Well hello there,
Back in December I built a S3X kit with some modifications. I added an input selector switch for 3 inputs, an output impedance switch to select 4 or 8 ohm opt wiring. Then added a Beequit attenuator on the front of the base. I used octal sockets as I have quit a few 6dn7's, I also made a set of octal to compactron adaptors so I can use 6fj7's also.
I use this amp at my work bench. I ordered another S3X when on sale last time. Now stick with me here, I built the second amp pretty much stock except I installed the impedance switch and octal sockets, I will refer to this amp as the "Slave".
On the amp with the Beequiet and 3 inputs (I will refer to this amp as the "Master") I added a single rca output jack to feed the slave with only the right channel output of the Beequiet to the slave amp. I then added a dpdt switch that selects stereo/mono operation of the master amp. In the stereo mode the amp works as normal but in the mono mode this switch takes the left output of the Beequiet and sends it to the grids of both channels and sends the right line level out to the slave amp.
Then strapping both amps to mono and impedance to 4 ohms I now have a pair of 4 watt monoblocks that are controlled by the master amp.
It was a fun project and sounds great to boot.
Thanks Bottlehead.
Stay tuned for my next project which will be a homebrew Foreplay III with some twists.