Old Rat / New Rat Differences

[GGBB]

I've not been happy with my stock vr whenever I've plugged it in.

You might want to look over the circuit carefully.  I have a friend who was also disappointed with his VR.  I bought it from him and took a look inside and found that it had BAT41 Schottky diodes instead of 4148s, and the 30pF compensation cap and the 100pF feedback cap had been swapped during manufacturing.

[mremic01]

Well, it's been about a year and half, and I finally got around to revisiting the Rat circuit.

I put the .0027 and .0033 on a switch, and it does seem to account for the differences I was hearing between the Chinese made Rat2 and the original circuit. The .0027 is a little nastier, in a good way. I can see why a lot of people don't like it though. It's certainly less organic.

The Ruetz mod is pretty cool too. I put it on a stompswitch and not it's like a distortion and overdrive in one box.

[Gus]

The Rat is a circuit that one or two caps type can make a difference.

IIRC The older ones I worked on used tants and the two tant caps in the - input to ground leg can make a difference.  The difference will be because of ESR difference between a Al and tant at low uf values and the use of 47 and 560 ohm resistors. You can also try films at both places.

[GGBB]

While it's definitely true that the first RATs used tantalum caps instead of aluminum (except for the 100u), the vast majority of RATs including many of the first production model variety used aluminum.  I would also argue that the RAT sound was made famous mostly by the original small-box white-face RAT which never had any tantalum caps.  I think the tantalum RAT being the holy grail of RATs is more urban legend than anything else.  But that's just my take on it - never done nor heard an A/B comparison.  Would like to, but even then, with cap tolerances being what they are, it would be difficult to know if you are hearing cap composition differences or cap value differences.

[Gus]

While it's definitely true that the first RATs used tantalum caps instead of aluminum (except for the 100u), the vast majority of RATs including many of the first production model variety used aluminum.  I would also argue that the RAT sound was made famous mostly by the original small-box white-face RAT which never had any tantalum caps.  I think the tantalum RAT being the holy grail of RATs is more urban legend than anything else.  But that's just my take on it - never done nor heard an A/B comparison.  Would like to, but even then, with cap tolerances being what they are, it would be difficult to know if you are hearing cap composition differences or cap value differences.

Urban myth?

To be clear I am a person who will test  an idea and I have worked on a number of rats some for friends who are pros.  I have measured caps and worked on what understanding what matters and what does not matter in uses of caps in audio circuits.  Different characteristics can make a difference in limited uses.  I have done AB comparison, not controlled double blind but I have adjusted effects and let people test them they did not know what was changed often I would leave one stock and let them tell me what they heard.

IMO sometimes cap type makes a difference however the web sometimes seems to exaggerate cap changes in circuits.

[GGBB]

IMO sometimes cap type makes a difference however the web sometimes seems to exaggerate cap changes in circuits.

Then we agree.  That was basically my point.  The legend surrounding the tantalum RAT has been largely a product of the internet IMO.  I am not dismissing measurable differences between tantalum and aluminum as "myth" - I am just pointing out that the sound the RAT is famous for isn't because of tantalum caps as some would suggest.

[Gus]

IMO sometimes cap type makes a difference however the web sometimes seems to exaggerate cap changes in circuits.

Then we agree.  That was basically my point.  The legend surrounding the tantalum RAT has been largely a product of the internet IMO.  I am not dismissing measurable differences between tantalum and aluminum as "myth" - I am just pointing out that the sound the RAT is famous for isn't because of tantalum caps as some would suggest.

No we don't agree 100%.   I do think the 2.2uf and 4.7uf in the feedback legs make a difference tantalum or film do seem to make a small difference. 

IMO the lowpass part of the overall EQ set by the limited gain bandwidth product of the compensated opamp when the gain control is set at max does seem to be more important.  This is also why a 741 gain bandwidith product is important in a distortion + type circuit.

[GGBB]

No we don't agree 100%.

Not trying to be an ass, but for the record I haven't disagreed with any of your statements.  What did I write that you don't agree with?

I do think the 2.2uf and 4.7uf in the feedback legs make a difference tantalum or film do seem to make a small difference.

As a huge RAT fanatic, I would be really interested to hear how you would describe the sonic differences between tantalum and aluminum caps in those positions based on your experience.  I might give it a try if I think I would like it.

[Gus]

This being the web sometimes things are not clear with posts.  I don't think the rest of the electrolytics make a difference in a Rat.  I was not sure if you had tried changing the 2.2uf and 4.7uf to different types.

