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Hi there, welcome to my blog - La Revolution Deux. It's an odd name - but I like it! Here you will find all the info on my various DIY Guitar effects builds, amplifiers and guitars. Everything from a humble Ibanez tubescreamer to the holiest KLON Overdrive.

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Tuesday, 20 May 2008

Wanna Build a Timmy Overdrive?


Go wild! Here's the scheme, as you can see it's the standard setup now-a-days of opamp with clipping diodes. Paul C, the designer of the timmy has commented alot on the subject of his pedal over at freestompboxes.org. He still sells the originals directly from himself for around $100 I believe - that is simply the deal of the century when your looking at the bootweek industry! GET ONE FROM HIM NOW! If you fancy trying to build one yourself, here's the scheme!



The Timmy has been cloned the world over due to it's great versitility and tone - the Danelectro Cool Cat Transparent OD 1 was a direct clone and the Lovepedal Amp eleven and OD eleven are both Timmy clones. It's a very nice little circuit and well worth playing with. Here's a nice demo video for you:


And here's another interesting mod - using a feedback arrangement ala the BJF Honeybee and my own Hummingbird to reduce the overall gain and brightness of the unit:


And some interesting options for clipping diodes using a couple of switches. Point A is the - input of the opamp point B is the opamp output:


However if you are going to play with diodes heed this advice from PaulC himself:

"I've stated this above, but if you do play around with other diodes/no diodes you have to adjust the output amp or else you may get nasty rail clipping. As is with the gain on zero you've got 6db of gain on the first stage feeding into 6db of gain on the second stage for a total of 12db. Without diodes (and ignoring rail clipping) that 1st stage swings from a gain of 2 up to about 153 in the Tim (500k pot), and 304 in the Timmy (1M pot). This will totally puke out the output amp.

If you want to leave out the diodes for a clean boost, but keep the tone controls I'd mess with dropping the output amp, and just make it a buffer. Then back down the gain of the 1st stage so you don't get clipping. Now you've got a simple opamp booster with bass/treble controls which is actually the original circuit (what a minute - does that mean it didn't start out as a yats??). If I was going with LED's or true mosfet clippers I'd also switch the output amp to a buffer so it wouldn't clip under the larger signal. Better yet if you've got things on a switch have the switch also change the gain of the output amp when you're switching different diodes. You could remove the gain for the large diodes, and put it back for the small. That would solve the loss of volume you get from the standard diode selectors. You could also have some EQ'ing around the output amp to shape things even more. Have it set up to short out the feedback resistor for a flat buffer when using LED's/boosting, or add a cap across the feedback loop and another in series with the inv input to maybe put in a slight mid bump along with the extra gain when using small threshold diodes. Those caps would be added to the circuit, and one pole of the switch would just short out the loop.

I really wouldn't just pull the diodes if I was wanting it to be just a flat booster. There's better ones with more headroom for that.

Later, PaulC"

And some advice on a possible opamp substitutions from twangquack:

"What was not fruitless was experimentation with op-amp substitutions. Unlike a OCD clone on which I did some further tweaking, it was hard to find an op-amp that was a total failure -- that's how sane and well-behaved this circuit is (but in a good way). After trying about fifteen options, alone and dual-stacked, I found that I really liked the TL072 (socket soldered on top) with a BB OPA2134. This is a combo with a bit of added "oomph" that retains the nice treble qualities without adding somewhat extreme tonal qualities that sometimes happens with certain stacked op-amp combinations. I also liked a RC4559 (alone) but it seemed a bit too dark to me, although it had really nice drive -- sounded pretty cool at higher drive levels. But I think I like this pedal to be spankier and used at lower drive levels (hint of grit, or a bit more than a hint) so the TL072 + OPA2134 works very nicely in this particular build."

