Saturday, 14 December 2013
Proco Rat 2
Now, there is only couple of small changes to the output buffer and volume control when compared to the original Rat. The volume control looks like it could give you some trouble with the output level. If it does, just snip the 10K resistor from volume 3 to ground. I would personally use linear taper for that too.. If you want to turn this in to Turbo Rat, then just swap the 2M2 resistor for 220K and use 3mm red LEDs for clippers. Or use 1N34A germanium diodes to make it YouDirtyRat. (fixed clipping info accordingly)
I always thought that turbo rat used leds for clipping. Was I wrong?
ReplyDeleteYou Are right.
Deletecheck out my build notes and the multi rat schematic with the various options. I had some really great results. Goes really well with a VOX amp and humbuckers.
http://fuzzquest.blogspot.com/2012/11/the-flying-rat.html
Great layout Mirosol, highly recommended build.
Hmm..
DeleteThis image found from the most reliable source, the internet :) lists Turbo Rat clippers are Ge:
http://www.diystompboxes.com/pedals/rstrand/rat/pcratrev.gif
But then again, the lists are different here:
http://www.diystompboxes.com/pedals/rstrand/rat/rat_versions.htm
Could be that it is with LEDs. I don't have any original Rat unit myself, so i have to rely on the internet... So i'm not sure. :)
+m
turbo rat is with led's. you dirty rat is with germanium! Thanks for the layout !
DeleteI tought Prco You Dirty Rat was Ge. Give your opinion, If you had a handful of diodes 1n270, as you implement these on the circuit?
ReplyDeleteDoes a mix of 1n270 and 1n914 sounds good for you?
DeleteFixed the description accordingly.
ReplyDeleteNote that i placed the diodes so that they can be taken on a switch :) So swap the 2M2 for 220K and have your way with the clippers.
+m
Could please anybody give some explanation how to implement the switch / how to take the diodes on a switch? Thanks a lot for any help!
DeleteNo help please? Or any adwise where to find an answer?
DeleteHI. Just remove D1 & D2, take a wire from where one side of D1 (or D2) to a switch (pin2) and another wire from where the other end of the diode was to the switch (pin 5).
DeletePlace your diode choices across pins 1 and 4, and 3 and 6 for a DPDT switch and hey presto.
Use this link for an example
http://tagboardeffects.blogspot.co.uk/2014/05/blakemore-effects-rous.html
Thanks for your help! I`m just on the beginning to understand those things. One more step!
DeleteThere are also a lot of mods which can be implemented, of course, like the Ruetz mod for chaning the 47R resistor to a pot for smoother overdrive.
ReplyDeleteI guess you can verify it. Built it and all functions work. Not 100% sure on the filter thou. Seems to be cutting to much treble. I'll check my values.
ReplyDeleteCall it good. I think the doides on a switch would be well worth building in also. Got a nice little bit. Thanks guys.
ReplyDeleteCheers!
DeleteThe Filter control is something that i've hated on every Rat i've ever build (which is the reason i'm still prefering my build of Arion MMP), so i do believe that is a feature. You could swap the pot for 50K or even smaller to make more usable.
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I've built the early version from here for a friend. After some playing around we decided to use a 1nF cap instead of the 3.3nF, that gives you a much more useful tone/filter range too. Also it is worth to play with the clipping section in the basic Rat layout, as that can really give you different tonality. In the latest one he decided for a Si + LED combo, but my personal favourite is the Si + Ge combo.
Deletequick question, does the resistor change for turbo version apply to dirty rat too or is that 2m2?
DeletePlayed with this some more. Sounds good on a Vox type amp. One question on the resistor change. There are two 2.2m's on the board. Which one gets changed?
ReplyDeleteThe one going from input to ground (the one on the left) is just a pulldown resistor, so that won't make a big difference. Try the other one.
DeleteYup. The other one from vref rail to 1K resistor.
Delete+m
Hi, I've just build this board, but got several problem at first. First is the feedback which is ear piercing. Then the sound drops of gets cut when I strum power chords like chug-chug. I've made some changes and somehow improves playability and tone. But still I get a bit of sound drop/cut on power chords.
ReplyDeleteI replaced the 1uF electrolytic with 100uF; the 2.2Mohms with 1Mohms and will soon try the 220K. I put a 1nF cap on LM308 pins 3 & 4. I also did a 1K pots Ruetz mod. I also put in switch for clipping selection, 1-RedLED/RedLED; 2-BlueLED/Zenr-Zener; 3-Si-Ge/Si-Ge.
