NEW QUESTION- VINTAGE FENDER 400 PS

[Lonesomedave]

ok, guys, i have another question about the fender 400 ps.

look at the pic below:



i already asked if it would be safe to run just one of the 3 power outputs, say with a 4 x 10 cabinet, yielding only 1/3 of the amp's power. the consensus was, it would be ok as long as there was a load on at least one of the outputs.

now my next question is: would it be ok to run 3 different cabinet setups on the amp? say a 4x 10 on one, a 2 x 12 on another and a 2 x 15 on the third?--as long as the load of each was 4 ohms?

what is the impedance of doing it this way? for example, i know that if you have two 8 ohm cabs on one power output, the resulting impedance will be 4 ohms....right?

well, what about here? can i run, say a 4 ohm cabinet on each of the power outputs of the 400 ps and still just have a 4 ohm impedance load?

what about the sound? assuming I could safely mix cabs and assuming that each power output had the required 4 ohms, what would it sound like? would i encounter phase/out-of-phase problems etc.

sorry for my ignorance, but just asking

/s/ Dave

[will33]

You'll get phasing any time you mix cabs regardless of what amp you use. Some blend better than others, won't hurt anything to try.

And yeah, as far as impedance think of it ad 3 separate amps. They can each push a 4ohm speaker load and the whole thing is still 4ohms.

With tube amps, if you don't have an exact match err on the side of lower impedance, not higher. The opposite of SS. A match is best though.

[Lonesomedave]

will33;

thanks; you put it better than i did-- is this amp the equivalent of three 145 watt amps? i thought so, and your answer confirms it.

/s/ Dave

[beans-on-toast]

Each output is separate and has its own pair of output tubes associated with it. Think of it as three power amps built into one chassis.

Plug in one cab and two of the output tubes are enabled, you get 1/3 of the max power out. Plug in a second cab and another pair of output tubes are enabled and you have 2/3 of the max power. Plug in another cab and the third pair of output tubes are enabled and you have full power. The neat thing about this amp is that you can run it without the speakers connected because the power tubes are switched off when a cab is not connected. This feature allows you to select power in 33% increments. You can't do this with any other tube amps that I can think of.

So as long as you use a 4 ohm cab on each output there will not be any impedance issues.

There will be differences in the sound from each cab if they are different cabs. You can think of this as an advantage and mix different cabs to tailor your sound.

[KramerBassFan]

Woosh, imagine 6 x 8 ohm cabinets.....

[will33]

What you have there is a very powerful, very nice and fairly rare piece. I'd take good care of it just meaning using matched impedances, letting it cool down before moving it, etc.

I don't have the knowlege to explain in detail but they use a different power tube than the common ones you see everywhere and there's enough different stuff going on in the circuit to where not just any amp tech can work on one and get it right.

Where it mine, I'd try a few different cabs until I found one I really liked the sound of, then get 2 more of the same and scale your output needs up and down like beans explained.

With 3 cabs and the amps full output, it's an SVT killer although 2 caba @ 2/3 power would be enough to play about anywhere, the third is just gravy.

[Lonesomedave]

any other thoughts? thanks to all who responded.

/s/ Dave