Here's a vero layout for you:
And the freestompboxes.org forum topic: http://freestompboxes.org/viewtopic.php?f=7&t=140

21 comments:

  1. Any vero or pcb layouts? :)

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  2. Can you tell me where can find a schematic for the "Tim"?

    Cheers,

    Christophe

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  3. What is the component that is in the clipping section right above the 100 pF mica cap? It has a 1 and a 2 in the component.

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  4. @jeremy, its a dip-switch

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  5. On the IC do The leads 4 and 8 need to be connected to anything.
    Im new
    I dont know what to do.

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  6. Could you, please, make a video demo after setting the amp in use to provide totally pure clean tone without any additional color!?! Because in this demo the pedal runs into already overdriven amp and you can't recognize what the stomp box does - more amount of overdrive can be resulting just from the "Vol" pot which lies about the effect! Set the amp REALLY CLEAN, adjust the pedal volume so the apparent loudness doesn't change when you turn the pedal on and off, and only then you play with the other controls - this is THE ONLY FAIR WAY to demonstrate what and how a pedal does!!!

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  7. It's not me playing! That's just a demo video from youtube. In my opinion you should show a "clean" tone before the pedal is engaged. But as for being "really clean" I wouldn't agree - to sound their best OD pedals often need to have an amp set to slightly dirty/on the edge of breakup so they combine their own clipping with that of the amp. I'd say that distortion pedals should be running into a completely clean amp though..

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  8. I'm new to building pedals and I had some question about the schematic I was hoping someone could answer. I was wondering what the V+ on the schematic refers to and what the taper on the pots should be. Any help would be appreciated. Thanks.

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  9. Hi there, the V+ is the power supply to the dual opamp (pin8), the pots are supposedly log taper but I use linear, it's whatever suits your taste.

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  10. hey, had a question about the clipping diode switches. does that clipping option go on top of the diode clipping that is already in the stock timmy? if so, i was wondering if instead of having sw1 a footswitch, i can get another toggle on/off/on and so if the sw1 is off, it should bypass all the clipping options so that it'll be stock timmy...right?

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  11. The clipping diode mod switches allow you to get original timmy clipping. To install it you remove the original clipping diodes..

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    1. Thanks! That makes much more sense now

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  12. All of the schematics I've seen specify a 10K level pot including the one on the vero layout.

    The parts list on the vero layout specifies a 100K pot. Is this a typo or do you suggest using a 100k pot for volume?

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    Replies
    1. 100k/10k try each and see which you prefer - a 100k will give you more output...

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  13. I have just finished the Timmy, but the bass and treble works very strange, they only have an effect on between 4 an 5 o'clock. What did I do wrong?
    Thanks in advance!

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  14. I'm having trouble with the bass and treble too.

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  15. Guys, there seems to be a mistake with the bass pot wiring on the vero layout, just check the actual schematic and compare - as I understand it, it should be Bass 1 by itself going to R3 and Bass 2&3 together going to C3. Remember they are "cuts" - you get most of it when the control is CCW. Treble control seems alright. I shall build this one soon.

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  16. This comment has been removed by the author.

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  17. So, "soon" became 9 months...
    That's it guys: Bass 1 alone and Bass 2&3 together.

    Also: Drive 1/ Treble 2&3 and Drive 3 alone.

    Do that and it will work like a real Timmy does.
    The DIP switch works as follows:
    both up = compressed mode
    one up, one down: assymetrical
    both down: "normal" open mode.
    I like them all!
    Also, I'm using a JRC4558 but I'll try an LM1458 tonight since it seems these are the ones being used currently.

    Thanks Fred for making this layout available!

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  18. First, thanks for the layout. It is great! I built one yestarday. I did some changes, in the same way Iago appointed. I used LM1458 and was clean!! Far better than 4559 IC. Worth it!

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  19. Hey guys, I know this thread hasn't had activity in a long time, but I was wondering if someone could help. Could someone explain how I might go about using a toggle switch instead of the DIP switch on the vero layout?

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