Guitar amp for bass - convert?

[pieterv]

There don't seem to be any budget valve bass amps (around £200), so I was wondering if it would be possible to convert a guitar amp or combo to bass use.

Where are the main differences, in the amp or the speaker? The Fender Bassman was used many guitarists, so some bass amps can be used for guitar. What about the other way around?

You would probably need another frequency response from the amp, would you be able to change this by adjusting filter capacitors?

What about the speaker, could you stick with the same driver or would that die a quick death? Bass cabs or combos are closed back (apart from a smallish hole) to dampen the speaker, I read, so would modifying the cab in that way be sufficient, or would you also need another driver?

Any ideas? Anyone actually done it?

Thanks for any feedback.

Pieter

[Mr. Foxen]

Mostly its the preamp voicing that's different, guitar amps tend to have less head room also. You could fiddle with the preamp to make it bass. You also need to run bass speakers if you want any bottom, if not, don'[t fiddle with the preamp either.

Wouldn't bother with a combo, score an old head and get it fixed up. I'd guess a peavey windsor with some fiddling would do ya, kinda Peavey budget take on an old single channel head.

Probably best is score an old no-name valve amp and use that, a PA one would be cheap.

[dannybuoy]

Unless you're trying to sound like a guitar, you would need a proper bass cab in order to reproduce the low end, but you could use a lot of guitar valve amps as long as the pre-amps in them don't roll off the low end. The trouble is, most budget guitar valve amps are pretty low powered, e.g. the Orange Tiny Terror or Epiphone Valve Junior are typically <30W. These would be great for recording or using as a distorted rig alongside a regular bass rig but wouldn't really be loud enough alone for gig volumes.

Here's some clips in this thread of an Orange Tiny Terror with a P-Bass: [url="http://www.talkbass.com/forum/showthread.php?t=560354"]http://www.talkbass.com/forum/showthread.php?t=560354[/url]

Edited January 2, 2010 by dannybuoy

[pieterv]

Thanks for the ideas.

[Cat Burrito]

I have an old valve Bassman head which of course has a guitar input and a bass input. I've actually never tried the guitar input but presumably would want a different cab to get a halfway decent tone. My thoughts are that it's all a nice theory but ultimately I suspect more effort for less results. Probably best off lurking around the 'Bay as they often have decent bargains cropping up, especially old 70s stuff

[The Burpster]

Isnt the Orange Terror dual head usable for g'tar and bass.....?

I seem to remembr reading that somewhere...

[stevebasshead]

If you intend running at any significant volume you'll definitely want speakers that can cope with bass, normal guitar cab speakers will be stressed and likely fail sooner or later. This is because reproducing bass frequencies requires that the cone moves in and out more which puts more load and stress on the voicecoil and the rubber surround which joins the cone to the outer edge.

You won't damage a guitar amp though. As others have said, you may not get enough headroom before it starts to distort and the EQ points may be a little less ideal but then again it depends on what sort of sound you want, you may just get exactly "your tone". If your local rehearsal rooms have valve heads and bass cabs you could experiment there.

[lojo]

I used a fender valve combo designed for guitar for a band doing pubs and weddings during the early 90s

Could keep up with the footy scores on the radio through the amp during those long sit arounds at the wedding gigs as well!