#1
I have some questions regarding channel switching and master volumes:

1. Should connection be broken between the incoming signal and the preamp that isn't connected to the poweramp at the time? I've made a couple pictures incase I asked in a weird way:

Must channel switching be done like this?


or

Is this okay?



2. This may be easier to answer. Does anyone know how to have channels switchable by both a footswitch and a panel mounted switch? I've done a footswitchable amp, and I've done panel switchable amps. I guess there is a shorting jack involved some how, but I can't find a schematic for it.

3. Does putting a master volume before the phase inverter of a push-pull amp sound any different than putting the master volume after the phase inverter? If so, how?
#2
Use the first diagram, that is true bypass. The second diagram will lead to problems.

2. Check out the Dumble ODS schem (PM me for a good version). The ODS has a nice setup for a manual switch and a footswitch. Basically it uses a SPDT to either ground the relay coil or send the coil to a footswitch, which in turn can ground the coil. Only issue is the footswitch can not "over ride" the manual switch.

3. Yes, very much so. It's not an easy answer. There are tons and tons of threads on amp building forums about all the different types of MVs and how they interact and sound. You could research that topic for a long time. My personal favorite is the PPIMV (post phase inverter).


Btw you want your channels to meet up before the phase inverter, obviously don't send them right to the output section. Some people don't think of the PI as part of the output section, just confirming.
Last edited by kurtlives91 at Sep 15, 2009,
#3
To answer #2 -

the easiest way to do that is to use a flip flop. Check out Merlin's website under "other stuff"...
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#4
Quote by kurtlives91
Use the first diagram, that is true bypass. The second diagram will lead to problems.

2. Basically it uses a SPDT to either ground the relay coil or send the coil to a footswitch, which in turn can ground the coil. Only issue is the footswitch can not "over ride" the manual switch.

3. Yes, very much so. It's not an easy answer. My personal favorite is the PPIMV (post phase inverter).


Btw you want your channels to meet up before the phase inverter, obviously don't send them right to the output section. Some people don't think of the PI as part of the output section, just confirming.


Quote by DLRocket89
To answer #2 -

the easiest way to do that is to use a flip flop. Check out Merlin's website under "other stuff"...


Thanks you guys.

1. I've never actually done what's in the second diagram, and I thought it might lead to some issues of signals bleeding through.

2. That sounds simple enough. I'll try to work it out myself, and PM you (Chris) if I can't make sense of it.

DLRocket- That's about the only spot I didn't look on his website. Thanks.

3. I googled and got tons of websites. Rather than sifting BS/Mysticism from fact, I thought I would ask. I guess I'll just experiment.

BTW part- Yeah, I think of the PI as part of the output section. I'm not sure what convention is. I'm picking it up as I go along.
#5
I think it's typical to consider PI as part of output stage...so much of the powertube action is determined in the PI...
Quote by kcdakrt
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