Tremolo-matic X build report - layout

[Morocotopo]

Hi, here´s my build report for this FX

Some time ago I built the fender-type tremolo that R.G. has in his site, discussed in this forum, with my own layout and then with Markm´s layout, but got ticking and volume issues, so eventually I left it aside, but reluctantly because I really liked how it sounded. Eventually I found a project that imitated the same type of tremolo here:
http://moosapotamus.net/IDEAS/stompboxology/MoTremLo.htm
It´s the Tremolo-matic X project. The article proposes a layout hat is, let´s say, hmmm... Awful!!! Way too big and disorganized, so I made my own layout.
Someone on the forum built it before me, so I had confirmation that it worked, but I hadn´t built it myself till now.
Yes, it works!

Layout:

http://www.aronnelson.com/gallery/main.php/v/Morocotopo/Tremoo-matic-X-PCB-LAYOUT-2.jpg.html?g2_imageViewsIndex=1

PCB:

http://www.aronnelson.com/gallery/main.php/v/Morocotopo/Tremoo-matic-X-PCB-2.jpg.html?g2_imageViewsIndex=1

Awful cell phone pic:

http://www.aronnelson.com/gallery/main.php/v/Morocotopo/Tremolo-matic-X+placa.jpg.html?g2_imageViewsIndex=1

Audio:

http://www.aronnelson.com/gallery/main.php/v/Morocotopo/tremolo+matic+x+test.mp3.html

The audio sample goes from minimum to maximum speed (with the mods explained below) and at the end I work the high and low pots. Humbucker guitar>FX>buffer>mixer, a bit of verb. There´s a faint hi freq noise at some place, thats my mixer.

Some comments/mods (parts numbers are in the original article):
- Playing Townshend-like brings a bit of peak clipping, playing like a normal human being doesn´t
- I believe the chip can be NE570, NE571, or even SA570/571
- No ticking at all... at least before putting it in a box. It doesn´t even have a shielded input cable. in the article it´s explained that the oscillator has a R and a C added to soften the square wave to avoid ticking. Might be an interesting idea to use in other schems that have ticking problems...
- IC1 (78L05),R26 (trimpot), R27,C16 are for controlling "feedtrough" of the NE570, first I left them out, then I installed them, no noticeable diference.The trimpot is a tight fit in the layout
- I added two resistors and two caps in the 9V traces (at the top, in red, one of the caps is not drawn) just in case I had to decouple the chip´s power to avoid noise. Not needed, just replace the resistors with a jumper and leave out the caps.
- I also added a pulldown resistor (down right, in red). Use it if you get switching pops. I don´t so I haven´t installed it
- I put the protection diode across the power instead of in series with the 9V, to avoid losing voltage
- Depth pot: I used 10KB instead of 10KA
- I wanted to get more range of speeds from the oscillator, so I did the following mods: Rate pot--> 50KB / R20 y R21: I added a dpdt switch to simultaneously change R20 from 10K to 15K y R21 from 10K to 56K.That gave me a bit more speed range, not a dramatic difference but a bit more.
- The schem doesn´t have a vol control, I had doubts about volume differences with the FX on/bypassed, and also because of the type of processing, there might be perceived volume differences according to the controls settings. As the article says, gain is set in two places: R14/R13 set the first opamp´s gain (IC4d) at about 6,9 and R17/R16 are a resistive divider that attenuate the signal at the output by a factor of 4. They call this configuration quasi-companding, and it´s done like this to control noise. I arrived at the following mods: R14 -->270K, R13 -->33K (this I believe lowers the input impedance. Anyone can comment?), so gain: about 8,1 / R16/R17: replaced by a 20KB pot wired as a resistive divider vol control, so I get variable output attenuation.

One last comment: through a fender hot rod Deluxe, the thing is a bit noisy (white noise), not unusably so, but, what could be done to work on that? Any ideas?

Well, hope someone finds this interesting

Morocotopo

EDIT: Sorry, the layout link was wrong. corrected.

[moosapotamus]

I'm really glad to see folks starting to build more of the Bosc stuff and tweaking the circuits to get to what works best for them. I guess it's coming a bit after his time, but I have to think this is how "the man" would have wanted it. 

Nice sounds, Morocotopo! Good job on the layout, too! 

~ Charlie

[Morocotopo]

Thanks Charlie, your page has been an inspiration for some time now for me! Some mad stuff there!

Morocotopo

[John Lyons]

Nice soundclip! The pitch bend almost sound like a Univibe on the slow speeds.
Thanks for sharing your work on this.

john

[Morocotopo]

Thanks John. Yes, the thing has some vaguely univibe-like sounds, I guess that, even if the schem doesn´t have phase shifting networks, the imperfections of the physical parts in the circuit DO shift the phase somewhat between the lopass and highpass signal routes, and that makes the sound go in that direction.