Question For You Marshall Mod Guys?

STRATDELUXER97

STRATDELUXER97

Stratoblaster Tone Meister
Regarding the 500 pf cap that goes across the 470k mixer resistors in a NMV Marshall(1959/1987)circuits.....

Do I Increase this cap across the 470k to get less brightness or raise that value? In other words.....250/330 pf or say 560/680 pf.....This is on my bright channel...I'd like to take a bit of the toppiness away and get a bit more range on this channel's treble pot...I don't have the .005 across the volume pot and went with just a 47 pf there...I just want to knock out a bit more of the highs and not have to have my treble pot on like 9 o clock or less...I don't want to remove the cap because I'll lose gain..

I have the stock tone stack and slope resistor values of .022/.022/500pf and the 33k and since the Normal channel is perfect,I want to solely hone in on the bright channel...

My bright channel has a .022 replacing the .0022 with the 500pf across the 470k....

Lew,Jeff Seal.Kevlar,Christian,Scott,etc(Anyone I've missed here sorry)....Please chime in...
 
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Re: Question For You Marshall Mod Guys?

remember when Seymour said he'd sometimes use a 250k pot on a JB that was too bright (as opposed to the 500k)?

Go lower young man.
 
Re: Question For You Marshall Mod Guys?

For the 500pf/470k mix resistor arrangement, the RC time constant works out to this:

F= 1
------------------------------------ = 678 Hz
6.28 * 00000000050 * 470,000


Meaning that every frequency below 678 rolls off. Change the capacitor value to find out what frequency you'll get by changing the cap.
 
Re: Question For You Marshall Mod Guys?

shredaholic said:
For the 500pf/470k mix resistor arrangement, the RC time constant works out to this:

F= 1
------------------------------------ = 678 Hz
6.28 * 00000000050 * 470,000


Meaning that every frequency below 678 rolls off. Change the capacitor value to find out what frequency you'll get by changing the cap.
Click to expand...

LOL.....Without all the math....Just was looking for higher or lower...LOL....Scott got it....:) Your way is too techie for me buddy...Ha.Ha.....
 
Re: Question For You Marshall Mod Guys?

Scott_F said:
remember when Seymour said he'd sometimes use a 250k pot on a JB that was too bright (as opposed to the 500k)?

Go lower young man.
Click to expand...

Well I needed to ask cause sometimes raising the cap value does the opposite,like in a tone control....We're almost talking about what a treble bleed cap does across a volume control...
 
Re: Question For You Marshall Mod Guys?

I just had a non-coffee moment and realized that I was talking about variable resistors and not capacitors! duh! But go down anyway.
 
Re: Question For You Marshall Mod Guys?

in all seriousness, I wired up a brigth switch with a 120pf cap and 47pf cap and the 120 was brighter.
 
Re: Question For You Marshall Mod Guys?

Scott_F said:
I just had a non-coffee moment and realized that I was talking about variable resistors and not capacitors! duh! But go down anyway.
Click to expand...

I Lowered that 500 pf mica down to a 330 pf already and I was on the right track,but thought I should check with you guys...Maybe I should try a ceramic there instead? It's grainier,but it might be less bright there also? Have to try it and see...

I'm waiting on one of Trace's Custom MM output transformers and choke..The amp rocks already overall even with the O.E.I in there....Trace talked me into spending more money "again".....Bastard....LOL:laugh2: :smack:
 
Re: Question For You Marshall Mod Guys?

Scott_F said:
in all seriousness, I wired up a brigth switch with a 120pf cap and 47pf cap and the 120 was brighter.
Click to expand...

See now you're doing the same thing as me on this cap Scott? :laugh2:

The 120 pf is (I think) brighter than the 47 pf across the Fender bright switch...The 47 pf comes out of the circuit quicker on the volume pot as you volume up towards 10 also....The smaller cap only allows the "higher" frequencies to pass...And this stuff always confuses me! LOL
 
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Re: Question For You Marshall Mod Guys?

On it's own, when the value of the capacitor increases, the lower frequencies let through increases.

When parallelled with a resistor, it forms a tone network. Increasing the value of either the resistor or capacitor now, will result in less lower frequencies going through.
 
Re: Question For You Marshall Mod Guys?

shredaholic said:
On it's own, when the value of the capacitor increases, the lower frequencies let through increases.

When parallelled with a resistor, it forms a tone network. Increasing the value of either the resistor or capacitor now, will result in less lower frequencies going through.
Click to expand...

Now you're talking my language! :laugh2:

Great info....Appreciate that...
 
Re: Question For You Marshall Mod Guys?

STRATDELUXER97 said:
I'm not going to get into the whole tone issue with caps....LOL...

I Just try different caps and different values until I happen upon something that I Like....That's the only thing that really matters!
Click to expand...
You're right!! Nothing beats experience!! But it's fun to compare what you're ears tell you and what some theory tells you ...
 
Re: Question For You Marshall Mod Guys?

Marcel said:
You're right!! Nothing beats experience!! But it's fun to compare what you're ears tell you and what some theory tells you ...
Click to expand...

Yes....That's pretty much where I was trying to go and agree with you brother...:smack: :laugh2:
 
Re: Question For You Marshall Mod Guys?

shredaholic said:
On it's own, when the value of the capacitor increases, the lower frequencies let through increases.

When parallelled with a resistor, it forms a tone network. Increasing the value of either the resistor or capacitor now, will result in less lower frequencies going through.
Click to expand...

I Love the Sozo caps as they've loosened up and smoothed out a bit more...Trace likes using the 715 Orange Drops....
 
Re: Question For You Marshall Mod Guys?

How's the Marshall sounding now, John?

One of common mods done to those amps, and the JMP/JCM 2203/4 was to remove the 470p cap that is parallel to the 470k resistor between the first and second gain stages. That instantly took any brightness away.
 
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