great. Also a resistor in series with the bright cap works to tame its effect. That way you can tune the frequency and amount of boost independently. BTW that 50mA isnt the cause of a amp being too bright; the gain cap in combination with gain setting does that.
 

Marcomel79

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BTW that 50mA isnt the cause of a amp being too bright; the gain cap in combination with gain setting does that.
To be honest that was just a guess, but it seems that thats what solved my problem.
I tried every possible combination to try and tame the brightness but bringin up the bias did the job. Now i can even have the treble on 8! The sound is warm and organic. Lots of edge, but sweet edge.
 
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