Tremulus Lune troubleshooting help...?

[alltherightpills]

Hi all,

I just got done with a Tremulus Lune build on perfboard, based on the layout @ Tonepad.com (http://tonepad.com/getFile.asp?id=84). 

Fired it up, and it passes signal when switched on, but no tremolo-ing.  The rate LED does not flash - it's just steady on.  Also, when I adjust the 'Smooth' control, the rate LED gets brighter or dimmer.  I moved the gain trimpot to the outside of the enclosure, and it seems to do its job (raises/lowers volume fine) - but when its more than 1/4 of the way up it distorts (and not in a pretty way...). 

I used all of the parts on the Tonepad parts list (including the VTL5C2) except for some changes to be closer to the updated Commonsound schematic/layout (http://commonsound.org/tremulus/tremulusboard.pdf):

2.5k instead of 100ohm off of pin 7 of the 4558
10uf instead of 100uf off of pin 4 of the 4558
150k instead of 47k for the resistors after the input (commonsound calls for 220k; this is the closest i have)
B100k/B10k speed and fine pots
500pf in place of the 310pf across the lugs of the gain trimpot on the commonsound layout
added the symmetry pot mod (http://commonsound.org/tremulus/symmetry.pdf)

Unfortunately, my DMM is out of commission, and I haven't had a chance to buy another yet, so I can't post voltages.

I do believe the problem to be in the LFO section, so that's where I'm going to start my hunt. 

Can anyone offer any suggestions/ideas?  Thanks a lot!

David

[alltherightpills]

Well, it turns out I just missed a single connection on the board.  Made that, and everything functions now.  I guess my double check of the circuit wasn't enough.

So it works very well, and all the hype around this circuit is definitely well-deserved.  But there's a fair amount of hiss/BG noise in the circuit.  I've got a metal film resistor assortment coming sometime soon, so I intend to switch the resistors in the input/output section to metal film.  Would metal film make any difference in the LFO section? 

Layout wise, could any noise come from the fact that the rate LED connections are located right next to the input on the board?

I searched the forums here, and didn't find too much, but I may be using the wrong terms...?

any help with this stuff would be greatly appreciated.

[1978]

If the background noise/hiss "cycles" in and out it's likely the LFO.  See  http://fuzzcentral.tripod.com/tremulus.html  for a fix for that.

[alltherightpills]

Thanks for the direction, 1978.  I just went and checked it out.  Good Stuff!

I added those two caps, and they did seem to make a bit of a difference, but the hiss is still there.  It's not terrible, though it does seem a bit noticable on the higher depth settings.  Maybe I'm just a perfectionist . 

I'm wondering if the gain pot being mounted right next to the controls for the LFO is picking up some of the noise from that circuit.  I don't know if lead dress is important in pedals like this as it is in tube amps, but it seems plausible (something about 'knowing just enough to be dangerous' seems to apply here... ).

Anyone know if metal film resistors will make a big difference?

[1978]

I don't know enough to say whether the gain pot near the LFO is causing problems, but it seems from scouring the web and this forum for advice that lead dress isn't as important for most pedals, as it is for amps.  Of course, if you're a perfectionist... or if you're using germaniums or unshielded wire or using cardboard boxes as enclosures. 

I would suspect the gain pot being partly, if not wholly responsible for the noise.  I made an earlier version, which had just a trimpot for the gain (one , obviously, was supposed to set the effect and bypass at the same level).  I swapped out the trim for a regular pot to get a volume boost for solos--and it was quite a boost in volume--which of course means both louder guitar solos and louder pickup, etc. noise.

let us know if you get it quieter

[alltherightpills]

Well, I rerouted the gain pot leads so they stay as far away from the LFO + Controls as possible (Not too far, though, since I've got this stuffed into a BB enclosure w/7 pots [stock 5 + gain and symmetry] and two LEDs [one for rate, one for on/off indication]).  I also moved the board's input further away from the Rate LED connections on the board. 

Both of these changes seem to make another minute (but audible!) drop in noise.  It's still there, though.  I should get my metal film resistors sometime soon, so I'll definitely post back with my findings at that point, too.  Until then, though, if anyone else has other suggestions, I'm all ears...

[alltherightpills]

An idea - while I'm thinking about it.  The rate doubler mod for the Lune adds an equal value cap in parallel with the 10uf (or 100uf) from Lug 3 of the Spacing pot, correct?  So this basically doubles the cap's value and thus doubles the speed.  Would halving that cap's value decrease the minimum speed by 1/2?  Sounds interesting - that would be a REALLY slow trem, but it could be pretty cool.  Maybe use two switches - one to double rate, one to halve it (like this thing needs any more controls ). 

