Proco RAT Ducetone, BASS mod.

[anacrusis]

I want to use this pedal for bass, but need to make sure the low frequencies don't get cut, is there a simple mod to remove the bass cut? or boost the bass?

[knutolai]

the "Ruetz mod" might be something to check out


Similar thread to check out:
http://www.diystompboxes.com/smfforum/index.php?topic=98216.0

[GGBB]

Since that thread I've experimented with boosting the bass without changing the sonic signature of the RAT and came up with this (click for bigger image):



Those are switching options, but you could easily just solder one in permanently.

There isn't any actual bass cut in the rat - both the input and output caps are big enough to let everything in and out. What it does do is boost different ranges of frequencies at different levels, so that the mid and hi frequencies are boosted more than the low frequencies. The problem with the Ruetz mod is that by changing the resistance value through the pot adjustment, you not only change the boost level or gain of that frequency band, but you also change the bottom frequency of that band and as a result, the entire sonic character of the rat changes. My rat "BB" mod increases the gain for the frequency band that includes the lowest frequencies, but it does not change the range of frequencies. The resulting effect is more apparent bass, but the sound of the rat is the same.

So for a permanent always-on mod, parallel the 560ohm resistor with another 560ohm, and parallel the 4.7uF cap with another 4.7uF cap. Or for more bass use 270ohm and 10uF. If you would rather replace parts than tack extra ones on, use a 270ohm and 10uF or 180ohm and 3.3uF.

[rocket8810]

Ive actually done this and built a few for some other people. Here's what I did. I altered the two high pass filters in the circuit.  This would be the 47R + 2u2, and the 560R + 4u7 networks. Increasing those resistors will reduce the cutoff frequencies when the attenuation starts and so there will be less bass frequencies taken out of the signal.

You ca also try increasing the input and output cap can alway help because more bass frequencies will get into the circuit in the first place, but it's those high pass filters that kill the bass frequencies.

Just socket those resistors and keep increasing the value until you get the response you want.

Conversely you can increase the caps in the filter networks, so that will prevent a change in the gain, which occurs when you change the resistors. This is because the filters are part of the drive circuit. I also, changed the diodes to Ge to smooth it out, as well as a few other mods to make it suit me better, but diode changes and such are another story and just socket and experiment.

[mwynwood]

Hi All,
I've decided to have a go at Gord's BB Mod. (http://www.aronnelson.com/gallery/main.php/v/diyuser/GGBB/RATBassBoost.gif.html?g2_imageViewsIndex=2)
I have a "Centre OFF" DPDT switch, and I was wondering if this is a correct interpretation of the schematic.

In these locations:

Thanks for your help!!

[GGBB]

Yes - that's correct.

[mwynwood]

Awesome, thanks heaps for double checking that for me.
It should be great on bass guitar:)

[GGBB]

If you would rather replace parts than tack extra ones on, use a 270ohm and 10uF or 180ohm and 3.3uF.

Just noticed a typo in my earlier post - should have been 180ohm and 15uF or possibly 120ohm and 22uF.

[mwynwood]

Thanks for your help!
Here's my result: https://marcuseffects.wordpress.com/2016/06/20/proco-rat-bass-mod/

[patricks]

Holy moly, this is filthy!!