ISO REGEN launch thread! (product web page up; photos, etc.)

[Superdad]

Here is a link to the ISO REGEN User Guide booklet that is included in the box.

[asdf1000]

Hi John @JohnSwenson

 

I'll ask this really silly question to you because Alex has enough on his plate at the moment (please no more spam jokes fellas  )

 

Just reading the ISO REGEN manual and seeing "and an ultra-low-phase-noise clock" reminded me of a dumb question I had previously thought of but forgotten to ask a long time ago, even before getting an original REGEN.

 

So if you have an isochronous asynchronous USB DAC that is the MASTER clock then what function/s does the clocking in the ISO REGEN (or original REGEN) perform?

 

Just for learning purposes only.

 

Even if you don't answer this very silly question I love the difference the original REGEN makes so it's clearly doing something (as thousands of customers would attest), even if I'm clueless as to what, and am obviously REALLY looking forward to upgrading to the new ISO REGEN.

 

Again I'm just asking about the clocking only, not the function of improved signal integrity etc, which (as above) is clearly obvious to everyone with an original REGEN - unless they're intertwined?

 

Again, sincere apologies for this very silly question. There's probably a really obvious answer I'd never thought of 

 

Cheers again, Sean

 

[Solstice380]

Not John or Alex (of course!) but my understanding is that signal timing to the USB receiver in the DAC is also important to help minimize the work (noise) that it does (creates) translating the incoming data.  

[asdf1000]

3 minutes ago, Solstice380 said:

Not John or Alex (of course!) but my understanding is that signal timing to the USB receiver in the DAC is also important to help minimize the work (noise) that it does (creates) translating the incoming data.  

 

Understood. Probably the basis of my (very clearly wrong) understanding was my assumption that the USB DAC's MASTER clock (apologies for the all caps there) ignores all up-stream clocks ? 

 

I probably need a lesson on the relationship between a USB DAC's MASTER clock and all the SLAVE clocks up-stream. Do they still do 'stuff', except the MASTER has more control? 

[Solstice380]

Just now, Em2016 said:

 

Understood. Probably the basis of my (very clearly wrong) understanding my assumption that the USB DAC's MASTER clock (apologies for the all caps there) ignores all up-stream clocks or those clocks do nothing ? 

 

Yes, the clock in the DAC is used for timing the signal from the USB receiver to the conversion stage but the USB sending from the computer is timed also (8 kHz frequency).  Improving the accuracy and stability of that makes it easier on the USB receiver.  

[asdf1000]

Just now, Solstice380 said:

 

Yes, the clock in the DAC is used for timing the signal from the USB receiver to the conversion stage but the USB sending from the computer is timed also (8 kHz frequency).  Improving the accuracy and stability of that makes it easier on the USB receiver.  

 

Ahhhh. I thought the MASTER clock in the DAC only talked directly to the USB sending from the computer (and nothing in between). That's probably where my mis-understanding stems from.

 

So if the USB receiver is also involved then that's crystal (pun intended) clear why a REGEN helps a lot, right at the DAC's USB input.

 

[Solstice380]

3 minutes ago, Em2016 said:

 

Ahhhh. I thought the MASTER clock in the DAC only talked directly to the USB sending from the computer (and nothing in between). That's probably where my mis-understanding stems from.

 

So if the USB receiver is also involved then that's crystal (pun intended) clear why a REGEN helps a lot, right at the DAC's USB input.

 

The clock in the DAC is between the receiver and the conversion stage. The sending computer clocks out the signal from its USB.  That is the timing that a REGEN or some other re-clockers improves.  Helpful?

[asdf1000]

21 minutes ago, Solstice380 said:

The clock in the DAC is between the receiver and the conversion stage. The sending computer clocks out the signal from its USB.  That is the timing that a REGEN or some other re-clockers improves.  Helpful?

 

Thanks mate. Where does asynchronous fit it in here, for an isochronous asynchronous USB DAC.

 

In this case, the DAC controls the timing of packets from the sending computer directly? Or from the REGEN?

 

Or is it exactly the same as you've described.

 

[Solstice380]

11 minutes ago, Em2016 said:

 

Thanks mate. Where does asynchronous fit it in here, for an isochronous asynchronous USB DAC.

 

In this case, the DAC controls the timing of packets from the sending computer directly? Or from the REGEN?

 

Or is it exactly the same as you've described.