I'll probably try it out, but does anyone see a terrible problem with the idea?  I'm not going to cause the world (or, more specifically, my pedal) to explode, am I?

[Paul Perry (Frostwave)]

You are close Mr Pills, but.. doubling the cap HALVES the speed. (think of it as, the current takes twice as long to fill twice as big a cap!) In any case, go for it. You won't break anythng there swappig cap values!

[343 Salty Beans]

Hahaha that'd be like a delay, but without the notes after.

So not really like a delay at all.


But a fun sounding idea. You might want to add a switch so you can flip between doubled mode and normal mode.

[alltherightpills]

So doubling the cap value halves the speed?  It looks to me that the rate doubler mod (http://commonsound.org/tremulus/tremmods.pdf) puts a cap in parallel across the existing cap.  You add parallel caps' values together, correct?  Am I off base here?  When I get a chance, I'll try it out, but can someone check my book knowledge?  I'm still pretty new at this stuff.

Thanks...

[Paul Perry (Frostwave)]

I havn't checked out the ratedoubler mod, but i suspect that you halve the original cap & have another switched across it (not connected = doube speed).
Or else it is really a ratehalver, but if you turn the speed up via the corresponding pot, it looks like a doubler when you swich the new cap out!

[alltherightpills]

Well, I tried out this rate doubling and halving idea, and Paul Perry was right.  With just one 4.7uf, the rate is indeed doubled.  With two 4.7uf in parallel (~10uf) it sounds like the same rate as stock.  With another 10uf paralleled across that combo, stock rate is halved.  And that's REALLY slow . 

So I put in two push-pull pots - one to switch each mod.  This thing now goes from unbearably slow (which is cool) to normal speeds (we all know this sounds great) to unbearably fast (also cool).  My Tremulus Lune just got more tweakable...

Thanks for the help, guys.   

[danngreen]

nice idea for the multiple rate selection... as for the noise, there's a post on the commonsound forum here:

http://commonsound.org/fud/index.php?t=msg&goto=1075

if you're suspecting the gain pot, you might want to try doug's advice and replace it with a single resistor to set a boost, and then have a volume pot at the output.

Also, putting a 330pF cap directly soldered to the gain pot can make a difference.... as well as filtering the powersupply extra well with a 100uF on pin-1/"input" of the 7809 to ground (not just on pin 3 to ground).

[alltherightpills]

Thanks for the advice!  You'll have to forgive my ignorance, but what are you referring to when you say 7809?  I don't have any parts by that #.  You mentioned a cap from pin 3 to ground - I see a cap from pin 3 of the TL072 to ground.  I think pin 1 is the input on that IC, so is that where I'm supposed to put the 100uf to ground?

[danngreen]

but what are you referring to when you say 7809?

sorry, I should have made myself clear. the 7809 is a voltage regulator, only used for power-wall-adaptor operation. If you use a 9V battery or a regulated bench supply, you won't need the 7809.

You mentioned a cap from pin 3 to ground - I see a cap from pin 3 of the TL072 to ground.  I think pin 1 is the input on that IC, so is that where I'm supposed to put the 100uf to ground?

I was referring to pins 1 and 3 of the 7809. Of course, if you're not using a wall adaptor, this won't apply!

[bensoniski]

Well, it turns out I just missed a single connection on the board.  Made that, and everything functions now.  I guess my double check of the circuit wasn't enough.

I don't suppose you could say which connection that was? I finished building the tremulus today and I have a similar problem - great tremolo when switched on for about 2 seconds and then just the clean signal (with the LED on).

I can't post any voltages either right now because I am in a foul mood and don't want to go near it for a while.

Thanks in advance!

[bensoniski]

Victory!

There was a broken trace on the board for the 100k resistor by IC1 that leads to the 10uF cap. Fixed that and now the circuit works a charm.

And how come I didn't spot this last night? Simple really. I was tired, the light was a bit poor and I was looking way too hard. I knew the problem was in that area and this morning, after a good amount of sleep and plenty of thought I saw the tiny break in the trace straight away.

My next problem is with the LED. It flashes when the effect is switched off. Any ideas? Is it (maybe) supposed to do that?

[danngreen]

congrats on getting the tremulus working!

Victory!

My next problem is with the LED. It flashes when the effect is switched off. Any ideas? Is it (maybe) supposed to do that?

Do you have the LED running through the 3PDT stomp?