Is it possible to have both a Jubilee and 2203 style preamp in a channel switcher?
Moderators: pompeiisneaks, Colossal
Is it possible to have both a Jubilee and 2203 style preamp in a channel switcher?
Parden my green, but is it possible to design an amp that shares these two designs? As I understand, one is plate followed and the other is cathode followed. I'm still too new at this to be able to just throw the schematics down and be able to "read" how or if it's possible to bring them together. But it's something I'd like to try and work towards!
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Stevem
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Re: Is it possible to have both a Jubilee and 2203 style preamp in a channel switcher?
Yes it's fully possible to build a amp with those 2 separate preamps and to switch between them, the thing you can not do due to the poor tone and gain that will result is use them both at the same time.
This is due to them being out of phase with each other.
Every time signal goes into a tubes grid and gets taken off the the plate its 1) amplified to some extent and 2) its phase is swapped, whereas when signal goes into the grid and gets taken off the cathode there is a small loss of signal gain levels and the phase does not flip.
Note that it does not even have to happen the way I discuss above, just 2 different preamp sections with a different number of gain stages, even without a cathode follower stage will be out of phase with each other, and then as above if used at the same time will sound strange!
The way this can be shown on a Schematic is as in this photo.
This is due to them being out of phase with each other.
Every time signal goes into a tubes grid and gets taken off the the plate its 1) amplified to some extent and 2) its phase is swapped, whereas when signal goes into the grid and gets taken off the cathode there is a small loss of signal gain levels and the phase does not flip.
Note that it does not even have to happen the way I discuss above, just 2 different preamp sections with a different number of gain stages, even without a cathode follower stage will be out of phase with each other, and then as above if used at the same time will sound strange!
The way this can be shown on a Schematic is as in this photo.
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Not screaming like the passengers in his car!
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pdf64
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Re: Is it possible to have both a Jubilee and 2203 style preamp in a channel switcher?
There should be no problem to build a amp with both 2203 and 2555 type preamps, and a switching arrangement to select between them. But I don't think it would be feasible for them to share any of the triode stages, hence 5 x ECC83 would be required, as each preamp requires 2, then another for the LTP. And another if a shared fx loop is required
It's nice to provide links to schematics of the amps being enquired about
https://drtube.com/schematics/marshall/2203prem.gif
https://drtube.com/schematics/marshall/2555amp.gif
It's nice to provide links to schematics of the amps being enquired about
https://drtube.com/schematics/marshall/2203prem.gif
https://drtube.com/schematics/marshall/2555amp.gif
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