TMK Build Questions

[phraxman]

Has anyone built Tim's TMK circuit (located here http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html#tmk ) ? I have a few questions about it, firstly what chips could I use instead of the tl062. I was thinking a TL072? Secondly has anyone got a PCB of this layout as that would save me lots of time as I don't have any pcb design software. . . .
Thanks

[jmusser]

I would say that you should be able to use either the TL072 or TL082 either one in there, and they should work. If you thought later on that it wasn't performing up to snuff, then you could replace it with the one Tim called for, because all the pinouts are the same. If you don't have a TL072, then Radio Shack carries the TL082. That's what I used in my Crash Sync, with good results. As for the PCB, I'd guess not. There is free PCB and schematic software available on the Moosapotamus site. I always perf board all my stuff. I have everything bagged up to build this widget, but I haven't actually built it yet, because I'm waiting on some pots(Maybe because it needs too many pots, to go with too many knobs).

[Dragonfly]

i think Munky might have a pcb on his site, www.geocities.com/diygescorp ....

[phraxman]

Thanks dragonfly. I'll check it out....... jmusser, I have loads of tl072's but cant find tl062's anywhere in uk!

[Jakeb]

I've built one and I think it is a great little gadget!

I made it using one half of a TL084, wich has two TL082's inside. I made my unit on piece of a veroboard.

[phraxman]

Ok, I've got the circuit on a breadboard but I'm getting nothing. No sound at all. This is getting frustrating! Is one of the LEDs supposed to light up? Because on my current breadboarded layout the bottom most led is lighting up. . . I just cant see the problem, I'm giving the chip its +9v and gnd link and I've checked the pinout several times (I got my TL072's from www.maplin.co.uk ) :cry:

[aidoru1]

Hi, I'm working on a TMK in my breadboard. The sound comes out and seems to be good but I've some problems with "Gain-Colour" Pot. When fully down it makes a sort of hi-freq noise; around the center Gain increases and fully maxxed the gain fall down again. Is it the normal behaviour? I've used not exactly the same pots values bacause I couldn't found them. (for example: 47k instead of 50k, 470k instead of 500k an so on...)
Another question: can you explain what "crossover distorsion" and "input Z" knobs should do?
Thanks from Italy

[phraxman]

Jakeb : Any photos or layout pic of that veroboard layout? I would be interested to see them.

I am using replacment value pots as well and I don't think the impact will be massive on the tone of the cicuit. I just wish I could get it working :-(

I've audio probed the circuit and I am getting a signal into pin 3 of the ic (TL072) , which I believe is the correct pin to be inputting to after checking the datasheet however I am getting no output from pin 1 or any other. Just this damn led lighting up! Any ideas anyone? Please!!!

[phraxman]

:oops: Bump  :oops:
Anyone any suggestions ??

[jmusser]

Well Phraxman, I don't have a clue as to what you've done or not done, but, you've obviously got something wrong, and it could be one of a million things. Be sure and read through debugging on this site, and RGs notes on "What to do when it doesn't work". Lets go through the chip real quick. First op amp is + pin3, - pin2, output pin 1. Second op amp is + pin 5, - pin6, output pin7. Pin 8 is 9V, pin 4 is ground. You can see the power supply section off to the upper left, that tells you to bring off Vr (1/2 of 9V) in between the two 100 K resistors, and the ten uf cap. That's going to pin 5, and the 10K resistor at the bottom of the P2 Input Z pot. I'm more of a mechanical guy instead of  a tech type, but as near as I can tell, the LEDs should not light up, as they look like a feed back loop for the first op amp. To keep you from getting confused on the input and output jacks, go to Tim's "Jinx" circuit on his Snippets page (although there are several others there), to use his stomp switch and jack wiring for your circuit. You can see where it comes off the switch to the input and outputs of the circuit, and that will be the exact same for the one you're building. One thing I always tell people, is to give your components designations (R1, C1, D1, etc.) on your schematic, and then label them on your perf board, so you can tell which components you're dealing with when you're turning the board from bottom to top to solder. Next, make sure that you don't have your chip wired bassackwards when going from bottom to top. Pin 1 can turn into pin 8 real quick if it's not labeled on the bottom side of the board. Lastly, I always have a clean schematic to mark over with a highlighter as I'm tracing my circuit through, to be sure everything is where it's supposed to be. That procedure alone will find you 9/10 of your problems. Keep me posted.

