GFS Brownie/Biyang Mouse users - IMPORTANT (Rat content)

IMPORTANT (with PICS illustrating):

Since Biyang discontinued their DS-8 Mouse (from the Tonefancier series) and obviously companies like GFS and Eagletone stopped them too, I suddenly wanted one, knowing that it was a confirmed Rat clone.

I have to say that I was VERY curious as to why so many owners of the Brownie/Mouse/DS-8 didn't think it sounded all that great. Well, I got my better half to score one of the remaining "mice" for me for Xmas.

I've been holding off from posting my thoughts about it, because I also noticed that "something was wrong." It has a nice, tight, punchy quality with midrange by the boatload, but it didn't have the girth or gonads that a good Rat has. When I rolled down the guitar's volume or cut the gain/dist on the pedal, it sounded like a cocked wah pedal in a really bad way.

Well, I had to know what wasn't quite right, and I wanted to confirm that the Mouse also has the LM308N chip from the factory, which it does.

Upon disassembling it, I started looking for some sort of smoking gun. In the event there were numerous variations to the actual original Rat circuit, I was prepared to make whatever tweaks necessary. The first thing I do with ANY Rat pedal is measure a pair of caps and resistors to see how close to "factory spec" they are, because they determine much of the EQ character.

...Lo and behold, Biyang substituted a whopping 56K ohm resistor where the Rat uses a tiny 560 ohm resistor. The 10 to the 2nd power difference is MONUMENTAL - it sucks all the life out of the Biyang clone, and it actually makes any filtering at that frequency to be nonexistent (in stock form, the filter goes well into the bass range anyway).

So, after changing ONE FREAKING RESISTOR, this pedal sounds absolutely on par with some of the best Rats that I've used/tried/built. It will do the girthy fuzz thing, it will do the tight distortion thing, and it will get that wonderful light breakup tone that Scofield and Frisell employ so masterfully. What's not to like?

And when I say it NOW sounds good, I mean REALLY good. The Turbo Rat mode is equally as impressive. This thing will run rings around ANY OCD, Crunchbox, or any of those "improvements" to the Rat. Long live the rodent king! IMO, of course...

I installed a green LED to go with the really cool chrome plated box, and this thing is QUICKLY going on my pedalboard.

BTW - if anyone wants to dissasemble theirs (or any of the other Biyang Tonefancier/GFS/Eagletone/etc. line), you will need a 2.5mm and a 1.5mm metric allen wrench to get off the box top nuts and chicken head knob setscrews. That is a nice touch (if a bit inconvenient), as it really holds things down well.

Pics follow of the offending resistor to be swapped. Its number designation on the PCB is blocked, so I took a bunch of pics and highlighted it. I also have pics of the LM308N chip, the "fancy box metal caps," and two shots of the pedal exterior with the green LED installed.

Oh - I used a 680 ohm resistor instead of 560 ohm. A 820 ohm would probably be okay, too. You could even "piggyback" a pair of 1K resistors in parallel, for 500 ohms, and that would be fine, too IMO.

 

Whatever the reason, it is a PITY. I originally thought that they discontinued this pedal because they ran out of their stock of LM308N chips, but I now have to believe that it was killed because the average impression was that it sounded not so good, and certainly not as good as even a mediocre Rat!

And - the chrome box is cool, the chicken head knobs are cool. The freakin' German box metal film caps are cool!

 

Unless word of this spreads fast from this subforum, I'm hoping it comes in REALLY handy.

I imagine that most folks who got a Brownie/Mouse/etc. probably could not get rid of it fast enough, so there has to be a ton of these things floating around for nothing.

And even if word does spread, it could likely take a long time before it's common knowledge - I'd imagine a lot longer than how to fix the volume drop in an older Boss trem or something along the lines of that.

The build quality on them is just so much better than the ProCo Rat 2, AND they cost less, AND they have the "right style" of D.C. jack, AND they have the LM308N factory installed, AND the in and out jacks are on the SIDES...

