Sonic Titan problems

[bagudan]

Hi. i´ve been messing around with the sonic titan, from this layout:
http://www.aronnelson.com/gallery/main.php/v/Renegadrian/DAM+Sonic+Titan.gif.html

I get no sound when the effect is turned on.
It´s not a wiring problem.

When audioprobing, I get a loud and clear signal, until I reach pin 3 of the IC. (JC82AC LM386 N-1) The signal is significantly lower when passing through the 4n7 cap befor pin 3. On pin 5 og the IC, the signal is barely noticeable. I´ve tried swapping the IC, double checked component values, made sure there are no solder bridges...

I´m clueless. Am I using the correct chip?

[Earthscum]

The only thing I can see wrong is that pin 4 should go straight to ground, do not pass go... I was looking at the schem (HERE).

Basically what it looks like to me (and I could be wrong) is that the 386 is seeing zero impedance to apparent ground on pin 2. From my experience, taking either of the input pins to the same ground as the chip takes your signal away. You are supposed to have 50k resistor to tie straight to ground. I would try a 100k trimmer between pin 2 and pin 4 and see if you find a sweet spot. 0k makes the 386 work harder, 50k is what's recommended... you should be able to find a sweet spot in between that will give you good interaction from all the controls.

The way I like to set things is turn the gain up, adjust whatever dictates total gain (the trimmer should, in this case), find a sweet spot, then crank it up to barely tolerable. Then I check the lower end of the gain sweep to make sure it's acceptable, turn it to my sweet area and see where it sits. Usually it's around half to 2/3 way up.

*Looking at that schem again... I'm wondering if pin 4 wasn't supposed to be tied straight to ground. Maybe just a typo? http://www.diystompboxes.com/smfforum/index.php?topic=84410.msg703717%3Btopicseen

And looking at other designs, it should be working. Maybe check the 10u cap between pins 1 and 8, and make sure all your traces are cut, no bare wires laying across traces, etc etc, blah blah (all the stuff you already did). Also... maybe make sure you didn't wire your pots backwards. I ripped out about 5 components in a big muff build before I figured out I just had my pot wired backwards and had the sustain turned all the way down... that on top of doing the same with my tone, so it kept sweeping the wrong way. I about ripped my hair out. Good luck with this!

[bagudan]

Thanks for the reply. I have to be honest. Looking at the layout again, it looks as if the jumper from pin 2 to ground, is also meant to be connected to pin four, making pin 2 and 4 directly connected to ground? well, my pin 4 is not connected to anything. i´ll try correcting it tonight. Thanks again for a thourough reply

[Earthscum]

Thanks for the reply. I have to be honest. Looking at the layout again, it looks as if the jumper from pin 2 to ground, is also meant to be connected to pin four, making pin 2 and 4 directly connected to ground? well, my pin 4 is not connected to anything. i´ll try correcting it tonight. Thanks again for a thourough reply

yep... I bet that's it. If it works, get back to the thread and let us know how it sounds. I'm gonna try it out tonight before I hit up a filter idea I got yesterday (using a 386). This circuit looks to have some potential, and I'm dying to know how it sounds. I got myself stuck on FF's last night.

[bagudan]

Yup! that fixed it. Well. it´s a nice sounding unit. Have only tried it through the soundcard and amplitube...the kids are asleep:9. the real test in front of a tube amp will have to wait till tomorrow. It´s not too harsh. a bit more bite than an overdrive i think. the tone control seems to do very little, at least if you expect it to change the bass/treble response. It does give a volume boost when turned to the treble side. But then again... distortion pedals are not treated fairly when run straight into a computer.
Thanks for your help

[Earthscum]

I went and looked at the tone control, and no wonder... that thing should have a buffer after it. SEE HERE (SWTC) and HERE (SWTC2)

Also, I noticed a thing with the stripboard layout. I was tracing the stripboard against the schem, and there's a couple things that are different.

SB (Stripboard): Volume 3 wire should be soldered to the strip that the 4.7n cap straddles. The way it's shown it's DC coupled, and that 10u is just hanging there. That may be why it doesn't do things quite right. You should probably get a .01nF cap between the input switch and the gate of the jfet, as well as a 1M bleed resistor from input switch to ground.

