Speaker / Amp impedance mismatch...

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Re: Speaker / Amp impedance mismatch...

Post by calling card »

Yeah balance, moderation etc...

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Re: Speaker / Amp impedance mismatch...

Post by GrantB »

MikeC wrote: Fri Jul 22, 2022 8:07 am Don't mismatch - safest.
It's not really living life on the edge though, is it?!
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Re: Speaker / Amp impedance mismatch...

Post by AiRdAd »

GrantB wrote: Fri Jul 22, 2022 9:27 am
MikeC wrote: Fri Jul 22, 2022 8:07 am Don't mismatch - safest.
It's not really living life on the edge though, is it?!
instead of eadge of breakup sounds - it would be edge of breakdown sounds :-)
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Re: Speaker / Amp impedance mismatch...

Post by RectifiedAmps »

Remember that the impedance rating of any speaker is for a specific frequency and impedance will vary widely above and below that, so any impedance tap on an OT will have to handle a range of impedances anyways. That said, it’s still safest to match the speaker to the right tap.

I always subscribed to the view that a speaker should be the same or higher than what the OT asks for, but Merlin Blencowe gives solid reasons behind why the opposite may be safer (speaker equal or lower than requested impedance):
“Connecting a higher impedance speaker will cause the load line to rotate anti-clockwise around the bias point, possibly causing screen-grid failure due to passing below the knee of the grid curves (although if you're lucky, the screen resistor will fail open first). It can also cause arcing in the transformer due to much higher anode voltages being developed when the valve is overdriven. Connecting a lower impedance speaker will have the opposite effect; the load line will become more steep, pushing the valve into cold Class A operation which may or may not cause over dissipation of the anode (thankfully it usually doesn't). It is therefore always safer to plug in a lower impedance speaker than a higher one, if you have to.” (http://www.valvewizard.co.uk/se.html)

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Re: Speaker / Amp impedance mismatch...

Post by MikeC »

GrantB wrote: Fri Jul 22, 2022 9:27 am
MikeC wrote: Fri Jul 22, 2022 8:07 am Don't mismatch - safest.
It's not really living life on the edge though, is it?!
With my vintage Marshall cranked, yes.

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Re: Speaker / Amp impedance mismatch...

Post by wavesofffear »

Fenders should be fine with the mismatch (Marshall less so).

I hope you didn't decide to replace the OT!

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Re: Speaker / Amp impedance mismatch...

Post by Bg »

wavesofffear wrote: Tue Aug 02, 2022 3:16 pm Fenders should be fine with the mismatch (Marshall less so).

I hope you didn't decide to replace the OT!
Words of wisdom and a very welcome to the forum if I haven't done that to any of your previous 20 posts :D
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

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Re: Speaker / Amp impedance mismatch...

Post by wavesofffear »

Bg wrote: Tue Aug 02, 2022 3:43 pm
wavesofffear wrote: Tue Aug 02, 2022 3:16 pm Fenders should be fine with the mismatch (Marshall less so).

I hope you didn't decide to replace the OT!
Words of wisdom and a very welcome to the forum if I haven't done that to any of your previous 20 posts :D
Thanks Bg. Happy to be here!

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