Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jul.elec on June 02, 2020, 08:48:38 am
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Hi,
I want to customize my 100W guitar amplifier : I want to switch the output power from 100W to 50W.
I want to add a power switch to use only 2 valve instead off 4 valve like the orange rockerverb 100H mkiii.
I attach file the power stage schematics.
1) Can I insert in serie a power switch between FS6 (or FS5) and the ground? (I need 1 pole)
2) And to respect the audio transformer impedance adaptation I think I need with the same 3PDT switch (two other poles) to toggle the 16 ohms output to the 8 ohms output, and switch off the 8 ohms output transformer : it is the good way?
Thanks for your ideas, yours answers.
Jul
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Hi,
I want to customize my 100W guitar amplifier : I want to switch the output power from 100W to 50W.
1) Can I insert in serie a power switch between FS6 (or FS5) and the ground? (I need 1 pole)
That will work. I would not bother to switch output jacks. Just know that the 16Ω output will become 32Ω and the 8Ω output will become 16Ω. Before installing a switch you may want to simply remove FS5 (or FS6) temporarily just to see if doing this is even worthwhile to you.
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Hi, thanks for your answer.
I Will remove the fuse before to add the switch.
For the out impedances I was wrong, thanks for the clarification.
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I doubt that many users find features such as a 'half power switch' beneficial; the reduction in the sound pressure level generated at power amp overdrive is minimal, 3dB at best, but probably less as the lower current from the HT supply will tend to make it stiffer.
https://www.audiocheck.net/blindtests_level.php?lvl=3
Noticeable yes, but not perhaps significant. Even at half power, for many situations, overdriving the power amp will still probably result in it being too loud.
But whatever, it may be a useful learning exercise for you :icon_biggrin: