Converting a MK IV combo to head: results

[WireNut]

I've seen several folks post regarding converting their combos to heads. This is something I've wanted to do for a long time, as the combo is just too clumsy to move easily.

I finally took the plunge and made myself a prototype head. I'd like to re-do this someday with a nice hardwood and dovetail joints, but I don't have a dovetail jig at the moment. I used high quality, cabinet grade 11 ply void free Birch, which is nice because it's very strong but light, and lightening this beast up was a major goal. I used plate joinery (bisquits). Finish is 5 coats of marine grade spar urethane.

For cabinets, I wound up making 3 identical 1x12 cabs out of the same birch ply, but with different back options: one is a full closed back, one is ported, and one is a half-back I can run open or add the top have to configure it as a closed back. I re-used the EV 12 from the combo in one, and a Celestion Vintage 30 in the others.

I used the closed back cab playing out this weekend, and I was pretty happy with the results. In spite of it being ply, it sounded pretty warm and pleasing, no nasty harshness that I could hear.

Bottom line, it was well worth the effort - 100 bucks or so in materials and a few hours in the shop with the football games on. If you're inclined to give it a try, I say go for it, it wasn't real complicated.

Now I've got an empty combo shell, StudioSlips cover, and flight case to get rid of.

-WireNut

 

[dodger916]

Real nice job. I like the look of the plywood layers.

 

[Bourque]

Nice work man! Sounds like a nice evening. Did ya think about getting the "Boogie" logo for the head?

 

[WireNut]

Thanks, this was a fun project (and it took several evenings...weeks, really, given all the home remodeling I was doing at the same time).

I'm glad you reminded me about the logo. I'll take the one off the combo.

 

[PRS-Ian]

Excellent job. I've looking to do this for some time and have been experimenting with some African Walnut and dove tail joints for a 18W Marshall clone that now matches the Boogie cabs, but I'd love to have a go at a Boogie head. Obviously most of the dimensions come from the combo itself, but what about overall high of the head? Also what have you done about the reverb unit and fan?
Ian

 

[WireNut]

Excellent job. I've looking to do this for some time and have been experimenting with some African Walnut and dove tail joints for a 18W Marshall clone that now matches the Boogie cabs, but I'd love to have a go at a Boogie head. Obviously most of the dimensions come from the combo itself, but what about overall high of the head? Also what have you done about the reverb unit and fan?
Ian

Thanks. A nice hardwood cab with proper joinery would be a great project.

Part of the reason I built this proto first was to work out the dimensions and get the chassis mounting holes, etc. all lined up. The instructions for the dovetail jig I'm looking at (Rockler) imply you might need one or two passes on scrap of the actual stock material to get the jig aligned right. I figured I'd better nail the final dimensions first, then transpose those to another version one day.

I used the dimensions off of Mesa's site to verify the outside dimensions that I'd taken from the combo case. I drew a 3D CAD model of the shell, and also modeled the amp's chassis and reverb tank to check the clearances.

I also stared intently at any picture of a MK series head I could find. A while back, someone posted here about a gorgeous MK head/cab that was on the 'Bay. The seller had about half a dozen pics from all angles, including the back. That really helped me see how Mesa aligns the reverb pan and fan, though it's not like there's a lot of choices there. In those pics, it appears as if the botton of the shell is actually routed out to lower the reverb tank and increase clearance between it and the transformers and tubes. Good idea - I didn't do this, and things barely fit. If you're into swapping tubes a lot mine isn't the head for you, 'cause I can barely fit my hands in there to get the preamp tubes back in. Also, Mesa appears to mount the tank upside down, which I also didn't do.

I made a set of 2D shop drawings from the modeling to fab up the parts, then dry fit everything a few times and made some adjustments. I could try to get you a set if I can make them .pdfs. I'll have to update them with the final measurements, as I did have to trim the width after dry fitting. I also have a model and drawings for the cab design I went with.

-WireNut

 

[trickyrick]

The instructions for the dovetail jig I'm looking at (Rockler) imply you might need one or two passes on scrap of the actual stock material to get the jig aligned right.

Hey man, I'm not sure about the rockler jig, but I am pretty sure it's just a clone of the porta cable jig I use which is really easy once it's set up.

All it takes is a 1/2" dovetail bit set to something like a 7/16 H and your good to go. Also, I believe rockler sells set up blanks as well, They are plastic blocks with cuts in them of the bit you need to set up. Set your router to that and you should be set up. If they don't have them MLCS does but you really won't need them, it's just an option.

Furthermore, most hardwood, including exotic is milled oversized. It is considered 1" stock even though we as consumers expect it to be 3/4"
like you would get from a big box store if you were to go there to get a pc. of standard pine or something. Hardwoods get milled to a rough cut of about 1 1/4" and both faces are planed until blade marks are gone and then it is sold as S2S, which is 2 sides finished. The thickness is never 3/4". It is always oversized. You can find oak in a bigbox store planned to 3/4" but you could buy like 30 board feet of S2S lumber from a local supplier for the same amount as you would pay bigbox for the 6 foot of 3/4" hardwood needed to build a head.

