Bass amp

[Hallingamp]

Hi all.

Our bass player turns 40 around Christmas time, and I'm thinking of surprising him with a new bass amp. I have built three guitar amps so far, so I do have some experience with building tube amps. But I have never built a bass amp before.

We play rock'n roll ala Tom Petty, ZZ Top, Bon Scott-AC/DC etc, and he is now using a totally beat up Ampeg.....something 350W transistor amp into an Ampeg 4x10" cabinet. Lots of crackling and humming etc. He really needs a new amp. We mainly play clubs/large pubs.

I have been looking at the West Grande amp, schematic here:

http://westlabs.com/Schematics.HTML

It looks very straight forward, few components, probably a fairly easy build, and I can easily get the parts. My first tweaks on this would be to increase the PI input cap and decrease the amount of negative feedback. And use KT88's.

My questions:

Do you think this will make a good bass amp?
Do you think 2xKT88 is enough for a bass amp?
How many plate volts do I need to get the KT88's sounding at their best?
(No voltages are shown on the schematic.)

Thanks in advance.

Jan

[Don Moose]

For a Bass rig, there's no substitute for headroom (power).
If the guitar players are running anything bigger than a Deluxe Reverb, I'd encourage you to go for the Fillmore over the Grande.

I notice that the output tubes and OT are an Ultralinear setup - that's supposed to be a good way to get more power out of a given set of tubes - but I can't really say anything intelligent about it.

[Enzo]

I agree, power in an amp is very different between guitar and bass rigs. A guitarist might be looking for 100 watts of loud. A bassist might want to move from 200 watts to 800 watts not so much to be a lot louder, but more to have a nice clean effortless sound, and all the peaks come through well instead of rounded off. That is why the tube bass amps are like SVTs 300- 400 watt jobs, and they weigh a ton from all the iron.

100 watts is a pretty small bass amp.

A good overhaul would probably have the Ampeg singing again.

You might also consider building an interesting tube preamp for use with a nice powerful solid state power amp.

[Hallingamp]

Thanks for the replies.

That was the answers I was afraid I'd get, but I'm sure you're right.
Takes a lot of power to get that rumblin' bass out.

A cool preamp sounds like a good idea, Enzo.
Do you have a good candidate that could fit in f.i. a 2u rack unit and isn't too hard to build? I really don't know much about bass amps, so suggestions are most welcome.

TIA

Jan

[Enzo]

2 space is easy, it isn't hard to fit a 1 space for that matter. I don't have any particular faves, the preamp section of any amplifier can be built without the power amp section.

[Don Moose]

The Alembic ... FB-2? was a pretty popular tube preamp for Bass - as I recall it was either a Fender 5F6A Bassman or a Fender AB763 Blackface Bassman in a 1U or 2U chassis.

I have the schematic in my library at home, I think.

Hope this helps!

[Don Moose]

This looks a lot more blackface than 5F6-A.

Hope it's at least sort-of accurate.

[Hallingamp]

Thank you, Moose.

That schem looks like - well, almost anything else!
It will be a very easy build, and I guess I can fit a 5F6-A in there as well to make it a 2-channel preamp.

Our bass player will definately get a new preamp for his birthday.

Jan

[xakoss]

HH

HY!

Please help me! i need schematics for HH bassamp 100!
its only a head, and it doesnt work so pleas send me if u can.

thanks A.

[Gtr_tech]

For a Bass rig, there's no substitute for headroom (power).
If the guitar players are running anything bigger than a Deluxe Reverb, I'd encourage you to go for the Fillmore over the Grande.

I notice that the output tubes and OT are an Ultralinear setup - that's supposed to be a good way to get more power out of a given set of tubes - but I can't really say anything intelligent about it.

NAh....my bass player uses a Grande sometimes...although I advise him *not* to use it until he gives it to me to overhaul and make some desperately needed changes (3 way guitar p-up sw for an impedance selector ??!!...open frame telephone style leaf switch for pwr/stby ??!!). I think they were rated at around 60w or so...basically a SUNN knockoff. It hangs just fine and we play fairly loud. When he plugs that Rick 4001 into it and a 4-10 cab...lookout. Chris Squire and Geddy would be proud.

The ultralinear output section cleans up the output (a little) and tends to shift the freq response more toward the upper midrange. Perfect for bass, terrible for guitar.

To get an idea of what this kind of setup sounds like check out the Rush bootleg show on this page:
http://boogiewoody.blogspot.com/

Scroll to the bottom of the page and go up about a quarter of the way. Its called "Fifth Order Of The Angels"...the show was recorded for radio broadcast (super ex quality!) in 1974 and is one of the first shows Neil did after replacing Juhn Rutsey. Geddy's bass just *jumps* out of the mix. He was using Sunn heads at that time and prob'ly the J Bass. Recommended for Rush fans...there's a couple songs that never made the first album as well. The whole show just rocks and sounds so good for such an old recording.

[David Schwab]

HY!

Please help me! i need schematics for HH bassamp 100!
its only a head, and it doesnt work so pleas send me if u can.

thanks A.

Try this place

http://www.majelectronic.co.uk/