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Old 1st Jul 2006, 9:39 pm   #1
adibrook
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Default preamp o/p stage

I'm workign on a 1st stage preamp at the moment. The design philosophy behind it is that my bass would plug into it, and it will not provide much distortion itself. Rather, it will provide gain and over-drive the amp in fornt of it. Keepign the 1st stage preamp seperate (with it's own psu) will help stop instability.

It will probbaly only be two triode stages one fo them being the output.

Now here comes the tricky bit. What would the o/p stage look like?

It needs to feed the grid of a valve amp, BUT it would also be good if it can feed a semiconductor amp input too just incase my valve poweramp fails.

A class A r/c anode couple amp stage would want a high output inpeadence...right? So it may not be happy with being connected to a dirty silicone amp.

A transformrer coupled amp will have an impeadence mishmatch. I dotn know what happens when you put a low z signal into a high z input?

Also, someone suggested a cathode coupled amp.

any ideas anyone?

BTW...this preamp will be very cool for reasons which i wont reveal yet.
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Old 3rd Jul 2006, 12:41 pm   #2
peter_sol
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Default Re: preamp o/p stage

I think you will find that any guitar amp has an input impedance of at least 500k ohms so don't worry too much unless you are going to have very long leads between them then you should use a cathode follower to give a low output impedance to your preamp which then will feed into virtually any other input. anyway you can feed a low imp into a high imp but not a high into a low (because it loads it too much)
Regards
Peter.
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Old 3rd Jul 2006, 5:42 pm   #3
adibrook
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Default Re: preamp o/p stage

So an ordinery c/r coupled ouput taken from the anode will be allright, even plugged into the input of a solid state amp (mine has 741 op-amps on the inputs).

Cool. That amkes thigns alot easier.
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