So after trying a design for my Tremolo using a 555 timer and opto isolator using an LED and failing to get rid of a clicking sound at the output,
I bread boarded another design using an op amp instead of the 555 and guess what?.....STILL had the clicking sound so it wasn't the fault of
the 555 crowbarring the supply rail, I removed the LED from the circuit and it made no difference so I have given up with the
opto versions and have just built this circuit and so a new problem OF COURSE!!!!

the top of the waveform is a beautiful sweeping curve, the bottom however is very different, it seems to dive into the ground
then sharply bounce back up......where do I go first to remedy this please?

Only the circuit in yellow has been built so far.

Neil.

 

A bipolar junction transistor doesn't work well as a variable resistor - they are not very linear and in this circuit you are expecting it to work with the collector both forward and reverse biased. You really need a FET.
http://www.vishay.com/docs/70598/70598.pdf

 

The only parts of that circuit built so far is the parts in yellow, I need to figure this out before I get to the variable resistor part.

Neil.

 

Oh I forgot to mention the only thing I have changed is to make all the phase caps the same value (10 uf) I don't know why they were different in the circuit in the first place.......not that it made any difference to the shape of my wave form which is still crippled lol

Neil.

 

Here's a mod of the 'yellow part' which biases the first transistor differently to overcome the distortion. The second transistor buffers the output.

 

I haven't seen anything like that oscillator before. It is odd. I have simulated it in LTspice and it produces the waveform you show when the frequency adjust is set to a low value. When it set to a high resistance the waveform is even worse - more like a sawtooth.

It is not easy to make a tuneable sine wave oscillator using a single adjustable component. The wien bridge circuit can produce a good sine wave but to adjust the frequency requires a double gang pot.

 

Thank you....I'll bread board that modified circuit when I get home from work..

Neil.

 

So after trying a design for my Tremolo using a 555 timer and opto isolator using an LED and failing to get rid of a clicking sound at the output,
I bread boarded another design using an op amp instead of the 555 and guess what?.....STILL had the clicking sound so it wasn't the fault of
the 555 crowbarring the supply rail, I removed the LED from the circuit and it made no difference so I have given up with the
opto versions and have just built this circuit and so a new problem OF COURSE!!!!

the top of the waveform is a beautiful sweeping curve, the bottom however is very different, it seems to dive into the ground
then sharply bounce back up......where do I go first to remedy this please?

Only the circuit in yellow has been built so far.

Neil.

An NE555 does cause a lot of that sort of problem for various reasons when used in conjunction with high gain audio circuits which can be difficult to filter out even with lots of decoupling etc, try using a 4047 multivibrator as your timer IC, It is a very versatile chip that can work as mono, astable, flip flop, can produce +ve or -ve output, with complementary outputs wit 50% duty cycle, plus the oscillator output is available from a separate pin at twice the +/- output frequency. It has very low power consumption and does not need much decoupling to prevent switching noise on the supply rails. 5 to 15Volt operation, altogether, a better option than a 555 when used with audio circuits.
Also remember that when breadboarding a circuit, lots of strange things can happen due to transient fast switching spikes being coupled across adjacent contact rows and via link leads.

 

Hello,

For an other way of modulating, have a look at the attached PDF.
This PDF comes from this page with more info.
http://www.generalguitargadgets.com/effects-projects/tremolo/ea-tremolo/

Bertus

 

Excellent.....thank you so much, I will be experimenting this weekend

 

The circuit Bertus has posted is one that I built for a friend around 2010 and it is still working today! sounds like the tremolo used in a Vox AC30. From memory, i used a pair of J113 FET's . Also between R15 and R16 junction I fitted a 100k pre-set and connected the gate of Q4 to the slider and adjusted for best sine wave on a scope. Jfet's can have a wide tolerance even with samples from the same batch.

 

Did you get round to comparing the sounds of triangular and sinusoidal modulation via the .wav files that I posted on 7 Feb in your other thread ?
If you're happy with triangular modulation then making a triangle-wave generator frequency-adjustable is much simpler than for a sine-wave generator.

 

Did you get round to comparing the sounds of triangular and sinusoidal modulation via the .wav files that I posted on 7 Feb in your other thread ?
If you're happy with triangular modulation then making a triangle-wave generator frequency-adjustable is much simpler than for a sine-wave generator.

No I didn't but that may be an option since I don't need a perfect wave for this application, but I'm sure I can do better than what I have since I am OCD which doesn't help lol

 

The reason I am trying to use a sine wave is I am trying to get away from sharp transients which my be creating the clicking I am hearing.

Neil.

 

With a triangle-wave generator it is fairly straightforward to round off the pointy bits with diodes.

 

Hello,

I have generated two sounds using audacity:
http://www.audacityteam.org/
One is a 440 Hz sinewave with 66% 3Hz sine tremelo.
The other is a 440Hz sinewave with 66% 3Hz triangle tremelo.
I do hardly hear any difference.

Bertus

 

With a triangle-wave generator it is fairly straightforward to round off the pointy bits with diodes.

Tell me more?

 

I do hardly hear any difference.

I didn't hear any difference either, with the .wav files mentioned in post #12. I believe some commercial tremolos use triangle modulation.

Tell me more?

Here you go :-

 

An NE555 does cause a lot of that sort of problem for various reasons when used in conjunction with high gain audio circuits which can be difficult to filter out even with lots of decoupling etc, try using a 4047 multivibrator as your timer IC, It is a very versatile chip that can work as mono, astable, flip flop, can produce +ve or -ve output, with complementary outputs wit 50% duty cycle, plus the oscillator output is available from a separate pin at twice the +/- output frequency. It has very low power consumption and does not need much decoupling to prevent switching noise on the supply rails. 5 to 15Volt operation, altogether, a better option than a 555 when used with audio circuits.
Also remember that when breadboarding a circuit, lots of strange things can happen due to transient fast switching spikes being coupled across adjacent contact rows and via link leads.

The 555 has a triangle wave spanning the middle I/3 of Vcc at the timing capacitor, if you buffer this for enough current to drive a filament bulb, it rounds it off a fair bit.

An LDR is by far the best variable resistance element, but I haven't seen many listed since RoHS. A couple of years back I ordered a few packets from China - whether they've clamped down on that...........

 

That Spice software looks interesting, is it free and where can I download it?

Neil.