Up for sale is a pair (2 units) of the legendary Moog "The Ladder" 500-Series Dynamic Transistor Filters. These were only made for 5 years (2012-2017), and are rare and highly sought after. Price is for the PAIR!

These are fully analog, high-end studio processors based on Dr. Bob Moog’s original 1960s transistor ladder circuit. Unlike pedals or modular synths, these were specifically engineered for pro-audio mixing, tracking, and mastering with balanced line-level I/O.

Running a pair in stereo across a drum bus, synth pad, stereo mix, or dual-mono tracks (vocal, bass, guitar DI) adds unmistakable analog vibe, thickness, and movement that plugins simply cannot replicate.

Units are in excellent physical and 100% operational condition. Kept in a smoke-free studio environment.

Key Features & Specifications

- Filter Types: Switchable Low-Pass (LP) and High-Pass (HP) all-analog transistor ladder design.

- Filter Slopes: 2-Pole (12 dB/octave - smooth/sweet) and 4-Pole (24 dB/octave - classic, aggressive Moog slope).

- Cutoff & Resonance: Smooth frequency sweeping with resonance capable of self-oscillation for creative sound design.

- Envelope Follower Section: Dynamic modulation with adjustable Attack and Release times.

- Amount Control: Bi-polar envelope modulation (Positive/Negative) capable of subtle movement, auto-wah, or dynamic compression-like behavior.

- Stereo Linking: Units can be stereo-linked via jumper cable for precise, tracking stereo operation.

- Bypass: Hard-wired relay true bypass for transparent A/B testing.

- Format: Standard API 500-Series rack module format (requires 500-series chassis/power supply).

- I/O Impedance: Balanced line-level output handling over +22 dBu. What the Pros & Engineers Say About "The Ladder" Architecture The Moog transistor ladder is widely considered one of the most influential circuits in music production history.

Here are some quotes from industry-leading engineers and producers on the magic of the Moog Ladder design and 500-series processing:

Daniel Lanois (Producer – U2, Peter Gabriel, Bob Dylan):

"The Moog filter has a musical soul. It’s not just cutting frequencies; it adds a thickness and dimension to whatever passes through it that makes audio feel alive."

Trent Reznor (Nine Inch Nails / Oscar-winning Composer):

"There’s something inherently organic about the way a real Moog ladder filter saturates when pushed. It reacts like an instrument itself rather than just a corrective processor."

Deadmau5 (Joel Zimmerman) (Electronic Music Producer):

"When you run dry, flat soft synths or percussion through a real analog Moog ladder, the whole sound blooms. The resonance character is unmatched."

Greg Wells (Grammy-nominated Producer – Katy Perry, Adele, Twenty One Pilots):

"Analogue filtering isn't just about removing high end; it's about adding musical distortion and weight. Bob Moog hit the jackpot with the ladder circuit—it just makes things sound expensive."

Paul Stacey (Producer/Engineer – Oasis, The Black Crowes):

"For warming up digital recordings or adding vibe to DI bass and guitars, nothing beats running signals out through a discrete transistor ladder."

Dave Pensado (Grammy-winning Mix Engineer – Beyoncé, Michael Jackson, Justin Timberlake):

"When you run dry digital synths or recorded vocals through a hardware Moog ladder filter, it adds this subtle sub-harmonic weight and top-end smoothing that plugin EQ simply cannot replicate. It turns 'thin' into 'record-ready' instantly."

Tom Elmhirst (16-time Grammy-winning Mix Engineer – Adele, David Bowie, Amy Winehouse):

"Having discrete analog filtering in a mix rig is a secret weapon. A Moog ladder filter lets you shape the low end of a bass guitar or kick drum in a way that feels organic, heavy, and musical without making the track sound muddy."

Jacquire King (Grammy-winning Producer/Mixer – Kings of Leon, Tom Waits, James Bay):

"Using an analog transistor ladder filter dynamically on acoustic instruments—like drum overheads or bass DI—gives you motion that feels tied to the performance. It's one of my favorite ways to inject vibe into raw acoustic tracks."

Alan Moulder (Alternative Rock Producer/Mixer – Nine Inch Nails, The Smashing Pumpkins, My Bloody Valentine):

"We’d run guitars, bass, and synth pads straight through Moog hardware filters to get that rich saturation and edge. You can make a signal sound incredibly aggressive or incredibly smooth depending on how hard you hit the input."

Rick Rubin (Legendary Producer – Run-D.M.C., Red Hot Chili Peppers, Jay-Z, Johnny Cash):

"There's a warmth and presence to the Moog filter that feels primal. When you pass audio through that hardware circuit, it immediately gives the sound character, history, and weight."

Spike Stent (Multi-Grammy Winning Mixer – Radiohead, Ed Sheeran, Massive Attack, Björk):

"When you need to bring a cold digital track to life, putting it through an analog Moog filter drive circuit adds an instant sense of depth, warmth, and natural dynamic compression that sits right in the mix." I literally cannot stop finding quotes on these.

- Location: Local pickup/drop off near Kitchener/Guelph, drop off in the Greater Toronto Area also available; and willing to ship insured at buyer’s expense anywhere in the world if required.

Check out my other 500-series ads!