Thanks to all of you, I have a new pet Siberian Hamster. Meet Marvin, he’s a pure-bread
Filigree Siberian Hamster!
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BUILD REPORT:
I bought the L’il Mouse PCB from BYOC a couple years ago. Last February’s Chinese New Year, I thought it appropriate to finally do something with it for Year of the Rat. I set aside all the bits needed to build it up in its own little project tin, and then the whole world turned upside down for everyone.
Fast forward to the waning days of the Year of the Rat (following the Chinese Lunar Calendar, it ended earlier this month), and a bunch of people are having wayyy too much fun in a thread here on TB (I won’t say which one, but I think you know very well…). So I dug out my old soldering iron — using it is like threading a needled with boxing gloves on, but it can and does work, just not as well as my solder-station.
Hand-drilled the cheapo-enclosure ‘cause my drill-press is kaput, and I didn’t have time to head over to my friend’s Atelier to use his press: so the holes aren’t as precise as they should be, but precise enough that everything fit, barely.
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Note how the jack hovers over the DPDT
MODS & SODS
Added 2N5817 polarity protection
LEFT WHISKER: Clipping Switch SPDT on-off-on
UP: Stock 1N914 /
CENTRE: Turbo red LEDs (socketed so can try op-amp clipping or mixnmatch colours) /
DOWN: Fat Rat BS170/BAT41
RIGHT WHISKER: Tranter Fat Mod Switch #2 (Retains Rat tone while retaining some bass!) DPDT on-off-on
UP: Bass
CENTRE: Stock
DOWN: BASS-BASS
Meant to add a minimum gain resistor, but forgot

and was too far in when I remembered. This bit me in the butt when I was first testing it and got... nada. I was bummed. Then I remembered — the Gain has to be turned up a bit, duh… ahhhh…success! Some more mad-mod-kajiggering and … dead. You’d think I’d have learned from the first time the Gain was down, and I did ‘cause the gain was up — I got clean sound but it wasn’t Ratting little Fuzzballs out the speakerage — well, these fuzzer things work much better when testing if you click the 3PDT to "on"

. Hey! I didn’t have the LED installed yet, cut me some slack.
POTS:
I used a 1590A pot-helper daughterboard, which indeed helped a lot, when it wasn’t hindering things like fitting switches.
VOL: STOCK
TONE-POT (Filter-whatever)
Swapped some tone wires around, got it wrong so went for the easiest fix with the least amount of desoldering and re-soldering — one wire — and…
it behaves just as I’d intended, with turning clockwise giving more treble, and counterclockwise cutting treble (I can’t say it gets more bassy CCW).
Some mods call for 50k with an associated cap swap, I opted for a B100k to the stock A100k.
GAIN: Stock A100k, cause I forgot the dad-gum-min-gain-mod-resistor. Didn’t want to try a 500k mod I’ve seen, will try that another time with more space, but mind... 500k might make it more difficult to dial it in.
CAPS
Bumped up the input 22n>220n, coupler before transistor 22n>220n and output 1µ>2µ2. I’ve read doing so does jack-all, that the real place to tune the rat is those filters where you stick the Reutz Mod… but I’ve also seen some much Bigger Values on other peoples’ mods. It can't hurt, can it?
C8 4µ7 Tantalum… I was going to make it a 2µ2 Film Cap, ‘cause that’s still plenty big and higher fidelity… but I chickened out and put a stock value but tantalum for arguably better sound than electrolytic, and to SAVE SPACE.
Caps for Tranter Mod #2: Tantalums to save space.
LM308’s slew cap: went with 33p with a 60p trimmer, just to experiment with, haven’t dialled it up to 93p yet. Stock Rat 30p vs some mods suggesting as high as 100p, so I can get close to that.
C9 3N3 bumped to 4n7, shoulda monkeyed the associated resistor a little too, but didn't.
C6 on the BYOC schematic calls for 1µ, it’s some power filtering for the 4v5, I bumped mine up to 2µ2.
RESISTORS: All stock, except of course the Tranter Sw, and the CLR I dropped to 2k2 from the recommended 4k7. I was going to put in a Bi-colour LED (red=off/blue=on), but changed my mind to just a simple bright-white 5mm.
IC: stock LM308 — I’ve got some of the metal-cans, but I didn’t even try to fit them under the lid, so plastic DIP Chip.
Q1: stock 2N5458. Socketed, can try a 5459 or whatever...
JACKS: Had to clearance the IN jack so the DPDT Tranter switch wasn’t shoved around.
Marvin’s Eyes: Got a bunch of Googly eyes in different sizes to mod a pair of sneakers; for Marvin I opted large&friendly as opposed to tiny-beady.
Marvin’s Nose: Thought I had pink, I didn’t have pink, and red was too dark, so I went with light-orange.
SOLDER-MASK: before I started a trace looked like it was lifting, but turned out to be just the solder-mask. Could’ve left it but decided to nail-polish it (didn’t have any SuperGlue).
Rat Fur: A large off-cut donated by my Amp-guru, he gave me enough to breed several more Siberian Hamsters. I gave the enclosure a little bit of a skirt, to hide the plate. Didn't want to cover the plate, as I want a good surface for pedal tape.
I’ve played other people’s Rats, very briefly, but never owned one. Since it’s my first Rat build, I thought I shouldn’t get too crazy with mods and parts-value substitutions, hence the stock 100k for all the pots. Yet, I still went a little crazy and every time I did my mentor-friend tried to reign me in (‘cause he thought I was building it for our mutual guitar fiend, uhm friend. As noted, I still managed to bump up some cap values for bass).
Next time:
- Remember the minimum gain resistor;
- Use a lot less wire, it doesn’t need to open like a book as shown in the instructions;
- Plan better (some of my solder-springs weren’t needed — some work-arounds could’ve been avoided — things forgotten this time wouldn’t be next time…)
- Don’t use thick-goopy adhesive that squeezes out the wrong end when the smallest bit of force is applied, use appropriate glue media to affix material to enclosure.
- Even out the volume between clipping positions; Add a resistor to the LEDs, do whatever other little tricks I’ve seen in the past. I don’t mind the volume bump, but I can see where it could catch a person off guard if the switch gets bumped or you just plain forget to lower the volume.
I really liked the sound of the Turbo’s LEDs, then the stock 1N914s and lastly the Fat Rat’s MOSFET and Shottky. Interestingly, that’s the same order of volume loudest to softest. I didn’t get to crank it in earnest, though, and while normally I test everything with my DB, thus far I’ve only tested the Hamster with my YooBaSS, and it’s a completely hollow body and wants to feedback BIGtime, more than my DB. ;-D
The Tranter switch is more subtle than I expected, but that could be due to the neighbour-friendly feedback-fighting volume I was playing at. There is a distinct difference, just not a dramatic one; also, as the bass is bumped it causes all that much more distortion and upper-order harmonics that comes with extra gainy-wool. So while it’s bumping the bass, it feels like its bumping the upper mids and highs, too. Hard to describe, no way of providing you with sound-clips.
Well, since I’ve got a few odds’n’ends out for this build, and a discounted blem-1590B enclosure I found online just arrived — may as well keep the solder flowing…