[stuartmc]

He he

 

[rb2013]

I'm sorry pal my Regen sounds so crappy and well, "oily" that I couldn't possibly foist it upon another head-fier. I've decided to keep it in my system as a means of penance for my shameful materialism. As a bonus, I find that taping it in place at the end of a long USB cord makes for a most efficacious flagellum.

HA! LMAO!   We all need 'Audio Falgellum' in our system.  Can I get a Regen/cable with a 'rattle' on the end?
 

 

[rb2013]

More awesome John Swenson on the 4 layer board and impedance matching and back wave reflection.
 

The regen uses a 4 layer board, primarily to allow a proper impedance match. With a standard thickness 2 layer board it is impossible to attain a proper impedance match to the hub chip. The pins on the chip are small and close together, this necessitates very thin board traces, with a two layer board the distance between ground plane and these traces (BTW this is called a differential micro-strip configuration) produce an impedance that is much greater than the spec. With a four layer board the ground plane can be much closer to the top layer which allows for appropriate impedance with the very narrow traces. The regen also uses SMD USB jacks which allow for appropriate trace width and spacing to continue the impedance matching through to the USB jacks. The result of this is that there will be very minimal reflections at the regen side. Even if the DAC does not have good impedance matching (which is pretty common) which WILL cause a reflection at the DAC end, it will be absorbed at the regen because of the proper impedance matching.

The regen has a frequency optimized Power Delivery network (PDN), which turns out to make a very significant improvement in SQ. This is quite a technical subject, WAY beyond what I can post here, but here is the mile high summary:

In order to properly respond to the load variations of what the supply is powering, it needs to have a low impedance over a very broad range of frequencies. For digital audio this is from low Hz to hundreds of Mhz range. The entire supply flow from mains AC to board layout and capacitors on the board play a role in getting this right.

The regen is what got me focusing in on this. I was testing the first prototype and was seeing some noise on the supply right at the hub chip power pins that shouldn't be there. After a lot of detective work I traced it down to some frequency ranges of the PDN that were much higher impedance than they should be. I included a fix for this in the second version. With this I couldn't detect the noise any more, and it sounded much better, but Alex was still not super thrilled with the SQ. I then did a mathematical analysis of the PDN and found another frequency range that had a higher impedance than it should, made a fix for this, and sent the result to Alex, he was thrilled, this was much better than anything he had heard before.  

 
I will send an email to Uptone to request they considera S/PDIF coax impedance matching box as a possible new project - a Regen for SPDIF.  After my second order.
 
"The result of this is that there will be very minimal reflections at the regen side. Even if the DAC does not have good impedance matching (which is pretty common) which WILL cause a reflection at the DAC end, it will be absorbed at the regen because of the proper impedance matching."

 

[prot]

Is there any proof to this statement? I ask because I have not seen one single bit of evidence other than the written word.
IF the reduction is "dramatic" it should be very easy to measure and observe.

That did work great for you

I was quoting a noted very talented engineer - why don't you ask him - on another thread.

Very good idea. May I also ask you to post all that regen&jw lalala in the regen thread?

 

[rb2013]

Well thanks for policing my thread. But the posted information is very pertinent to the discussion of USB bridges and USB audio in general.

Sorry if it's a bit over your head. They're calling for you over on the MSB thread, your commentary is urgently needed.

 

[Core32]

That did work great for you

 

 
Actually I got exactly what we both expected. 
All deflection and no answer.

 

[rb2013]

Great story on the Regen 1.1 upgrade - amazing the insight from these folks!  I'm a true audio skeptic - but they have really impressed me.
 
So on to the story of the Corning 3 cable and the Regen 1.1 mod:
 

RESISTANCE IS NOT FUTILE! 

Let's cut right to the chase:  
We have added $0.40 worth of tiny resistors to the circuit board of the USB REGEN and increased its musical performance by 40-50%—most especially in the bass! Anyone who has a REGEN will be astonished by the improvement, and anyone who hears the new one for the first time will be even more amazed. Given the already unanimous rave reviews being heaped on the REGEN by people around the world who got one from the mid-April first run—it is hard to fathom how the thing could get that much better. But it has. And John Swenson and I are feeling rather gleeful about it.  It really is a huge advancement for this already extremely effective device.

