Convert Guitar Combo

[acook]

Hey TB'ers

A friend recently has given me an old Carvin XT112 guitar valve amp Combo.

http://www.carvinguitars.com/manuals/X-AMP.pdf

http://www.carvinmuseum.com/decade/images/91-xv212.html

It's in pretty bad shape with a ripped speaker cone but according to him (I've yet to use it) it turns on.

SO I was looking at repairing it and maybe selling it or giving to my brother when the idea struck, is it possible to use this as a small bass combo? It already needs a new speaker so if changing it to a Bass Speaker could mean I get a nice little 50watt valve practice amp hell why not!

Tell me what you think TB!

- Acook

[JimmyM]

you won't be able to use it except at very low volumes, even with a bass speaker.

[acook]

Aaahh oh well no lose there! Just thought i'd ask the question as I have seen people play guitar heads with bass speakers and it sounds great.

[coldfoot_luke]

Take out the electronics, and find a small head to push your newly installed bass speaker. I have an old GK 15" combo I took the guys out of, and the space is as wide as a standard rack, so I stuck in a carvin amp, same idea.

An upcoming project is to frankenstein an old Marshall 2x8" guitar combo, currently being used as a drum stool behind my set (I'm not a traitor ) that I've been thinking of doing the exact same thing to.

Or you could just us it as is for a few hours of un-bassy tone until the poor guitar amp kicks it.

[T-Bird]

Hi.

What a cool find.

Originally Posted by JimmyM

you won't be able to use it except at very low volumes, even with a bass speaker.

Care to elaborate a bit Jimmy?


Since the OT is designed for guitar, You'll be able to get about half the wattage an octave below through it until it starts to limit the low end. Whether that's a problem or not is up to You. Anything above 80Hz (the first harmonic of E), will be as loud as with guitar.

With an efficient cab/speaker You'll be able to jam with it and do small club gigs. If the vintage tone is what You're after that is .

What I'd do is to build a combo enclosure for it since sealing the back of the existing cab can be pretty hard as the tubes require at least some ventilation. Then again, the Ibanez ValBee has the port located near the tube so the airflow cools the tube.

Regards
Sam

[acook]

Thanks T-Bird, I had a feeling that there would be some kind of limiting but I wasn't too sure. Regardless I see this as a good little project!

[Bmorefoozler]

I'm not sure what jimmy is getting at either, he gigs a 27 watt B-15...

The 3012HO is the most commonly recommended small enclosure 12" from what I can tell. Measure the insides and have someone WinISD it for you, maybe it will work.

[fdeck]

Most guitar combo's have open back speakers that provide ventilation to the tubes. Bass amps need closed-back speakers. That's probably what Jimmy is talking about.

Here's what I have seen some folks do with guitar combo amps. They chop down the cabinet and turn the combo into a tube amp head, then put it on top of a bass cabinet. That way the tubes have their proper ventilation and the speaker is happy.

[lbwdog]

Originally Posted by JimmyM

you won't be able to use it except at very low volumes, even with a bass speaker.

+1
Perhaps someone should make a sticky saying "An open back guitar cab does not a bass cab make" (even with a bass driver).

[Spino]

...I use a 15 w '68 Fender Princeton guitar amp loaded with a JBL for home practice and the tone is wonderous.I've been using this for years without problems because the volume is set on 3 at most ,plenty loud for an apartment .

[RickenBoogie]

+ another 1 It's the open back cab design of most every guitar combo that makes it useless for bass.

[JimmyM]

right. open back. that's what i was talking about. if it's not an open back, maybe you could get more out of it, but it'll still usually be limited by cab size and lack of porting.

[acook]

Ok Thanks Jimmy and everyone, So This is my Knowledge on the subject now :P Because of the open-back the combo itself would not suit a bass sound even with a bass speaker and changing it to a closed back adds potential problems to the valves and not being a tuned cabinet could cause weak/poor sound. It could be turned into just an amp head but due to the Limiting of guitar circuits it wouldn't fully satisfy the the bass tone unless the circuit was modified (not really want I plan to do at this stage).

Thanks everyone for your input!

[will33]

Originally Posted by acook

Ok Thanks Jimmy and everyone, So This is my Knowledge on the subject now :P Because of the open-back the combo itself would not suit a bass sound even with a bass speaker and changing it to a closed back adds potential problems to the valves and not being a tuned cabinet could cause weak/poor sound. It could be turned into just an amp head but due to the Limiting of guitar circuits it wouldn't fully satisfy the the bass tone unless the circuit was modified (not really want I plan to do at this stage).

Thanks everyone for your input!

I wouldn't worry about it being a guitar circuit, especially for a lower power, lowerish volume thing like you're describing. Plenty of guitar heads can sound good with a bass. I'd be most concerned with getting the speaker part suited for bass. If it's built with the valves hanging down into the openback, sealing the cab would overheat the amp. Might hack it up as a head only or build it into a sort of smallish "airhead" bass cab like a 112 or 210 with impedance that's suitable for the amp. Can look at making it a sealed bass cab if you don't want the overall package to get too big.

[acook]

I think it will be best once I pick it up (today) to decide, I only briefly looked through it all a week ago... I'll post back what I decide on Later

[JimmyM]

it'll do great for very light duty but that's it. might make a good recording amp. and it's always good to have a guitar amp around.