SOLVED Troubleshooting Hydra Delay: Brutal Bitcrush/Glitch on Wet Signal

[fabian1985]

Hi everyone,

I’m currently troubleshooting my Hydra Delay build using the Auditorium and could really use a second pair of eyes/ears/brain hemispheres.

The dry signal is 100% clean and pristine. However, the wet signal is a brutal, stuttering, bitcrushed noise/distortion. The important detail: The noise reacts to my guitar playing (it's not just random white noise).

I think I've gone through a rigorous debugging process with my multimeter and audio probe to rule out the usual suspects:

• Audio Probe: The signal is perfectly clean at the input buffer (IC1.1) and stays 100% clean right up to Pin 1 of the FV-1. The glitching noise originates directly inside the DSP and comes out of Pin 28.
• EEPROM Check: When I remove the EEPROM (IC2) from its socket, the wet signal dies completely. So the FV-1 is not booting its internal programs and is at least trying to read the external memory.
• Power & Voltages:
  The 3.3V regulator (IC4) outputs exactly 3.32V.
  The analog op-amps (IC1 & IC5) have a perfect VREF of 4.40V. No analog clipping at all.
  The FV-1 has a perfect DC offset of 1.66V at Pin 28.
• Controls:
  CTRL1 (Speed) and CTRL2 (Age) provide a perfectly smooth sweep from 0V to 3.32V at Pins 20 and 21 of the FV-1. The Swell/Repeats sits cleanly at the FV-1's Pin 2 at ~1.58V while turning (DC successfully blocked by C17).
• Continuity & Solder Joints: I beeped out all connections directly from the SMD pins of the FV-1 to their respective destinations (I2C bus, crystal, audio paths). Everything is connected exactly as per the schematic. Since I have 100% continuity everywhere and also did a reflow on the crystal and C17 pins, I am confident in ruling out cold solder joints.

Since the analog side is flawless, the voltages are correct, and the chip actually processes the audio (but calculates total garbage), I narrowed it down to two possible culprits:

1. The X1 Crystal is dead and - from what I learned - the FV-1 might be falling back to its unstable internal RC clock, causing a massive sample-rate mismatch.
2. The EEPROM (IC2) is corrupted an reading a faulty algorithm and outputs digital trash.

Do you guys agree with this diagnosis? Is there anything else I might have missed before I go ahead and order a replacement crystal and a newly flashed EEPROM?

Thanks in advance for your help!

Fabian

 

[Robert]

Are all of the pins of the FV-1 IC soldered and making a good connection?

 

[fabian1985]

Hi Robert,

Thank you very much for your response.

I actually soldered the FV-1 as the very first component on this entire board. Right after doing so - since there was a "slight" misalignment of the pins and the pads - I meticulously checked every single pin for continuity with my multimeter. Since every pin beeped perfectly, I was 100% convinced that the solder joints were rock solid.

Thanks to your feedback I finally worked up the courage to go back in and do a proper reflow on all the pins using a generous amount of flux.The glitching is completely gone, and the delay sounds absolutely amazing. Thank you so much for pointing this out and saving me from ordering new parts.

Best regards,

Fabian