Very quick simple question

[ollie]

I'm doing electronics at A-Level and have not really encountered much to do with audio electronics except for filters really.

I just wanted to know if it differed much, if there were certain things you need to take into consideration whereas you might not 'normally'

For example, I drew this really quickly. Would this function as a very simple (and not necessarily 'proper') tremolo effect, with a variable frequency of pulses, or is there some big thing I'm missing that would stop it working?



I know it's kind of an odd thing to ask but I'm going to have to buy a load of stuff to start building pedals and I want to know how much of what I already know transfers over and how much I'd have to learn all over again

[SeanI]

*whoops doublepost*

[SeanI]

I've never thought of switching the power on and off to an op amp, which is essentially all you could do with your current arrangement.  It's definitely worth trying, you might get an interesting chopping effect.     

There are a few problems.  A first step would be to unground the positive power supply rail on your op-amp because it currently has no source of power. Try getting rid of the transistor arrangement and tying your positive rail to the output of the 555 (Assuming its not a CMOS 555). 

You'll also have to bias your op amp properly so that your guitar signal won't clip.  See, your op-amp can only replicate voltages within the range of its power rails.  Your guitar oscillates in both the negative and positive region.  Without biasing, the negative parts can't be replicated with a grounded ( 0 Volts ) negative supply rail.

[ollie]

Oh yeah, forgot about the signal going positive and negative (fairly big thing to forget...)

If I'm going to bias the op-amp would I need to attenuate the signal? We've done biasing using a coupling capacitor in lesson and that shifts '0' up but then would I need to attenuate the guitar signal so it would fit or would it be better just to have  dual power supply?

Also, what is wrong with using CMOS chips? I didn't intend to use a CMOS 555 but might go on to use CMOS 4093 NAND chips for any logic I might need

Thanks for the help

[gez]

It's not a good idea to switch the power to your op-amp on and off.  It's going to be as noisy as hell.  You might even damage the amp if the input signal is large enough when said amp is off (no power).  It's more usual to use a 'modulating element' (I think Mark uses that term).  such as a FET or LDR.

My advice would be to check out some trem schematics to see how it's normally done.

[gez]

PS  You've drawn a link between the transistor's emitter and earth.  This isn't necessary and if you did include it, your transistor would most likely be toast.  In fact, not that I'm advocating switching power on/off, you probably don't need the transistor (the 555 should be able to source current to the amp, which is relatively low-power).

[Dragonfly]

You might take a look at THIS tremolo for ideas, as it uses a 555 timer and is proven to be a nice, noise free design.

Tremolos are tricky beasts...easy to make one that "functions', difficult to make one that sounds good (and doesn't "tick" ) !