# Planning a RAT...



## Big Monk (Dec 3, 2021)

I've been told I need a RAT. I have this document in my files:




Is the move to find a commercial RAT and mod or to build one from scratch?

Any insights on what circuit to use? I've never used a RAT before so i am out of my element.


----------



## Harry Klippton (Dec 3, 2021)

Why not start with the basics? Get a proco. They're cheap and readily available. Then you know what you're starting with before you try to squeeze the kitchen sink in there.


----------



## Big Monk (Dec 3, 2021)

Harry Klippton said:


> Why not start with the basics? Get a proco. They're cheap and readily available. Then you know what you're starting with before you try to squeeze the kitchen sink in there.



No Kitchen Sink. Straight up RAT. Just wondering which version or component values people have found works the best. 

I know you said @thewintersoldier built one for you. Anything special about that one?


----------



## fig (Dec 3, 2021)

> Anything special about that one?


Do you mean other than @thewintersoldier built it?


----------



## Big Monk (Dec 3, 2021)

fig said:


> Do you mean other than @thewintersoldier built it?



Truth!


----------



## jimilee (Dec 3, 2021)

Check out the Triad distortion, that's a straight up rat, part for part.


----------



## Coda (Dec 3, 2021)

I built one based on the original specs (LM308). It’s decent. However, I built it with the intention of swapping IC’s out…which I did. I tried several. They all basically sound the same. I think I actually preferred the part that is stock nowadays (OP07?), but put the LM308 back in because I wanted to see if it would spout magic. It hasn’t. I regret not socketing the LED’s l, though…


----------



## thesmokingman (Dec 3, 2021)

if you go the mod route, plan ahead and buy three replacement pots from smallbear and a 3n3 film cap along with your mojonium op amp of choice (lm108/208/308)


----------



## JamieJ (Dec 3, 2021)

Does anyone have the DRV 1981? How does this compare to an OG rat?


----------



## benny_profane (Dec 3, 2021)

If you take a look at that sheet, there really isn't a lot of variance apart from clipping diodes, inversion of the TONE/FILTER wiring, those necessitated by choice of IC, bypass switching systems, coupling caps without appreciable changes in frequency response, and a pull-down resistor at the input. (Certainly not the wide variance seen with the BMP.)

In terms of mods, the Ruetz mod ("sweep" on the Aion board) or @Chuck D. Bones' CONTOUR control are useful and can be taken out of the circuit entirely. Clipping options are an obvious choice: I prefer 2x1 Si diodes (e.g., 1n4148 or 1n914), but usually include 1x1 LEDs (Turbo) and 1x1 Si (stock) as well with an On-Off-On toggle.

The 'White Face' small box Rat gets a lot of attention on the internet. It's the V2 FILTER control circuit. That being said, most Rat versions are the same circuit in different housings or aesthetics and claims about sonic differences are specious. The real change comes with the introduction of the OP07 chip (see below).

The Rat is definitely my favorite distortion. Stock, it's got a ton of options and is very versatile, but it can be easily modded to adjust things as necessary. It has a usable range from OD to distortion to fuzz [1] and it stacks well with (octave) fuzzes, ODs, and boosts. Frankly, I'm surprised I don't see more boards with two Rats on them. I don't really think it's terribly productive to argue about IC choice here [2], but I would encourage you to try different chips out and see what you like. The FILTER control can be narrowed to have more precision if you find that there's only a window that works for you.

It's a simple circuit and easy to bread board. I'd suggest building one stock and modding another one out. For inspiration beyond clipping and typical tone mods, the VFE Alpha Dog is a more ambitious take on a modded Rat.

1. There are a lot of varieties of 'fuzz'. It gets fuzzy at full-bore. We don't need to have an inquisition here.
2. There are a lot of questionable devices being sold as 'LM308' chips and not a lot of control over test methodology. Some unscrupulous stateside resellers purchase bulk eBay listings and pass them off as authentic. Are they? Who knows. SBE and other sellers with good reputations can be trusted, but there is a lot of uncertainty in the market.


----------



## benny_profane (Dec 3, 2021)

JamieJ said:


> Does anyone have the DRV 1981? How does this compare to an OG rat?


