how to decide on size / power

[lexington125]

I’m stuck trying to determine the required size/power of my next bass amp. My stupid loud RnR days are behind me - I play mostly traditional 50s blues and 50/60s soul / R&B. In a perfect world, I could get by with a Sunn 200s (2ea KT88) or one of the Fender heads: Bassman (2ea 6L6), Bassman 100/135 (4ea 6L6) or Showman (4ea 6L6) [driving a pair of modern, high quality 1-12 cabs]

But I no longer have the space to maintain my own amp inventory, so I’d hate to invest all of the time and money to build / have built / or restore one of these amps only to learn that I need something larger for some shows.

A lifetime of playing large tube amps makes me reasonably certain that an amp built around 4ea KT88s would cover any situation I’m going to find myself, But if I could get away with the 2ea KT88 configuration, that would be ideal. And I just don’t have enough experience playing with mid size amps to know if the 2ea KT88 format will cover all of the bars and clubs in my future.

In addition to an extra pair of tubes, the larger (4ea KT88) amp would have bigger power supply and output transformers, and some misc extra wire/components/other bits

A smaller, lighter amp (+/- 35 to 40lbs) that covers most gigs versus a bigger, heavier amp (+/- 45 to 60lbs) that should cover any stage I’ll ever play. There should also be some cash savings on the smaller amp, though probably not enough to really influence the decision

how do I determine the correct choice?

[TomCarlos]

Lex...

Concerned about size, weight, cost? You have a bad back so carrying boat anchors is an issue? Have you scouted the Class D amps (a non tube option)? Very compact, powerful, good bang for the buck. A friend has a Gallien-Krueger MB200 200W Ultra Light Bass Amp Head. Nice, loud, compact. You can find these around town or on Musicians Friend.

[BasicBassVI]

Does your band typically run it's own sound or do you typically have a sound person? As long as the PA has adequate monitoring capability, you should be able to play an amp of any size (or no amp at all) without concern of being too quiet.

[lexington125]

Lex...

Concerned about size, weight, cost? You have a bad back so carrying boat anchors is an issue? Have you scouted the Class D amps (a non tube option)?

No bad back, I've just played a few thousand gigs over thirty + years and I'm just tired of the 80+ pound heads of my youth. 40 lbs or so I can handle at 2am without cursing the god of gear

I downsized from Mesa 400 (owned for 20 years) to Aguilar TH500. 4lbs, 500watts, sounds great. But this is show biz and a 50s/60s blues band plays pre-CBs Fender guitars and old tube amps. I carry the Aguilar as insurance.

[lexington125]

Does your band typically run it's own sound or do you typically have a sound person? As long as the PA has adequate monitoring capability, you should be able to play an amp of any size (or no amp at all) without concern of being too quiet.

I've played theatres with huge stages and dive bars where we have to push the pool table out of the way so we can stand under the bare red bulb that normally hangs over the table. But most gigs these days are hipster bars that have PA for vocals only (maybe drums) so I need to carry up to a 300 person room. The two cabs I have can do the job (when fed by megawatt SS amp or SVT sized tube amp) I just don't know if the smaller version of the amp (2ea KT88) will work, and if it doesnt, is it worth the effort / cost for the larger amp for the few times its necessary.

[BasicBassVI]

Having spent my first ten years of gigging on a blackface bassman and later a dual showman, both through a 2x12 bassman cab with JBL clones, I would imagine a pair of KT88's would handle most or all of your gigs. When it isn't enough, just leave the standby off and stick the Aggie behind one of your cabs. What the audience can't see (or discern) can't hurt them.

[Justin Thomas]

Agreed. My 50W Bassman w. A 2x15 CTS cab gets more complaints of being too loud than my Bassman 100 going through an Ampeg 350Wcab. My point? Those old-fashioned non-megawatt handling speakers put out more sound (at least perceivably) than the new plastic&rubber options that we get today. I bet 2xKT88 vintage-style amp AND vintage-stlye speakers get you there. And you said it yourself - use the real deal if you're playing the old timey music. As long as you've got enough headroom to clear a boisterous drummer, which I think is 100W, you're good to go. Need more? Add a couple speakers. If you need any more than that, they'll have the facility to mic/line/whatever you.

Justin

[Leo_Gnardo]

When it isn't enough, just leave the standby off and stick the Aggie behind one of your cabs. What the audience can't see (or discern) can't hurt them.

