Just got in the mail information on the new TI ultra low noise regulator, the TI TPS7A4700
- Can source 1 A of current
- Noise figure of 4.5 uV, puts it at the top of the regulator list
- Voltage configurable evaluation board can be purchased for $20.
Is there a reason to use anything else?
The TPS7A47 is designed with bipolar technology primarily for high-accuracy, high-precision instrumentation implications where clean voltage rails are critical to maximize system performance. This feature makes the device ideal for powering operational amplifiers, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and other high performance applications…
Seems they designed this part for us diy audio nuts!
I’ve been thinking about what to use to power Ian’s FIFO reclocker board. This is its perfect match.
Load Step Transient Response
The load step transient response is the output voltage response by the LDO to a step change in load current whereby output voltage regulation is maintained. The worst-case response is characterized for a load step of 10 mA to 1 A (at 1 A per microsecond) and shows a classic critically-damped response of a very stable system. The voltage response shows a small dip in the output voltage when charge is initially depleted from the output capacitor and then the output recovers as the control loop adjusts itself. The depth of the charge depletion immediately after the load step is directly proportional to the amount of output capacitance. However, to some extent, the speed of recovery is inversely proportional to that same output capacitance. In other words, larger output capacitance act to decrease any voltage dip or peak occurring during a load step but also decrease the control-loop bandwidth, thereby slowing response.
The worst-case off-loading step characterization occurs when the current step transitions from 1 A to 0 mA. Initially, the LDO loop cannot respond fast enough to prevent a small increase in output voltage charge on the output capacitor. Because the LDO cannot sink charge current, the control loop must turn off the main pass-FET to wait for the charge to deplete, thus giving the off-load step its typical monotonic decay (which appears triangular in shape)
The company is called “Amanero Technologies” located in Pisa, Italy.
I am excited about this device because, well, it is cheap!. Technology is always changing. For the audio hobbyist, there is no such thing as the “ultimate device” or “last upgrade”. Therefore buying cheap but well designed products is the best approach because soon enough you will replace it with something better. As the subtitle of this blog says, “Lot of Value, Little Money”
The design is similar to other USB to I2S interfaces such as HiFace, XMOS, ExaDevices, etc, but it is priced substantially lower without sacrificing any of the essential desirable features (and also without adding extra features). For example, it does not use any kind of signal isolators as they may only benefit certain noisy environments but always introduce jitter. I like the minimalist, low power, low noise and low jitter approach.
Data Sheet: [link]
- Clean, very minimalistic design with no other feature than an I2S output and ready to be “plugged” into any DAC.
- The local regulators are the now-popular ultra low noise ADP-150 and ADP-151 from Analog Devices.
- The clock is taken from the two external local oscillators (and not generated by the FPGA) therefore keeping added jitter to the absolute minimum.
- The external oscillators are powered by the ADP-151 regulators through an LC filter which further decreases power noise (not an exotic implementation, but good practice).
- Supports up to 384 kHz and 352.8 kHz sample rates.
- Supports DSD
- Schematic for the USB interface (the Atmel chip): [link]
- Schematic for the data clocker (the Xilinx chip): [link]
- This is important for us diyers that can’t leave any design alone!
- Self powered (USB VBUS). USB power goes through a π filter (CLC) before the local regulator. The second regulator (another ultra-low noise ADP device) takes its input from the first LDO. This results in even cleaner power to the CPLD, the data clocking device
- In the output connector you have 3.3V from the LDO. For example you can use this pin to know when the cable is plugged.
- If you don’t like the USB VBUS supply, you can remove the LDO and power the module directly from the 3.3V pin present in the output connector.
- Power consumption is about 600 mW at maximum speed
OTHER NOTABLE FEATURES
- Supports MAC OS, Linux and Windows
- Single: US$97
- 60+ units: US$49
The USB interface is an Atmel microprocessor (SAM3u1C). The choice of using a general purpose microprocessor as the usb interface makes this device different from all other interfaces which implement a specialized usb interface chip. I don’t know the reason, but perhaps this makes it much easier for upgrading the firmware of the microprocessor itself and also for updating the firmware of the Xilinx CPLD.
