Osiris PHILter State Variable Biquad Filter

Sometimes, a really special pedal comes along that completely blows me away, and today’s effect unit is up there at the top of the all-time list for me, as a basically life-long Deadhead. From 1974 to 1979, bassist Phil Lesh used a heavily-modified Alembic bass, known as Osiris, aka Mission Control. The new Osiris PHILter takes the filters and electronics from that bass, which was thought lost for years, and reverse engineers them to create a wonderful one-channel active variable biquad filter unit. Yes, that is a mouthful, but you’re really gonna dig what’s going on here, especially if you love that ’70s era Phil tone…

From the Osiris team: “In 1973 George Mundy was tasked with designing the filters that would be used in the legendary Alembic bass known as Osiris, aka Mission Control, built by the late legendary master luthier Rick Turner. Osiris was played on stage with the Grateful Dead from June 16, 1974 through July 1, 1979. After its retirement Osiris was gutted of its electronics and left in storage for many years. We were able to first acquire the bass in December of 2019, and acquired the ORIGINAL pickups shortly thereafter. Then in March of 2024, we were able to acquire the ORIGINAL filters and electronics removed from the bass 40 years ago. With these acquisitions, as well as our talks with both Rick Turner and George Mundy, we were able to reverse engineer and faithfully reproduce the pickups preamp and hum cancelling preamp as well as the filters used. We were then able to extract and produce the filter section into the outboard unit we call the Osiris PHILter.”

“The Osiris PHILter is a one channel active State Variable Biquad Filter. The Osiris PHILter Type Switch has four filter positions available, Low Pass, Band Pass, High Pass and a Notch filter. These are controlled with a 4-way rotary switch. The Direct Volume controls the dry signals volume and is independent of the PHILter Volume. The PHILter Volume sets the overall volume of the filter and is independent of the Direct Volume. The PHILter Volume and the Direct Volume can be utilized at the same time. This allows the Direct Volume to be used by itself with no filter, or use the PHILter Volume by itself with no Direct Volume, or a mix of the two in phase with each other. The Philter Volume mixed the Direct Volume allows for the deep low end tones or crispy high end tones, or anything between, depending the filter type chosen and the setting of the Frequency control. The Frequency Control sets the center frequency (FC) of the filter type used. The last control is the Q Control and it sets the bandwidth of the center frequency selected.”

Not only is the PHILter reverse engineered from the ORIGINAL filters that were installed in Osiris aka Mission Control in 1974, but the EXACT same PHILter electronics have been installed in Osiris (October 2024). This gorgeous unit not only pays tribute to some of the most iconic and beloved bass tones of the ’70s, it also pays homage to the man who created them. We lost Phil last October, but his muci, and now his beautiful bass tones, will continue to live on and inspire future musicians for decades to come. Cheers to Jason and the Osiris team for making this project a reality – go visit the website for more info, use code POTD15 to get 15% off your own PHILter, and don’t forget to check out our Bass AND guitar demos on our YouTube channel – cheers!