So the point I am making, is if you intend on building the head out of something other then what the bigbox stores offer, like oak or poplar you will need to either have the lumber planned to 3/4" to match mesa's specs, or go with the thicker lumber and set up your router jig accordingly.

Some lumber suppliers will plane, cut and ship exotic woods to your door. I lived in AZ for a few years and went to a company called woodworkers Source
http://www.woodworkerssource.net/

They have a lot of very cool lumber and a great web page. I live in VA now and I still get some things from them. It is a little pricey but they really do have some nice stuff. They even run montly specials. You can order say 8 board feet of exotic lumber, ask them to plane it to 3/4" then crosscut the wood to 4 pc @ 24" and then ship it out and they will. Great web page, check them out.

I hope I didn't rant too much, just trying to educate. Good luck.

 

[trickyrick]

one more thing Wirenut, Rockler makes a poly gel with Michael Dresners name on it. I have been using this stuff for years and have found nothing else that gives as good a finish. It goes on really easy and it protects well. The finish begs to be touched when done. I have used this stuff on desk and table tops so it is durable. No sanding between coats and 3 coats works great. Just a thought.

 

[WireNut]

Hey man, I'm not sure about the rockler jig, but I am pretty sure it's just a clone of the porta cable jig I use which is really easy once it's set up.

All it takes is a 1/2" dovetail bit set to something like a 7/16 H and your good to go. Also, I believe rockler sells set up blanks as well, They are plastic blocks with cuts in them of the bit you need to set up. Set your router to that and you should be set up. If they don't have them MLCS does but you really won't need them, it's just an option.

Thanks, that is good to know. The part I wondered about was how to deal with the angle at the top of the cab. I wasn't sure how the dovetails would lay out, getting the bevel on the top cut so it matched well, etc. Turns out it was pretty easy on the prototype without dovetails. I really have to spring for a dovetail jig - I love the look of cabs done that way.

Furthermore, most hardwood, including exotic is milled oversized. It is considered 1" stock even though we as consumers expect it to be 3/4"
like you would get from a big box store if you were to go there to get a pc. of standard pine or something. Hardwoods get milled to a rough cut of about 1 1/4" and both faces are planed until blade marks are gone and then it is sold as S2S, which is 2 sides finished. The thickness is never 3/4". It is always oversized. You can find oak in a bigbox store planned to 3/4" but you could buy like 30 board feet of S2S lumber from a local supplier for the same amount as you would pay bigbox for the 6 foot of 3/4" hardwood needed to build a head.

So the point I am making, is if you intend on building the head out of something other then what the bigbox stores offer, like oak or poplar you will need to either have the lumber planned to 3/4" to match mesa's specs, or go with the thicker lumber and set up your router jig accordingly.

Yep, over the years I have learned this as well. I generally try to avoid the big home centers, and stick with a couple of lumber yards and a hardware store that have great customer service and knowledge. The first time I bought some hardwood stock from a "real" lumber yard I didn't realize all the boards were differing widths, and without a proper jointer I had to kludge up a way to straighten up the edges and edge join the stock into suitable boards. I'd love to have a planer, jointer, band saw, etc. but I'm very space-constrained in my garage shop.

Some lumber suppliers will plane, cut and ship exotic woods to your door. I lived in AZ for a few years and went to a company called woodworkers Source
http://www.woodworkerssource.net/

They have a lot of very cool lumber and a great web page. I live in VA now and I still get some things from them. It is a little pricey but they really do have some nice stuff. They even run montly specials. You can order say 8 board feet of exotic lumber, ask them to plane it to 3/4" then crosscut the wood to 4 pc @ 24" and then ship it out and they will. Great web page, check them out.

I hope I didn't rant too much, just trying to educate. Good luck.

Cool, thanks for the link, I will check that out. I appreciate your help.

 

[WireNut]

one more thing Wirenut, Rockler makes a poly gel with Michael Dresners name on it. I have been using this stuff for years and have found nothing else that gives as good a finish. It goes on really easy and it protects well. The finish begs to be touched when done. I have used this stuff on desk and table tops so it is durable. No sanding between coats and 3 coats works great. Just a thought.

Cool, finishing is something I've been experimenting with as well. For all the interior doors and wood trim I've done lately, I've used a treatment of Daly's Benite followed by 3-4 coats of Daly's oil. This has come out very nice. I used this on a desk I built, and it has held up very well. I put Spar urethane on a new exterior wood door, and had some left over that I put on these last cabs I did. It gave the birch a slightly yellow or amber hue that is more pronounced in the pics than in person. I'll try that poly gel, sounds like a great option. Thanks for the tip.