Reducing low end going into an amp?

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SteveDay
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Reducing low end going into an amp?

Post by SteveDay » Sun Dec 08, 2019 4:12 pm

Hi everyone, first post here.

Hope this is the right sub for this, if not, please feel free to move.

I was hoping someone could tell me - or at least point me in the right direction - as to how to reduce the low and at the input of an amp.

I have a late 70's JMP, and it has a nice amount of gain, but it's a bit muddy, even with the p/u moved down a bit towards the body, and with backing off of the preamp. One way to deal with this is to put an EQ in front of the head (like a Boss GE7), and reduce some low end, but I would rather go pedal-less. Of course I could also try different p/us, but that's the easy way out, IMHO. I am looking to learn something here :)

Is there any way to do the equivalent of the EQ in front of the input, and reduce the low end, either by doing something to the head, or maybe by adding a resistor/capacitor to the guitar wiring?

To be clear - we are not talking about power amp stage low end; turning the bass knob counterclockwise doesn't do the trick here, because the excess low end is in the pre amp stage (or at least, I think that's that proper way to say it... if not, feel free to correct me).

Any ideas will be very much appreciated.

Thank you!

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herbvis
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Re: Reducing low end going into an amp?

Post by herbvis » Sun Jan 05, 2020 2:37 pm

If you have a large electrolytic bypass cap on your preamp cathode, lowering this will help. Lowering coupling cap value. Adding a voltage divider early in the circuit. Upping your first stage grid resistor may help. Those are a few of the common places to tinker with.

danman
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Re: Reducing low end going into an amp?

Post by danman » Sun Jan 05, 2020 6:07 pm

Is it the 4 hole version or a master volume model? Are you filter caps original or have they been replaced recently?

danman
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Re: Reducing low end going into an amp?

Post by danman » Sun Jan 05, 2020 6:08 pm

Is it the 4 hole version or a master volume model? Are you filter caps original or have they been replaced recently?

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neikeel
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Re: Reducing low end going into an amp?

Post by neikeel » Mon Jan 13, 2020 4:47 pm

danman wrote:
Sun Jan 05, 2020 6:08 pm
Is it the 4 hole version or a master volume model? Are you filter caps original or have they been replaced recently?
Hi,
Danman raises important questions!
JMP what model, what year, modded already.
Answer those questions an post a circuit board pic and we can point you very firmly in the right direction.
Neil

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wdelaney72
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Re: Reducing low end going into an amp?

Post by wdelaney72 » Tue Jan 14, 2020 12:25 pm

The only spec I recall having a ton of low end as described are shared cathode and the .1uF PI couplers. I doubt that amp would have that, but as others said....need to see what's inside. Maybe it's been modded?
Walter

"There's no great thing in being a soloist. I think the hardest thing is to play together with a lot of people, and do it right." - Angus Young, 1984

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