The RedLED/RedLED is not lit when I use it but has sound. The BlueLED blinks fine when selected and I like the sound. The Si-Ge/Si-Ge is weak in volume.
What have you done to get rid the feedback? mine is squealing in a insane way, when the cable is unplugged. What can be done to solve this?
DeleteRunning a buffered pedal in to mine took care of that
DeleteHad to put a 22nf cap from pin-3 of chip to ground. Only way I could get rid of the squealing when gain gets to noon. Started with a 2.2nf then increased until I could get the gain to full without the squeal. (Skipped 15nf because I couldn't find one at the time)
DeleteI'm not sure how much gain this has taken away from the pedal but it still sounds fat with a fuzzy-ish gain (LM308).
I had to do this too. The cap you added is a 1nF on the actual RAT and is missing off this build.
DeleteI can literally tune my squealing. I'm not sure why. Please help, Anyone.
ReplyDeleteis there a difference between lm308n and lm308 ?
ReplyDeletehttp://www.diystompboxes.com/smfforum/index.php?topic=96351.0
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ReplyDeleteThis layout seems to be missing a 1nf cap to ground after the 1k resistor feeding the noninverting input of the op amp. This maybe the cause of the squeeling some people have noted when nothing is plugged into the input.
ReplyDeletejames must be right. Increase that cap value in case you face lots of noise, at the expense of decreasing the max gain available :P
DeleteI just finish building a second one of these and it's really gated, like, I get sound if I hit the strings then it cuts out. I checked for solder bridges, what super obvious thing am I missing?
ReplyDeleteYes, hopefully very obvious. It's just the simple matter of checking the circuit through until to find it. Double, triple check all your cuts and layouts. Then move onto component values, off board wiring, etc. Take a break, and come back to it fresh. Check FET orientation, are you using an alternative op amp? Some wont use the the compensation cap 33pf.
DeleteI went back through it tonight, everything checks out, I even compared it to the last build I did. I can't figure it out. I'm using the correct fet and opamp. I either messed up a cut somewhere or one of the caps I didnt replace is faulty. Luckily I socketed the fet and opamp.
ReplyDeleteDid another build, it fired right up. Thing is such a beast
ReplyDeleteHi I've just finished my second build of this circuit neither working correctly. The circuit shows no sign of Volume gain until about 3 o'clock on the volume pot, but the main problem is that when I turn up the Distortion I get a really high pitched squeal which lowers in frequency the more the Distortion pot is turned up. I am using the OP07 Opamp if that helps, also I have tried more than one opamp with no difference, tried different JFET's and checked their orientation and run a knife between the tracks. Any Ideas?
ReplyDeletehttp://www.analog.com/static/imported-files/data_sheets/OP07.pdf
Deletehttp://www.ti.com/lit/ds/symlink/lm308-n.pdf
OP07 is not pin to pin equivalent with LM308. Since the LM308 compensation pins are used for offset nulling on OP07, your behavior is expected. There is no straight on replacement for LM308, so to get your circuit working right, you'll need LM308 chip. Or you could read the application notes on OP07 datasheet to figure out how to set up an offset nulling trim for the OP07. I'd still recommend getting the correct chip as the Rat won't sound like a Rat without LM308.
+m
Thanks, for some reason I thought they were pin equivalent as I see some people use them. That will teach me not to check my data sheets.
DeleteIt can be used, but not as is. The circuit will need tweaking for it to work properly with OP07 (or any other single opamp). LM308s are widely available through ebay and the prices are not that bad either.
Delete+m
Cheers for setting me right miro. I'll get some and see what happens
ReplyDeleteIf you use a 308 and still get the squealing try putting a buffered pedal in the chain.
DeleteAlso, try using a linear pot for the volume pot
DeleteRight Got me some LM308 opamps and stuck one in, and it's acting exactly the same as it was with the OP07. Volume and Tone seem to be working but all the Distortion pot does is turn the pedal into a really shitty frequency generator :( I'm going to put it to one side until i don't feel like destroying it and then i'll post pin voltages for the opamp and JFET
ReplyDeleteSame Problem here. Did anyone experience the same / found a solution?
DeleteHey guys, shouldn t the clipping filter cap / res pairs be matched the other way around (that is, 2.2uF / 47 Ohms and 4.7uF / 560 Ohms instead of 2.2uF / 560 Ohms and 4.7uF / 47 Ohms)? At least that s the way it appears in most schematics... I have implemented the original rat version from your vero layout and the pairs there are also the opposite way than what appears here.
ReplyDeleteGiven the chance, I cannot even start telling you how great your work is. I m grateful!
