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Regen and length of USB cable?


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I have a 3' USB cable (PI Audio) going from my Mac Mini to the Regen and then a short cable (Curious) to my USB-SPDIF converter. This setup is unwieldy on my rack.

 

Most of what I've read has stated that USB cables should be at least 3' in length to prevent reflections.

 

Does the Regen mitigate this need? I would like to use a shorter cable from my Mac to the Regen to keep my cables separated and neat.

2010 Mac Mini (8GB RAM, SSD, LaCie 4TB HD)>PI Audio USB Cable>Singxer SU-1>PAD Aqueous Aureus Praesto Digital IC (BNC)>Lampizator Amber II>Kaplan GS Mk2.5 ICs>Rogue Cronus Magnum (modded & NOS signal tubes and Reflector 6P3S-e)>Kaplan GS MKII SCs>Aural Acoustic Model B speakers. Furutech outlets, TWL PCs, and PI Audio Digi-Buss & Buss-Stop power conditioners.

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I have a 3' USB cable (PI Audio) going from my Mac Mini to the Regen and then a short cable (Curious) to my USB-SPDIF converter. This setup is unwieldy on my rack.

 

Most of what I've read has stated that USB cables should be at least 3' in length to prevent reflections.

 

Does the Regen mitigate this need? I would like to use a shorter cable from my Mac to the Regen to keep my cables separated and neat.

 

That is not true for USB. It came from coax S/PDIF which operates at a much lower frequency. The issue is that impedance mismatches cause reflections, with S/PDIF the round trip time of the reflections in medium length cables can cause problems with the PLLs in many S/PDIF receiver circuits.

 

The same thing actually does happen in USB, but due to the much higher frequencies the length is going to be in the half inch or so length, so any cable you get is going to be considered "long".

 

John S.

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Thanks John; very useful info.

2010 Mac Mini (8GB RAM, SSD, LaCie 4TB HD)>PI Audio USB Cable>Singxer SU-1>PAD Aqueous Aureus Praesto Digital IC (BNC)>Lampizator Amber II>Kaplan GS Mk2.5 ICs>Rogue Cronus Magnum (modded & NOS signal tubes and Reflector 6P3S-e)>Kaplan GS MKII SCs>Aural Acoustic Model B speakers. Furutech outlets, TWL PCs, and PI Audio Digi-Buss & Buss-Stop power conditioners.

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John,

 

Going from the Regen to the DAC, do you recommend an extra short cable or the usb adapter Uptone provides?

 

Thanks.

 

I recommend whatever messes up the signal the least. The adapters are good inexpensive way to do this, although they may not be the absolute best in the known universe. There will undoubtably be short cables that can be better, but they will almost certainly NOT be as inexpensive as the adapter that comes with the REGEN.

 

Neither Alex nor I have the time to test every possible cable/DAC combination, so it is going to have to be some combination of reading what others have said about certain combinations and trying things yourself.

 

John S.

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  • 3 months later...

Sorry if this has been covered already but...

It would be good for me to site the Mac next to my chair and the dac next to the amp, this involves about 5m of USB cable between them. Is this too long? Should the regen be at the computer end driving the cable or at the dac end boosting and cleaning the signal before it gets to the dac?

My dac doesn't need the 5v from the computer.

Thanks stewart

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