5w bass amp

[Matty_V]

A couple years ago I bought all the parts to build a GA-5 but never did. I would like to have a practice bass amp in the jam room. With a few tweaks here and there could a 5w bass amp provide enough thump to be heard in a practice room? I'm thinking yes but just want to check first. What would be the best tubes to use? Probably want to go with SS rectifier yes? Thanks a bunch

Matt

[bigsbybender]

A GA-5 could provide enough bump with the right speaker/speaker cabinet.

I'd recommend a fairly efficient 10" with decent low end (Eminence Beta 10, or Delta 10). Putting that in a small-ish cabinet should give the impression of strong low end.

It won't be able to keep up with much without distortion. It could jam along with CDs or other recordings fine, but don't expect much when jamming with a drummer or electric guitarist.


j.

[Matty_V]

It would need to keep up with an electronic drum kit and my 18w rig. So even with some higher B+ from SS diodes and unbypassed cathode resistors it still couldn't cut it without clipping? My gf wants to learn bass and also be able to jam along with us in my basement.

[bluesbear]

It'll never keep up with an 18 watt.... if you turn the 18 watt past 1. Even with a 6L6, you'd have to play really quiet.
Dave

[Matty_V]

Duly noted guys. I'll forgo this idea and look into a cheap bass combo for her to learn on. Just for my own knowledge, what would it take to contend with regular jamming levels? Are bass rigs in the 200w range really that necessary? I'm still impressed with what my little 18w can do.

[echuta13]

I'd think a lite version of the Ampeg B-15 would be about right. 

[Matty_V]

Thanks for that suggestion. Its the b15n model correct? I'm not familiar with ampeg models. 6sl7's in the preamp and 6l6s in the power. I think if I dumped the extra channel it would be a pretty straight forward build. As far as bass is concerned, would SS diodes be easier than a 5ar4? You don't really want a bass to sag do you?

Never built a bass rig but would like to add one to my arsenal some day.

[echuta13]

Yep!  A single-channel version with SS rectification is probably what I would do.  There's a schematic of the B-15 Heritage amp in the owners manual on page 10.  :-)
http://www.ampeg.com/pdf/Heritage_B-15_OM.PDF 

I like the fact that they also give you a switch to enable cathode bias or fixed.  I'm a simpleton, and would probably just go with cathode bias unless you need a little extra power...

[Matty_V]

I don't think I'll be including said switch. Cathode bias and get on with it! I might keep some of the switches on the front end for a little variation, or maybe not. I like to think of it the way a potential customer would, knobs and switches are attractive. Simplicity rocks tho. Reverb what?!?

[bluesbear]

My bass player used to use an old Traynor, (2 - 6CA7's). Great amp but to get a decent tone, he had to turn up beyond comfort level in smaller clubs. I built him a simple single channel 5F6a with SS rectifier and 5881's. At the voltage it's running, I'd guess it's 35 - 40 watts. It's plenty for gigging and sounds great. Where it's not enough, it would need miking anyway.
For learning, I'd look for a used SS bass amp. They can be had cheap and when she's ready for a better amp, you can probably sell it for about what you paid.
Dave

[Matty_V]

Thats good advice dave. I would however like to build a bass amp of my own at some point. Of course, I'd like to build one of everything if I had the time (and money). I was going thru that heritage b-15 schematic last night and drawing up my own simpler version. I don't understand how that tone stack works or whats going on with the phase inverter. I don't like to build things I don't understand. I'm thinking maybe using a more fendery/marshally type stack with a standard long tail pi. A 5f6a would be sweet, but I wouldn't be satisfied unless I put my own spin on it (whether thats good or bad).

Matt

[echuta13]

I'm pretty sure the tone stack is a Baxandall, so there's a good place to start looking for more info on it.  The phase inverter it uses is a floating paraphase which is part of the tone of the amp as well: http://www.freewebs.com/valvewizard/floatingparaphase.html

Another option might be to use Alembic's F-2B preamp (BF preamp) with the output section of your choice.