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Topic: Changing Slope Resistor in T,M,B Tonestack |
Tom Gorr
From:
Three Hills, Alberta
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Posted 19 Nov 2007 8:40 pm |
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Another thread mentioned the 'slope resistor' in the tonestack.
Some boogie amps use a 150k, others use a 100k slope resister on their clean channels.
Anybody know what the difference is ?
Is one better than the other for HB's or SC P/U's ? |
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Brad Sarno
From:
St. Louis, MO USA
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Posted 20 Nov 2007 6:20 am
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Tom.
That resistor determines the frequency of the midrange dip. The higher the value, the lower the frequency. Stock classic Fenders is 100k. Down to 47k or so will scoot the dip up higher giving more low mids and a thicker, warmer tone. Up at 150 would scoot the dip down pretty low giving stronger treble and upper mids giving a very clear tone. For an amp where that's a fixed value I still tend to like 100k on both steel and guitar. For a more "Webb"-like dip you could try 120k. I wouldn't want to go higher than 125k in general.
Also, remember that the midrange dip ALSO moves up and down in response to where the treble knob is set. More treble also scoots the dip downward. On a stock Fender Twin, if you put the treble down around 3.7 or so, the midrange dip frequency winds up around 800Hz, the popular steel guitar mid-dip frequency. Webb's are down around 550Hz. I think some Evans were down even lower like 375Hz or so. In a Fender you can experiment with that slope resistor to find a midrange voicing you like. If you find that you like to set the amp's treble control up high like 5-8, then you may want to consider a slope resistor value of 56k to 80k.
Brad |
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Tom Gorr
From:
Three Hills, Alberta
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Posted 20 Nov 2007 11:54 am
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It looks like it would be handy to add a 150k pot in series with a 50 k resistor - thereby giving an extra dimension of tone control ?
Also, Brad, have you ever analysed the 'Marshall' tone stack - and how the various freq interact with its design ?
Thoughts ? |
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J Fletcher
From:
London,Ont,Canada
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Posted 20 Nov 2007 12:20 pm
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| If you were replacing the 100k resistor with a pot, I think you will need to put in a capacitor to block the DC voltage on the plate. You probably knew that.... |
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