12.05.2003
Custom Input Jacks
From meo@rru.com Tue Mar 26 10:37:58 CST 2002
Article: 404226 of alt.guitar.amps
Date: Tue, 26 Mar 2002 07:32:02 GMT
If your amp has more than one input jack per channel, you can set it up so that each jack has a different flavor - different volume attenuation and tonal response - simply by using different value resistors.
Look at almost any old Fender or Marshall, and you'll find 68K inputs. Gibson used all sorts of values, from 47K to 220K. Magnatone was partial to 47K, Vox used a variety but especially liked 100K, and HiWatt seemed to like none at all. Ampeg was one of the earlier to mix them, for instance using a 100K (with a .005u bypass cap) for the bright input and a 47K for the normal input.
You can try any values you like. I recommend at least one input having no resistor, just a wire straight to the grid of the first preamp. Then try a mix of resistors on the others.
I just finished rebuilding a Gibson GA-6 that's a cross between a 5C3 and a 5D3 tweed Deluxe, but now with cathode biased preamps. This amp has a single "mic" input on one channel, and three "instrument" inputs on the other. I left the mic input with no resistor; this is an incredibly quiet, full sounding channel. I set the other three jacks up with 100K, 47K, and 22K resistors, and each jack has a very distinct flavor now. I also added a 1M resistor across the #1 input jack. (This is the only shorting jack on this channel.) You can also experiment with these resistors that go across the jacks, but don't go real low (say, 220K) or real high (say, above 5M).
Using a (non-shorting) 1/4" plug in the #1 slot while using the #2 or #3 jack changes things up, too, by cutting out the short to ground so that the 1M resistor kicks in. *Lots* of possible input sounds here, folks!
NOTE: changing resistor values will affect channel input noise as well as volume and tone.
-Miles
From meo@rru.com Tue Mar 26 10:37:58 CST 2002
Article: 404226 of alt.guitar.amps
Date: Tue, 26 Mar 2002 07:32:02 GMT
If your amp has more than one input jack per channel, you can set it up so that each jack has a different flavor - different volume attenuation and tonal response - simply by using different value resistors.
Look at almost any old Fender or Marshall, and you'll find 68K inputs. Gibson used all sorts of values, from 47K to 220K. Magnatone was partial to 47K, Vox used a variety but especially liked 100K, and HiWatt seemed to like none at all. Ampeg was one of the earlier to mix them, for instance using a 100K (with a .005u bypass cap) for the bright input and a 47K for the normal input.
You can try any values you like. I recommend at least one input having no resistor, just a wire straight to the grid of the first preamp. Then try a mix of resistors on the others.
I just finished rebuilding a Gibson GA-6 that's a cross between a 5C3 and a 5D3 tweed Deluxe, but now with cathode biased preamps. This amp has a single "mic" input on one channel, and three "instrument" inputs on the other. I left the mic input with no resistor; this is an incredibly quiet, full sounding channel. I set the other three jacks up with 100K, 47K, and 22K resistors, and each jack has a very distinct flavor now. I also added a 1M resistor across the #1 input jack. (This is the only shorting jack on this channel.) You can also experiment with these resistors that go across the jacks, but don't go real low (say, 220K) or real high (say, above 5M).
Using a (non-shorting) 1/4" plug in the #1 slot while using the #2 or #3 jack changes things up, too, by cutting out the short to ground so that the 1M resistor kicks in. *Lots* of possible input sounds here, folks!
NOTE: changing resistor values will affect channel input noise as well as volume and tone.
-Miles
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