[Tim Escobedo]

A TL072 should work, at least to some extent. I specifid the TL062 because it's lower performance specs actually seemed to help stability, this being a high gain circuit with lots of flying wires.

Which brings me to the next point. there are lots of knobs, and correspondingly lots of ways to miswire the circuit. If something's not working, double check everything. Then double check again.

The LEDs might light up some when there's a signal. They introduce crossover distortion when the parallel pot is a max resistance. That it, they don't conduct very well until the signal level reaches a certain threshold. This causes the waveform to look a bit "disjointed" around the zero level as it transitions from positive to negative and back.

The "Gain-Color" Pot may indeed do some high frequency oscillating/weirdness at any setting. This is completely intentional. It may be worse if using a "better" op amp than the TL062. If it's too annlying, you can try upping the 220pF cap, at the expense of some brightness.

The "input Z" control changes the input impedance from a reasonably high 260k Ohms to 10k Ohms. At lower impedance settings, there's more "tone sucking", or loading of the input signal, which means a bit less gain overall, mellower sound, and more interactivity with the guitar's volume pot. Keep in mind that this is best exploited if the T.M.K. is driven directly by a guitar with passive pickups.

[phraxman]

Thanks alot guys, I should be able to get back to building this over the weekend. Thanks Tim for an awsome (But tricky) circuit. I can't wait to have a working version!

[col]

UK supplier of TL062s, www.rapidelectronics.co.uk 38p each + VAT unless you want lots in which case they are even cheaper. I just got my first order off them VERY quickly. Everything well packed. Postage is free above £25, just remember that all the prices are less VAT.

[snorky]

Lets go through the chip real quick. First op amp is + pin3, - pin2, output pin 1. Second op amp is + pin 5, - pin6, output pin7. Pin 8 is 9V, pin 4 is ground. You can see the power supply section off to the upper left, that tells you to bring off Vr (1/2 of 9V) in between the two 100 K resistors, and the ten uf cap.

OK.  Resurrecting an old post.  Just finished the build - no sound and some dumb questions about the TMK...

1) I assumed that Vr was setup by the circuit.  I don't have to somehow generate 1/2 of 9v, right?

2) On the datasheet for the TL062, pin 8 gets VCC+ (9V?) and pin 4 gets VCC- (ground?).  This isn't shown (I don't think!) on the schematic.   I can obviously set this up, but just wondering if my assumptions are correct?

Sorry for the dumb questions.  I built an Ugly Face and it's one of my favorite builds so I thought I'd try a TMK.  If the chip isn't getting power, it makes sense that I would get no sound.

Thanks much in advance!!!!

- Mark

[octafish]

1) I assumed that Vr was setup by the circuit. I don't have to somehow generate 1/2 of 9v, right?

2) On the datasheet for the TL062, pin 8 gets VCC+ (9V?) and pin 4 gets VCC- (ground?). This isn't shown (I don't think!) on the schematic. I can obviously set this up, but just wondering if my assumptions are correct?

1)Vr is setup by the little circuit in the top right of the TMK schem near the volume pot. This is a very common opamp voltage divider, chances are if you built anything with an opamp that runs off a battery then you have built one of these. So what do you have the Vr point attatched too? It does need 4.5v and this little two resistor one cap arrangement gives it. The resistors don't have to be 100k they just have to match though I always try to stay in the ballpark, say a pair of 82ks or 120ks.

2) No the power and ground supplies aren't shown. The chip does need 9v of positive power, and a 0v ground point, and the reference voltage of 4.5v. If the datasheet says it is those pins then I guess it is those pins. Those are the power supply pins for most dual opamps.