Tube bass head

Most guitar tube heads have high-pass circuitry through the preamp to tighten up overdrive sounds, making the bottom end thin. Also, the output transformers on guitar tube amps are usually not very effective in the bass frequencies.
Not all guitar tube heads are like this, though, and could work great with bass. You should just try and listen how it sounds.

 

Bass heads are designed to reproduce the lower frequencies of the bass. All other things being equal (which of course, they seldom are) a bass head will probably give you more clean volume in the lower frequencies than a comparable guitar head.

However there are lots of bass players who've gotten excellent results using guitar heads (and also guitarists who use bass heads). Personally, I use a 50 watt solid state Quilter guitar head as my backup/practice bass amp.

Here is a recent discussion on the topic: Guitar amp heads for bass?

Are there specific amps you want to compare? I think that would be a much more interesting conversation.

 

Is this your first amp, or do you already have an amp and you're looking for a fun toy?

5 watts might be fun for playing by yourself at home. Not enough wattage for playing in a band.

Wangs amp has come up a couple of times on TalkBass, according to the Search feature, but I don't see any threads where anyone was like, "yeah, it worked great for me as a bass amp."

 

I've toyed with the idea of getting one of those cheap micro tube heads as well, and my research has led me nowhere.

I played a H&K Tubemeister 18 with a bass cab for quite some time and that worked great. The EQ was tuned for guitar so more or less useless, but the clean headroom on the clean channel was very good, even in the 5W setting and the bass was solid.

 

I very highly recommend Ampeg PF20T (it's what I use for this purpose).

 

If you are shopping for low-wattage tube heads, I recommend browsing through this mega-thread:

Low-Wattage Tubesters Official Club

 

Where the rubber really hits the road for the difference between bass and guitar, are the speakers/cab.

For guitar, throw any driver in a box and it will be OK-ish.
Not so, the case for bass.

The speakers and cab designs for bass come from alien technology we found in the back of the movie lot where we faked the moon landing.
Yeah! I did that... aliens are real and the moon is fake.

Seriously, the speaker and cab designs make a world of difference for bass. So that's where you need to pay attention to what's going on, regardless of what head you might use.