I haven't played one, but take a look at the schematics. Beyond the same FILTER control (with a value change) and hard clipping after the gain stage, there are a lot of differences. Though many of the differences are fulfilling the same functions as the corresponding Rat circuit blocks, the increased voltage, buffered bypass scheme, two-stage gain block, and JFET IC op amps used throughout make it a pretty different circuit. It certainly wears its inspiration on its sleeve, but I don't think I'd call it a 'Rat'.


----------



## Matmosphere (Dec 3, 2021)

It's really all about the diodes. I have owned a couple Rats, my old bandmate had a Turbo Rat, and I've built a few as well. The diodes make a much bigger difference than using the modern op-amp vs a lm308. If I were going to build one again I'd do the standard clipping diodes and red LEDs on a switch. 

The stock Rat is pretty great. The Turbo Rate (which is identical other than red leds for clipping) is a monstrous high gain beast of greatness that is loud AF. Both are worth having.

If I recall properly the You Dirty Rat is the same as the original but with no clipping diodes, just op-amp clipping. It's okay, but I don't like it as much. The nice thing is that if you use a three way switch instead of a two way you can have leds, the regular diodes, and no diodes without much trouble.

On top of that the Ruetz mod is also worth trying. I have made Madbean's Slow Loris. It that incorporates both a clipping switch and the Ruetz mod. I made a Runt as well, that one is a solid little board, dead stock rat, if you are a glutton for punishment and really want a 1590a Rat.

I'll leave you with this partia schematic for a Rat I believe to be from the development stage. (sorry if I already shared this here, I don't remember)


----------



## benny_profane (Dec 3, 2021)

Matmosphere said:


> If I recall properly the You Dirty Rat is the same as the original but with no clipping diodes


The You Dirty Rat uses antiparallel germanium diodes.

Edit: @mdc is correct below. New production uses BAT-41 diodes instead of the Ge used initially.


----------



## Matmosphere (Dec 3, 2021)

benny_profane said:


> The You Dirty Rat uses antiparallel germanium diodes.


Couldn't remember, I know I don't like the germanium sound in there. Not terrible, just not very Rat.


----------



## mdc (Dec 3, 2021)

AFAIK, The Dirty Rat hasn't used Ge diodes for years. It uses BAT41s or BAT46s with similar Vf ratings and (surprise) no one can tell the difference. 

I love Rats a *lot* but I also kinda feel like the attempts to improve them are sorta missing the beauty of the pedal. It's just sort of a perfect thing as it is. Also, I honestly don't think the Rat2 and the Turbo Rat sound too different from one another, the Turbo Rat just has a lot more output volume. The Rat was my main (only!) pedal for years when I was touring in bands, and I switched to the Turbo eventually as it basically gave me the same sound with a bit of a volume boost.


----------



## Big Monk (Dec 3, 2021)

To be clear, and I know my history of tweaking things is coming into play here, I want to build a straight ahead 3 Knob Rat. I think the only thing out of the ordinary may be a 3-way clipping switch.


----------



## benny_profane (Dec 3, 2021)

mdc said:


> AFAIK, The Dirty Rat hasn't used Ge diodes for years. It uses BAT41s or BAT46s with similar Vf ratings and (surprise) no one can tell the difference.
> 
> I love Rats a *lot* but I also kinda feel like the attempts to improve them are sorta missing the beauty of the pedal. It's just sort of a perfect thing as it is. Also, I honestly don't think the Rat2 and the Turbo Rat sound too different from one another, the Turbo Rat just has a lot more output volume. The Rat was my main (only!) pedal for years when I was touring in bands, and I switched to the Turbo eventually as it basically gave me the same sound with a bit of a volume boost.


You're right about the BAT-41 diodes. I edited my post above.

I tend to agree with you about modding the circuit (beyond clipping diodes). Any mod I like to do with a Rat should be able to be taken out and the circuit returned to stock. Pedals like the VFE Alpha Dog are completely different circuits—that's not an appraisal or valuing of them, it's just that they aren't Rats.

I disagree w/r/t LEDs. You do get a volume boost when switching to LEDs from 1n4148/1n914, but you also gain an amount of headroom. If you normalize the volume between a Rat with LEDs and one with Si diodes, the LED-clipper will have less compression and more headroom/nuance comparatively.


----------



## benny_profane (Dec 3, 2021)

Big Monk said:


> To be clear, and I know my history of tweaking things is coming into play here, I want to build a straight ahead 3 Knob Rat.


