Calling Supro experts: which version of the 1624T to build?

[Badside]

Let me just get the elephant out of the room first: I don't care which version Jimmy Page used. This is not about reproducing anyone's tone. I just want to build a Supro-esque amp for fun + I have a pair of 6973 tubes that I want to put to good use.

Among the modern reissues, the 1624T Dual Tone is my favorite.
However, researching the history of the amp, it seems the Dual Tone was the least liked version (tamer, brighter, thinner is what I read) of the 1624T.

Add to that: the reissue is NOT the same circuit, it has an extra 12AX7 (4 in total). What is it used for? I have no idea.
(Potentially as a recovery stage after the tone circuits to make up for insertion loss and reduce interaction between the two, it does seem to have more gain than the vintage ones)

Here are the schematics I've been analyzing:
1624T ("single tone"): http://dirtygirlamplification.net/Amp_s ... /1624T.pdf
6424 (aka Dual Tone): http://el34world.com/charts/Schematics/ ... _s6424.pdf

Biggest differences:
- Grid leak bias on Channel 1 of the original circuit. (I do want to try this)
- Different tone control implementation (Dual Tone's is lossier but reduces interaction)
- Paraphase inverter: Dual Tone has split cathodes with small (50nF) bypass cap on the first one. Likely to make up for the higher loss of its tone controls. Gain boost would be above 1.5KHz so more of a treble boost.
- Dual Tone uses both triodes on V2 for the tremolo circuit.

I don't "need" dual tone controls, so I'm thinking I'll stick with the original circuit unless anyone knows of a reason not to.
What worries me is I find the modern "Black Magick" (which is a single tone knob model supposed to replicate Jimmy Page's amp) a bit muddy in comparison with the modern Dual Tone, but it's not exactly the same circuit (still has 4 preamp tubes, and is called a 1695T).

And I do wonder about the tremolo. The unused 2nd triode on the original circuit seems like a waste to me, so perhaps I could use the later dual-triode trem within the original preamp circuit (shouldn't have an effect on tone since they both just "wiggle" the bias on that channel's cathode).

[dcribbs1412]

No expert by any means
but always on the edge of getting one of Ken's 24 kits to see
what tones would/could be available. Not sure how close it is to a dual tone
http://tubeamplifierparts.com/amp-kits/ ... -kits.html#!

D

[Badside]

No expert by any means
but always on the edge of getting one of Ken's 24 kits to see
what tones would/could be available. Not sure how close it is to a dual tone
http://tubeamplifierparts.com/amp-kits/ ... -kits.html#!

D

It's pretty much exactly a 60's Dual Tone (the 2nd schematic I shared):
http://tubeamplifierparts.com/schematic ... ematic.pdf
Except he put the Standby switch right after the rectifier (totally unnecessary). The original's Standby switch simply muted the power amp.

Again, can't compare to the Dual Tone reissue, that has an extra tube.

Looks like a great kit, but I prefer to build from scratch

Think I'm going to do the "single tone" preamp into the Dual Tone's PI. This way I can easily revert to the shared cathode version of the PI for experimenting.

[Badside]

I guess I figured out why the change in tremolo circuit: the original one had the Intensity control as a plate load, aka it had B+ on it. It'll work (Alpha 24mm pots are rated for 500V), but it's not ideal.

So I guess I'll stick with the 2 triode tremolo (which keeps DC off the pots)

[Smokebreak]

Hey I built one of those. Here's my thread w/clips :http://ampgarage.com/forum/viewtopic.ph ... ight=supro