On a side note, the SAM3U microprocessor will also be used in the upcoming Arduino DUE
The data clocking device is a Xilinx CPLD (XC264A). A CPLD is like an FPGA but lower complexity and lower power. Another guess: the designers choose the smallest device necessary just to do the I2S data and DSD clocking. No extra features like clocking a SPDIF stream.
Two low jitter clocks for deriving the master clock for the different sample rates
(Manufacturer’s data from post 78 at diyaudio)
-78dBc @10 Hz,
Using a jitter calculator we get the following value:
Not bad. The crystek CCHD-950 80MHz originally used in the BII measured at 2.286 psec [link]
Pin description [post 238]
- DSDOE: = 1 when a DSD stream is incoming.
- MUTE: has been assigned to PIN 11 and is asserted to 1 when a sample rate change is incoming or when there is a stream format change DSD / I2S. You can use this pin to avoid noise when the dsd is detected.
- Pin 6 is the Master Clock MCLK 22,5792Mhz or 24.576Mhz. (I think this is pin 5 FSCLK)
- TWC.D is an I2C bus, I m preparing a ConfigTool that let’s the user configure Events in the module. For example you can assign I2C address and values to put in the I2C bus when the volume is changing or when a sample rate is changing.
There are a couple of fuzzy videos on youtube where you can get a glimpse at the driver user interface.
AUDIOPHILLEO ALSO USES A MICROPROCESSOR…
The Audiophilleo USB interface chip is also implemented in a general purpose microprocessor. According to 6moons,
(The Audiophilleo uses) an ARM9 microprocessor… The processing power is considerable and allows the Audiophilleo to provide advanced dithered digital attenuation, ramped muting, balance and polarity reversal on the fly. New firmware containing the code for all these functions can be downloaded in a few moments which in turn enables easy field upgrades. The resulting processed data are passed to the output stage through miniature galvanic isolators that are much faster than the usual optical types. A TDK Lambda regenerative power supply separates the rails and grounds of the two subsystems. So now we’ve got clean power and data neither of which is contaminated by dirty power or clocks.
… The “non-minimalist” design approach.
On paper (since I don’t have one yet ), this device seems like a winner; and considering the price, it should be at the top of the list. For the next level of improvements, you will have to look at something like Ian’s FIFO device. The only “unknown” at this point is how well has the USB h/w and s/w been implemented.
HOW ABOUT MUSILAND?
Readers know that I have been a long time fan of Musiland Devices. They are very affordable, have good drivers, and are fairly easy to mod. For the diyer, this device addresses the two things I wished Musiland had improve, namely lower noise regulators and clocks from external oscillators (rather than generated in the FPGA). Feature-wise though, the Musiland devices still pack a lot of things for the money: more interfaces, built-in DAC, built-in headphone Amp, user-interface with lost of controls, etc. For an all-in-one USB solution, the Musiland devices are still on the top of my list.
You can join the discussion at diyaudio.
Here is the new Crystek Oscillator which is tailored for audio applications (my own device and photo )
According to this, here is the crystal inside a Crystek CCHD-957 module (which was used to mod an XMOS board)
Lets take a peek inside the clock unit.
Peeking inside from one side of the clock module. (I am not going to remove the metal shield. This thing costs over $30 )
Peeking through the other side of the clock module. Indeed there is a can crystal inside the clock module as reported.
Just the basic components for a Pierce oscillator?: capacitors, resistors…
and a digital inverter?
More photos. I took these with a high intensity LED flashlight and set the aperture way down to get larger depth of field.
The following two photos on the same side of the clock module, but different angle…there is another integrated circuit/transistor on the other side (see left side of first photo) …
Another view of clock module, this time the can crystal is more clearly shown.
Shining the flashlight through the PCB.
View from the other side of the module
Jitter values compared
Comparing the specification of the CCHD-957 with the CCHD-950-80 (which I have on the Buffalo II DAC) we find a “huge” decrease in jitter RMS (as calculated with jitter calculator)
Impressive reduction of jitter (but can anyone even hear 2 psec jitter?) In any case, this new breed of high performance clocks does not cost any more than the older CCHD-950 versions, so it is a very welcome improvement. Plus the fact that they are available in frequencies tailored for audio applications makes them even more suitable/desirable.
