Hi! With my second Rat building I tried some tricks I read around here and there to get more bass from this pedal.
I tried with my first Rat the Ruetz mod with the pot control (replacing the R6 47R with a 1k Linear pot).
Now I tried to replace the C7 2.2uF with a 10uF. Then I back with the stock caps.
Then I replace the C6 4.7uF with a 10uF, and even the R7 560R with a 220R.
Nothing of that gets more bass, I got just a slightly dull sound, but this is not a Fat/Bass Boost mod I mean.
I guess it's very hard to get more bass from this circuit!
Who knows the real trick to get more bass?
Thanks!
So, here is what I do. uF caps don't carry audio. Film caps do. So I would take the first film cap in the audio path which looks like a 22n, and make it a 220n, then I would do the same thing to the last film cap. I've never done this with overdrives, but I have done it with filter pedals.
Have you tried looking at how the VFE Alpha Dog adds the Fat control? Might be a good possibility.
The Rat is not a bass booster. It's not in the nature of the circuit. The Ruetz mod replacing the 47R with a 1K trimpot is the correct answer to reduce the fizzy quality of the Rat (you will also reduce its gain somewhat, I think), but it won't be a bass booster. You don't need to change any of the caps. The 47R + 2.2 uF cap has a corner frequency of 1500 Hz and because of its location - it's part of the feedback voltage divider for a non-inverting op amp amplifier - it makes the gain of bass frequencies less than treble frequencies.
If you want more control over EQ, you can build an Idiotbox Blowerbox, which is a Rat with a Baxandall/James tonestack, giving you treble and bass tone controls. I did this, but I also still did the Ruetz mod to it.
The only way I could ever get a rat to have the bass I wanted was to blend in some clean signal and use a hpf and lpf.
All the ones I have tried worked well this way... Rat2, Whiteface Reissue, Duecetone(all settings), VFE Alpha Dog. I have a two loop mixer/blender and a variable lpf and hpf that I used to experiment with.
I don't know if I like the blend mod. So the Rat really seems "bass unboostable"?
But the Fat Rat version has a bass boost, some demos show it works pretty fine.
I heard that it adds a 6.8uF in parallel to the C6 4.7uF, thing I tried replace C6 with a 10uF, but... it's not a really bass boost. :(
Maybe you can add a gyrator that can boost and cut at a low end frequency?
Some clue how I could do it? ???
Please? :D
Google Geofex, Equalizer and Gyrator, or alternatively Electric Druid Metalzone Analysis. Two excellent examples with gyrators.
Thank you very much, I'll try to take a look. ;)
Unfortunately, it's not a very simple solution I was thinking.
R7 and C6 are already dominated by the gain from R6 and C7. The corner frequency of those is 1500 Hz (as reddesert already told you).
You can boost the base as much as you're boosting everything else by making C7 220uF. You'll boost literally every frequency. You might as well remove R7 and C6 now as they aren't doing anything. If you turn the treble cut all the way up, ta-da, you have a bass booster. Of course, now you sound like you're playing underwater, but you did ask for a bass booster ...
http://baritones.tumblr.com/post/92511266453/darrell-rants-about-the-proco-rat-and-the-ruetz
Further reading...
Quote from: midwayfair on September 05, 2018, 02:47:53 PM
[...]
You can boost the base as much as you're boosting everything else by making C7 220uF. You'll boost literally every frequency. You might as well remove R7 and C6 now as they aren't doing anything. If you turn the treble cut all the way up, ta-da, you have a bass booster. Of course, now you sound like you're playing underwater, but you did ask for a bass booster ...
I would like to increase the bass without cut the treble (or the gain) this is the problem.
Quote from: marmora on September 05, 2018, 11:54:40 PM
http://baritones.tumblr.com/post/92511266453/darrell-rants-about-the-proco-rat-and-the-ruetz
Thanks for the link. I tried some mods like that, but the all of them are pretty subtle about the increasing of the bass. Rather those was a cut treble.
This has worked really well for me in the last 2 or 3 rats I modded.
(https://2.bp.blogspot.com/-EkiqYCnUhD0/W5HM6y5lHII/AAAAAAAACsc/Uzg92XPDezctgWvQSmDJcYEuAgu6eziRgCLcBGAs/s1600/rat-bb-mod.png)
small improvement? remove the 560R/4u7 rc filter completely. the bigger improvement is the proco fat rat style of changing the filter
I also like the timmy treble cut values in the rat
Thanks guys. I knew that BB Mod. I tried a 220R and a 10uF.
The Fat Rat add a 6.8uF in parallel to the 2.2uF. Indeed, I tried to replace the 2.2uF with a 10uF.
I noticed just the usually tame of the highs.
I can't try again all these. Next time I should try harder, or I'll let it go.
one last thing, I don't know how anyone else does it but if I cut less bass before clipping I like to up the Vf of the clipping diodes some to compensate. ymmv
There is no real way of adding Bass to the circuit without adding more active circuitry to it. Everything else is a compromise between reducing highs and apparently increasing the bass. Once that happens we loose the character of this circuit and in my opinion it's no longer a Rat because it loses it's bite. Ideally, a parallel active circuit should be created and a low-pass filter taken out of it. By adding a mixing stage to blend both the original Rat signal plus a Bass boost control we could possibly achieve greatness.
