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I have been trying out RAT type pedals recently and when I came across this one on ebay. I bought it immediately.

Vick Audio  http://vickaudio.distinctiveturnings.com/index.php?route=common/home is a relatively new pedal builder out of Arizona. The 85 Classic Rat pedals “use the original LM308N chips that were considered the “secret” to these vintage Rat’s amazing tone.”

As soon as the pedal arrived I plugged it in and was greeted by an extreme, almost fuzz, tone from the pedal even with the gain set very low. It did not sound like an original Rat at all. I thought maybe there was something wrong with the pedal and that’s why the price was so low (retail price is $109). I opened it up as I do with all new pedals and started trouble shooting.

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The circuit does indeed use the LM308N op amp with what appear,at first glance, to be the original component values. The PCB was “floating” inside the case only being supported by the leads attached to the board. There is a thin layer of orange foam on the trace side of the board to prevent shorts if it flops around inside the case.

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If you look closely at the side view of the PCB above you can see there are four electrolytic capacitors ( the black cylinders with white lettering). There are two 100uf 16 v capcitors and two 4.7 uf capacitors on the board. One of the 100uf caps is used as a filter for the power input but the second is out of place in a RAT circuit. The traditional RAT circuit uses a pair of series resistor/capacitor circuits to set the high pass gain of the op amp. One pair is a 560 ohm resistor and a 4.7uf capacitor with a 60Hz roll off and second pair with a 47 ohm resistor and a 2.2uf capacitor with a 1.5kHz roll off. More technical analysis of the RAT circuit is available here. In essence the Vick Audio circuit had a 100uf capacitor in place of the more traditional 2.2uf.  This extended the full gain of the circuit down to 31Hz, well below any standard guitar fundamentals. This should create a fuzzy, flabby sound which is exactly what it sounded like.

I searched my parts bins for a 2.2uf cap but the smallest electrolytic I had was a 4.7uf so  I removed the 100uf and replaced it with the 4.7uf. Instant RAT tone! The 4.7uf does give a much lower roll off (677Hz) than the stock value but it still sounds quite good at lower gain settings. Once you wind the gain up past noon it does give  a fuzz type quality to the sound. I think most RAT users find the best sounds below 12 o’clock on the gain knob. One other change I made before closing up the pedal was to add a 150 ohm resistor in series with the gain control. This helps smooth out the first little bit of gain jumpiness when you start to turn the gain knob from the fully counter-clockwise position.

One last thing. The PCB is silk screened with the words “Rat Tail”. Vick audio does not sell a pedal called Rat Tail but these guys do: http://fuzzrociouspedals.com/product/rat-tail/. Wonder if there is any connection?

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2 Comments

  1. Hi, I can see quite clearly on the picture that the part labeled C5 on your board ( to the left of the IC) is indeed a 100uf cap. I double checked my schematic and build document and I have it listed as 2.2UF in both. I apologize for the error, I guarantee you it is not standard and I should have caught it when testing the pedal.

    Also no relation to the Fuzzrociuous I just was not aware another company was marketing under that name when I designed and ordered the boards. Since I don’t print the name on the enclosure I just changed the name I marketed it under to avoid confusion.

    Again sorry, let me know if their is anything I can do to make it up to you.

    • Thanks for your comments Mike. No need to apologize I understand how this stuff happens. I did end up selling the pedal and the new owner was very happy with the performance.


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