Use in Ian’s FIFO board
I plan on using this oscillator in Ian’s FIFO Jitter eliminator. The clocks included in the kit are the “generic” types and are included for checking the baseline functionality. They are also of lower frequencies.
Using this frequency provides support for all sample frequencies
|45.1584MHz / 49.152MHz||1024Fs||512Fs||256Fs||128Fs|
|22.5792MHz / 24.576MHz||512Fs||256Fs||128Fs||Not supported
|11.2896 MHz / 12.288MHz||256Fs||128Fs||Not supported||Not supported|
Is 40-50 MHz optimal?
For the Sabre DAC, it seems that it “likes” having a master clock in the 40 to 100 MHz. Since the FIFO needs frequencies that are multiple of 44.1KHz, and the Sabre32 “likes” frequencies above 40 MHz for the master clock (not sure if this is a requirements, but all implementations seem to use frequencies of 40 Mhz, 80 and 100 Mhz), this clock at 45.1584 MHz seems to be optimal for interfacing the FIFO to the Sabre32 chip in the Buffalo DAC.
The following arguments may indicate that this frequency range may be optimal for the Sabre32 DAC
According to Dustin [link]:
…by the way, running the DAC at 80MHz with a good crystal you can expect to only see a 1dB DNR loss from the 40Mhz boards, if that. Some show no diff, some showed 1dB.
In addition, the power requirement of the analog supplies (AVCC) with the lower frequency is about 40%-50% less [link] resulting in a cooler running electronics.
Example of some implementations also show the use of 40-50 MHz frequencies:
The $32K Accuphase DC-901 uses a 40 Mhz clock
The Resonessence DAC uses a 50 MHz clock [link]
Both analog boards are preceded by a Crystek CCHD-950-20 low-phase noise clock. We chose the 50MHz part as it has the lowest phase noise at offsets that are in the audio band. The clock has its own dedicated ultra low-noise power supply
Historically, the frequency of the on-board oscillator has been moved up from 40 Mhz, to 80 Mhz and then to 100 Mhz.
The evaluation board from ESS is designed with a 40 Mhz clock. The desire to support 192K sample rate, moved the frequency to 80 Mhz. Then playing 352Khz material, required moving the frequency to 100 Mhz.
Mounting the Clock
Since these are SMD parts, one needs to first mount them in a suitable adapter board. At first I was thinking of crafting something myself, but one can now buy adapter boards from Ian such as this:
Other diy projects
Here is a summary of the information regarding the FIFO reclocker (mostly from Ian and mostly from diyaudio). It is getting hard to sift through all the good information.
In particular, I have focused on its application with the Buffalo III DAC which seems a very popular combination.
1- “Normal” connection to Buffalo III DAC
That is in asynchronous mode: Bitclock, LRclock and Data. The master clock signal from the FIFO reclocker is not connected. BIII operates in asynchronous mode generating its own local master clock. This is the default operation of the Buffalo DAC (I, II, III)
(Most photos-which are excellent- are also from Ian)
Buffalo III DPLL setting: default
According to the documentation, the default setting is the same as the “BEST” setting. Best setting works all the time for any input configuration. It is said that with this setting, the DPLL is set “automatically”. I think this is what “automatically” means: the DPLL sets the bandwidth depending on the incoming sample rate. It likely selects wide bandwidth values. It definitely does not attempt to choose the lowest bandwidth possible.
Then I connected the FIFO I2S output into BIII via U.FL coaxial cables…The result was quite impressed. I don’t want to say it’s perfect, but I have to say it’s very close to (perfect). I tried a couple of different kind of XO and found that the sound of ESS9018 still quite sensitive to the jitter from the input digital audio stream. I suspect the internal DPLL still has to trace the input clock to get lock with it. So, the clock jitter, outside the DPLL bandwidth, will still be introduced into DAC, which usually, is the close in phase noise. While the final phase noise within the DPLL bandwidth will be decided by the performance of the internal DPLL (phase noise floor).
