Proco Rat build

ivan H

ivan H

Ambassador of Tubes & Grooves
Country flag
So, I've never owned a Rat, not even tried one before, so when I heard Thatbastarddon's demo of his build I was impressed, enough to want one, thanks Don. With the Aussie BYOC distributor out of "mouse" stock I decided to scratch build. Ordered up some parts, including a couple of metal can type (TO-99) Motorola LM308's, as used in the very first Rat's & got to it. I did the circuit board "point to point" style on prototype board like soWP_20170701_005.jpg & its undersideWP_20170702_004.jpg
Circuit wise I also used all values of the first Rat variant. I did use a different cap "type" in a few places. Instead of using electrolytic caps, which have a very large tolerance, I used close tolerance tantalum caps for the filter's two frequency dumps, also for the two places where electrolytic's are normally used in the audio path. All other audio caps are mylar types as used in originals. The only other mod I did was an added 3 position switch for asymmetric clipping. One position adds another diode to the positive clipper so its not clipping as much, another position lifts the positive diode clipper so that only the negative half of the wave form is being clipped. The 3rd switch position is stock Rat clipping. So, here's the enclosure drilled & primedWP_20170630_001.jpg note cotton tip stand offs. Here it is painted matte black WP_20170701_001.jpg
All hardware fittedWP_20170701_004.jpg
Positioning boardWP_20170701_008.jpg
Circuit board with fly leads attachedWP_20170702_006.jpg
All connected up & completedWP_20170702_007.jpg
Except for labeling WP_20170702_010.jpg
Man, these things sound freaking awesome. So glad you inspired me to build this Don. This is definitely gunna kick something off my board. Not sure which clipping configuration I like best yet, they all sound great. Asymmetric with two positive diodes is a bit more aggressive sounding & a tad tighter, no positive clipping is again a bit more aggressive & tighter. I only tried it with my LP traditional with an overwound T top (8.8k) in the bridge & BB1 in the neck, through a 1987 clone & also through my 50 watt "Tim Caswell #39 mod" amp. Does equally well through the lower or higher gain amp. Cant wait to stick my Jackson with Duncan Distortion's through it. How did I ever get by without one of these. Be interesting to see how a strat sounds through it. Cheers
Edit; I also deviated from the originals in that I wired the filter control the opposite way. I had read on stompbox forums to either use a linear pot or wire it in reverse so as to get a better sweep. I don't often make mistakes wiring up a pedal, but did with this. In my haste to get it done & fire it up I also wired the distortion pot back to front. I'll fix it tomorrow before I label it. Actually, I'll more likely plug my Jackson through it & make some serious noise first. Cheers
 
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Thanks for the kind words guys. I apologise for the poor quality pics. I am pretty well computer illiterate (digitally challenged) & post via a cheap Nokia windows phone which I take the pics with. Often I need to resize them to get them to upload. Probably a camera setting that I don't understand. I know its ridiculous, I have electronics knowledge but know so little about computers. Really should learn & stop using "I'm too old now" as an excuse.
Don, I either by buy the enclosure already powder coated or paint them so I can tell them apart on my board. Labelling is usually done with a sharpie type marker. If I put ont together for someone else I drill out the enclosure & give it to them to add whatever graphics they like, then finish putting it together. I cant promise a clip but if I can enlist someone's aid in recording one in a suitable format & uploading it I'll get one done. The asymmetrical clipping is quite easy to do. I choose to clip the negative half of the waveform as is done in say, a 2203/2204 Marshall or soldano SLO. This shows which diode clips which half of the waveC__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_images(11).png
Figure 2 shows that the diode with the band end (cathode) to ground clips the positive half of the wave. If you temporarily lift that end from ground (or either end), it will be only clipping the negative half. Instead of putting it straight to ground I took it to one outside terminal of a SPDT, on off on type mini toggle switch. I took another diode oriented in the same polarity from that same terminal to the opposite outside terminal. The middle terminal goes to the diodes ground on the board. I read on a few stompbox forums that of all the Rat's clipping mods, most prefer only asymmetrical so didn't bother with any others.
Sysco, I had intended doing a BYOC mouse but the Aussie distributor was out of them & only had the mini mouse. Besides that they wack a chunk on the price making it cheaper to order & ship from the US. The mouse is a versatile pedal with three variations on the Rat's hard clipping diodes, plus another 3 options where the hard clippers are switched out & soft clippers are switched in. Soft clippers are the same arrangement as hard but instead of being positioned in the IC's output, they are placed in its feedback circuit (tube screamer style). This results in OD type distortion. I've built BYOC & GGG kits, both are very good. Cheers
Edit; the BYOC Phase Royale, for instance is out & out the best phaser type pedal I've used. A take on the MXR Phase 90, it has speed, depth, resonance & mix controls & switchable 4 or 6 stages of phasing. The mix control alone, which goes from 100% dry to 100% wet makes it infinitely more useable than any other I've tried. Internal trimpot allows dialling in as either a "script" phase 90's sound or modern phase 90. Cheers
 
