Lotus JohnH M2 Simple Attenuator 60 Watt

Over the years I have tried just about every attenuator made and tried my hand at a few original designs. They all exhibited the same problem, the more attenuation is added the more the tone suffers. 

Long story short, my search is over, I found the JohnH Simple Attenuator on the Marshall forum. The M2 has been a DIY project started in 2017 by John Hewitt (JohnH). I contacted John about my thoughts on producing these for sale as a finished unit or possibly a DIY kit. He thought it was a great idea and his help in getting this to completion has been amazing. We have a licensing agreement so hopefully he can make some money from this design he has been working on and supporting for over 6 years. 

Like the title suggests, operation is simple. Output from the amp goes to input on Lotus, output on Lotus to speaker. There are multiple outputs for different speaker configurations. Different levels of attenuation are available starting at -7db in 3.5db steps all the way down to -31.5dB via 3 switches.

For reference, at minimum attenuation of -7db a 50watt amp has 10 watt output, perfect for making other bandmates and the sound person happy and every one can enjoy your cranked tone. Knock it down to -14dB to -21dB and take your half stack to the coffee house gig. At max attenuation it takes a 50 Watt amp down to 0.04 watts for a true bedroom amp volume with no tonal loss. 

Lotus can also be used as a load box for direct connections to DAW, Console, IR sim, etc. 

Lotus comes in 2Ω, 2.7Ω, 4Ω, 8Ω and 16Ω models. Choose your model based on the output on your amp. For example a Super Reverb is 2Ω, Deluxe Reverb is 8Ω. If you have multiple output taps on your amp the 8Ω model is the most versatile. 

This is a passive device and requires no external power to stay cool. There is a fan powered by the output of the amp which turns on when needed to cool the unit. The rest of the cooling is through the venting on the top and sides. 

The vented top is 3d printed using engineering grade polymers which are incredibly strong and heat resistant. 

Specs/Features:
60 Watts Max Input
Reactive Load
Low Profile 5A Switches
Neutrick Jacks
40mm silent fan.
Engineering grade 3d printed vent lid.
Extra tall feet to clear most amp handles!
Compact - 165mm X 103mm X 54mm
Light enough (500g+/-) to mount directly to a pedalboard if kept well ventilated (heatsink version recommended).

For more details on the operation, and history of this project you can download the manual here.

Optional heat sink enclosure with mounting flanges (+$50) is available for permanent mounting inside a combo or on a pedal board. Flanges and bezel are glass filled reinforced nylon. 

Currently all models are in stock depending on color and case choice. If the configuration you choose is not ready to ship, it will be assembled when ordered and ship in 5-7 business days. The site will be updated regularly with updated lead times. 

Custom color lids are available on request. I can make just about any color you want which can be useful if you have a few of these. The material I use is rated to 150ºC (really hot). Most 3d printer filament is not so heat friendly but should be fine if you don't leave it in your car (think ABS guitar case). 

A portion of each sale is donated to FRC - Team 8248 - Chain Lynx. They build robots that compete against other robots!

This is an open source project. I encourage anyone interested in learning more about this circuit and improving on it to join the discussion on the Marshall forum. The design files for Lotus are open source as well, so far only the schematics have been published, other files available on request.

License: Creative Commons Attribution-Noncommercial. In sum, improve with the project, remix, share, improve. Always give credit and keep it non-commercial.