The tone control is funky as well... it's set up as rat, but it has a min and max resistor on either side. If you want to make it SWTC, cit the trace between the 4.7n and the 1k, put the lug 2 of the tone control to where Vol3 is listed (and should be moved from). Turned to the right, the tone should go above 20kHz (about 33k). All the way to the left should be a low pass of about 330Hz. Halfway will be sitting at about 660Hz.

I figured out that there's no resistor from the pin 2/4 junction on the SB layout... it just goes straight to ground. But there IS a minimum gain resistor not listed in the schem (1k). Nice! Also, the resistor/capacitor/diode shown on the schem between pin 6 and V+ is not there on the SB.

[Renegadrian]

Yes pin 2 and 4 are tied together and go to ground. Nice you figured it out and got it working, I got mine LOUD and I personally like the use of a JRC instead of a LM. Seems the type matters so much in this ckt!

[Renegadrian]

My bad, you're right about the output...vol. pin 3 is at the - of the 10µ cap, second row from the bottom.
http://blogs.yahoo.co.jp/jan_jack_jackle/29583664.html this page shows a perf layout which hasn't got the res. before the tone pot, while even the original pictured below has it (the metallic resistor going to the pink wire)
there is no res. between pins 2 and 4. and the tone control is correct compared to the original. I used Mcelroy0717's layout in the other forum as a guide and made my own. Just removed the diode, seems like a polarity protection and nothing else, so get rid of it without thinking it twice.

[Renegadrian]

layout updated fiy

[bagudan]

Hi. I tried moving lug 1 and 2 from the tone pot, to where the volume lug was connected before. This silenced the pedal. Should I only have moved lug 2, and let lug 1 of the tone pot stay put?
Fixed the volume pot wiring, but the tone control as it is now, is not really a tone control. it still has  huge effect on volume though?

Thanks
-Kasper

[Earthscum]

Hi. I tried moving lug 1 and 2 from the tone pot, to where the volume lug was connected before. This silenced the pedal. Should I only have moved lug 2, and let lug 1 of the tone pot stay put?
Fixed the volume pot wiring, but the tone control as it is now, is not really a tone control. it still has  huge effect on volume though?

Thanks
-Kasper

Did ya cut the trace between the 1k and 4.7n so that the cap connects only to the lug? Also, lug 1 should stay where it was, lug 2 is the only one that gets moved. That's all that's needed to convert it to SWTC, is taking the wiper lug to a cap to ground. After that, if you think the tone should filter more, try 10n... if the sweep needs less, try 2.2n.

The Rat tone (which this is modeled after) needs a buffer after it, or else it causes volume drop as it's turned down because you have 110k resistance that's getting varied by 100k to sweep the tone. The SWTC fixes this problem. Basically, instead of varying resistance to the cap, the cap just slides along the resistor. Resistance to the output is the same. If you were to scale the tone to 10k, the tone cap to 47n, and the volume pot to 100k, the interaction would be much less because you would be varying only 10k/110k (however, I don't think the tone would be quite the same... I'm just illustrating a little how it works). This varying resistance to ground, on a second thought, may very well lend to the tone by loading and unloading the output of the 386 as the tone is swept. Give it a try, you can always re-solder the trace and the lug, or if they are both useful, use a DPDT and make it switchable.

---
BTW, Adriano... I'm diggin your layouts. Nice and tidy wiring. I never use stripboard, but have been considering it more and more I come across your stuff. Great contributions!

[bagudan]

Thanks man. I´ll give it a try tonight
-Kasper

[Renegadrian]

David, thank you for the kind words, hope my layouts can be useful to someone!!! I am glad to share!

[bagudan]

Well, everything is wired up now. I cut the trace and moved the wire from lug2 of the tone pot. It´s acting like a tone control now, and the pedal sounds quite convoncing. The funny thing with the tone control is, that it is trebly to the right side (of course), and then turning it counterclockwise makes it bassier (of course)....but when we get halfway, it starts to get treblier again. The position with the most bass is around 12 a clock on the tone pot.It dosn´t really bother me though, because the range is ok.

Thanks for all the help