 

 

You've got me there!  Which DAC is ISO/async?  Asynchronous USB just means that the DAC USB receiver talks to the computer to send data at the correct rate to keep the receiver's buffer from running out.  The REGEN is transparent - it just passes through (but reclocks) whatever the computer sends.  

[asdf1000]

Just now, Solstice380 said:

 

You've got me there!  Which DAC is ISO/async?  Asynchronous USB just means that the DAC USB receiver talks to the computer to send data at the correct rate to keep the receiver's buffer from running out.  The REGEN is transparent - it just passes through (but reclocks) whatever the computer sends.  

 

Isn't every asynchronous USB DAC also isochronous ?  

 

[Solstice380]

1 hour ago, Em2016 said:

 

Isn't every asynchronous USB DAC also isochronous ?  

 

Inside the DAC from the USB receiver to the conversion module (chip or low pass filter) is iso using the DAC's clock.  The current USB implementations are asynchronous to keep the buffer from going empty.  Some DACs do use an external clock that may, or may not, control everything.  I'm not sure about that.  

[scan80269]

2 hours ago, Em2016 said:

 

Isn't every asynchronous USB DAC also isochronous ?  

 

In another thread you started, I mentioned that modern USB DACs implement "isochronous transfer mode with asynchronous feedback".  This is on the USB side.  Asynchronous means the USB DAC has the ability to pace the USB sender (e.g. streamer or PC). In USB the data packet rate (8KHz) and data bit rate (480Mbps) are essentially constant, so the USB DAC requests the sender to vary the amount of data carried within the USB data packets.  The USB DAC is essentially the timing master for the USB transfer of digital audio.

 

Once the USB receiver (e.g. XMOS chip) inside a DAC retrieves the data stream, it is sent into a FIFO (first-in first-out) data buffer.  The data is clocked into this buffer with a local USB clock (e.g. oscillator driving XMOS chip), and clocked out of the buffer using one of two audio reference clocks: for example 22.5792MHz for 44.1K/88.2K/176.4K/352.8K sampling rates, and 24.576MHz for 48K/96K/192/384K sampling rates.  The USB clock and the audio reference clocks are completely asychronous (i.e. no fixed timing or phase relationship) relative to each other, since they are all free-running clocks done by individual crystals or oscillators.  The audio stream coming out of the buffer is sent to an oversampler (except for NOS DACs) before finally reaching the digital-to-analog converter for conversion to analog.  This is an over-simplified but I believe technically accurate description.  Some DACs use oversampling capability built into the digital-to-analog converter chip, others use external DSPs to perform the oversampling.  NOS DACs do not oversample the audio before digital-to-analog conversion.

 

 

[asdf1000]

6 minutes ago, scan80269 said:

In another thread you started, I mentioned that modern USB DACs implement "isochronous transfer mode with asynchronous feedback". 

 

Thanks, yes that was useful in that other thread but in this different context I was wondering how a USB reclocker fits in this PC to Async USB chain, where the USB Dac is the MASTER. As in, if the USB Dac controls the overall timing of the sending PC, then what is the reclocker (like in the REGEN) actually doing?

 

But I think it's answered now by you 2 guys above.

[scan80269]

11 minutes ago, Em2016 said:

 

Thanks, yes that was useful in that other thread but in this different context I was wondering how a USB reclocker fits in this PC to Async USB chain, where the USB Dac is the MASTER. As in, if the USB Dac controls the overall timing of the sending PC, then what is the reclocker (like in the REGEN) actually doing?

 

But I think it's answered now by you 2 guys above.

In a nutshell, USB reclockers like REGEN and ISO REGEN provide the USB DAC with a USB stream of very high signal integrity, which enables the USB receiver inside the DAC (e.g. XMOS chip) to work less hard to retrieve the digital audio stream and thus generate less electrical noise to contaminate the digital-to-analog section.  Electrical noise coupled to the digital-to-analog converter translates to increased jitter for the conversion which degrades the sound.  A USB reclocker helps minimize noise incoming over the USB cable (e.g. from noisy PC/Mac USB ports) and noise generated within the DAC by the USB receiver circuitry to realize a SQ payoff.

 

Additionally, the ISO REGEN implements galvanic isolation (between its upstream and downstream sides) to break AC leakage loop(s) that are known to impact SQ as well.

 

 

 

[Middy]

Thanks gents interesting and we'll explained...

