Comparing the firmware dumps from the 2 EEPROMs - the firmware from Accuphase has blocks of nulls. A clear sign corruption has taken place.
So how did the EEPROM get corrupted? Paraphrasing what Steve told me:
Accuphase left the write PIN of the EEPROM permanently on.
In layman speak this means the firmware on the EEPROM is not write protected. At all.
The word EEPROM is short for Electrically Erasable Programmable Read Only Memory. i.e. this chip is supposed to be in read only mode most of the time.
In other words, there is no write protection on this USB firmware. On a stock DC-37, it’s USB firmware can be erased anytime, and any unintended erasure will result in corruption. (Note my DC-37 is one of the first, if not the first unit for sale. Later editions of DC-37 may not have this problem). You can think of EEPROM as a computer BIOS - if the BIOS is corrupted the computer cannot boot. It’s the same idea here, for reasons unknown Accuphase made an unfortunate decision to make this chip erasable. Perhaps this is required for Windows? Too bad this decision has a disastrous consequence when operating this DAC in a Linux OS.
What could trigger the corruption? Simple tasks like remove/insert the USB cable, turn the DAC ON/OFF, or reset a computer. Do any of this in quick succession, and you increase the risks of corruption. If you perform any task that will cause the Bravo chip to start reading the EEPROM multiple times in quick succession, you are incurring a high risk of corrupting the firmware. A simple operation like this is enough to kill it.
The corrupted firmware is the reason why a DC-37 will no longer be recognised as a USB 2.0 asynchrous DAC.
What I did before - powering multiple times on/off at a very high rate trying to get PS Audio P5 to power up - is the reason why my DAC’s USB input went dead.
So, the morale of the story is - DO everything slowly. Treat the DAC with more respect, wait a few seconds when performing any operation. It’ s not a good idea to power cycle the DAC, or reset the computer when the DAC is off.
Comment from: Evgeny Visitor
Thanks you very much! I had the same issue with Accuphase DC-37 and your guide helped us to get the device back to work!
Happy to hear that. Was it a bad receiver or a corrupted EEPROM in your case?
Comment from: Clark Visitor
My device has the same problem. What model of EEPROM is replaced? Thank you.
You don’t replace the EEPROM per se, just need to reflash it with a working firmware and your DAC will be back working again.
Comment from: Eugene Visitor
Hi, Agent Kith. My name is Eugene and I think I have th same problem with DC-37 USB port. Windows cannot identify it, says "the USB device is not working proper" or something like this (please, exuse me for my english). Please, can you kindly help me - how can I reflash the usb port? I’m really stressed now, don’t know what to do…. Please help!
You need to reflash the EEPROM on your DAC. This is a electronic component inside the DAC and require a technician with specialist tools. Or you can replace the EEPROM with a working one meant for the Bravo chip.
You can check around your area and see if any audio technicians with the ability to do this. Send them this article for reference.
Comment from: Clark Visitor
Successfully resolved! Thank you very much!