Simple amplifier channel switching?

[tednet]

Hey guys

So I am making a guitar amplifier for the school science fair... and I am having a major problem.... I don't know how to deal with the switching

I was thinking maybe a 2 (3) channel amplifier with a footswitch. I spent hours upon hours searching the forums but I can't find anything that works for me.
I am trying to go with the simplest approach there is. No led on the footswitch, just on the amplifier, if that's a limitation.

Can anybody give me some examples how I could implement channel switching? Maybe a schematic. If you can't help me with my 3 channel idea, I suppose I could settle with 2 channels. The footswitch is important.

Also, let's suppose we omit the footswitch, how would channel switching work? Would it be as simple as an A/B box? Wouldn't there be popping?

Please be so kind to help me 


PS Can you recommend me a simple clean channel, that is not originally a stompbox? It would be nice to have some real clean headroom and run it at more than 9v.

Best Regards

[d95err]

The easiest way to do automatic channel switching is probably with a relay. Just let the footswitch turn the ground connection to the relay coil on or off.

But it seems to me you're starting at the wrong end. If you're designing an amplifier, the first thing you need to decide on is the power supply and power amp. What kind of power level are you planning? You're talking about 9V, so I assume you're building a low power (e.g. 0.5W) amp. Is this correct? What kind of poweramp will you use? Chip-amp? Discrete transistors? Once you know that, you can start with things like what kind of preamps and features you want.

If it's a school project, my recommendation is to make it as simple as possible. Do a one channel amp with Gain, Tonestack, Master and no switching. It will be a pretty big job just to get that working.

[tednet]

lm3876 based 50ish watts. So i will be dealing with around 20 volts

It's just that 9volt preamps don't sound as clean as you would want them to. Atleast fet ones. You need to run them at higher voltage but the circuit requires many modifications then.

And concerning the relays, what would be a good schematic? I just can't seem to understand the concept of relays...

[Ripthorn]

Geofex has an awesome explanation of relays.  I used three relays for the switching in my tube amp that I built and it works great.  Make sure you get a relay have has a fast response time so that there isn't any delay in switching from clean to dirty channels.  As for schematics, sign up at ssguitar and search for relay switching.  One of the members there created a great schematic for me that helped me with my switching scheme (a link to the thread is here http://www.ssguitar.com/index.php?topic=1055.msg6457).