Updated Layout for Matchless Tornado -- Adding One Tube Reverb

[mebond11]

My first build of the Matchless Tornado was successful, and I am building a second one for a friend.   I am attaching an updated layout (sans PT, rectifier and output layout), in case anyone is interested, with a few modifications:

grid stopper resistors directly connected to valve, and shielded cable used from the inputs

filter caps moved to adjacent to valve stages (which necessitated moving tremolo ground to the preamp ground)

mellowed out the tremolo with .1 uf cap to ground and a resistor in series to the intensity pot.

On the first build, I used a 290-0-290 Marshall transformer, instead of the specified 280-0-280 on the schematic.  I couldn't find a 280-0-280 (though I subsequently found a Hammond).  It didn't look like the dozen extra volts materially changed the operating point of the tubes, but curious if I should use the Hammond or increase the voltage dropping resistors to something like 33K from 22K.

I'm also attaching the schematic.   Thanks again for all the help on the prior build!  The amp sounds great.

[PRR]

> or increase the voltage dropping resistors

Why?

In tube amps, if nothing is smoking, more is better.

[vampwizzard]

Looks great! Wish I had those layout skills!

Shielded inputs = good idea. I built my lightning without them its the only knock on it. Dead quiet until the second or third pedal goes in front.

The PT voltage differences youre discussing are inconsequential.. if it biases up the same itll be more or less the same amp.

[mebond11]

As always, thanks for the comments!  This forum is invaluable.

I was thinking of incorporating the one-tube tremolo circuit into this build.  Is that truly "drop-in", or do I have to add a gain stage or reconfigure the values of components downstream?  Also, I am thinking of tapping the Phase Inverter power supply node for the reverb tube.  If I do so, do I need to reduce the voltage dropping resistor or the PI plate resistor because the load on that power supply node is now doubled with the addition of another 12AX7?  Does the reverb tube need it's own power supply node?

[tubeswell]

Does the reverb tube need it's own power supply node?

You can split the power supply to the two triodes to different PS nodes. I had a Morgan SW22R in a while back and reverse engineered a schematic based on the layout. The driver triode gets its PS from the screen supply node, and the recovery triode from the pre-amp supply node. And there is no hum, and plenty of reverb

[2deaf]

I had a Morgan SW22R in a while back and reverse engineered a schematic based on the layout.

Did you determine the turns ratio for the reverb transformer?  What pan was it using?

[tubeswell]

I had a Morgan SW22R in a while back and reverse engineered a schematic based on the layout.

Did you determine the turns ratio for the reverb transformer?  What pan was it using?

(Edit: it had a specially made Mercury Magnetics 'Morgan RT'* and Type 4 pan

*I went back and looked at the pics I took. I think that would want to be 50k to 100k reflected load

You could use a 12DW7 with the AU triode as a driver, which would work better with a 27k load run at B+ 300V (or capacitor-couple it to a hi-impedance pan, to save parts)

[mebond11]

Does the reverb tube need it's own power supply node?

You can split the power supply to the two triodes to different PS nodes. I had a Morgan SW22R in a while back and reverse engineered a schematic based on the layout. The driver triode gets its PS from the screen supply node, and the recovery triode from the pre-amp supply node. And there is no hum, and plenty of reverb

Thanks, that was my plan...reverb driver transformer tapped at screen node, just after the two 32 uf reservoir caps, and the recovery driver tapped at the PI 22 uf cap.