No click noise at all with same 192Khz input.
I use BIII default setting so far with all the switch jumpers at off position. I don’t think this optimized for all the sample rates..
Buffalo III DPLL setting: lowest (post 523):
Yes, when I set the switch to “lowest”, I got drop-offs too. It sounds a little bit better for me, but I gave up after half hour ‘warm up’
DPLL setting for 192KHz sample rate material (post 528)
I have to set bandwidth to ‘low-middle’ to achieve long term stable lock with 192Khz I2S
Earlier experiments have shown that the “warm up period” – the time it takes for the local clock in combination with a source clock to stabilize and thus allow the DPLL to operate with no drop-offs in its lowest bandwidth setting- could be up to one hour. It seems that using the FIFO reclocker did not improve this condition. If feeding a signal with jitter approaching a practical zero value still causes drop-offs -even after half an hour, then one may conclude that the lower settings in the Sabre32 DPLL were specified perhaps to push the limits of the design and not so much for “normal operation”.
2- Synchronous connection to Buffalo III DAC
If the source signal is of low enough jitter, then there is no advantage of using the asynchronous reclocker in the Sabre32 DAC to eliminate jitter since there is practically no jitter to be eliminated. The FIFO reclocker is an excellent candidate (at the present, I would even say “the best”) for synchronous connection with the Buffalo/Sabre DAC. In addition, high quality clocks -similar in quality to the clock used in Buffalo DAC- can be used in the FIFO clock board which further eliminates the need of generating a high quality local clock.
Because the Buffalo DAC was not designed for easy switching to synchronous operation, in order to use it in synchronous mode, the local clock needs to be disabled or removed (see post 542)
Then some king of connector is installed. Here, a U.FL socket is installed.
The external clock is delivered though a coax cable.
With this setup, Ian reported the following results:
It runs right away without any hesitating. The LOCK LED keeps lighting all the way indicating it is synchronized with the input I2S stream unconditionally even I set the bandwidth switches to ‘lowest’ and run music at 192KHz from an USB.
In my configuration, ESS9018 sounds great in both of the modes, sync and async. I even couldn’t tell which one is better. But there is slightly difference on the sound style. Async is more like ESS9018 while sync is more like classical high-end DACs. I usually don’t talk much about the sound, because too many psychological factors and personal feelings mixed. I’ll left this part to others, trust your ears and try to find out the best parameter settings of 9018 for the sync mode.
3- Switching between synchronous and asynchronous mode (post 745)
If the source clock is not of the best quality, then it is advantageous to use the local (high quality, low jitter) clock of the Buffalo DAC and leverage the ASRC function to remove jitter. The Buffalo DAC was designed to always work in asynchronous mode and does not have an easy way to switch the local clock in and out of operation.
Ian designed a small carrier board that allows manual switching between synchronous and asynchronous mode. The clock carrier board is connected to the Buffalo III board through a 3-pin header. The Buffalo III DAC was designed with this kind of mod in mind so there are through hole connectors under the clock; the Buffalo II does not have such connectors making the modification a bit more challenging.
For asynchronous mode, manually insert the clock into the socket
For synchronous operation, remove the clock and connect the external clock signal
It would be nice to have some electronic way to switching the clocks (so switching can be automated with an external microprocessor such as Arduino)
What to do with a Buffalo II?
Here is an implementation reported at the TPA forums:
Pin 24 on the ESS chip is the Xtal in pin. As wktk smile said, R17 (RHS of this resistor when the TPA logo is at the top of the board) is connected to the Crystek clock output, which makes a convenient soldering point.
I unpowered the separate supply to the Crystek crystal, then connected up the Hiface clock output to this resistor pad using some Mil coax cable I had lying around. Note I grounded the source end of the coax but not the destination to avoid a ground loop but shield this high frequency signal.
Mental note – pinouts from the dot on the ESS chip go counter clockwise…and the Crystek pinout then would have made sense too…for the Crystek, pin 1 is bottom left, pin 2 bottom right, pin 3 is top right (Clock out)…
Anyhow, it works and initial impressions are positive with the music having excellent drive (PRAT), the bass is very solid, and great inner detail (OK it had lots of the latter before). Well worth trying this guys!
