Tuning amps for different pickups

[vibratoking]

slope control in the tone stack works good.

A guitar 5way switch as a selector works for say brite and tone shift, and bypass caps.

the real approach is to vary the input impedance to match or mismatch the pickup

Andy, what techniques have you had success with as far as changing the input impedance?

[Andy Le Blanc]

looking at old schematics you'll see a variety of input circuits.

fenders typically has a 1M to ground at the input jack.

vary or put a switch there, this value and the series grid resistor vary widely from mfg to mfg, you can dress the inputs as a high normal input, and the other as a lower impedance input.

nothing new there, just noodling with inputs and a switching jack

you just have to look back explore and try it.

[Structo]

Now you have me wondering what I actually did as far as that circuit goes.

If I recall Henry had told me about this as far as a simple strat switch goes.

Maybe I have a larger resistor to ground.

(checking notes)

OK this was the description.

Install a toggle right next to V1 on the rear panel, connect the ground side of a 5uF cap(4.7uF is ok) to one leg of the switch and ground the other leg of the switch. Attach the positive side of this 5uF to your cathode pin on V1a. Then install a 4k7 resistor between the switch lugs (this eliminates hum when the cap is not grounded). Change your V1a cathode bypass cap to a .68 on the main board. Now your amp will have .68 for your les paul and when you throw the switch, 5.68uF for your single coils. Works like a charm.

[titser_marco]

I think this is a great solution. Just a question: should this switching scheme be done on all gain stages? Or would having switchable bypass caps on the first gain stage be enough?

Now you have me wondering what I actually did as far as that circuit goes.

If I recall Henry had told me about this as far as a simple strat switch goes.

Maybe I have a larger resistor to ground.

(checking notes)

OK this was the description.

Install a toggle right next to V1 on the rear panel, connect the ground side of a 5uF cap(4.7uF is ok) to one leg of the switch and ground the other leg of the switch. Attach the positive side of this 5uF to your cathode pin on V1a. Then install a 4k7 resistor between the switch lugs (this eliminates hum when the cap is not grounded). Change your V1a cathode bypass cap to a .68 on the main board. Now your amp will have .68 for your les paul and when you throw the switch, 5.68uF for your single coils. Works like a charm.

[Structo]

Well, on my amp (100w ODS) I have 5uF bypass caps on both clean and the OD tube cathodes.
I was having a problem with too much low end with a Les Paul so the low bypass value tames that with a humbucker guitar.

Just that first stage gets the strat switch.

Also I just remembered, that I was really battling too much bass in my amp.
I changed the PI coupler caps to .05uF instead of .1uF.
This is what the #183 ODS amp has although it uses EL34's.

I use 6L6's and that helped to clean up any mud left.

[titser_marco]

Thanks, so I guess I will just be making two switches for each of the "entrance" gain stages. I'm thinking of using on-of-on DPDT switches I have and implement this scheme:



Bottom ON position: 5.5uF (4.7uF + .68uF)
Middle OFF positon: .68uF
Top ON position: 22.68uF (22uF + .68uF)

What do you think? It's odd having the low value, but I'm finding it hard to come up with a scheme that has the cap values going up from top to bottom using this switch.

Well, on my amp (100w ODS) I have 5uF bypass caps on both clean and the OD tube cathodes.
I was having a problem with too much low end with a Les Paul so the low bypass value tames that with a humbucker guitar.

Just that first stage gets the strat switch.

Also I just remembered, that I was really battling too much bass in my amp.
I changed the PI coupler caps to .05uF instead of .1uF.
This is what the #183 ODS amp has although it uses EL34's.

I use 6L6's and that helped to clean up any mud left.

[Structo]

I'm not sure I would go that big with the 22uF cap.

Try a 10uF first.

[titser_marco]

I was thinking along the lines of switching a between a Fender spec and D-style spec cathode bypass cap. So I figured 22uF would best approximate that

I'm not sure I would go that big with the 22uF cap.

Try a 10uF first.

[Structo]

Can't hurt to try it.

The old Fenders certainly used that value.

Might work good with a single coil real well.