Guyatone PS-104 Crossover Auto Wah – MIJ 1980 – vintage autowah/envelope filter

Vintage Guyatone PS-104 Auto Wah, made in Japan around 1979–1980. This is an early envelope filter design built around an envelope-controlled band-pass filter, producing a pronounced, vocal “quack” with strong midrange emphasis. Battery-only, there is no power input jack on this pedal.

Key details

• Made in Japan (MIJ)
• Analog envelope-controlled filter (band-pass type)
• Controls: Drive (sensitivity), Decay (envelope timing)
• Fully functional

Condition

• Cosmetically worn (see photos) but aurally awesome
• Typical vintage wear but no structural or mechanical issues
• All controls work as expected
• Pedal only (no box/manual)

Sound & performance (important)
This pedal has a distinctly vintage envelope filter response:

• Strong, dynamic “quack” with midrange focus and percussive attack
• More aggressive and less smooth than modern envelope filters
• Low-end content reduced as the filter engages (not great for bassists unless you've got a frequency splitter ahead of this pedal in your chain, which I do, and which I recommend, because the pedal sounds funktastic with it)

Because of the band-pass design, this pedal works best with guitar or midrange-forward signals--think '70s funk and stoner rock.

Power notes

• Accepts 9V battery only (probably easy to upgrade w/a mod, but this is a vintage piece)
• LED stays on regardless of whether the pedal is engaged or not--this is how the pedal was designed, they all behave this way, it's a feature, not a bug
• Will not function properly if you try to use TRS cables

Shipping

• Will ship promptly and securely packed

Feel free to reach out with any questions.