4- Additional enhancements
Further enhancements to the FIFO kit has been implemented through both experience and user feedback.
U.FL signal input connector board for BIII DAC (post 743)
Ian reported the following improvement:
I did some test with this new adapter on my BIII yesterday. It works very well. I’ve noticed some improvement: With BIII (DPLL bandwidth set to lowest) working with I2S FIFO at SYNC mode, If feeding signals with this adapter and U.FL cables, DPLL locks solid never lost; However, without this adapter and U.FL cables, it will lost lock occasionally(every 10 minutes roughly).
Hmmm… this means that the bitclock, even if derived from the same master clock, can experience some disturbances resulting in phase noise with respect to the master clock (the master clock was already connected with a U.FL socket). I think even in asynchronous mode, the use of U.FL would be beneficial.
Multi-frequency clock board (post 837).
After Ian reported good results with the Silicon Labs Si570 clock, I decided to do some research on my own and documented my findings here: link. The advantage of the Si570 programmable clock is that you can generate “any” frequency you need by programming the registers through an I2C connection. This is useful especially since good clocks in frequencies that are “common” to audio equipment are no longer manufactured.
In this post, Ian explains the advantages and disadvantages of a Si570 based clock board:
- Generates low jitter audio clock for multi-frequencies with one chip solution. Especially for some frequencies for which very hard to get good audio clocks.
- Not that sensitive to the power supply.
- To cover the full digital audio frequency range, the cost will be less than using CCHD957 or other low jitter oscillators.
- Supports almost all kinds of applications which need low jitter digital audio clocks such as CD players, SACD players, Network/HD players, DACs, USB interface, ASRCs,DSPs…… (If used as a standalone board)
- Integrates seamlessly with FIFO project to allow switching between different Fs.
- Very flexible and can be calibrated under the software support.
- Close-in phase noise performance is not as good as CCHD957 or sc-cut oscillators.
- Need software driver when switching frequency (not all the time).
- 100mA power consumption which is a bit higher than normal oscillators.
I can think of yet another advantage: Since the frequency can be adjusted in 1 Hz increment, the frequency can be adjusted in order to match the frequency of the incoming data. With this capability, the FIFO fill levels can be adjusted in order to reduce its latency.
Notice the ATMEGA 8 microprocessor which is used to program the Si570 clock which is an I2C device
The first prototype of Si570 based clock board was down. With the single programmable XO, now I got 11.2896, 12.2880, 16.9344, 18.4320, 22.5792, 24.5760, 33.8688, 45.1584, 49.1520, 90.3168, 98.3040 MHz. Switching between frequencies will take only a couple of ms. Pretty amazing for such a small gear. More information here [post 881]
Phase noise comparison with the Crystek 957 device and the Crystek 950:
|Frequency||Si570||CCHD-957 (49.152 MHz)||CCHD-950 (80 MHz)|
||-112 dB||-129 dB||-102 dB
||-122 dB||-153 dB||-135 dB
||-132 dB||-162 dB||-160 dB
||-137 dB||-168 dB||-166 dB
||-144 dB||-168 dB||-166 dB|
Most of the phase noise comes from the close-in frequencies. As can be seen in the table, the Si570 clock cannot match the Crystek 957, but compared to the on-board clock in the Buffalo DAC, and especially compared with the original clock that came with the Buffalo II (the model I currently have), the close-in phase noise values are comparable or even better.
If we calculate the RMS jitter we obtain the following:
(Assume the 10 Hz jitter value for the Si570 can be obtained by extending the graph following the same characteristics slope as that shown by other clocks. We will assume a value of -82 dB)
- For Si570 (assume 90.3168 MHz): 052 psec RMS
- For CCHD-950 -80MHz: 1.90 psec RMS
According to Ian’s impressions (with a evaluation board) [link]
I’m having an original Si570 evaluation board, so I got chance tasting it on my FIFO platform before I really finish the clock board. During the real listening test, the sound of Si570 was quite impressed. It comes with much more details and crystal clear wide and deep 3D imaging. Actually I tested a whole bunch of clocks. Si570 beat all of them except CCHD957. It’s better than what I expected. So, I decided giving the Si570 clock board a try.