...IMO, it's a no brainer, unless you happen along a Rat 2 for LESS, since you will probably want to replace the chip! Given the choice between replacing a chip or just a resistor, I know which one I'm going with. And since the Biyangs use 1% tolerance metal films, the resistors are probably in much better spec...

The Biyangs also use "Millenium Bypass" and not truly true bypass, which is actually a plus IMO. You get all the benefits of true bypass, but with a footswitch that should easily outlast a Taiwan blue 3PDT. If it is good enough for pedals like the Carbon Copy, it is great in the Biyangs.

I like this Mouse so much that I'm contemplating grabbing 3 from a store in the UK - it's still a better deal IMO than the new Rat 2 pedals (and cheaper shipped across the pond!).

It's also great for folks who don't really want to build a DIY Rat kit. The price is about the same, and it comes pre-assembled (and has Turbo and diode lift modes). Just swap that one pesky resistor, and play that thang...

 

I think that's where mine came from. Price is about the same, and some guy from the store actually signed the invoice.

I'll have to check if they have any more. I could be like a junkie with these things.

 

Since I design pedals, this was a huge red flag. When I heard complaints about this pedal, I never heard it described this way, though.

The Rat has a filter (not the tone control) that only passes frequencies above ~1.5KHz. But it also has another filter that passes frequencies all the way down to about 60Hz or so. The 1.5KHz filter has to have a higher "gain ratio," or the pedal would be a muddy, boomy mess.

...So what would happen if the 60Hz filter had a LOWER gain ratio? In a stock Rat, a "quasi ratio" with a 47 ohm on the high filter and a 560 ohm on the low filter is about 12 to 1 (it isn't really, but bear with me). Now - change the "low filter" resistor to 56K, and the ratio jumps to 1191 to 1.

The low filter might as well not even be there with as big of a resistor as the 56K. And - the resistor size actually alters the frequency that the cut starts at. It is tied to a 4.7uF cap, so that combo gives a high pass of less than 1 Hz! So it really isn't doing anything unless the distortion knob is set to max, and even then the effect is mostly negligible.

It's a clear case of "designing" and producing something without any calculations being done (these filters are very basic audio concepts). Even someone with mild audio design experience would spot that "error" almost immediately. If anything, it is amazing that the rest of the circuit is correct. I immediately checked the tone cap to confirm that it was the oddball Rat size of .0033uF, and it is. Oddly enough, the tone pot is a "reverse taper" 100K, but I've actually seen those subbed in place of an ordinary linear taper pot (which is the semi-standard for many tone controls of the Rat-ish type). I can only guess that companies are going with the reverse taper pots for the tone circuits because they can be directly board mounted (i.e. they are extremely common).

It's just really a shame, because everyone likes a good deal, and lots of folks are really into the Biyang/Joyo/Behringer/Rogue/Daphon/etc. pedals, but errors will happen when it is just the intention to duplicate, IMO. For it to happen with a cool Rat pedal with the original chip is just too bad. Even the T Rex Mudhoney (which differs from a Rat a little bit) doesn't have a LM308N in it.

I would love to know the real reason why Biyang killed it off. I guess they have so many other copies that ones like the Dyna Comp clone or 808 clone make the DS-8's failure irrelevant. Either it is popular and sells, or it is discontinued and something else is offered. That's my guess, anyways.

 

The Rat circuit is really very simple, but that means that every component that was chosen is quite significant.

The Rat uses a single op amp while the vast majority of other drive pedals (especially distortion pedals) use a dual op amp.

The Rat uses an op amp with what is called "external compensation." It is the reason for the "extra" 30pF cap that you won't find in a TS or 99% of other traditional drive boxes. We won't get into the "308 difference" other than to say that the external compensation is a very important feature - it is an obsolete quality that is horrible for hi-fi gear, but wonderful for a guitar pedal.

