Teac has issued an End-Of-Life for that product and will announce a replacement model shortly.Sold out at $1800. Not sure what "sold out" means - no more ever or currently out of stock.
CG-10M Master Clock Generator
The TEAC CG-10M Master clock generator keeps precision time for digital-to-analog converters (DAC). Shop Now.teacusa.com
Haven't heard it.
This may be oversimplifying it a bit. How exactly would a dac make use of a 10MHz clock? It is not generally a frequency dacs use internally. A dac which synthesises MCK/word clock out of a 10MHz clock relies on a pll circuit which already is a compromise. Or it may still rely on its internal clocks and use the external for reclocking. None of this sounds great to me, or perhaps I am missing something.
With asynchronous sample rate conversion it would be possible to use 10Mhz directly in a DAC but I have never seen this done in practice. I also think that the algorithms that make asynchronous sample rate conversion possible are currently of rather low quality. Synchronous algorithms are nearly always superior. DACs circuits generally uses a clock such as 22.5792Mhz or in the case of an ESS based DAC 100Mhz or similar. To generate these frequencies from a 10Mhz clock you have a couple of choices, but they all have significant drawbacks. One issue with all of them is that the wideband jitter is completely dominated by the local clock circuit. Perhaps the best method is to use a local low phase noise Voltage Controlled Crystal Oscillator (VCXO) that is adjusted with a software controlled DAC until it is frequency matched to the 10Mhz source, this is also known as a Frequency Locked Loop (FLL). I like to use this system for transports which must be synchronous to a clock feedback channel from an external DAC. This is the lowest jitter method I know of for generating a DAC compatible clock from a 10Mhz source. However that same crystal oscillator circuit without the voltage control circuitry would have lower wideband jitter…. So the only thing you could possibly gain is frequency stability. Your effort would be much more effective increasing the stability of the DACs local clock instead, such as putting its oscillator in a thermally stable enclosure (known as an OCXO). Other possible circuits like analog (non-crystal based) PLLs or Frequency Synthesizers are all much higher jitter than a simple average “jellybean” crystal oscillators so they are not worth getting into their technical intricacies. In my view, if a product supports external clocks it had better be for a really! good reason, because the inevitable drawbacks of supporting them. The best reasons I can think of are, transports that need to be synchronous to the DACs they feed, and studio DACs and ADCs which need to be synchronized to function correctly as a coherent system.
And probably just as many who agree with him.With the UTMOST respect to you and your decades of recording experience Bruce, it is not hard to find thousands of audiophiles who will differ with your assessment.
Dustin, a question:
I think I naively omitted basic architecture details that I thought people would pick up on or already were already familiar with. In my previous post I was talking about 10Mhz clocks, most circuitry does not use this frequency natively at all. USB generally uses a multiple of 24Mhz, Ethernet a multiple of 25Mhz, DVD based transports 27Mhz, CD players 11.2896Mhz, DACs and ADCs 24.576Mhz and 22.5792Mhz. So 10Mhz must be translated to “something else…” That translation is the problem addressed in my last post. The second detail is that all of our DACs, and the majority of high quality DACs, change their operational frequency based on the sample rate of the media. For example a 22.5792Mhz clock is used for 44.1Khz media and a 24.576Mhz clock is used for 96Khz media. If your external clock does not have two frequencies available then the receiving product must translate the clock or asynchronously sample rate convert the data, with all of the loss that translation entails. That translation is a more expensive, and a lower performance option than simply using a cheap jellybean crystal oscillators in the first place. Your external, ultra stable, super low jitter external clock is cut off at the knees by the clock conversion circuitry and is therefore irrelevant to performance of the product in question. In our DACs the oscillator is a dual frequency oscillator and it directly clocks the DACs, there is no translation. That clock is also sent back to the processors and back to the transport, renderer, USB, etc. In the case of the Cascade DAC it is sent back over fiber for use in the Digital Director, no translation necessary. The unused oscillator is also turned off to prevent coupling to the active oscillator. So if your DAC had an interface that sent the clock signal directly into the converters without any translation, and also had a control interface to select the correct operating frequency for the media being decoded then you would “only” have the loss incurred in the cabling and reception circuitry. However it would still be advantageous to put that same clock closer to the converters with less cabling and interference. In the case of a transport or other digital source the best option is to synchronize it with the DACs clock. This is optimally done by sending the DACs clock back to the transport. The industry standard for this is a “Word Clock” (a square wave at either 44.1Khz or 48Khz depending on the media). Our ProISL uses a more directly useful clock feedback frequency that is used to clock the data interface directly which results in even lower jitter and interference.
appreciate the details on optimal implementation approaches, but i'm no closer to an answer to my actual question (that "i" can discern from your response). but it's not your problem and i do thank you for your time. loved my time with my MSB.....and your team took great care of me.
Nope. While the Stanford units are fine for their purpose, their phase-noise performance is quite mediocre.
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