Hammond 63 conversion to Matchless Clubman

[luthierwnc]

Hi All,

Almost finished with a project that has been languishing for a while.  It is the chassis and iron from a Hammond 63 organ amplifier that I've converted to (more-or-less) the schematic of an EF86 Matchless Clubman.  Others here have used these chassis before with success and I thought I'd give it a go.  Unlike the original I used a Lar-Mar master and an ECL82 pentode/triode for both sides of the reverb driver.  The latter is quite strong and I keep dialing back the dwell trimmer.  A capectomy might be coming there too.  Don't know that I'll ever use the loop.

I kept it point-to-point but stripped everything inside.  To cover holes in the wrong places I had aluminum faceplates milled to receive the vinyl skins.  Had to punch a couple holes for newer canister caps and a reverb tube.  The LC filter setup remains as it was.  To my surprise, the voltages were knocked-down very close to those shown on the schemo -- most right on or within 5%.  I ran A/C through the output transformer and got an impedance ratio of 761:1.  For a four-ohm cab that's 3k which was close enough for a pair of EL34s.  My only 4R cab has a Scumback H55 and a Celestion 12-65.   

The amp is quiet.  There is a huge difference between the hi and lo inputs.  The tone controls are very sensitive.  The amp is very bright.  I haven't brought it upstairs yet because I suspect that bright-cap on the volume pot is a goner.  I may also increase the Brilliance cap.  That depends on me dragging a couple guitars into the shop.  I keep an Epi Les Paul Junior down there.  It is exactly the wrong guitar for this amp but perfect for testing because it bleeds with every bit of EMF, fluorescent flicker and soldering iron hum.  If I can make that guitar quiet, the rest will certainly be better.

The cab is Peruvian walnut and the face is Morado.  Nice stuff.  I use if for fingerboards.  Doesn't take Arm-R-Seal finish very well though.  Bit of history there.

At any rate, hope you find this interesting and good luck with your projects.  Skip   

[luthierwnc]

Made a few mods.  First was replacing the PI 12AX7 with a 12AT7.  It takes some of the volume off but I'm not going to miss that.  Much more manageable.  The bright cap is gone.  The Brilliant control can add back quite a bit.  The reverb volume was changed from 2-meg-l to 1-meg-l which makes the effect usable past 2.  The dwell pot is set around 5 of 10.  The last change was putting a 220k grid stopper on the EF86 tube.  It seemed a little raw and not controllable from the treble and bass.  I'm not sure I can tell a difference but with a Godwood bridge pickup it was quite playable.  I've amended the schematic in the first post to show the changes.

All-in-all a happy project.  Lord knows if I'll every play it past my front door but I will haul it out from time to time.  Now I have to get to work on several guitars looking forlornly from their hangers.  Cheers, Skip
 

[vampwizzard]

Looks great Skip! How did you make the faceplate?

[luthierwnc]

It's not something I would do for a production amp but for my one-offs I just have an MS Paint gif printed on adhesive vinyl at FEDEX office -- same thing you would do for a sign on the side of a car.  This one has a gloss lamination over the matte finish.  Both sides combined are something like seventeen bucks.  Print one at home using the 'adjust to 100%' sizing option so it is exact before you place the order.  I imagine they can print from a variety of file extensions.  sh

[darkbluemurder]

I have built a Chieftain based amp which is very similar to the Clubman, apart from the fact it is an all triode based preamp whereas the Clubman has a pentode.


That bright cap on the volume control needed to go quickly after the first test.


On a different amp I used the same circuit as a modifying platform for the preamp.


I really like the bass control - it is very useful to tighten up overdriven sounds. The mid control in the Chieftain is also useful but I did not like the treble control as I don't think it does a lot. So I did the following:


1) Teamed up the bass control with a gain control after the first stage and added a cathode bypass cap to the first stage. This allows to clip the second stage (a little) whereas in the original design there is no way to make the second stage clip - all clipping comes from the phase inverter and power amp - at the cost of monstrous volume.
2) Moved the mid control to after the second stage and replaced the 250k volume control with a 1 meg volume control. As you don't have a mid control in the Clubman, skip this step.

Cheers Stephan

[luthierwnc]

Thanks Stephan.  Now I'm wondering if I should try an HC30.  A couple years ago I repurposed an older 2x6BQ5 head into a 'Morph' along the lines that Tubeswell explored.  It came out really well which satisfies my EL84 Jones in the 14-watt range.  Unfortunately, one of my lame excuses of having a lot of the parts won't work here.  Except for a few resistors in the bin this calls for all new components. 

Needs more thought.  Cheers, sh

[shooter]

If you're bored, hunt through some of the best "home-brew" amps in the matrix 


PC Express and JSchem - Schematics and Layout diagrams (el34world.com)

[luthierwnc]

I've already got the schematic, layout diagram and BOM.  The DXF CNC program to laser-cut the chassis is already done.  Now it is just money, commitment and where would I put/play it.  sh