The Muse I Adorn

eSGEe said:
my Peavey addiction is far beyond your Godin one my friend--- here is one rendition of the "P" collection -- thought it NEEDs updated/////
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DO I see 6 Basses? and one Neck? or are there 7 basses in this pic?

peavey-museum-jpg.21366
 
chilipeppermaniac said:
Now I will blow your Abbott and Costello minds.
Try on this Corona California switcheroo. This Hi LO switch takes Fender THE Twin amps from 100 to 25 watt capability. But I believe one must remove the right tube(s) to do so. Likely re-bias as well. DonP has one and if he reads this, he can clarify this 100% if he gets there before I refresh my memory and read the manual.
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chilipeppermaniac said:
As I said and Adrian said it is too much work, "This Hi LO switch takes Fender THE Twin amps from 100 to 25 watt capability. But I believe one must remove the right tube(s) to do so. Likely re-bias as well."

I researched a bit more as I have often somehow found myself somehow with the amp in LO power but never took out any tubes. SO I found this on a Les Paul forum

"To answer the original question, on the Twin 100/25, Fender is dropping the HT voltage down by approximately half. They use a switch on the totem-poled main filter caps to select either the top cap positive or the bottom cap positive. They have wired the power transformer in a way to use the center tap or not."
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chilipeppermaniac said:
Now of course to add to my confusion I read this at the Fender Forum. I believe the OP and responders are going by a TWIN and not a "THE Twin" instructions. I read both and definitely see their quote about the LO power and pulling 2 tubes on the "TWIN" version. SO, I am not sure about the "THE TWIN"

Here's what the manual says:

"Low Power Option: The Fender TWIN amplifier can be run with only two output tubes instead of four. This is done by removing the two inner 6L6-GC tubes... and setting the IMPEDANCE SELECTOR switch to one-half of the total speaker load impedance... (Remember-- half the tubes, half the impedance.) This will produce 60 Watts R.M.S. in the HI power setting and 15 Watts R.M.S. in the LO power setting.

Also from the manual:

"The Fender Twin is supplied with two 8 ohm speakers connected in series therefore the total load impedance is 16 ohms..."

The problem is, if I remove the two tubes, and change the impedance selector from 16 to 8 ohms per the instructions, now I have an impedance mismatch, because the speaker impedance hasn't changed; it's still 16 ohms. I've always heard that the amp and speaker impedances should match.

I think the answer is this: yes, if the speaker and amp output impedances match, you get the maximum efficiency; the maximum transfer of power to the speakers. However, if the speaker impedance is more than the amp impedance, there will be a larger voltage drop across the speakers and less in the amp. Less efficient, less power transferred, but not harmful. However, if the amp impedance is higher than the speakers, that's bad, because more voltage will drop across the amp's output stage, and will cause it to overheat.

Could someone more knowledgeable tell me if that is correct?

Fender® Forums: View topic - Output impedance and Lo Power mode on Fender Twin

Twin Amp.

https://www.fmicassets.com/Damroot/Original/10001/OM_leg_gtramp_94_Twin_Amp.pdf

The Twin.
https://www.fmicassets.com/Damroot/Original/10001/OM_leg_gtramp_The_Twin.pdf
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OK After getting clarification from DonP, I was right. Fender did make it simple to go from Hi to LO ( 100 watt to 25) just hit the switch ( amp off before doing so) DonP explained that the switch reduces the Voltage from the HT to the Anodes of the power valves.

Now my understanding also goes like this. IF the user wants to reduce the overall power of the amp, THEN 2 power tubes can be removed, the impedance adjusted and then the amp will basically go from a 100/25 watt version to a 60/15 watt when the Hi Lo switch is set to the desired position.
 
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