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ivan H said:
Edit; the BYOC Phase Royale, for instance is out & out the best phaser type pedal I've used. A take on the MXR Phase 90, it has speed, depth, resonance & mix controls & switchable 4 or 6 stages of phasing. The mix control alone, which goes from 100% dry to 100% wet makes it infinitely more useable than any other I've tried. Internal trimpot allows dialling in as either a "script" phase 90's sound or modern phase 90. Cheers
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You're killing me... I'm about to blow...:run:
 
Ivan, Nice work and very informative as usual. I will need to go through in more detail.

How are the plastic standoffs for the board affixed to the enclosure?

I'm dying to get back into pedal builds.
I have the parts but no time and have forgotten most of what I learned earlier.
 
syscokid said:
Well... I hope your happy now.

Last night, I ordered the Phase Royale kit. I'm a wimp when I get gassy... :boobpoke:

... to be continued
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Cool. I use mine quite a lot for clean passages, where without the mix control I wouldnt. I have it so its barely noticeable. Great with arpeggiated passages and things like that. Look forward to the thread.
Jtcnj, the Standoffs have a double sided adhesive pad on the bottom so its a simple matter of inserting them through the board, removing the plastic film from the underside & positioning the board in the enclosure. They have a small cam that locks the board Down. A pair of long nosed pliers can be used to squeeze the cam in to remove the board, leaving the standoffs attached to the enclosure. I had to trim the outter edge of the bases on this one so they'd fit. They have a small cam that locks the board down (can be undone for removal of board).
RobV, its a very rewarding hobby. I'd recommend starting with one of the easier General Guitar Gadgets or BYOC (build your own clone) kits & progressing from there. Check out forums like diy stompboxes, freestomboxes, tagboard effects etc where you can find Vero board layouts for countless fx. Cheers
 
Nice job! I guess that LM308 is very close to the metal can tranny in the picture. I bet it sounds awesome. My favorite stock Rat is the YDR ( You dirty rat ). Even the stock Rat2 sounds way cool. If you decide to put up some sounds clips it would be sweet to hear them. I just realized the metal can is actually the original type LM308. My mistake sorry!
 
Thanks C man. Yes, I was lucky to score two of the TO-99 cased (metal can type) Motorola LM308HZ chips very cheaply on ebay.au, so they arrived very quickly too. Cost me 3 bucks more for the two of them than what one new production chip would cost over the counter at my local electronics outlet. After playing through it for a few days I also like the stock rat clipping configuration. For rhythm type riffing, power chords etc I find it best. Lifting the positive clipper's ground so only the negative half of the waveform gets clipped I also like. To do it over I would use only those two options & put the ground lift on a footswitch as, as well as sounding more aggressive & tighter, it also gives a noticeable volume boost. Would be a handy feature when taking a lead, roll up the guitar volume & step on the footswitch. I might replace the SPDT switch with a SPST & do away with the other clipping option. I could still manage then by kicking the toggle left or right. I have the other chip so may well do a YDR one day. Cheers
 
Cool build , here's my old war horse! I think it's a pretty early version. Probably needs new Electros + but sounds fine

DSCN3927.jpg


I've read if one has reverse threads on adjacent screw heads they sound better or sumptin like that, I don't know?
 
ivan H said:
Thanks C man. Yes, I was lucky to score two of the TO-99 cased (metal can type) Motorola LM308HZ chips very cheaply on ebay.au, so they arrived very quickly too. Cost me 3 bucks more for the two of them than what one new production chip would cost over the counter at my local electronics outlet. After playing through it for a few days I also like the stock rat clipping configuration. For rhythm type riffing, power chords etc I find it best. Lifting the positive clipper's ground so only the negative half of the waveform gets clipped I also like. To do it over I would use only those two options & put the ground lift on a footswitch as, as well as sounding more aggressive & tighter, it also gives a noticeable volume boost. Would be a handy feature when taking a lead, roll up the guitar volume & step on the footswitch. I might replace the SPDT switch with a SPST & do away with the other clipping option. I could still manage then by kicking the toggle left or right. I have the other chip so may well do a YDR one day. Cheers
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Sounds like you got it going on pretty good with this build. Now you got me curious about the Moto chip! I will check out my ebay here also. I put a socket in my Rat2 so I can swap out opamps. Just out of the box these things are cool but, my YDR blows away my Rat2. I'm always learning from ya! Thanks!
 
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