Considering building a Small Special for bass

[professormudd]

Greetings,

I have been wanting to build myself a bass amplifier for a while now, but I am not sure just yet.

I have read a bit about the Small Special. From what I read it is described as the clean channel of an ODS and sold as a bass or guitar amp. Is this really as straight forward as that, or are there special considerations for doing a build for bass, specifically? Changes to the power supply, filter caps, tone caps, etc? I was also under the impression that bass amplifiers typically required quite a bit more power, like 150-300 watts or more. Is 100 watts sufficient?

I appreciate any knowledge anyone is willing to share.

[pompeiisneaks]

The generic answer to this, without going into too much depth is as follows:

1. coupling caps and cathode bypass caps should be increased to match the frequency range you want to handle for the bass guitar
2. a much stiffer power supply is usually needed
3. much more output power is needed... many bass amps will find 100W as anemic... and they often were 200W or more.

This is my generic understanding, and could be flawed but that's the gist of it...

~Phil

[Mr. dB]

Whether or not 100W is sufficient for bass depends on the speaker system, and the size of venue, and whether or not you're going through the PA.

[talbany]

Greetings,

I have been wanting to build myself a bass amplifier for a while now, but I am not sure just yet.

I have read a bit about the Small Special. From what I read it is described as the clean channel of an ODS and sold as a bass or guitar amp. Is this really as straight forward as that, or are there special considerations for doing a build for bass, specifically? Changes to the power supply, filter caps, tone caps, etc? I was also under the impression that bass amplifiers typically required quite a bit more power, like 150-300 watts or more. Is 100 watts sufficient?

I appreciate any knowledge anyone is willing to share.

A few things that come to mind would be? use a lower gain 12AY7 in V1 (like an original Bassman)
You could also use a 12 AT7 for the phase inverter (look at the PI in 2nd generation ODS) This will handle more current therefore it would be a bit punchier
I would up the value of the grid resistors on the power tubes to help with blocking distortion
I would also consider increasing the amount of GNFB by either lowering the FB resistor or upping the tap off the output transformers sec.
If you want to get a little crazier with it you could use an output transformer off an old 70's Fender that has the ultra linear taps,run the screens off the taps to increase damping factor
Those would be the simplest mods to do unless you wanted to design it differently and use something like a Baxandall tone stack, 6550/KT88's and or the PI from something like an Odyssey all would help with headroom, bandwidth therefore be better suited for Bass guitar.
It all depends on how loud you like to play

Good Luck!

Tony