Hey Guys,
I've taken a break from building for alittle while, and now want to begin building a few guitar amps.
I've been looking at some different amp schematics, and trying to wrap my hands around push-pull phase splitters.
So, in the two diagrams below (Fender Tweed Deluxe and a Vox AC30) I am unsure about how the slpitters work. The Fender diagram seems fairly straight forward where the first half of the 2nd 12AX7 drives the 2nd half and this is where the two opposing phases are taken from to feed the power tubes...
But, with the second diagram, I don't see how the phase is split.... Any help here would be great.
Thanks,
Bryan
I've taken a break from building for alittle while, and now want to begin building a few guitar amps.
I've been looking at some different amp schematics, and trying to wrap my hands around push-pull phase splitters.
So, in the two diagrams below (Fender Tweed Deluxe and a Vox AC30) I am unsure about how the slpitters work. The Fender diagram seems fairly straight forward where the first half of the 2nd 12AX7 drives the 2nd half and this is where the two opposing phases are taken from to feed the power tubes...
But, with the second diagram, I don't see how the phase is split.... Any help here would be great.
Thanks,
Bryan
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It's a clasiical so named Long Tail Phase splitter.
Both triode share tne same cathode load resistor.
You may consider the top one as a usual common cathode inverting stage, and the bottom one as a grounded grid cathode driven non inverting one.
Ideally, the common cathode load should have an infinite impedance and is sometime replaced by a constant current source.
This way, another view is that, if the sum of the current in the two triodes is forced to be constant, then, when the current of the top one changes (because the signal at its grid) in any direction, the current in the bottom one must changes too in the oposite direction to keep current constant.
Yves.
Cross post !
Hi SY, no journey planned for "Vendanges en Ardeche"
Both triode share tne same cathode load resistor.
You may consider the top one as a usual common cathode inverting stage, and the bottom one as a grounded grid cathode driven non inverting one.
Ideally, the common cathode load should have an infinite impedance and is sometime replaced by a constant current source.
This way, another view is that, if the sum of the current in the two triodes is forced to be constant, then, when the current of the top one changes (because the signal at its grid) in any direction, the current in the bottom one must changes too in the oposite direction to keep current constant.
Yves.
Cross post !
Hi SY, no journey planned for "Vendanges en Ardeche"
Exactly as Yves says - a good explanation. [BTW, a long-tail split definitely tastes better with currant sauce ]
The first schematic is questionable use of a concertina splitter, very much like the Dynaco ST70. It would be better to have a driver stage between the splitter and the OP tubes, like Williamson did, to provide enough headroom so that the splitter doesn't overload before the OP tubes.
] The first schematic is questionable use of a concertina splitter, very much like the Dynaco ST70. It would be better to have a driver stage between the splitter and the OP tubes, like Williamson did, to provide enough headroom so that the splitter doesn't overload before the OP tubes.
The Vox AC30 had a very popular option. I can't recall the name, whether this option had an additional chassis, or built in etc... I do recall that is was additional early gain stage; the purpose of which was to get some overdrive and crunch.
If you google for schems, you'll find this mod/option. I've seen it in several places. If not, holler, and I'll retrace my steps and find the info.
Not sure about this , but I don't think an LTP (diff stage) is really the right beast for overdrive.
If you google for schems, you'll find this mod/option. I've seen it in several places. If not, holler, and I'll retrace my steps and find the info.
Not sure about this , but I don't think an LTP (diff stage) is really the right beast for overdrive.
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