Converting combo amp to head. Any gotchas?

[ZombieCat]

After plugging my Fender Blues Deluxe Reissue into my 2 x 12 cabinet with greenbacks this weekend I realized how much I like the sound better than the built in speaker of the Blues Deluxe. The downside, I really do not want to carry a combo amp and a cabinet to gigs. So I have been thinking of converting the Blues Deluxe into a head. I know replacing the speaker is easier but greenbacks are only 25w and the amp is 40w.

 

I am a pretty decent DIYer and this seems like a fairly straight forward process. Build a new cabinet for the amp big enough to house the amp and provide good air flow, cover in tweed, transplant amp and it is done.

 

For those that have done this (with any combo amp), did you run into any gotchas you were not expecting?

[mrbrown49]

The thing you'll run into with that amp is that the jack plate is on top. That means when you build the head the jack plate will be on top as well, and your head will be gigantically tall. (It's not a good idea to run tubes on their side because the plates can sag over time and short out.) You'll also run into issues fitting the transformers in that form factor so you'll probably need to build a chassis to transplant the components into so that the tubes and transformers are oriented 90 degrees too the control plate and on the same side of the chassis.

[ZombieCat]

I do not think the height will be that bad. I have not really looked into it and made any measurements as I am just kicking around the idea right now. I was envisioning a head cabinet about 1/2 as tall (about 10 inches) as the combo cabinet with all the controls and jacks located on the top just like the combo amp. The height will be slightly taller than my Crate V33 head.

 

In theory, it would still be more convenient than carrying the combo amp and 2x12 cabinet.

[mrbrown49]

I don't know dude. Look at this picture. Your head will only be 4 inches or so shorter than your combo, pretty much as tall as the back panel.

 

[Rezrover]

Rick Nielson from Cheap Trick runs 2 Silver Face Deluxe Reverbs and a Fender Hot Rod Deluxe in a rack. Sorry I can't find a better picture.

 

[mrbrown49]

^That sort of amp is much easier to convert because the tubes and transformers are already oriented 90 degrees to the controls. It's a much more efficient use of space that way.

[ZombieCat]

I don't know dude. Look at this picture. Your head will only be 4 inches or so shorter than your combo, pretty much as tall as the back panel.

 

Good point. Like I said I was just kicking around the idea and had not taken a serious look or measurements. Maybe the best thing to do is take the speaker out and drop some of the weight which is the main issue not so much the size. If only greenbacks came in a higher wattage.

 

Thanks for the pic.

[mrbrown49]

 

Good point. Like I said I was just kicking around the idea and had not taken a serious look or measurements. Maybe the best thing to do is take the speaker out and drop some of the weight which is the main issue not so much the size. If only greenbacks came in a higher wattage. Thanks for the pic.

 

 

Oh it's totally doable, I just think you'll have to build a new chassis and relocate the electronics to really make it worth it. Save all the old stuff and you can always convert back if you need. I've actually been toying with this idea myself recently with a couple of my combos and they are the same layout, controls on top. I still may do it if my amp tech is up for the work. I'll pm you my estimated cost if I end up getting one.

[ZombieCat]

Oh yes still totally doable but more of a project than I currently want to take on right now. Definitely keep me informed on what you find out as I might want to take this on at a later date.

[ZombieCat]

Pulled the back panel off my amp last night to take a look. From what I saw, this project is looking a lot more doable. The sockets for all the tubes are on separate PCB from the rest of the amp circuit and connected by ribbon wire. It should not be difficult at all to move the tubes to a different location and eliminating a lot of height from the cabinet and keep them at a 90 angle. The ribbon wire will probably not be long enough but it would be easy enough to solder in longer wire as needed.

[WRGKMC]

If the wires get too long you're going to introduce hum and buzz like an ungrounded guitar jack. I suggest you put brass or steel screen like the stuff they use on screen doors on the surface where the chassis mounts. This acts as a RF shiels as it grounds to the bottom of the and is commonly used in fender heads. You may need the same stuff for the power tubes and wiring or your amps going to hum badly without it. All screen should be grounded to the chassis.

 

Next, I'd have a few holes drilled in the bottom to allow air convection to occur. As hot air rises out of the top cool air is sucked in from the bottom keeping the chassis, caps, Tranys, and tubes cool and eliminates the ness for a fan in most cases.

[matou]

Simplest solution would be to get/make a 1x12 cab, and put one greenback in the amp and one in the extra cab, and stack 'em.

 

I'd use G12H30's.

[ZombieCat]

WRGKMC, that is some good info, thank you.

 

matou, sadly I do not possess the simplicity gene but I do like the idea of splitting the speakers that way. I never thought of that.

[Belva]

Simplest solution would be to get/make a 1x12 cab, and put one greenback in the amp and one in the extra cab, and stack 'em. I'd use G12H30's.