[scan80269]

Most DACs in the market today have not achieved total immunity from USB signal quality issues, which is why the reclockers can make audible differences (for the better).  Ideally a DAC should be insensitive to how good or bad the incoming USB signal is, but in practice they are all vulnerable to various degrees.  Designing to achieve this immunity is far from trivial!

 

If inserting a REGEN (or other reclocker) in front of a USB DAC yields no SQ improvement, then it suggests the DAC was very well designed and achieves a high degree of USB noise immunity, making the reclocker redundant & unnecessary.  The vast majority of DACs are not in this category.  Until DAC designers can create better designs to achieve USB noise immunity within the box, the reclockers continue to have a place in digital audio transmission over USB.

 

 

 

[tboooe]

33 minutes ago, scan80269 said:

If inserting a REGEN (or other reclocker) in front of a USB DAC yields no SQ improvement, then it suggests the DAC was very well designed and achieves a high degree of USB noise immunity, making the reclocker redundant & unnecessary.  

I am very interested to see if adding the IsoRegen in front of my modded SU-1 DDC powered by an LPS-1 makes any difference.  The SU-1 already uses very good clocks and I recently had the power regulator replaced with a very high quality one.  Definitely looking forward to receiving the IsoRegen to test.

[Forehaven]

So I thought someone might've received their ISORegen's yet?

[BigAlMc]

1 hour ago, tboooe said:

I am very interested to see if adding the IsoRegen in front of my modded SU-1 DDC powered by an LPS-1 makes any difference.  The SU-1 already uses very good clocks and I recently had the power regulator replaced with a very high quality one.  Definitely looking forward to receiving the IsoRegen to test.

 

Hi @tboooe, yeah likewise I'm interested to hear whether the IsoRegen offers an improvement here. Let us know how you get on please. 

[Superdad]

2 hours ago, scan80269 said:

In a nutshell, USB reclockers like REGEN and ISO REGEN provide the USB DAC with a USB stream of very high signal integrity, which enables the USB receiver inside the DAC (e.g. XMOS chip) to work less hard to retrieve the digital audio stream and thus generate less electrical noise to contaminate the digital-to-analog section.  Electrical noise coupled to the digital-to-analog converter translates to increased jitter for the conversion which degrades the sound.  A USB reclocker helps minimize noise incoming over the USB cable (e.g. from noisy PC/Mac USB ports) and noise generated within the DAC by the USB receiver circuitry to realize a SQ payoff.

 

I swear that @scan80269 is not on our payroll, nor does he look anything like John.  But with all his on-the-nose replies and clear explanations, he is certainly racking up points in our non-existent UpTone Rewards Program! Thanks Sam. 

 

[R1200CL]

2 hours ago, scan80269 said:

Most DACs in the market today have not achieved total immunity from USB signal quality issues, which is why the reclockers can make audible differences (for the better).  Ideally a DAC should be insensitive to how good or bad the incoming USB signal is, but in practice they are all vulnerable to various degrees.  Designing to achieve this immunity is far from trivial!

 

If inserting a REGEN (or other reclocker) in front of a USB DAC yields no SQ improvement, then it suggests the DAC was very well designed and achieves a high degree of USB noise immunity, making the reclocker redundant & unnecessary.  The vast majority of DACs are not in this category.  Until DAC designers can create better designs to achieve USB noise immunity within the box, the reclockers continue to have a place in digital audio transmission over USB.

 

 

 

 

And this is maybe a good reason to use a very good DDC. (USB to SPSIF converter).

 

I've notice the SU-1 use the same clock as the ISO regen by the way. 

 

I hope @Superdad and @JohnSwenson will come up with a super DDC soon. 

 

I think replasing my F1 or hiFace EVO (think they sound equal in my system) must be my next upgrade.

I can't see an UltraRendu will make any difference, as long as I have an ISO regen.

 

As my understanding is to put the best clock as close to your DAC as possible. This may also be a reason for not adding an audiophile switch I guess. 

 

Any thaughts ?

[Superdad]

35 minutes ago, Forehaven said:

So I thought someone might've received their ISORegen's yet?

 

Shipment promise date for the first batch was always May 16th-19th.  We got slowed down by the logistics of this first batch (6 variations when you consider the 3 power supply choices--none, SMPS. or LPS-1 bundle--plus standard or 90-deg. rotated 'B' plug on USPCB), plus an error I made in SKU set-up that is forcing me to do a lot of manual stuff for the international-bound units.

