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I have decided with that I will do the 5G9 for my next build, but add an FX loop (instead of building a Princeton 6G2 style amp with an extra nine pin socket for a single tube reverb). That way I can plug in an FX reverb unit at-will later on. I will save the single-tube reverb project for a subsequent build.
So... I can run the FX send to a plain 1/4" socket tapped off the signal path after the .02uF coupling cap that follows the parallel volume controls.
I can make the FX return using a switching socket, and wire it so that the FX return socket is bypassed if there is no plug inserted. I will put an additional .02uF blocking cap in the signal path followed by 1M resistor to ground in this part of the return signal path (but wired so that this setup is bypassed when there is no plug inserted). This additonal blocking cap and resistor would prevent accidental DC entering the signal path from a malfunctioning FX unit, and the 1M resistor would provide the right bias to ensure the FX unit is functioning at the same potential w.r.t. ground as the amp is. (At least that's how I think it works?).
I am not proposing to add any extra gain stages in the FX send or return parts of the loop in the amp (partly because I don't think I want the extra complexity, partly because I don't really think that extra gain stage in the FX loop is really necessary, and partly because I don't think I have enough tube sockets/Volts amps rating in my PT, to run a tube-driven FX loop gain stage. Incidentally my PT has a 50V bias winding, but this will be utilised on the fixed bias part of the circuit, so I also don't know if it would have enough juice left over to cater for FET-driven FX loop gain stages).
Before I start drilling holes and bending-up the chassis aluminium sheet-metal, I would like some feedback on the FX loop idea - namely, will this work?
Secondly I would also like some feedback on the attached control panel layout diagram.
In the attached layout diagram, I have the FX loop sockets situated about 1" away from the 6.3VAC pilot light (which is a standard vintage fender pilot light socket). The Snd and Ret sockets themselves are 7/8" apart.
Are these distances adequate to prevent cross-talk/unwanted coupling entering the signal path (esp from the 6.3VAC source)?
Or would I possibly need to put a steel L-bracket between the FX sockets and the pilot light assembly?
Comments please. :-)
So... I can run the FX send to a plain 1/4" socket tapped off the signal path after the .02uF coupling cap that follows the parallel volume controls.
I can make the FX return using a switching socket, and wire it so that the FX return socket is bypassed if there is no plug inserted. I will put an additional .02uF blocking cap in the signal path followed by 1M resistor to ground in this part of the return signal path (but wired so that this setup is bypassed when there is no plug inserted). This additonal blocking cap and resistor would prevent accidental DC entering the signal path from a malfunctioning FX unit, and the 1M resistor would provide the right bias to ensure the FX unit is functioning at the same potential w.r.t. ground as the amp is. (At least that's how I think it works?).
I am not proposing to add any extra gain stages in the FX send or return parts of the loop in the amp (partly because I don't think I want the extra complexity, partly because I don't really think that extra gain stage in the FX loop is really necessary, and partly because I don't think I have enough tube sockets/Volts amps rating in my PT, to run a tube-driven FX loop gain stage. Incidentally my PT has a 50V bias winding, but this will be utilised on the fixed bias part of the circuit, so I also don't know if it would have enough juice left over to cater for FET-driven FX loop gain stages).
Before I start drilling holes and bending-up the chassis aluminium sheet-metal, I would like some feedback on the FX loop idea - namely, will this work?
Secondly I would also like some feedback on the attached control panel layout diagram.
In the attached layout diagram, I have the FX loop sockets situated about 1" away from the 6.3VAC pilot light (which is a standard vintage fender pilot light socket). The Snd and Ret sockets themselves are 7/8" apart.
Are these distances adequate to prevent cross-talk/unwanted coupling entering the signal path (esp from the 6.3VAC source)?
Or would I possibly need to put a steel L-bracket between the FX sockets and the pilot light assembly?
Comments please. :-)
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