^^^^this^^^ A blender board would be the ideal way to go on an over drive or fuzz.
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Everything, even adding more circuitry, is a compromise.
Look, your signal is a flat line if you do no tone shaping:
-----------------------
If you add more bass, you get something that looks like this:
-----____________
If you cut treble (with a shelf filter), you get something that looks like this:
-----____________
It's the same thing.
If your complaint is that the RAT cuts bass, do what I said and make that negative feedback cap 220uF. 10uF is almost meaningless, it's giving you a little more midrange but doubling the cap is only 1/10th of an octave. You'll have more bass and exactly the same amount of everything else, because the cutoff frequency will be the threshold of human hearing. It'll also probably sound like the treble is out of balance, because now you've got full bass in a circuit that already cut treble, but you didn't notice because the circuit used to cut bass.
Hey man,
Maybe this will help out:
http://www.muzique.com/news/quick-rat-pedal-mod/
Quote from: jimilee on September 03, 2018, 03:09:41 PM
So, here is what I do. uF caps don't carry audio. Film caps do. So I would take the first film cap in the audio path which looks like a 22n, and make it a 220n, then I would do the same thing to the last film cap. I've never done this with overdrives, but I have done it with filter pedals.
That's what I thought as well. C12 it's a 22n and looks to me at least like it's making a high pass filter with r10 @ 723Hz. Or am I missing something?
Anybody try a different opamp along with the other filter mods?
https://www.electrosmash.com/proco-rat
"In the Clipping Amplifier Stage, there is a double RC network which places two poles and attenuates harmonics below 1.5KHz.
There are several high pass filters, but the Tone circuit and the op-amp bandwidth limit will roll off harmonics higher than 1KHz."
Quote from: Matt on September 17, 2018, 09:04:00 PM
Quote from: jimilee on September 03, 2018, 03:09:41 PM
So, here is what I do. uF caps don't carry audio. Film caps do. So I would take the first film cap in the audio path which looks like a 22n, and make it a 220n, then I would do the same thing to the last film cap. I've never done this with overdrives, but I have done it with filter pedals.
That's what I thought as well. C12 it's a 22n and looks to me at least like it's making a high pass filter with r10 @ 723Hz. Or am I missing something?
C12 is 22nF and R10 to ground is 1M. That makes a corner frequency of f = 1/(2pi R C) = 7.2 Hz. It shouldn't have any effect on audible signals. Sometimes the first and last coupling caps don't filter out audible bass.
BTW, I have read the datasheet for the LM308 op-amp a few times and have never persuaded myself that its slew rate or gain-bandwidth are so low as to make a difference at guitar frequencies (up to 5 kHz or so). The Rat circuit just kinda sounds like a Rat. I think if one wants something that sounds different, maybe a DOD 250/MXR Distortion+ ?
Quote from: reddesert on September 18, 2018, 12:23:03 AM
Quote from: Matt on September 17, 2018, 09:04:00 PM
Quote from: jimilee on September 03, 2018, 03:09:41 PM
So, here is what I do. uF caps don't carry audio. Film caps do. So I would take the first film cap in the audio path which looks like a 22n, and make it a 220n, then I would do the same thing to the last film cap. I've never done this with overdrives, but I have done it with filter pedals.
That's what I thought as well. C12 it's a 22n and looks to me at least like it's making a high pass filter with r10 @ 723Hz. Or am I missing something?
C12 is 22nF and R10 to ground is 1M. That makes a corner frequency of f = 1/(2pi R C) = 7.2 Hz. It shouldn't have any effect on audible signals. Sometimes the first and last coupling caps don't filter out audible bass.
BTW, I have read the datasheet for the LM308 op-amp a few times and have never persuaded myself that its slew rate or gain-bandwidth are so low as to make a difference at guitar frequencies (up to 5 kHz or so). The Rat circuit just kinda sounds like a Rat. I think if one wants something that sounds different, maybe a DOD 250/MXR Distortion+ ?
Looked at it in a hurry that's my bad
JHS has a made a "little discovery :P" of using the NE5534 chip(I think), which I have heard referred to as the "glass mod". They also state that they make "a few value changes along the way for optimum bass response and smooth silky highs."
https://www.jhspedals.com/products/mod-shop/proco-rat2-pack-rat/
Just saying...
With all the above changes, we might as well build another pedal that is designed for bass. This is getting complicated. I've played bass for over 30 years. Try not to over think it too much. That's why we play bass, Right?
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Quote from: jimilee on September 18, 2018, 06:35:53 PM
With all the above changes, we might as well build another pedal that is designed for bass. This is getting complicated. I've played bass for over 30 years.
Sorry if I misunderstood, I didn't think we were talking about mods for using it
with a bass... That would likely just be a clean blend, which Jack said he didn't want to do.
I do enjoy the exploration of available options so I was just throwing out some info that I ran across to see if it sparked a discussion on an angle that maybe had not been explored to deth :D
Sorry, I'll shut up now