 

The first 120 units are leaving here in about 3 hours.  (My assistant showed up at 7:00 a.m. this morning, and I was preparing the shipping labels and docs until 11 last night.)  So despite this being not all 250 of the first run (see the other thread for the draw of that saga), we once again are shipping a new product on time!

 

[To those of you who got in on the mid-May promised batch (up through order #5449): If you do not receive a notice with tracking number around 2:00 p.m. (Pacific time) today, then your order will be filled within days of our receiving back the boards that were sent to have the one defective part swapped out.  That should be right at the end of this month.  And if your order (#5450 and above) was promised for early-June delivery, we are still on track for that as parts production is concurrent with everything else.

[Superdad]

41 minutes ago, R1200CL said:

 

And this is maybe a good reason to use a very good DDC. (USB to SPSIF converter).

 

I've notice the SU-1 use the same clock as the ISO regen by the way. 

 

I hope @Superdad and @JohnSwenson will come up with a super DDC soon. 

 

I think replasing my F1 or hiFace EVO (think they sound equal in my system) must be my next upgrade.

I can't see an UltraRendu will make any difference, as long as I have an ISO regen.

 

As my understanding is to put the best clock as close to your DAC as possible. This may also be a reason for not adding an audiophile switch I guess. 

 

Any thaughts ?

 

Folks are still getting DAC/DDC clocks mixed up with processor clocks! (Please reread scan's posts or John's on the subject.)

 

Even though Crystek (for example) makes the ultra-low-phase-noise CCHD-575 in both audio DAC frequencies (22.5792MHz, 24.576MHz and multiples of) and, on a custom basis at whole number rates as used for Ethernet, USB, FPGAs, and other processors (e.g. 24.0MHz and 25.0MHz)--they really are in different worlds.  There is no doubt that the 575 in the ISO REGEN is highly worthwhile (we directly compared SQ between identical boards with different clocks), but we think the 575 is about the limit of what is needed for a USB data clock.

 

However, for a DAC's audio master clocks (or the audio freq. clocks in a USB>S.PDIF converter which get embedded in the SPDIF/AES stream and supplant the DAC's clocks (though often a DAC will reclock that input), that is where no expense should be spared (though the rest of most DACs add more jitter from their circuitry and never get the full benefit of an über-expensive clock).

[Daudio]

6 hours ago, Em2016 said:

I thought the MASTER clock in the DAC only talked directly to the USB sending from the computer (and nothing in between). That's probably where my mis-understanding stems from.

 

I see that you have gotten some very good answers to this and subsequent questions, but I thought I might pipe up and answer you in a slightly different way. I certainly don't know everything about USB, but I did spend some significant time rummaging through the USB 2.0 Spec documents, so here goes.

 

 

I think of the clocks in the host computer, any internal/external hubs, and the PHY receiver chips in the endpoint device as controlling the USB pipeline, syncing the signals that enable bits to flow, whether those bits are commands, status, data, markers, or whatever. The 'pipeline' is designed to work at various rates for low-level activity, as well as different, specified, application data flows.

 

This is true for all the different USB modes. Where 2.0 Async is different is that it adds the capability for the endpoint (DAC) to watch it's input buffer and respond to pseudo-interrupt messages from the host (which come from the 2.0 Async driver code), polling the DAC to allow it to request more data, or idle until it needs more. USB is a purely host-controlled interface and endpoints can't control the bus.

 

So the DAC is sending info (need data/don't) back to the host, based on the DAC's clock gating audio data out of its buffer, through the USB pipeline (which is managed by it's own low-level clocks). Said another way, is that the Async timing info tunnels thru the existing, separately timed data pipe.

 

USB Signal Integrity is a very important factor for the electronic pieces of the pipeline, at the physical level, but isn't really a part of the Async mode.

 

 

I hope this may help you, or some others understand screwy USB a little better. If I've gotten something wrong here, I'm responsible and expect to be corrected, and we will all learn    Apologies if this is too off-topic...

 

[BigAlMc]

1 hour ago, Superdad said:

 

I swear that @scan80269 is not on our payroll, nor does he look anything like John.  But with all his on-the-nose replies and clear explanations, he is certainly racking up points in our non-existent UpTone Rewards Program! Thanks Sam. 

 

 

Ooh Alex, how do I sign up for the non-existent rewards program and is there much of a waiting list