According to Ian’s next impression with his finished board [Post 913]
…Another discovery is, ESS9081 sounds different for a same 44.1 KHz stream with different MCLK frequencies, for example 45.1584MHz and 90.3168MHz. Hard to tell which one is better, but the sound style is a bit different indeed. I know it’s the internal up-sampling digital filter, different performance for different MCLK.
Plans for having the clock board be battery powered
Although the Silabs official document mentioned that Si570 is not quite sensitive to the PSU noise, I found it’s not true, at least for this application. The close-in phase noise performance of Si570 is not as good as CCHD950, 957. So, to compete with them, Si570 need better low noise PSU. Both 1/f noise of PSU and the XO crystal itself contribute to the close-in phase noise. After I bypassed the on board low noise LDO and make the Si570 directly powered by a LiFeP04 3.4V battery cell, ESS9018 sounds better with more details and more liquid.
Si570 is a bit special case. It comes with whole DSPLL circuit but a pure XO. I’ll design a battery manager board later on to make the battery as a standard equipped power supply rather than just a testing configuration.
With a programmable clock, you can also experiment with different oversampling and oversampling bypass as documented in this post [link]
There is a V2 of the Si570 Board [post 1512]
- More frequencies
- More connection options
- Support for different regulators
Here is comparing V1 and V2
5- Firmware capabilities
This set-up summary is derived from the documentation available for download at diyaudio. So far there has been two major versions of the firmware: The firmware that came with the devices from the first group-buy and the firmware that came with the devices from the second group-buy.
- First group-buy information and documentation: [link]
- Second group-buy information and documentation: [link]
- The firmware is factory upgradable for free and you only have to pay for shipping [post 724]
|Feature||Original Firmware (v. 3.30)
||Updated Firmware (v. 3.80)||Comments|
|FIFO Input format
||I2S (32bit and 16bit)
||I2S, LJ (32bit and 16bit). RJ (16 bit and 24 bit)||Most “modern” sources are I2S 32bit. Upgraded FW makes it a universal re-clocker. For example, you can connect to the I2S connections of a CD ROM
|Output Master clock (single clock board)
||Fixed 256 Fs
||Fixed 256 Fs and Fixed 512 Fs
||The single clock board does not detect the input sample rate so the XO frequency must match the input sample rate to produce the fixed output master clock FS (Note 1)
|Output Master clock (dual clock board)
||Automatic switching 128Fs, 256Fs, 512Fs and 1024 Fs
||Automatic switching 128Fs, 256Fs, 512Fs and 1024 Fs||Automatic input sample rate detection. (Note 2)
||32bit I2S and 32bit LJ
||LJ to integrate FIFO with some DSPs or DACs which do not accept I2S input, for example, PMD100, SM5842, SM5843|
1- For example, if the input sample frequency is 44.1 KHz, then the user must choose a XO of 11.2896 MHz (44.1×256). This also means that for 44.1KHz, the maximum speed XO that can be used is 22.5792 MHz (with the new firmware). This is the lowest frequency available for the Crystek CCHD-957 clock and was the main reason Ian increased the FS for the single XO board. This board is only suitable if you only have to deal with a single sample rate because changing the input sample rate requires that you manually change the XO and/or set jumpers.