The Rat uses a pair of those high pass filters, one of which was screwed up in the Biyang clone. The other one is what gets altered with the Ruetz mod, the Keeley mod, or any builder/company that wants to knock out or alter that unique "mid push."

The Rat has a simple "variable low pass filter" - the Filter control cuts treble frequencies at 3 dB/octave slope (passive filter), but the frequency of the treble cut varies as you turn the knob. Many other pedals simply cut the same frequency more or less (the OCD is a good example), or they cut/boost a fixed frequency if they are active tone circuits (the treble and bass controls in the Xotic 4 knob dirt boxes are a prime example).

And - the Rat has a very good output buffer that is really just a "unity gain recovery stage," since the clipping diodes and tone control suck a bit of the level off. If you compare it to a D+ or OD 250 (both of which don't have the OP buffer), it becomes somewhat apparent that ProCo was clever by adding it. The buffering system in the Rat also allowed ProCo to use a DPDT switch wired in a non-TBP method with no tone suck and a status LED. Not only were they ahead of the curve on that, but it led to R.G. Keen developing the BRILLIANT Millenium Bypass, which I would argue is on par with/better than TBP. It is certainly better than MXR's hardware bypass, which was the only other mechanical thing with a status LED back then TTBOMK.

All these years later, nothing else is a Rat. As cool as stuff like the OCD can be, it really just borrows from the OD 250/Voodoo Lab OD. As cool as those pedals are, they don't hold a candle to the Rat, IMO.

Pedals like the Fulltone Plimsoul and BJFE/Mad Professor/Bearfoot Dyna Red Distortion use a pair of those dual high pass filters just like a Rat, but they still aren't a Rat either. I like that some of the BJFE/MP/BF pedals actually use externally compensated op amps (like the Honey Bee and DRD), but they still aren't a Rat, either.

But what pedal will go from a Sco/Frisell fusion-ish slight drive, to a Marshall-esque tight mid distortion, to a Muff-approved fuzz, all in one box? And these days, many guitarists seek out such a pedal with 4, 5, or more knobs, multiple switches, etc. to get that flexibility, and the Rat does it all with just the traditional 3 knob format. It's nothing short of mind blowing, IMO. I know guitarists who are purchasing their first one after 30+ years of playing (the Rat has now been in production for 34 years), and wondering how they passed on it for all that time.

 

Switch up is stock pair of silicon diodes. Switch middle is "diode lift," or none. Switch down is Turbo Rat, or pair of LED clippers.

I'm venturing a guess that all/most of the drive boxes from Biyang with the 3 way toggle will be similar.

Even my Baby Boom Fuzz Star has a 3 way with a combo of silicons and (in this case, one) LED. The difference with that one (since it is a Big Muff clone) is that it only messes around with one of the two diode clipping circuits in the Muff. Instead of silicon/none/LED, it seems to be:

- asym silicon (more compressed than stock - 2 types of sil's used)
- stock silicon pair
- two silicons in series, in parallel with a single LED (again asym)

I'd really think that all of the "proper distortion" Biyang pedals are all verbatim with that switch to the Brownie/Mouse. The OD's may differ, but the same combo is very popular in TS's and such - the TS9-DX has a LED clipper mode, as does the Clay Jones OD, Rockbox Boiling Point, CMAT Sigma Drive, and most DIY TS kits.

...There might be some 1N4001's/1N34A's/BAT41's in some of the drive boxes, since those are used in the Fulldrive/Zendrive/Gristle King/one of the Pigtronix pedals (with germanium in the name - it's a single 1N34A germanium transistor), and give more variations on asym. clipping with slightly more or less compression than a stock TS.

 

None, IMO. Under a microscope, it is the same silicon circuit. It's just a nostalgia thing IMO - just like with the metal can 741 op amps, metal can transistors, and "button with gold pin" transistors.

They all have modern production/lower noise/lead free equivalents at a lower price, so I know which one I'd prefer to actually use, and which one I'd sell!