I was adjusting a rat for a friend that is a bass player.  This was an older turbo rat with LED clipping I added switchable 1n4148 clipping.  They played it for some time then I changed the two Al to tant it seem to have a little more "grit" with the tants that sounded good using a nice Jazz Bass.  Now maybe the use of a bass instead of a guitar made a difference.

[UnexplodedCow]

After lurking for years, and listening to many myths about Rat versions, I decided to join, and have this be my virgin post (hooray?).

I bought a Rat2 new in January '99, and pot codes show it to have likely been made in '98. It's a white board with LM308N, CTS pots, Arrow switch, and the standard Rat2 LED and glow in the dark graphics. It's flat box, with flat knobs...none of the slanted nonsense. I've played through it for years, and it's seen plenty of use (not abuse..it looks almost new).

About a year ago I bought a Deucetone Rat used to try and compare the circuitry and (hopefully) mod it. Both have happened.

The Deucetone uses the OP07DP chips, and has the modern 3 hold 3 board circuitry setup, so not any different than other rats (save for the clippers and switches for them).

I've spent the past 3 days comparing them, using multiple guitars (Ibanez, Carvin, Guild, Ovation, and Fender electrics) through a Carvin Vintage 16. The only thing I noticed is that at the same knob settings, the two pedals don't sound the same at all. However, minor adjustments (I used the Rat2 as the benchmark) to the filter (turning it to be slightly darker) and gain (turning it down somewhat) lead me to as identical sound as I could hear, save for some extra harmonic content in the Deucetone (which I preferred). The sounds are there, but it takes some tweaking to find them.

All said, I think the myth is simply that; a myth. Does it mean I'll get rid of my Rat2? Nope. It has its purpose, and I can always let someone borrow it if need be (and a backup is nice, too).

[GGBB]

There certainly is a lot of RAT misinformation out there.  When I was trying to sort it all out like you, I put together a comparison guide as a result of my efforts: http://www.aronnelson.com/gallery/main.php/v/diyuser/GGBB/Multi-RAT.png.html

[Renegadrian]

I was never a fan of the Rat pedals until 2 months ago. Ive owned a prodcution model for years but have never been able to get the juicy tones from it that others rave about.

I decided to breadboard and played with the values using some internet sources.

I ended up with an incredibly fat and rish soudning pedal. Here's a list of the subs I made. (Part numbers from the schem on Analogguru's website).
http://schems.com/bmampscom/effects_misc/Proco_TheRat-1986.gif

C1 – 220n
C2 - 47uf
C8 – 10uf
C7 – 47pf
R10 – 22k
C11 – 10uf

I also played around with the diode clippers, adding in an LED, using 2xLEDs/Ger, but I kept coming back to 2xSil. No switches. Simple.

The substitutions that made the most sonic impact was C1 and R10. C1 to 220n made the sound a lot fuller; changing R10 to 22k gives a fatter sound and more usable filter. I tried 47K at first but that was just too dark. Not sure electronically what I doing by changing R10 – it does alter the filter range and overall bassy-ness of the circuit.

Whats interesting is that I tried the circuit with both an OP07 and LM308. I found very little between the 2 but preferred the OP07. I sounded ever so slightly more compressed.

In summary, the LM308 and OP07 both work fine, other circuit components have much more impact.

I built the latest RATs with those mods, they sound good on full throttle, but my last customer doesn't like them that much, here's the reason.
He doesn't use it with gain all the way up, he may use 50% to 75% of its
Tone should be the same at all gain settings, not adding bass turning up the gain...
Shall I put back a 1.5k at R10 or something similar?! like something between 1.5k to 22k, say 10k!?

[GGBB]

Tone should be the same at all gain settings, not adding bass turning up the gain...
Shall I put back a 1.5k at R10 or something similar?! like something between 1.5k to 22k, say 10k!?

Increasing R10 is the same as turning up the filter control, and since the filter pot is log taper, using R10=22k with the filter pot at zero is like having the filter pot at about 7 with R10=1.5k. It also means you can turn the filter up past the effect of the original 10 pot position. The best way to change R10 and/or the filter pot is to the find the pot positions that are the absolute minimum and maximums that you would use, and measure the pot resistance at each. The difference will be the range - if it is less than 25k use a 25k pot; less than 50k use a 50k pot; otherwise keep the original 100k. Then for R10 use a resistor value closest to but less than the minimum filter pot value.

EDIT: Forgot to mention that to some extent there is no avoiding the tone shift as you turn up the gain since this is due to the design of the opamp feedback filter.