Oh, the horse is out of the barn. If you want a straight-forward stock three knob Rat, you already have your answer. I'm taking advantage of the opportunity to talk about a Rat beyond nonsense about the IC. In a sea of fuzz, tube screamers, and the LM308, this is a rare opportunity.

Edit: To your original question: I would say build it.


----------



## Big Monk (Dec 3, 2021)

benny_profane said:


> Oh, the horse is out of the barn. If you want a straight-forward stock three knob Rat, you already have your answer. I'm taking advantage of the opportunity to talk about a Rat beyond nonsense about the IC. In a sea of fuzz, tube screamers, and the LM308, this is a rare opportunity.



I edited my post above to include a clipping switch because that seams useful as well.


----------



## benny_profane (Dec 3, 2021)

Big Monk said:


> I edited my post above to include a clipping switch because that seams useful as well.


SPDT On-Off-On: LEDs always in circuit (Turbo), symmetrical Si 1n4148 or 1n914 (Stock), and WILDCARD (I like asymmetrical Si).


----------



## spi (Dec 3, 2021)

JamieJ said:


> Does anyone have the DRV 1981? How does this compare to an OG rat?


I built both.  I gave the Rat away before the DRV so I never had a chance to do it side-by-side. 

I think DRV is voiced toward the lower gain range of the Rat, and is more like an overdrive that gets to distortion, while Rat is an overdrive that quickly goes to distortion then to fuzz.

I've never been a huge Rat fan but did like it at the low gain settings, which in part is what motivated me to build the DRV.


----------



## JamieJ (Dec 3, 2021)

fig said:


> Do you mean other than @thewintersoldier built it?


Kiss ass 🤣


----------



## fig (Dec 3, 2021)

Quiet you...I'm working heyah.


----------



## fig (Dec 3, 2021)

Here you go, one Rat. Sounds heavenly!


----------



## jimilee (Dec 3, 2021)

This is a rat hole and then some. I have a modified rate 2. 3 clipping mods and a switchable ruetz mod. Got 2 rats with led 914 switching mods, then I bought a fat rat. Then I started with the Brat / Roadkill rat. That board should be here Monday. It has clipping in the feed back loop. I’m working on another one with mosfet clipping similar  the fat rat but with two misfits instead of just one. There are so many variations out there. The mosfet I’m working o. Will have 2 options and a diode lift for opamp clipping.


----------



## jeffwhitfield (Dec 4, 2021)

I cheated and used the AionFX Helios PCB for my Rat build (https://aionfx.com/project/helios-vintage-distortion/). I used a LM308N op-amp for authenticity. However, for the clipping diodes I altered the specs a little bit. The cool thing about the Helios is that it has a three-way switch for diode selection. A set of LED's is always kept inline for hard clipping. By default, AionFX specs it out with switch setting for a pair of 1N914 diodes and another for two pairs of 1N914's. I nixed the two pairs in favor for a pair of 1N34A's. So, basically, you get the standard 1N914 clipping (basic Rat flavor), LED clipping only (Rat Turbo?), and GE diodes (Dirty Rat?). Pretty much covers all the Rat most people would want I think.


----------



## fig (Dec 4, 2021)

My BB sounds even better after putting that 30p from 1-8 instead of 1-5 . I'll put some groovy pics of squiggly lines my scope put out in the Test Kitchen...

Jeff, I used 1N4148s, a 2N5457, and a LM308N.

Derek, have you decided on what mods?


----------



## Big Monk (Dec 4, 2021)

fig said:


> My BB sounds even better after putting that 30p from 1-8 instead of 1-5 . I'll put some groovy pics of squiggly lines my scope put out in the Test Kitchen...
> 
> Jeff, I used 1N4148s, a 2N5457, and a LM308N.
> 
> Derek, have you decided on what mods?



I’m going to keep it simple. 3 Knob with 3-Way switch for LEDs, Sym and Asym diodes.


----------



## fig (Dec 4, 2021)

Big Monk said:


> I’m going to keep it simple. 3 Knob with 3-Way switch for LEDs, Sym and Asym diodes.


Groovy! I'll see if I can add the same.


----------



## Big Monk (Dec 4, 2021)

fig said:


> Groovy! I'll see if I can add the same.



