Can you DI a valve preamp/solid state power amp, without a load?

[Young Angus]

We're in the studio right now and our bassist wants to use a bass head which will be a solid state head but with a valve preamp, but he just wants to DI it straight to the desk and won't have a cab or dummy load for the head. Is this okay since it's just a solid state amp for the most part or do they still need loads too?

[donnyjaguar]

Given the output level of the solid state amplifier will be profoundly more than necessary, this creates two problems: The noise level will be very high going into the board; the amplifier may damage the input to the board. I'd be inclined to put an attenuator inline. You could chose, or make, one that presents an 8 Ω load to the amplifier but its probably pointless as it would have to be capable of handling the power of the amplfier itself. I'm thinking a wire-wound 1k/1W potentiometer here. That way you can adjust the amount of attenuation from the amplifier going into the board. If you use too high a value then the output capacitor(s) of the amplifier will take too long to charge which could have an adverse affect on the board.

[cochese]

Chances are the bass head may have a preamp output that doesn't include the power section. I would go with a tube direct box. I use the Groove Tubes Brick and it works quite well.

[John Phillips]

I'm assuming he wants to use the amp's on-board dedicated Line Out or DI socket... in which case it should be fine. I've sometimes recorded bass like that with an older Trace Elliot amp (which has a nice transformer-balanced DI).

There are an extremely small number of solid-state amps which do require a load to be stable, but they're all very old designs and I don't know of any modern bass amp which would.

[Young Angus]

Okay well I like John Phillips' answer ;)

Yeah we just want to use the amp's line out / DI socket, and I think it's some modern Ampeg head. Hopefully their designs aren't too primitive that they require a load...it's not going to be cranked or anything anyway. It's just for recording purposes and the only reason our bassist wants a head instead of just direct DI is so he can EQ his tone a bit better.