2- The double XO clock board has a frequency management MCU. During normal operation, this MCU will run at deep sleep mode, or power down mode. In this mode, all of the clocks, include CPU clock, IO clock and watchdog clock, are stopped. That means the MCU do not generate any EMI noise at this time. When the frequency detecting logic on the FIFO board finds that the input I2S frequency has changed, it will wake up the MCU by pulling down the interrupt line, and at same time mute the I2S output. After the wake-up, the MCU will set a new MCLK frequency as well as the *Fs according to the information provided by the FIFO board. (Post 54)
Firmware version history (as of August 20, 2012):
- V3.30 For group-buy I
- V3.50 Implements 512Fs default XO support in single clock board
- V3.60 Implements left justified output format
- V3.70 Implements left justified, 16/24bit right justified input format
- V3.75 fixed a bug on switching between 44.1KHz and 48KHz with dual clock board running at dual speed mode
- V3.80 for group-buy II (Post 457)
6- Power Requirements
From the manual
- 6V 500mA DC
- Absolute minimum voltage: 4.5 V
- Absolute maximum voltage 6.7 V
FIFO Board Setup
There are 4 jumpers (The holes labeled TP41, TP42, TP43 and TP48 in the photo) that can be used to select input format, output format and single clock board FS operation. The jumpers are either left open in their factory configuration or can be shorted to ground.
FIFO Input Format
|Jumper TP41||Jumper TP42
||Open||I2S 16bit-32bit (Original firmware only supports this mode)
|Open||Ground||Right Justified 16bit
|Ground||Open||Left Justified 16-bit-32bit
|Ground||Ground||Right Justified 24bit
FIFO Output Format and Single Clock Board Master Clock Operation
||Jumper TP48||Master Clock|
|Ground||Left Justified (32 bit)
TP48 only takes effect if you use the single XO board. If you use the double XO board, this setting is ignored
Single Oscillator Board Setup
You must choose the correct frequency for the oscillator depending on what sample rate you desire:
If your source sample is 44.1KHz, then these are the only two choices for the oscillator frequency
- 11.2896 MHz (must set jumper TP48: open in the FIFO board)
- 22.5792 MHz (must set jumper TP48: ground in the FIFO board) -New FW
If your sample rate is 96KHz, then these are the only two choices:
- 24.576 MHz (must set jumper TP48: open in the FIFO board)
- 49.152 MHz (must set jumper TP48: ground in the FIFO board) -New FW
The board tells you which oscillator to use. With the new firmware, you can use double the speed by setting the jumper to support 512 Fs
Dual Oscillator Board Setup
The dual clock board also has two sets of jumpers that are used to tell the device whether you are using “high speed” or “low speed” oscillators. These jumpers are already installed from the factory as shown in the photo below.
Choosing the oscillators
Choose the oscillators in accordance to input sample rate and required/supported Master clock frequencies as shown in the table below. In addition, one oscillator is to support the 44KHz family of frequencies and the other oscillator is to support the 48KHz family of frequencies. Further, the frequencies of the oscillators can at most be one multiple apart. For example you can use a 45.1584MHz clock and a 24.576Mhz clock, but you cannot use a 11.2896 MHz clock and a 49.152 MHz clock in your dual clock board
|45.1584MHz / 49.152MHz||1024Fs||512Fs||256Fs||128Fs|
|22.5792MHz / 24.576MHz||512Fs||256Fs||128Fs||Not supported
|11.2896 MHz / 12.288MHz||256Fs||128Fs||Not supported||Not supported|
Master clock compatibility
Different DACs support different master clock Fs for the different input sample rates. I’ve summarized the supported master clock Fs for popular DACs. Before choosing the oscillators for the clock board, make sure the master clock Fs is supported by the target DAC.
9- Where is my own FIFO reclocker?
It is still in the box. I can’t believe I’ve had it since March of this year. Life has been taking away time from audio hobby . At least I started to review the available information and documentation (which I’ve summarized here, so I won’t forget)
However, based on what Ian has reported, I don’t expect it to behave too much different from my current source with respect to drop-offs. If you see item #1 above, drop-offs are expected with DPLL set to lowest.
Improvements are expected only with synchronous connection, and that would require removing the local oscillator which I am currently hesitant of doing.
In the mean time, I will send it back for firmware upgrade.
A diyaudio user had adapted the Hifiduino code to use a graphic display. Cool project.
A later implementation looks like this:
Another implementation by dimdim looks like this. bigpandahk based his design on dimdim’s code
Even though these screens are all text based, they are already pretty good looking. For those inclined to further modify the code, you can do much more with the graphic display like using icons and even using the touch interface to change DAC parameters and volume.
User DQ828 has this implementation here: [link]