[If you wish to skip the below story and just find out about what this means for the REGEN you either have in your hands or on order, just jump to the very bottom of this post.]

Actually, some of you have heard a bit of exactly the improvement made to REGEN, and there is a story behind that. It involves the recently popular Corning 3.Optical USB cable which some of you have bought (and some struggle with for compatibility/reliability reasons).  

The Corning is interesting, and is a more complicated device that it might seem. Corning engineers had to design a small ASIC circuit to translate the semi-differential USB signaling to a format that could work with the timing of their optical transceivers. And the receiving end of the Corning cable needs a small voltage to run (which may in fact be 12 volts converted with a switching regulator at the send end, as the USB 5V from the computer would not survive their shortest 10 meters length), so there is a pair of 28awg wires run alongside the optical fiber.  

So not only does the Corning not provide galvanic isolation from the computer, but there are some other things going on with its power and USB ground wires. (As many of you know, the REGEN ignores the pin 1 +5VBUS wire from the computer or the Corning and does not connect it to anything since the REGEN has its own power and also makes clean 5V for DACs that need it.) Still, aside from the REGEN as hub often helping the Corning work with computers and DACs, having the Corning feeding the REGEN sounds good—especially in the bass as many have reported.  

Now John had speculated that cutting the Corning’s wires and feeding cleaner power to the receiver near the DAC end might help it further, so he bought one to listen to and planned to then dissect it. When I was at his place last weekend (before and after the funComputerAudiophile Berkeley lunch get-together), we were listening to the Corning with the REGEN (I brought a thumb drive will all my favorite test tracks), and indeed the Corning seems to significantly increase bass detail. Quite a nice combination.

Then John began speculating about the extra resistance that 10 meters of 28awg wire presents to the USB ground wire. The typical ground path in an audio system measures between 0.3-0.5 ohms. But that 33 feet of thin wire is going to be more like 3 ohms, and that forces some of the USB ground currents to take other paths. Maybe that is a good thing? So he carefully cut open one of the 6-inch USB cables I supply with the REGEN kit (for those who can't use the solid adapter), disconnected the shield entirely, and inserted a resistor in series with the black ground wire.

Now we had just listened to that same, unmodified, 6-inch cable feeding the REGEN (straight from John’s Squeezebox Touch just inches away—so it was Touch>6” cable>REGEN>solid adapter>Bottlehead DAC), and as I have posted elsewhere, I don’t like the sound of that 6” cable at all—even before the REGEN.

But now we go and put the same short cable—with resistor in series with the ground wire—back between the Squeezebox Touch and the REGEN. Oh my!  Exactly the same sort of benefit we heard from having the Corning cable feeding the REGEN. Wow! No doubts at all. So we turned to each other and then raced to his engineering bench room to do the logical thing: Lift USB input pin 4 of the REGEN and put the resistor between it and ground. (The data +/- pair of USB really does need a ground reference to work reliably.) Back to the studio to listen to it fed by the much smoother Supra USB cable instead of that nasty 6-incher. Nice.

After that, we of course wanted to hear what if any benefit the Corning might still have feeding the REGEN. And guess what, to our ears it sounded a little worse.  We think that the Corning’s benefit previously (before modifying the REGEN) overshadowed whatever effects its complex circuitry has. 

So as far as we can tell, the Corning benefit was all about that extra resistance in the USB ground. The resistor we chose to use is greater than the 3 ohms John calculated that the Corning inserts, but I’d prefer not to say what value we settled on.

On my drive home I realized that while we cut the shield with the 6-inch cable, when we first modified the REGEN we did not lift or insert resistance on its input jack shield contacts (virtually all USB hosts and devices end up connecting pin 4 ground to shield at some point), thus some ground currents were finding a path over the shield. I asked John why we still heard such a big difference, and he thinks it is because USBshield wires are far more symmetrical around the +/- data wires and thus they are more equally affected by whatever ground-noise currents and cancel out. I think very few USB cables shield the data wires separate from the power and ground, so the ground wire is not symmetrical about the data lines.

