TipTop Audio 277t Signal Delay Unit

Patch-Programmable Delay Module

• Based on the unfinished 1972 Buchla Model 277 Signal Delay Unit project
• Clocked digital delay line with four simultaneous taps at ¼, ½, ¾, and full time
• Feedback and routing are entirely patch-based, with no preset signal paths
• Voltage-controlled delay time with a bipolar attenuverter
• Dedicated input for audio-rate FM of the clock: chorus, warble, and pitch shift
• Selectable short and extended original delay ranges
• Eurorack format, Tiptop Audio Buchla 200t series

The Tiptop Audio 277t Signal Delay Unit stems from a project that Don Buchla never completed. It’s 1972: digital delay is still virtually uncharted territory, and echoes are created using tape. Buchla’s idea was a clocked digital delay line with four separate outputs, set at ¼, ½, ¾, and full delay time. Not a ready-made echo effect, but a set of building blocks with which to construct one. Tiptop Audio started with the surviving schematic to finally bring this module to life, adapting it to the Eurorack format as part of the 200t series.

The Buchla 277t Delay: A modular block system to build via patching

The modular approach is what defines the 277t when you get your hands on it. You won’t find a feedback knob, a wet/dry control, or a predetermined signal path. Three inputs with attenuators feed the delay line, and the four taps output independently. You decide how to connect them.

Feedback and creative routing with the four taps

Feed one of the outputs back into one of the inputs to create feedback. Choose a different tap to change the timing of the repeats. Insert a filter, a frequency shifter, an LPG, or something decidedly less orthodox into the return path, and each repeat will be processed before re-entering the loop. The three-channel input mixer lets you precisely balance the source and returns, while the overload LED alerts you when you’re pushing it too hard.

Voltage Control and FM Clock Control in the Tiptop Audio Eurorack Delay

The delay time is adjusted via the main Rate control and is voltage-controllable via a bipolar attenuverter. A separate input, equipped with an attenuator, is designed for audio-rate frequency modulation of the delay clock.

From chorus to pitch shift: modulate time to modulate the sound

Varying the clock doesn’t just change the spacing between repeats—it also bends the pitch of the delayed signal. This opens the door to chorus-like effects, unstable warbles, and more abrupt pitch shifts. With the range selector, you can choose between the short delay of the original design and a longer setting, suitable for well-defined repeats.

More of a time-domain module than a simple delay

The 277t is best understood as a patchable time-domain module rather than a classic delay: you provide the routing, and it gives you four points in time to work with. It’s not your typical delay, and that’s precisely what makes it one of the most exciting modules to patch into your Eurorack case. A piece of Buchla history that’s been tucked away for over fifty years, now ready for your system.

Technical Specifications

• Brand: Tiptop Audio
• Model: 277t Signal Delay Unit
• Series: Buchla 200t
• Format: Eurorack
• Reference Design: Buchla Model 277 Signal Delay Unit (1972, never completed)
• Architecture: clocked digital delay line
• Outputs: 4 simultaneous delay taps (¼, ½, ¾, full time)
• Audio inputs: 3, each with a dedicated attenuator
• Input mixer: 3 channels
• Main Rate control for delay time
• CV input for delay time with bipolar attenuverter
• Separate audio input with attenuator for delay FM
• Delay range: short/extended (switchable)
• Feedback: achieved via patch by routing the taps back to the inputs
• Indicator: Overload LED