This. Or make a 212 amp. That's how I'd go. May take less wood. And, as I get older I end up having less wood than when I was in my teens.:poke:

That's what Viagra's for, I know. And to keep me from rolling out of bed.

[matou]

 

WRGKMC, that is some good info, thank you. matou, sadly I do not possess the simplicity gene but I do like the idea of splitting the speakers that way. I never thought of that.

 

 

It is much easier to carry two 1x12's than one 2x12. I think they may even makes one designed to stack like that. I know Peavey does.

 

Here you go - http://guitars.musiciansfriend.com/product/Fender-Hot-Rod-Deluxe-112-80W-1x12-Guitar-Extension-Cab?sku=600768

[Belva]

It is much easier to carry two 1x12's than one 2x12. I think they may even makes one designed to stack like that. I know Peavey does. Here you go - http://guitars.musiciansfriend.com/product/Fender-Hot-Rod-Deluxe-112-80W-1x12-Guitar-Extension-Cab?sku=600768

Good point here. Carry amp in one hand, speaker in the other and load the guitar in a gig bag with back pack straps. Then what to do with the pedal board.... I think this way because I always want to make one trip with my gear. Then I have more time to help with the p.a. and other "stuff". And more time to see which groupie I'm taking home that nite.....

[ZombieCat]

 

It is much easier to carry two 1x12's than one 2x12. I think they may even makes one designed to stack like that. I know Peavey does. Here you go - http://guitars.musiciansfriend.com/product/Fender-Hot-Rod-Deluxe-112-80W-1x12-Guitar-Extension-Cab?sku=600768

 

 

Matou, I agree about it being easier to carry two 1x12 then a single 2x12. Funny you posted that link for the Fender cabinet. I came across that this weekend as well and I am probably going to get it.

[Belva]

The only down side to 2 cabs I see is if you ever get the temptation to run without the xtra cab. Then the one speaker may beg for mercy until it just gives up. Now if you get 2 speakers, each capable of handling the amp's power, this would be ideal. But the ones you have may or may not each be capable. Why take the chance?

[matou]

The "rule of thumb" for speakers is twice the amp's power, but how often does anybody actually dime their amp, really?

[ZombieCat]

While the power rating is a valid concern, I barely turn my amp above 2 now as it is. The band I am with plays extremely small venues (dive bars for the most part). If I do run into the problem of needing to go louder, I can replace the speakers.

 

I like matou's earlier suggestion of running the speakers in the amp and the extension cab in parallel. It does limit me to having to always bring both pieces which is a downside but one I am willing to deal with.

 

The fender extension cab comes with a Celestion G12P80 and who knows, I might like the sound of it.

[mrbrown49]

 

While the power rating is a valid concern, I barely turn my amp above 2 now as it is. The band I am with plays extremely small venues (dive bars for the most part). If I do run into the problem of needing to go louder, I can replace the speakers. I like matou's earlier suggestion of running the speakers in the amp and the extension cab in parallel. It does limit me to having to always bring both pieces which is a downside but one I am willing to deal with. The fender extension cab comes with a Celestion G12P80 and who knows, I might like the sound of it.

 

 

Why do you need to run two speakers if you can't drive your amp properly as it is?

[ZombieCat]

This thread has spiraled a little from its original intent. What started it all was I hooked my 2x12 cabinet to my amp and liked the sound from the greenbacks in the 2x12 much more than from the stock speaker. It was never about needing more volume. This got me on the original idea of converting the combo amp into a head so I did not have to carry the combo amp and a 2x12 cabinet.

 

A key piece of info that never came up which might help explain why I like matou's idea so much is that my greenbacks are 16 ohm. If they were 8 ohms, it would be a no brainer to swap one into the combo amp and call it a day. I have looked at the schematics to see if it is possible to wire for a 16 ohm speaker since it does support an internal 8 ohm speaker and an external 8 ohm cabinet but it is not making much sense to me. I have a good knowledge (though rusty) of basic electronics but transformer outputs always made me go "eh?" unless it was very clear.

 

Here is the transformer output from the schematic:

 

[Somedayrockstar]

Sorry I didn't read everything so if this is redundant or useless info I'm sorry. I converted my blue's Jr into a head which is setup the same way with the tubes hanging down and it was a piece of cake. I just drilled a few hole's on top and moved some stuff. Turned out awesome. I need to work on tolexing though.

 

[mrbrown49]

 

Sorry I didn't read everything so if this is redundant or useless info I'm sorry. I converted my blue's Jr into a head which is setup the same way with the tubes hanging down and it was a piece of cake. I just drilled a few hole's on top and moved some stuff. Turned out awesome. I need to work on tolexing though.

 

 

Looks great. Problem with the OPs is that the tubes are in the same plane as the control plate, not right angled like yours, making it much more complex of a conversion.

[Somedayrockstar]

Do you mean hanging straight down off the back of the pannel?