Guitar amp power attenuator

Amps, Cabs, Speakers, etc
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laurie
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Guitar amp power attenuator

Post by laurie » Sat Apr 30, 2022 11:48 pm

Over in this thread we talked about attenuators: viewtopic.php?f=14&t=571

I finally got around to making one a few weeks ago. It uses non-inductive high power resistors. There are actually two separate attenuators in the housing - one for 8 Ohms, and one for 16 Ohms. They can be cascaded to give four levels of attenuation.

Initial tests are good. No discernable loss of tone.

On the "HIGH" setting it drops a 60W amp to 10W.
On the "LOW" setting it drops a 60W amp to 2W.

Can be used with amps up to 100W.

Total parts cost about USD$150. Time to make ... about 8 hours :roll: (the rectangular cut-outs for the switches were a bastard)
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Last edited by laurie on Sun May 01, 2022 4:22 am, edited 5 times in total.

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laurie
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Re: Power attenuator

Post by laurie » Sat Apr 30, 2022 11:49 pm

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laurie
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Re: Guitar amp power attenuator

Post by laurie » Sun May 01, 2022 4:10 am

Schematic for the 16 Ohm attenuator. The impedance seen by the amplifier is the same for either position of the switch - with a 16 Ohm speaker plugged into the "OUT" jack the amplifier sees close to 16 Ohms.

All resistors must be non-inductive (Ayrton-Perry winding). Resistors must be securely attached with heatsink compound to a heatsink with a rating of around 0.5 C/Watt. The heatsink in the pics above starts at 2.5 C/Watt in free-air and the fan lowers it to under 1 C/Watt. The fan is only really required when using the attenuator with a big amp at maximum.
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16 Ohm attenuator schematic.jpg
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Pepe
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Re: Guitar amp power attenuator

Post by Pepe » Sun May 01, 2022 7:30 am

This looks like a professional device that you can buy in a shop! :o Great work!
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fernieite
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Re: Guitar amp power attenuator

Post by fernieite » Tue May 03, 2022 1:18 am

That looks ace Laurie!

You'd probably enjoy this nerdy attenuator thread...
https://www.marshallforum.com/threads/s ... ing.98285/

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Re: Guitar amp power attenuator

Post by BearBoy » Tue May 03, 2022 3:15 pm

Pepe wrote:
Sun May 01, 2022 7:30 am
This looks like a professional device that you can buy in a shop! :o Great work!
It does. It looks amazing.

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