Wondering if there is some software available that would allow me to post a schematic here. I have a circuit in mind based on the S.E.X. 2.0 which I could probably describe but a schematic would be so much easier.
There is an iPad app called "iCircuit", which will let you export PDFs, among other things. I don't know if Macs can run iPad apps or if you have an iPad you could use...
If that didn't sound like English to you, you may wish for a native app. Not sure if anyone has ported gschem. I used that a few years ago on my Linux box.
I use a PC so cannot comment about whether this Mac version works. I can say that the LTSpice Windows version is a great tool and it is worth learning how to use it. It is especially valuable for documenting your builds. You store the schematic electronically and not on paper. I tend to lose pieces of paper but not items stored on my PC.
Symbols (and their mathematical models) for tubes are readily available.
I also found Microsoft Visio to be good for physically designing the layout of parts for amplifiers.