upgrading smokey amp help me..

[jogina111]

I m planning to build another smokey and I want to put an input buffer but I dont know what would its effect on the amp, they say it makes the sound sweeter..but I dont get it...can someone explain the buffer's function technically? I think its like a ruby amp from runoffgroove. Does it really require a volume and tone control? i cant find a 25ohms rheostat on local shops and I only got a 5k pot for the tone control would that do? They only got 10k pots as their lowest resistance pots.  I cant go buying online because of my country's low  currency rate like the £4 shipping can cost me my 1 day wage...please help.

[Seljer]

Yes, its like the ruby amp. The LM386 has a relatively low input impedance (the data sheet says 50kiloohms), which is no issue if you hook up something like a CD player to it, but a guitar is typically hooked up to a an input with an input impedance of 500kiloohms to 1megaohm.

If you plug into a your guitar (a high impedance source) into a low impedance input you lose amplitude and accenuate any cable capacitance, which makes it lose the high end. A buffer has a high input impedance and low output impedance so it solves this issue.


Volume control: thats up to you, you can use your guitar's volume knob with such a small amp. I don't however know what you would want to do with a 25 ohm rheostat.

[jogina111]

thanks for the explaination, what if I use a bipolar transistor buffer? What difference Would it make?would it make my smokey stop making my tone go octave down and howling like a gay wolf?
Damn! I hate getting this cheap but i got no choice..

[Seljer]

thanks for the explaination, what if I use a bipolar transistor buffer? What difference Would it make?
Damn! I hate getting this cheap but i got no choice..

JFETs have a higher input impedance that bipolar transistors but it would still be a improvement over the bare LM386. Plenty of pedals use buffers with npn transistors (e.g: the entire Boss lineup)

If you've got any opamps at hand (lets say a common TL072 or simliar) you can use one to make a buffer which will do the same thing.

[jogina111]

no i dont have one of those but  i got lots and lots of transistors

can anyone give me an image of a pcb pattern of a ruby amp with a bipolar transistor instead of a jfet?

[jogina111]

 would any kind of FET do?

[petey twofinger]

http://www.till.com/articles/GuitarPreamp/

i used these circuits in  front of 386 based amps with great results , you  can get the transistor from rat shack as well , if you like , but its a lil more $

these are great for what you are doing , or i have heard good things about the fetzer valve .

[jogina111]

ok, i built a buffer and shove it before my smokey..but output volume is attenuated..what could the problem be? The tranny in the buffer? .