So that night John drilled out the ground vias for the jack, and listened with and without resistors there too. The board we had modified with the one resistor was one of the pre-production prototypes (not a production REGEN board with the layer stack-up he optimized impedance matching for), and I took that one home with me to listen to. Thus the REGEN John further modified and listened to was the production unit I gave him (his first with a case!), and he said it sounded even better when he was all done.

So that’s the long story. Maybe you will or will not continue to like the Corning cable with the updated REGEN. But you WILL be absolutely delighted by the sound of the new version.

So like adding a bypass cap to a coupling capacitor circuit (or the NDK clocks) this addition of a small resistor across the data line yielded amazing results.  Any designer or advanced modder (sorry Core32 and prot - don't mean to exclude you erudite chaps- hope you enjoyed the story!), who has heard what a small .01uf bypass - my favs are the Vishay-Roderstein MKP1837's - can do to the SQ of a circuit can truly believe this.
 
Now a bypass acts as a very tiny conduit between the main caps +/- leads, and therefore a stabilizer and slight discharge link.  This small resistor acts in the opposite direction - adding resistance to the data lines -and as John explains with resistance the ground seeks a new path away from the connection.
 
Truly amazing how they came across this discovery and then the quick implementation in the Regen 1.1 (I call it that as it is a slight revision on the original circuit).  This is exactly why I have held off until now to make my purchases (that and awaiting the user feedback which has been overwhelming positive).
 
Keep going guys!

 

 

[Triplefun]

I am more intrigued than ever. So do I get a regen 1.1 to enhance my Gustard X10, or do I get the Gustard X20u?

 

[rb2013]

I am more intrigued than ever. So do I get a regen 1.1 to enhance my Gustard X10, or do I get the Gustard X20u?

Tough call...you know what I'd do of course...get both.

 

[abartels]

Hi guys,
 
I sold my heavily modded MX-U8 today to a VERY lucky guy, tomorrow it will leave my home 

 
Since I am planning to build a complete dac, I am willing to sell my Gustard U12 (modded with caps and NDK Crystals) too.
It is 230V version only.
 
If somebody is interested, send me PM please.
 
 
Regards,
 
 
Alex

 

[rb2013]

  Hi guys,
 
I sold my heavily modded MX-U8 today to a VERY lucky guy, tomorrow it will leave my home 

 
Since I am planning to build a complete dac, I am willing to sell my Gustard U12 (modded with caps and NDK Crystals) too.
It is 230V version only.
 
If somebody is interested, send me PM please.
 
 
Regards,
 
 
Alex

Good luck!
 
BTW to just get the terminology straight the Uptone calls the Regen 1.0 'Green' and the 1.1 'Amber'.
Cheers!

 

[crazychile]

  Good luck!
 
BTW to just get the terminology straight the Uptone calls the Regen 1.0 'Green' and the 1.1 'Amber'.
Cheers!

 
Yes, and from what I remember it was only the first batch (maybe 75 units?) that were the Green version.
 
 

 

[abartels]

 
Good luck!
 
BTW to just get the terminology straight the Uptone calls the Regen 1.0 'Green' and the 1.1 'Amber'.
Cheers!

 
Thanks Bob! 

 

[rb2013]

   
Yes, and from what I remember it was only the first batch (maybe 75 units?) that were the Green version.
 
 

I think it was a bit more like 100, as Alex posted that like 96 out of 100 took their upgrade offer - but close enough.
Solid chaps - Uptone offered a very gracious update policy for those folks.

 

[glip]

Hi hi!  I got the GUSTARD U12 a Mac Mini and a Analog Hi-Fi sistema… (SEA/NAD/VIENA ACUSTICS). I am using my Mac as sound machine… but I do not know how to connet my GUSTARD U12 to the analog sistme… can somebody help!!