[serengetiplains]

Steve, I understand that the USB board in the Pace Car USB is powered by the 5V line in the USB cable.  Would you see any sonic benefit to powering that board from a Hynes supply?

[audioengr]

Steve, I understand that the USB board in the Pace Car USB is powered by the 5V line in the USB cable.  Would you see any sonic benefit to powering that board from a Hynes supply?

Yes, this is the case in the Pace-Car USB, but not in the Off-Ramp 4.

This allows complete galvanic isolation from USB to I2S output.  If you wanted to use a non-cable 5V, you would have to introduce another DC supply just for this in order to maintain the galvanic isolation.

If you didnt need the galvanic isolation, then you can use the supply in the Pace-Car.

I dont believe it makes any difference for jitter.  Its all reclocked at that point in the Pace-Car USB anyway.

Steve N.

[serengetiplains]

Thanks for the advice, Steve.

On the matter of sonics, if a USB cable affects the sound, I would think the Pace-Car's USB receiver's power supply would even more greatly affect sound.  That's my speculative hunch.  In the next week, I'll hook up a 5V Hynes supply to the receiver.  I'll report my findings back here.

Btw, does the computer ground (the psu ground wire in the USB cable) need to be connected to the Pace-Car in order for data to transmit from the computer to the Pace-Car?

[audioengr]

Thanks for the advice, Steve.

On the matter of sonics, if a USB cable affects the sound, I would think the Pace-Car's USB receiver's power supply would even more greatly affect sound.  That's my speculative hunch.  In the next week, I'll hook up a 5V Hynes supply to the receiver.  I'll report my findings back here.

Btw, does the computer ground (the psu ground wire in the USB cable) need to be connected to the Pace-Car in order for data to transmit from the computer to the Pace-Car?

The power ground can be eliminated only if you replace the +5V supply to the USB module.

You still need the signal and signal ground wires.

Steve N.

[serengetiplains]

Thanks, Steve.  The supply I'll connect to replace the computer supply will be independent with its own transformer.  I'll let you know how it works.

[serengetiplains]

I connected the USB module in the Pace-Car to an outboard supply using the power wires I dug out of a USB cable.  The USB module wouldn't work in this arrangement.  Could it be that the power ground wire needs to connect both the outboard supply and the computer to the USB module---all three connected to the black ground wire?

[audioengr]

I connected the USB module in the Pace-Car to an outboard supply using the power wires I dug out of a USB cable.  The USB module wouldn't work in this arrangement.  Could it be that the power ground wire needs to connect both the outboard supply and the computer to the USB module---all three connected to the black ground wire?

There is a ground wire with the USB signal and ground.  You should not need the other ground wire back to the computer.  If the power supply is 5V, I'm not sure why it doesnt work.

Steve N.

[serengetiplains]

Ok, I'm back to this mini-project.  I connected an outboard 5V supply to power the USB receiver chip, eliminating the computer power supply.  To get this to operate, I had to tie the 5V supply ground to the computer ground (which means computer ground noise is now in the outboard supply ground supplying the receiver chip).  But it is now working!

Initial impressions are favourable, though I've only listened a few minutes.  I'll report back with further observations.

[serengetiplains]

Yup, this modification is sonically better.

[audioengr]

Yup, this modification is sonically better.

If you power the USB interface directly with a LifePO battery at 3.3V, this is even better.  Bypass the regulators on the USB module.

Steve N.

[serengetiplains]

Ooh, thanks for the tip.  Is the 3.3V reg (regs?) one of those SOT-223s?  I'm asking, btw, because my Pace Car is upside down and wired in that position, so it will take serious surgery to get at the reg(s).  Thanks, Steve.  I'm getting such fantastic sound from this little box it's shocking.  Incredible what info is buried in even 16/44.1.

[audioengr]

Ooh, thanks for the tip.  Is the 3.3V reg (regs?) one of those SOT-223s?  I'm asking, btw, because my Pace Car is upside down and wired in that position, so it will take serious surgery to get at the reg(s).  Thanks, Steve.  I'm getting such fantastic sound from this little box it's shocking.  Incredible what info is buried in even 16/44.1.

Yes, the 3.3V regs are the SOT223's.  The one connected to the empty 3-pin location is the key one.

I'm also having great results with 44.1, particularly with the new Turboclock.  No need to upsample anymore.

Steve N.