Making My Own Amp - Input Question

[LyleCaldwell]

OK, take three (sorry to any of you who read the previous versions).

I'm building my own "perfect" AC30, and I'm starting with the input stage.

Pin 2 of V1 is the "top boost" channel and Pin 7 of V1 is the "normal" channel.  I won't be using a vibrato channel, but I may put some dummy circuit in to make the phase inverter behave in a proper AC30 manner.  Anyway, I didn't want two jacks per channel, and I didn't want even one jack per channel, just the one jack and a way to "jumper" the channels.

This is what I've come up with:



I may or may not keep the pad feature, so the SW on the left may be history.  The middle SW will control whether the channels are jumpered or not, and the right SW (DPDT) will select the active channel when the channels are not jumpered.

Anyone see any drawbacks I'm overlooking?  Sometimes (a lot of times) it's easy to look so closely at a circuit for so long you don't really see it anymore.  Thanks.

[PaulC]

Why don't you just hard wire the inputs together doing away with the switch?  Since you don't have an electronic means to switch by foot you can't really do it on the fly anyway.  Just turn up the volume  for the channel you want to use. The way to wire it is to have a common 1M grid leak resistor on the jack, and then have it branch off to the two 33k grid stoppers going to the two stages.  You can teepee the two grid stoppers right on the tube socket (where they need to be) allowing you to use one shielded cable from the jack.

Of course if you had two input jacks (one for each ch) you could then use an AB box to select them.  You could set it up in a half normal connection where if you plug into just one jack you'd be running into both channels, and if you plugged into both jacks the shared connection would be broken allowing seperation of the inputs.  Plus this would allow you to have different effects running into each channel.

Also you could bring in the normal channel at the same side of the inverter that the vib channel used.  This would put it in phase with the TB channel allowing you to blend them together. 

If you really wanted to be slick you could have two different sockets for the normal channel.  One for a 12AX7, and the other wired for an EF86.

Later, PaulC

[LyleCaldwell]

Why don't you just hard wire the inputs together doing away with the switch?  Since you don't have an electronic means to switch by foot you can't really do it on the fly anyway.  Just turn up the volume  for the channel you want to use. The way to wire it is to have a common 1M grid leak resistor on the jack, and then have it branch off to the two 33k grid stoppers going to the two stages.  You can teepee the two grid stoppers right on the tube socket (where they need to be) allowing you to use one shielded cable from the jack.

Of course if you had two input jacks (one for each ch) you could then use an AB box to select them.  You could set it up in a half normal connection where if you plug into just one jack you'd be running into both channels, and if you plugged into both jacks the shared connection would be broken allowing seperation of the inputs.  Plus this would allow you to have different effects running into each channel.

I am going to be controlling A/B or both remotely, actually, but it does make sense to do the selection at the volume controls rather than at the input.  Very much appreciated.

Also you could bring in the normal channel at the same side of the inverter that the vib channel used.  This would put it in phase with the TB channel allowing you to blend them together.

More goodness.

If you really wanted to be slick you could have two different sockets for the normal channel.  One for a 12AX7, and the other wired for an EF86.

That IS slick.  Thanks for that.