I'll be referring to the front panel diagram in the previous post. Panels are 1+1/2" wide (I'm pretty sure: there's also the possibility to use 1+3/4" "U" channel; I'll only go to that if space requirements turn out to demand it). Panels are separated by 3/4"-wide strips of wood (Poplar or Tulipwood 1x2s). The longer horizontal panels (which are the three gain stage modules -- but other things can go here) are 7+1/4" long. From this, the other dimensions are implied: the overall perimeter of the collection of modules (not counting the surrounding 3/4" edge framing) comes to 8+1/4" high by 18+1/2" wide. There will be a 3/4" outer frame, and then the case of the amp may add another 3/4" to each edge, depending on my exact case design, yet to be determined in detail.
Thus, approximate overall width of the amp will be around 22". If the amp is also about the same height, i.e., a square front face, with the module panels in the upper half of the face, this leaves about the same area beneath the panels, where a side-by-side pair of 8" speakers would nicely fit.
As for depth, the plan is to use the narrowest standard lumber width which will work: possibly 5+1/2", but more likely 7" or even 10".
The plan is for the speaker cabinet to be closed-back, for the tonal and power-handling characteristics that this imparts (but both stereo speakers will be in a single enclosure, with no baffle or partition between them). Power-handling is a concern in particular, because I plan to use speakers that are just barely rated to handle the power that the amps will generate: this, to obtain speaker breakup and distortion at high volume levels, when desired.
However, into the closed speaker enclosure, other items will also need to fit, to keep the overall "square" profile. The two spring reverb tanks will be mounted in the bottom of the case. And, unlike most amps, in this design the tubes are "topside" of the chassis, but the transformers will hang underneath; i.e., the transformers mount to the underside of the partition between the tube circuitry, and the speaker enclosure; the wires pass through holes drilled in the partition (plywood). Note that there are four major transformers: the left and right stereo output transformers, and the two power transformers, for the preamp and for the power amps. (As noted elsewhere, the two power transformers are an extravagence mandated by the large number of preamp tubes -- and thus, the large amount of heater current required, by this overall circuit.)
So hopefully, the transformers will manage to stay cool enough, even though enclosed in an unventilated space. If this is not the case, i.e., if cooling becomes an issue for some or all of the transformers, then some may have to be mounted "topside", with corresponding re-arrangement of all the other components; probably, the result would be a larger total size for the combo amplifier.
For the separate head/speaker configuration, I assume that the general layout will try to stay the same as the combo wherever possible, so this would point to a rather tall-looking "head", with the 20"x10" (approx) control panel, above a blank rectangular area at least 4-5" high, enclosing the transformers (and reverbs). One nice thing is, the cabinets will be rather tall-looking, which may not be the most graceful proportion, but weight-wise, the center of gravity will be low.
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