Kind regards :)
i know that the original rat was setup that way, but i do not believe the rat 2 is. what you could do is take the rat 2 layout as it is and put sockets in place of the resistors and swap them to be like the original, or it gives you the ability to try different values and see what you like.
DeleteHi Zach and thanks for your comment :) What makes you believe that rat 2 is not set up this way? I haven't found any schematics showing it any other way... Swapping the resistor values would give you a 721Hz and 129Hz pair of low pass filters instead of 1539Hz and 60Hz - and this filters the input to the opamp (see here : http://www.electrosmash.com/proco-rat). The higher of those is practically almost identical to the Ruetz mod with the 1K potentiometer set somewhere halfway (see here in the 1k potentiometer section : http://www.diyguitaramp.com/rat.html) thus making the rat much more of a gentleman and I m not sure that this is the sound that most people expect to hear, at least at the start :) I d be interested to hear your opinion on those above, and please contribute any sources if available! The rat is such a great pedal!!
Deleteno problem buddy. i looked those sites and didn't see the schematic for the rat 2. now, there could be different versions of the rat 2, and have slightly different values for certain areas. i do believe that there is more of a difference between the rat and rat 2 then just the clipping section, just MHO, but i could be wrong. like i said i would just socket the resistors and put them as they are in the rat and see what happens. when i built my rat, i altered those resistors to help make it better suited for bass, but by doing this i also altered the gain.
Deleteabout that 1n cap. without seeing the schematic it's hard to say it belongs there. you can put a socket in that area for that cap, and see how it sounds with and without it. usually layouts don't get verified if there's something wrong with them, so i would say it's same to assume it shouldn't be there. but experiment and see what happens. i know there is a lot of sonic differences between the rat and rat 2, so the things you're seeing could be the reasons.
There s also a 1n cap missing between IC pin 3 and ground, as James Nettleton and a few others noticed. And while i m at it, you might want to use a larger value for that cap in case you are facing lots of noise, at the expense of reducing the gain :)
ReplyDeleteYes, had to use a 22nf :( Now I can max gain though :)
DeleteI built this today and it sounds amazing. However, the layout as depicted above is missing a component (if you examine closely the RAT 2 schematic and actual units). There should be an additional 1n cap to ground between the 100k resistor and pin three on the IC. I incoroporated this into my build by extending the width of the layout by one column. It still fits very comfortably into a 125B.
ReplyDeleteI also added a switch that toggles between yellow diffuse LEDs and the stock silicon clipping diodes... and I'm glad I did, because I prefer the LEDs.
Finally, I implemented the "Lube" mod from Beavis Audio and put the 560r resistor on an on/off switch.
All mods highly recommended. I feel like I have the most versatile RAT pedal ever!
Hey guys I have a proco rat distortion and I would like to mod it by adding a 3 way toggle switch like jhs mods ha and my questions is where do conect or witch componnent to remove to add my toggle switch. Please help me. Thanks.
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ReplyDeleteI bulit this last week, sounds good, but a lack of taste to me, I made a few mods, LM308 Metal can, D1 and D2 replaced woth BAT41 Ge diodes (sounds powerfull and I have too much overdirve/distortions with 4148) remove 47R to 1K pot (sweet spot there to find fine tune, and 560R one leg lifted to on/off swich. on most RAt 2 schemes seems that 2.2M from the left is replaced with 1M, I will try that change as well to low as 220k.
ReplyDeleteI mean the right 2.2M. Also can anyone tell me the cap between pin 3 & 4 What exactly does?
DeleteBAT diodes aren't Ge diodes there Schottky diodes, which are silicon and have a different clipping threshold, hence the different distortion characteristic you hear. If you used Ge diodes you would have a smoother, more compressed distortion and less output. The other things you mention are common mods done to the rat to control the frequencies affected by the distortion, I think it's call the Ruetz Mod, so more or less bass. As far as the cap, I don't see one between pins 3&4, there's one at pin 2 down to gain 2&3 which is 100pF, and a red one that's 22nF. The 22nF is the input cap, the 100pF is a lowpass for the distortion and cuts off the high end of the distortion smoothing/softening the clipping making it less harsh.
DeleteThanks Zach your are right about BAT, actually is a big cristal germanium diode with only 41 number writen, (bigger than clasin 1n60).
Deletethere is no cap in pin 3 and 4 I saw on several schematics from Rat 2 and the older ones, seems to be an standard, also I saw the JHS mod that changes the cap between pin 3 & 4 from 1n to 10n. So that's the question how affect that cap to the sound.
