treble boost

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geoff 1965
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treble boost

Postby geoff 1965 » Tue 05/14/19 8:00 am

hello,
when you fit a pf cap in parallel with a resistor it creates a pass for frequencies like the 470pf "bright cap"on the diagram,so if you only wanted to boost your mid's would you go up or down in value?
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JMPGuitars
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Re: treble boost

Postby JMPGuitars » Tue 05/14/19 8:53 am

In a passive tone circuit like the TMB, you can't boost anything. You really only shift or change the values to adjust the tone curve. If you want your mids in a higher range, you would raise the value of the mid resistor. If your mid resistor is .047uF, you would change it to .022uF. If it's .022uF you could try a .015uF or .01uF to see if it gives you the desired effect.
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geoff 1965
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Re: treble boost

Postby geoff 1965 » Tue 05/14/19 9:23 am

thank's Josh,
maybe "boost" was the wrong term to use,i've been through the whole amp now fine tuning the voltages and couplers and it's perfect for the tone,dissipation etc.
there is just one last area to fine tune and that is the gain stage of the cascade,i made the mistake of attenuating the signal using my strat which has 6K ohms pickups and my other guitar has a bridge pickup with 15K ohms output. with a 220K series in the gain stage i got perfect tone & breakup with the strat but i was getting squeal/oscillation on full volume & tone with the other guitar and with 470K in the series it cured the squeal but affected the tone&breakup with the strat.
so i'm back experimenting with voltage divider values and was trying to fully understand making use of the pf caps.these 2 have been the biggest "bugbear" tweaking this area!
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Re: treble boost

Postby JMPGuitars » Tue 05/14/19 10:53 am

Take a look at the schematic for the Superlite TMB tone stack, and the bright/thick switch and see if anything there helps.
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Re: treble boost

Postby geoff 1965 » Tue 05/14/19 2:12 pm

yes i've studied that circuit and others,at the moment i've been all around the ballpark with the dual 500K pot,the one i have'nt tried is the classic marshall 22n-470K-1 meg pot.
if i got a dual 1 meg pot and parallel a 1 meg resistor across one of the pot's that will give me the 500K volume & 1 meg gain.
just a point worth mentioning about voltage dividers,you can use the maths to get to a certain signal voltage but also use a variable resistor for actual testing,there is a width of about 30K to play with and quite a difference in tone & breakup between 0 and 30K.
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