Pulling Two Tubes ?

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PLX
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Pulling Two Tubes ?

Post by PLX »

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Useless fucking Internets :!:

When you pull two tubes out of a 100 watt amp, what do you set the output impedance to ? (to what do you set the output impedance ?) never end a sentence with a preposition



edit: Ok, so the Internets came through. If I pull two tubes, then I would just connect the 8Ω tap to my 16Ω 4x12 cabinet.. right :?:
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Re: Pulling Two Tubes ?

Post by lll »

.
Halve (divide by 2) the impedance.

So (i.e.), if you have:

- 4 output valves/t00bz

and

- you run your amp normally at 8 ohms

and then

- you remove the inner or outer pair (leaving only 2 output valves/t00bz in use)

then

- set your amp impedance selector to 4 ohms ( 8/2 = 4)


this article verifies:

https://www.premierguitar.com/diy/ask-a ... er-wattage
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Re: Pulling Two Tubes ?

Post by PLX »

lll wrote: Mon Jul 18, 2022 8:03 pm .
Halve (divide by 2) the impedance.

So (i.e.), if you have:

- 4 output valves/t00bz

and

- you run your amp normally at 8 ohms

and then

- you remove the inner or outer pair (leaving only 2 output valves/t00bz in use)

then

- set your amp impedance selector to 4 ohms ( 8/2 = 4)


this article verifies:

https://www.premierguitar.com/diy/ask-a ... er-wattage
Ok, now I'm really confused. :lol:

I normally run this 100w amp @ 16Ω into a 4x12 cab.. so is my edit above correct :?:

I would connect the 8Ω tap to the 16Ω cabinet ?
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Re: Pulling Two Tubes ?

Post by lll »

Now you're talking about/adding speaker cab mismatch.


Theoretically an amp + cab impedance mismatch is okay if the amp impedance is lower than the cab... at least from what I've heard.


Based on your gear if I'm correct, you normally run the amp at 16ohm in a 16ohm cab.

You pull two output valves/t00bz, and your amp needs to run at 8ohm on the impedance switch.

...which also means for a match, your speaker cab needs to run at 8ohms as well.
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Re: Pulling Two Tubes ?

Post by PLX »

I read that link, and if I understand it right that guy is saying the same thing..

In my situation, I would pull 2 tubes, connect the 8Ω output jack to my 16Ω 4x12 cab and rock out.

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Re: Pulling Two Tubes ?

Post by RockyStar »

If you pull two tubes then divide the cabinet ohm by 2. You said your cabinet is 16 ohms so you would be 8 ohms on your amp insert.
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Re: Pulling Two Tubes ?

Post by PLX »

RockyStar wrote: Mon Jul 18, 2022 9:30 pm If you pull two tubes then divide the cabinet ohm by 2. You said your cabinet is 16 ohms so you would be 8 ohms on your amp insert.
I'm reading stuff all over the Innerwebs, and that's what I'm understanding as well.

I just never tried this, so I wanna make sure I'm doing it right.
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Re: Pulling Two Tubes ?

Post by harddriver »

PLX wrote: Mon Jul 18, 2022 7:39 pm edit: Ok, so the Internets came through. If I pull two tubes, then I would just connect the 8Ω tap to my 16Ω 4x12 cabinet.. right :?:

YES this is correct.
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Re: Pulling Two Tubes ?

Post by PLX »

harddriver wrote: Mon Jul 18, 2022 10:26 pmYES this is correct.
Thanks guys !

This sounds awesome :!:

:D
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