Tuesday, 13 May 2014

Blakemore Effects R.O.U.S.

Info about the original souped up Rat:
To put it mildly, the R.O.U.S. is a versatile pedal. It’s based off of a classic distortion pedal circuit, but it can do so much more. There is a toggle switch to change the clipping diodes (or completely remove them) so you can go anywhere from a very light overdrive to fullbore rock distortion. Also, I’ve added more EQ options so you don’t have to settle for just having a single tone knob. There are knobs to control bass, treble, and then a texture knob that controls the clipping characteristics, and almost acts as a mids knob. And for those of you who are interested in such things, this pedal does use the coveted LM308 chip.






16 comments:

  1. if I had all the parts I would try and verify this one, ordering stuff today for this one

    thanks IVIark

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  2. Where's the Schem for this one? I'm interested in looking at the tone values.

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    1. Anonymous donation with a request not to publish I'm afraid, so you'll have to make do with the layout. But if you look at a Rat schematic you're not going to be very far away :o)

      Basically it's a Rat with the pot between the 47R and 2u2 in the pair of high pass filters at the inverting input to control the frequency, with passive high and low pass filters after the opamp stage replacing the simple tone control, and switchable diodes or LEDs shunted to ground (or a complete diode lift). And that's about it really.

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  3. I have an old early 80 s original big box RAT and this layout shall be my replacement LOL
    Great pedal for sure!

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  4. Hi Mark.
    This is a very good pedal until I increase the Texture to about 75% while the gain is over 50% at which point a siren sound comes out that gets higher and louder as gain or texture is increased. In my limited experience I thought it was a tranny based noise so I switch the tranny and put in a different 308. No decrease in the noise. The pedal is very usable until the gain AND texture are both increased to about 75%. Any ideas?
    Thanks for your pedal freak web site.
    Dale (Jeff)

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    1. The Texture control alters the frequency of one of the high pass filters at the inverting input of the opamp. There are two separate filters and the original Rat used a 560R + 4u7 (as per the other filter in this circuit) and a 47R and 2u2. This circuit adds a 1K pot in series with the 47R meaning the filter is variable as the resistance can vary between 47 ohms and 1047 ohms. That makes the high pass filter variable between 69 and 1539hz.

      So this basically cuts low end and starts rolling off those bass frequencies starting from the frequency selected by the pot. If anything I would expect oscillation to happen because of an increase in high frequencies (ie a low pass filter) and the thing is, no matter what setting of the pot the frequencies higher than 1.53khz aren't affected, and so the normal occurence that I would expect to cause oscillation isn't happening.

      Try swapping the 47R for a 68 to 100R (it may be worth socketing to test different values) which will reduce the highest frequency that the low end roll off begins. Let me know how you get on because I'm interested in what could be causing it.

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    2. But I suppose that means that it's still verified, just noisy until we sort the fix. :o)
      So thanks for verifying buddy.

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    3. Thanks man. Yes it works nicely until peaking the gain AND texture together. I'll socket the resistor and let you know.
      dale

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    4. Mark. You mean the 47R in the upper left corner correct?
      Have a good weekend and a safe Memorial Day. (I'm a veteran.)
      dale

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    5. Yes that's the one. Have a good one yourself, and much respect to you.

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    6. Morning Mark
      I went up to a 220R and the noise ceased!! Texture works great.
      Now I am going to put the Direct Drive Compact next to it in the 1590BB.
      Wish me luck.
      Dale
      p.s. Exactly where are you? City, State, Country......planet?
      The work you do for us guitarists/pedal pilots, is out of this world!!. Thank you!!

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    7. Fantastic, glad that sorted it out for you. It may actually be worth putting a low value multiturn trimmer in there, dime the Texture and Gain pots and then just adjust the trimmer until the noise starts and keep it just below that point. Then you will get the maximum frequency range from the Texture pot without introducing any noise.

      I'm from Manchester in the UK. And it's raining as usual :o)

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    8. Cloudy here too. No rain yet.
      Waiting for the Indy 500 race to start.
      If I put in a trimmer how do I connect the 3 legs in place of the resistor?

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    9. Just use the middle leg and either one of the other legs. It's just being used as a variable resistor so you only need to use 2 of the legs.

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  5. Is there a way to get a little more output? The best I get with the 1N914 mode is maybe unity.

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  6. I was wondering if someone could help me out on this. I made one of these a month ago and it worked perfectly but I made it again for a friend and I added a second gain knob that was activated by a footswitch in. I'm having problems because when the p and when engaged with no power feeding to it there still sound. Then when power is run to it when bypass there's a hum and then when engaged there's just a really loud hum. I've checked all the grounds and they look good and I replace the switch and DC jack but that hasn't sold the problem. I did find the 100uf capacitor was on backwards and started smelling and got very hot. So I took it out and replaced it with another one doing the correct way. Could someone please help me out?

    IC
    1: 8.60
    2: 4.63
    3: 4.18
    4: 0
    5: 0.002
    6: 4.63
    7: 9.29
    8: 4.71

    Q1
    G: 0.008
    S: 5.45
    D 9.29

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