It’s on my now short list for 2022. Next up on the bench is my Tearjerker overhaul.


----------



## jeffwhitfield (Dec 4, 2021)

fig said:


> My BB sounds even better after putting that 30p from 1-8 instead of 1-5 . I'll put some groovy pics of squiggly lines my scope put out in the Test Kitchen...
> 
> Jeff, I used 1N4148s, a 2N5457, and a LM308N.
> 
> Derek, have you decided on what mods?


2N5457 here as well. With the LED hard clipping in-line after the main clipping diodes, I would imagine the 1N914’s sort of clip in a similar manner with the LED’s. They’re there no matter what so the kinda clip a bit with the other diode selections…at least I think they do. 🤪


----------



## Big Monk (Dec 7, 2021)

thewintersoldier said:


> @Big Monk here's a video I took last night of my SG and the rat going into a deluxe. Sorry for the low volume I'm not sure what happened there. But you get the idea. The clipping is asymmetrical and the gain us at noon.



Nice!

This is definitely on the build list for 2022.


----------



## thesmokingman (Dec 7, 2021)

You've been planning this longer than Tayda takes to ship you the parts ...


----------



## Harry Klippton (Dec 7, 2021)

I


thewintersoldier said:


> So this can live in Will's head rent free @Harry Klippton


Hadn't thought about that song for like 25 years til yesterday


----------



## Mike52 (Dec 11, 2021)

I built two Rat pedals, having never played one. I tried to basically do the same thing you are doing. I installed sockets everywhere I thought a worthwhile mod could be installed. The differences are small, but I keep going back to one pedal. I thought I'd be tinkering with these a lot, but I haven't really touched them. 

But PCB boards are cheap, and Rat boards are easy to find. Wouldn't it be fun to build several and use plugs for the hardware (Like an Auditorium Test Platform) so you could swap versions into your enclosure.


----------



## Big Monk (Dec 15, 2021)

thewintersoldier said:


> Here's another clip for @bigmonk to sink his teeth into. This is into a completely clean blackface mind you. Gain at just below noon.



That’s sounds awesome!


----------



## Big Monk (Dec 15, 2021)

thewintersoldier said:


> It's gonna change your world



I hope so. I’m getting tired of finicky and temperamental vintage fuzzes.

Can’t a guy just cop the tones from Old Zep, Jeff Beck “Truth” and “Echoes” and “Time” without RF, oscillation and flippin mud?

Maybe I need a Dizzy Gnat instead of MK II/Supas and Fuzz Faces


----------



## thesmokingman (Dec 15, 2021)

So … will the universe suffer heat death before this rat happens?


----------



## benny_profane (Dec 15, 2021)

thewintersoldier said:


> That's why I went back to the Rat. Full circle. Push it with a tube screamer and it really sings.








						Hybrid Fuzz Face (Universal Fuzz Board)
					

I'm doing something a bit different here, I had already built this pedal and documented it in my Universal Fuzz Board Thread.   I've been talking a lot about fuzz lately, particularly about not feeling my Germanium units. As always, @thewintersoldier gets me thinking about things. In partocular...




					forum.pedalpcb.com
				








						Hitting the Brick Wall
					

You guys ever get that with building pedals? I just ran into my second brick wall since I got heavily into building in  late 2017. in 2019 I started really getting back into building and taking more seriously. When the pandemic hit I had nothing else to do in my free time and it became a great...



					forum.pedalpcb.com


----------



## Harry Klippton (Dec 15, 2021)

Hi, dumb question: what do y'all mean when you mention oscillation with a fuzz pedal?


----------



## Big Monk (Dec 15, 2021)

Harry Klippton said:


> Hi, dumb question: what do y'all mean when you mention oscillation with a fuzz pedal?



Uncontrolled, unmusical feedback.


----------



## Big Monk (Dec 15, 2021)

thesmokingman said:


> So … will the universe suffer heat death before this rat happens?



I’m planning on having @thewintersoldier build it for me in the New Year.


----------



## thesmokingman (Dec 16, 2021)

Big Monk said:


> I’m planning on having @thewintersoldier build it for me in the New Year.


----------



## Big Monk (Dec 16, 2021)

thesmokingman said:


>



Got a little nippy through the pass huh @thewintersoldier?


----------

