TLN-867 Tuner & Headphone Monitor

A 440Hz reference tone generator, a headphone amplifier, and a beat frequency indicator

No matter how large your synthesizer is, you don't need more than one A440 tone generator module. A dedicated A440 module would only have a single output jack which, IMHO, is a waste of an entire 1U panel. If, like me, you have just the one head with two ears on it (a mono head), then a headphone monitor is another useful module that you only need one of. Combining the two together makes even more sense should you want to tune your oscillators without sending the A440 tone to your output amp for everyone else to hear. Simply plug your oscillators into the headphone monitor and tune them to the internal A440 tone in complete privacy. The A440 tone has a dedicated volume control so it can be removed from the headphone mix entirely. This is useful for when you want to tune oscillators to some other frequency, or just for having a private mix of any two signals in your synthesizer.

The TLN-867 also features a handy beat frequency indicator with four LEDS that provide a visual indication of the frequency difference between the left and right inputs, or either the left or right input with the A440 reference tone.

The panel controls are as follows:

• PHONES pot: Sets the level of the signal at the PHONES jack.
• A440 pot: Sets the level of the A440 tone sent to the headphone monitor.
• MODE switch: In the STEREO position, the signal at the LEFT jack goes to the left headphone speaker and the signal at the RIGHT jack goes to the right headphone speaker. In the MONO position, the signals at the LEFT and RIGHT inputs are summed and go to both headphone speakers. MONO mode is also handy for checking for phase cancellation between two signals.
• BEAT switch: Sets which two signals are applied to the beat frequency circuit. This is a three position switch. In the upper (LEFT) position, the signal at the LEFT jack and the A440 tone are used. In the lower (RIGHT) position, the signal at the RIGHT jack and the A440 tone are used. In the middle position (LEFT+RIGHT), the signals at the LEFT and RIGHT jacks are used.
• LEDs: The four LEDS are the output from the beat frequency circuit. They provide a visual indication of the frequency difference between the two inputs to the beat frequency circuit.
• LEFT jack: The input for the left channel.
• RIGHT jack: The input for the right channel.
• A440 jack: Output for the A440 tone (always 10Vpp).
• PHONES jack: Plug your headphones in here.

Required PCBs are available at SynthCube!
https://synthcube.com/cart/tellun-corporation-diy-pcbs

http://www.tellun.com/motm/diy/tln867/TLN-867.html