Interesting I wonder what those diodes are then. If you're looking at the same schematic I just did, there's a 1nF cap from pin 3 to ground, which is what pin 4 goes to as well. It's just a high frequency roll off.
DeleteI went agian to store to find some info. ITT and 4 Was the only letters written on them. Also I bought a couple of gold bonded Oa47 for next proyect. Btw cap for pin 3 and 4 makes a good small improvement.
DeleteI got a question, where to wire toggle switch from the board for clipping
Deleteif you want to make a switch for multiple clipping, remove D1 and D2 and put two cables from toggle
DeleteJust built this and as noted by others, there should be a 1nf cap going from leg 3 of the IC to ground. I built this pedal according to the layout and it worked fine but I got a squealing sound when I stopped playing/strumming, adding the 1nf cap removed this squealing noise.
ReplyDeleteDid Anyone build the Rat with another IC like TL071 or similar ?
ReplyDeleteNo one has noticed that the 560R and 47R should be swapped around to be correct to the original pedal.
ReplyDeleteI got the squeal that somebody else got. I followed the original Rat schematic, so I added the 1nF between the two wires Gain 1 and Gain 2 & 3, but it is just a bit attenuated. Then I swapped the 2.2uF and the 4.7uF, replaced the output cap 10uF with a 1uF, left out the 10k resistor between the output and the ground, replaced the two 2.2M with two 1M resistors.
ReplyDeleteThe squeal seems come something wrong with the ground, I guess. If I low the guitar volume the pitch of the squeal change, even with the Distortion pot of the circuit. A bit like the Fuzz Factory effect.
More problem with humbuckers.
I built a pair of the modded version from Sabrotone without any issue, now I wanted a stock version, but this layout seems a bit tricky. Are you sure it's verified?
Yeah, my build acts exactly the same way. Has anyone found a solution?
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Deletehttps://i.imgur.com/F4BgTRC.png
ReplyDeleteHere's an updated layout that reflects the mistakes pointed out in this thread:
-Swapped the 2.2uF and 4.7uF around (top left)
-Added 1nF between IC pin 3 and ground
-Replaced the 10uF connected to the JFET's source with a 1uF
-Replaced the 1.6k in the Filter section with a 1.5k (negligible)
Thanks so much for this summation, definitely going to make these changes soon.
Deleteadding 1nf to ic pin 3 to ground will remove whistle noise.
DeleteWorks great for me. Replaced the diodes with blue leds and it roars. It has a bit of self oscillation which I think I can solve by cleaning up my wiring.
ReplyDeleteI made a video of the build here https://www.youtube.com/watch?v=1t_Yc_S-t4Y
Good for you, Liam!
DeleteDid you test the circuit out of the box or straight closed into it with all the offboard wiring?
Both. Just skimming through the comments, i think ill try to add the cap between leg 3 of the IC and ground also to see if this helps.
DeleteBe carefull of the fakes Lm308n from ebay.When power chords cutoff its for sure fake.I've lost so much time...
ReplyDeleteGreat layout and IMHO, a must for every rock guitarist (especially if you are a Foo Fighters fan)!
ReplyDeleteThis build sounds great with the OP07DP chip and even better with the original LM308 (Small Bear's picky and if they have them in stock, my experience they've been great). Just don't forget to add a 1n bleeder cap.
I've tried a lot of variations and my favorite is leaving out the 10K to ground resistor right before the volume pot and using 1n5817 for the clipping diodes. I also use a shielded coax pickup lead wire to go from the foot switch the vero board for the input, with the braided side grounded once (i.e. not connected on both ends).
Thanks for the design!
So I built this the other night with only a few changes. I used the OP07, 2n5457 and a 1.5K instead of a 1.6K from the filter pot. It sounds great, but my distortion control is working as volume control.
ReplyDeleteAnyone else run into this?
My build sounds great, except for one problem. If I turn the gain up any higher than 1/3 of the way, it starts to squeal, feedback, and oscillate. It also gets VERY distorted to the point of heavy fuzz. I'm not sure how crazy the distortion is supposed to be when you dime a Rat.
ReplyDeleteI used some *highly suspect* knockoff LM308s I found on Amazon, so I am wondering if they are just higher gain. If that is the case, I might just leave it as-is. The distortion sounds great when set correctly, and since I built this for personal use, I kinda like having the option of pushing it into crazy mode. But it would also be nice to get that heavy fuzz tone without the feedback and squealing.
Place a buffer before it and see if you get the same results.
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ReplyDeleteplease any one can share pin voltages?????
ReplyDeleteWould it be possible to add a blend knob between clipping types instead of a switch? How would it be done?
ReplyDelete