Or one step further, find a Fender amp head wreck, pull out the transformers and everything else but the pots, knobs & pilot lamp. Put in a small cheap 6.3V transformer to light the pilot. Plug a dummy guitar cable in the front & meanwhile use the Aggie. Every now and then lean over to the Faker Fender & twiddle the knobs with a concerned look on your face, then smile as you turn back to the crowd & go back to playing. It's show biz! Marshall faker heads have been around since forever, no reason you can't do the same with a Fender. And - it will need almost no maintenance, isn't that a treat. Just a fresh #47 lamp every now & then. Heck you could put in a resistor & LED then you would never even need that.

[The Dude]

Heck you could put in a resistor & LED then you would never even need that.

I've seen it done! 9V battery, switch, resistor, LED, Jewel. You don't even have to plug it in.

[Leo_Gnardo]

I've seen it done! 9V battery, switch, resistor, LED, Jewel. You don't even have to plug it in.

True 'nuff, but you should really have an AC cable, and plugged in at that, but dead-ended inside the amp. In case the Amp Inspectors have a look. There's only so much fakery we can put up with.

But if they see you packing out, carrying that amp out the door with the pilot light still on, you're busted.

[The Dude]

True 'nuff, but you should really have an AC cable, and plugged in at that, but dead-ended inside the amp. In case the Amp Inspectors have a look. There's only so much fakery we can put up with.

But if they see you packing out, carrying that amp out the door with the pilot light still on, you're busted.

With apologies to the OP for sidetracking the thread: I would mount an antenna on top and tell them it's powered with a Tesla coil.

[J M Fahey]

With apologies to the OP for sidetracking the thread: I would mount an antenna on top and tell them it's powered with a Tesla coil.

Close but no cigar.

Our friend Steve Conner HAS plugged his guitar into a 250 or 500KV tesla coil and played some tasty licks.

I've even seen the video

[R.G.]

The problem of how to deal with a variable amount of power needed is what was behind my idea of a modular amp.

I got this idea what won't leave me alone that if you had one amp per speaker, maybe 30-50W, and the amp built into the speaker cab, then you could use a preamp and one to N power modules/speakers as needed. Each module would weigh about one combo-amp, but they'd be set up so that they could all be connected in a chain or star from one preamp. So for a small room, maybe one or two. For a big setup, four or eight, and all of these get spread out physically so you get great dispersion, making your sound more even across the audience without frying your ears on stage.

[g1]

if you had one amp per speaker, maybe 30-50W, and the amp built into the speaker cab, then you could use a preamp and one to N power modules/speakers as needed. Each module would weigh about one combo-amp, but they'd be set up so that they could all be connected in a chain or star from one preamp.

RG, have you ever heard of GBX amplifiers? They were doing something like this in the early '70's, but maybe too far ahed (pun intended) of their time so they didn't catch on. Also bigger than what you propose so that may have been a factor.
Ahed - Wikipedia, the free encyclopedia

[R.G.]

I haven't. I'll have to go look. This idea was an outgrowth of my tinkering with Thomas Organ Vox amps. They used a common power supply on the big amps, all +/-31V. They change the power in the amp by changing the speaker impedance. That voltage into 8 ohms, allowing for some headroom in the output devices, gives you about 30Wrms. That's what the Viscount and Buckingham amps were.

If you double the current capability of the amp, but not the power supply voltage, and run it into two 8's in parallel, you get 60Wrms, and that's the Royal Guardsman. Finally, if you REALLY make it able to put out current, you can drive 2 ohms (4x 8 ohms in parallel) and get 120Wrms, and that's the Beatle and later Westministers.

In thinking about this, I was struck by how the +/-31V is a good power supply for the LM3886, and 30Wrms is a good conservative output for that chip, and how one could do a faux-Beatle 120Wrms by using four LM3886s, each driving an 8 ohm speaker. From there, it was a short step to theoretically table-sawing the 4x12 cabinet into four 1x12s, each with its own identical 30W power amp and power supply. And then you could carry ONE 12" speaker and power amp at a time instead of a 100 pound monster.

Then creeping featurism filled in the rest.

Hit send too soon...

Anyway, building several identical 30W amps from a chip and power supply is more than four times easier than building one 120W amp successfully, and you get the ease of picking a power and carrying it in smaller chunks, as well as having independence if something breaks.