Is a femto clock important if you aren't using asynch USB?

I am considering buying a used Wyred 4 Sound DAC2 DSD se for streaming from my Bluesound Node 2i, and the seller told me that this DAC2 se is one of the early ones that does NOT have a femto clock.  My Bluesound does not have USB output, so I won't be using the USB input on the DAC2.  My understanding is that the femto clock is mainly useful to sync up the digital stream from a computer; is it likely to make much difference if my source is a streamer and the input is SPDIF?


Why would you want to buy a ten year old DAC with ten year old tech?

Even if your funds are very limited you can buy a very good Chinese DAC with upto the minute tech.

For around $3k you can buy a world class DAC, many cheaper options available.

My guess is that the OP is correct, that since usb is the most jitter prone interface, the lack of the femto clock isn’t so important. I remember looking at the W4S DAC a few years back and they were offering the non Femto for about $1900 and the Femto for about $2600. Later I learned that the price of the Femto chip to the manufacturer was $10.

As to @lordmelton point, the DAC in the Node2i is a significant improvement over its previous DAC. The OP may not actually get much of an improvement using the older W4S DAC. If the W4S is going for a low price it might be worth it, but not if the seller wants more than $500 or thereabouts

While it is true that USB does not rely upon the streamers clock, it seems to me that you want a good DAC clock for stable sampling of any input.


What you really should want is a modern DAC instead of worrying about clocks.

I like buying used but never do it with Digital gear.    I did buy a R2R DAC ,  but I also have a DAC that can do DSD.     When I bought my streamer I wanted the latest tech and codecs.     I am a late adopter when it comes to everything else.....

Some DACs like my RME adi2 always use their internal clock regardless of input type.   It's Femto clock is used also when there is a Coax or Tos. Input,  it doesn't just use it's clock for USB.


The better the internal clock, the lower the DAC's jitter rejection can work, to a point.  If upstream jitter is extreme enough no internal clock will fix it.

I agree though that chasing a 10 year old DAC seems imprudent. That was just after the cut-off range, when I remember Redbook playback getting much better.

I had a W4S Dac 2 (not DSD).  It was the worst sounding standalone DAC I have owned.  I would pass.

I have an old W4S dac2 and it is indeed a good dac if it works in your system.  Since you're shopping in this price range, I doubt you'll hear the difference with or without a femto clock  (this was a flagship dac over a decade ago but worth a couple hundred dollars today).

Be aware that the Dac2 is not driverless.  I got it work fine with my bluesound node but then Roon will not see it.


femto clock is mainly useful to sync up the digital stream from a computer

Other than Asynchronous Rate Converter used in some DACs (like Benchmark), most of them use PLL (Phase Locked Loop)  and have variable D/A converter clocks with S/Pdif transmission, to adjust conversion rate to average incoming words rate (otherwise samples would be lost).  It used to be done with VCO (Voltage, Controlled Oscillator) adjusted by comparator comparing phase of incoming signal to phase of the VCO util they are even (same frequency).  Today it is likely all in digital domain, but still, D/A clock has to follow incoming signal rate, hence it is variable.  These "Femto Clocks"  are very stable, I'm sure, but average frequency stability is not important since we cannot detect such tiny clock differences/changes.  Jitter of the clock is important and likely audible when above about 50ps.  It is "picoseconds" - not femtoseconds, making me suspicious of snake oil.   With async USB samples come in packets (frames).  Each frame delivered at some fixed rate (like 1kHz) contains multiple samples.  DAC places them in the buffer and upon buffer over/underflow signals back to increase or decrease number of the samples in next frames.  That way D/A clock is fixed, but samples are not lost.  Unfortunately connecting computer also connects high frequency noise.  There are extremely low noise switching power supplies (SMPS) used by companies like Rowland or Benchmark, but those used in computers are cheap and extremely noisy.  This noise is finding any alternative return to ground, including one thru DAC grounds.  Optical isolation with USB would be my first choice of action.

Thank you all for your input, but I should have made my current setup more clear. I now have a Benchmark DAC1, which I like pretty well; I was not planning on using the Bluesound’s DAC, which I do not like as well. My goal with the W4S DAC is to improve on the Benchmark; what are your thoughts?

PS, the rest of my system is a McCormack DNA1 Gold rebuild with gravity base jr (LOVE), a Modwright 9.0 SE (meh), and Usher MD2’s (like very much).


I believe that many have already told you that the W4s is not a good choice, but you have ignored those posts and ask once again the same question.  If you are going to get it then go ahead, but please read reply’s of those responding.

@dirkjanl and @erik_squires I wish the two of you would get together and publish a book "DACs for Dummies". I love the insight you both provide on this forum, but sadly I can only follow what you're saying about half the time (my bad).  However, I do appreciate Erik's attempt to break through the fog by closing with a warning against chasing a 10 year old DAC...

The Modwright is a good unit, but it might make more sense to sell it and put the money towards a new (or at least <3 years old) DAC, and go directly to my DNA1 (using the Bluesound for volume control); any thoughts?

@vonhelmholtz I read each of the replies quite carefully, including yours.  My understanding is that a femtoclock will not fix an incoming bitstream unless it is operating in async USB.  Absent that, the clock in my Benchmark DAC1 is probably good enough that I would not detect the difference that a more accurate clock would provide.  If you have an opinion on that, I would appreciate it; if not, thank you for your original input.

My best sound is with my Aurender's SPDIF output into my LAB 12 DAC 1's coax input.  In my set up it sounds better with the N200's clock than the DAC's internal clock in my set up.   Maybe a new USB cable rather than the fairly generic one   would equal my DH Labs coax.   Not sure.    

I had a few drinks last night and put about $700 in DH Lab cables in my shopping cart....  I didn't pull the trigger but I could use a high Quality USB and some longer RCAs

Thanks oddio, hope your late night drinking/shopping binge pays off; if not, at least you had an interesting night. ;-)


What kind of budget do you have? There are much better new/new used to be had.

All the best.


I just changed USB cable on my NODE 130/Gustard X26 PRO from a DH Labs Silversonic maximum bandwidth to a Curious USB cable. The Silversonic was ok but had a hint of harshness in certain highs that really hurt my ears specially at mid to higher volume. The Curious has better clarity and brightness even so it actually is much easier on my ears, just much smoother all around, no hints of harshness anywhere meaning longer listening sessions. Just thought it might be helpful in your search.

Interesting to take the wav file from a CD/DVD and look at it in an editor.  Most are clipped at 0 or -1 dB.  This is a bad practice.