Schaller tremolo sounding terrible!

[RLawlor]

 I recently built a Schaller tremolo based off of IVIark's veroboard layout but the tremolo is really 'throbby' and doesn't sound as good as the demos I've seen online. I used 2N5088 transistors but I feel they may not be entirely appropriate for the circuit, I'm just wondering if anyone else has had this issue and whether they had any solutions, thanks.

[Rob Strand]

It would help if you posted links to the layout and schematic you are working off.

Is this the layout?
https://tagboardeffects.blogspot.com/2012/03/heartthrob-tremolo.html

Here's the original Schaller,


And here's the Heart Throb, which has a number of changes but matches the layout above more closely.  The schematic has an LED which is not on the layout.



You could have a build error.   So you need to check over your build first.

As for the excessive throb there are some possible causes,
- The oscillator is putting out a squarer looking waveform instead of a nice clear sinewave.
   If you have an oscilloscope you can check the waveform.  It's hard to check it any other way.
   The squarer waveform could be due a build error.
- Wiring errors around the Dwell pot.
- The transistor Q1 isn't quite suitable.

You can pursue the last option relatively easy.


The way transistor Q1 is used in that circuit can produce some unit to unit variations.   

You can swap the transistor and hope for the best but it's very much pot luck.

You could try adding a resistor in series with the base of Q1.   The value is determined by experiment.   Perhaps start at 10k, then increase in steps 47k , 100k until the throb is reduced.   This last method provides the most flexible way to tweak the circuit.   If you find you have a high value and it's still very throbby (but weak) then maybe the oscillator is putting out a square waveform.   That's one thing the added resistor cannot fix.

[Rob Strand]

As it turns out IVIark also did a layout the Schaller,
https://tagboardeffects.blogspot.com/2012/03/schaller-tremolo.html

(Doesn't change any of the recommendations.)