Fender Tone Stack-Low Loss Version?

[CJ]

is there a way to  make a low impedance version of the Fender tone stack that will have less loss?

got a Sears git amp with tons of mid range but not much treble,

in fact, the tone controls do not do too much, however, with a Fender stack in between the pre and power amp it has great tone, but not loud enough,

so just wondering if we changed some resistor and cap values if it would be possible to get the same curves only for solid state?

sounds like a simulator might help,

here is the tube version, somebody left the soldering iron on,  >

 

[CJ]

doh, if we want less loss, we increase the impedance, 

simulator says cut the mid range all the way off, set the treble at max and bring the bass up a bit to limit loss, pick the 250 pf cap to place the dip where you want it,

maybe adding an inductor could scoop the mid range without much treble loss,

 

[PRR]

Less loss means less boost. You sacrifice the extreme EQ settings. Standard values cut "everything" about 16dB then add-back whatever Bass and Treble you want to boost.

If you cut the standing loss to say 6dB then you can barely get 4dB-5dB of boom and sizzle boost.

If you can live with that, increase the bottom resistor ("MID knob" on hi-price models). Some dudes even cut it for a screemin'-mids solo tone.

> adding an inductor

You want over 100K impedance in upper mid-bass. Over 22 Henries. While the resistance can be many K, it will still be quite a chunk of iron. And because of the high impedance will suck-up all the magnetic and static hum/buzzz in the room. You can probably do it. Most will be disappointed.

> not loud enough

Find or make more gain. Tubes are cheaper than chokes.

 

[CJ]

free simulator here>

http://www.simetrix.co.uk/site/demo.php

doing some AC sweeps to give us a mid dip at around 100 to 200 CPS,

 

[CJ]

here is a graph showing curves for Max Treble, No Mids, and Bass on and off>

 

[CJ]

here is a sweep that shows what changing R1 from 100K to 200K does,

we are after a circuit that will dip at 100 to 200 Hz, also a little less signal loss at the treble bands which is also what we need,

 

[CJ]

next we try leaving the 200K resistor and upping the C1 cap value to 400 pf,

this drops us into the freq range we want, little less mid cut, but less treble loss,

we can turn the bass off and see what happens next,

 

[CJ]

bass on and off curves, the scooped mid sound is cool for guitar, so maybe we will leave the bass off and dial in the 100-200 hz dip with R1 and C1

 

[CJ]

graphs using R1 as 270K and 470K, getting there,

maybe use 470K and play with the C1 value to sweep out a broader area,

 

[CJ]

we are going to try this circuit, simplified simulator by getting rid of the mid pot and using resistors for the bass and Treble pots,

 

[CJ]

here is the curve after changing resistor values around,

time to build it and plug it in...

 

[PRR]

8dB/Oct slope suggests there is something VERY wrong. Maybe you should find the treble loss instead of trying to boost it out?

 

[CJ]

figured it out, there is a 4,7K resistor across the transistor input to the pwr amp,

trying to use a hi z circuit into a low z circuit chews up the voltage,

so we are going to a low z circuit, Pultec MEQ mid dip,

 

[abbey road d enfer]

8dB/Oct slope suggests there is something VERY wrong. Maybe you should find the treble loss instead of trying to boost it out?

What do you mean, VERY wrong? ?The graphs seem correct to me.
Are you saying that the tone stack is creating an 8dB/oct boost and it should make plenty of treble?

 

[PRR]

> What do you mean

Let us pretend the "correct" sound is flat.

CJ has empirically found that an added 8dB/oct rise gives the desired sound. 

This suggests the un-CJed amp had an 8dB/oct *drop*.

Now, some amps are bright and some are dark. But 8dB/oct over much of the audible band (in a non-special bit of gear) is more than a matter of taste. It isn't just "dark", it is a black hole for all but the boom.

I doubt even Sears sold something that dark/black.

I first thought some post-Sears pre-CJ modder had put, say, 4,700pFd where should be a 47pFd.

He now finds a 4.7K PA input impedance. Not sure how that is causing dark-black.

There's the added flip that he seems to want a sub-150Hz *rise*. Which is not just a wrong treble-cap. He may have a more complicated thing going on. Or he may just be asking for more deep bass than Sears budgeted for. (Sears had to shave something to get the low price point, and bass is real pennies.)

He could post the schematic for general group comment. But he's a big boy and is having fun tinkering and graphing, may not have time to listen to our kibitzing.

 

[abbey road d enfer]

> What do you mean

Let us pretend the "correct" sound is flat.

CJ has empirically found that an added 8dB/oct rise gives the desired sound. 

This suggests the un-CJed amp had an 8dB/oct *drop*.

Now, some amps are bright and some are dark. But 8dB/oct over much of the audible band (in a non-special bit of gear) is more than a matter of taste. It isn't just "dark", it is a black hole for all but the boom.

I doubt even Sears sold something that dark/black.

I first thought some post-Sears pre-CJ modder had put, say, 4,700pFd where should be a 47pFd.

He now finds a 4.7K PA input impedance. Not sure how that is causing dark-black.

There's the added flip that he seems to want a sub-150Hz *rise*. Which is not just a wrong treble-cap. He may have a more complicated thing going on. Or he may just be asking for more deep bass than Sears budgeted for. (Sears had to shave something to get the low price point, and bass is real pennies.)

He could post the schematic for general group comment. But he's a big boy and is having fun tinkering and graphing, may not have time to listen to our kibitzing.

OK. I wasn't sure I had caught it.