Amps

[trashbeast]

Hey guys, I have a Valveking 212 100W Combo, as well as a 16Ohm, 4x16 cab with celestion g75's.

The combo runs at 8ohms if you're just using the built-in speakers.  Is it possible to run both my built-in speakers, and the cab at the same time? I think it would sound great, but I don't wanna blow anything up.  so if I were to run a 8ohm and a 16ohm cab at the same time, which ohm setting would I set the amp to? If it's even safely possible.

Thanks in advance!!

[Viesczy]

If the speaker outs say that they're in parallel, 8 ohms & 16 ohms results in a load of approx 5.4 ohms.  If you were going to run that setup and if it is in parallel, you'd want to go with 4 ohms as that should be a safe mismatch as the ohm load is @ 5.4 and amp is set to 4 ohms.

I dunno how the speaker outputs are set on the amp, you'll need to confirm that.

Derek

[Wyatt]

8 ohms will be the safest setting.

But i think you'll be disappointed with the result because of an uneven power load. The 8-ohm internal load will seemed twice as loud as the 16-ohm speaker cabinet.

[Viesczy]

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Wyatt wrote:
8 ohms will be the safest setting.

But i think you'll be disappointed with the result because of an uneven power load. The 8-ohm internal load will seemed twice as loud as the 16-ohm speaker cabinet.

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That's wrong , if he's running the amp @ 8 ohms he has 50% of blowing the amp. 

If he runs it @ 4 ohms he's safe regardless of series or parallel.

Derek

[Wyatt]

No.

Not only is your math ambiguous (50% of what? How are you calulating the odds?), your advice is wrong.

First I'll add the caveat that from 4 or 8 to 5.6 isn't a sginificant mismatch and the amp will run fine either way (though with reduced output because the tubes aren't seeing their optimum Zout versus plate voltage), so this is for the sake of arguing theory. The safest setting is 8-ohms.

With tube amps you never want to run a load that is higher than optimum. You deal with flyback voltage. So, you a 5.6 ohm load he would NOT want to run the amp set to 4 ohms. It puts the output transformer and power amp at risk.

But it is safe to run a lower load than optimal. The amp will compensate and reduce it's output. The amp will never be at risk.

There is a tube amp MYTH that persists that it is safer to run a higher speaker load than a tube amp wants, and not safe to run a lower speaker load than the amp wants. And it's just that...a myth, the reality is just the opposite. With SS amps, its safer to run higher; with tube amps its; safer to run lower.