Spartacus said:
Excellent point. The EZdac board is very compact and separate supplies are not quite possible. The 3.3v for the oscillator is shared between all other digital ICs on the board. The only decoupling coming from a a tiny ferrite inductor and cap. As the oscillator supplies master clock to both the ASR and DAC it may be a good idea to provide at least a dedicated regulator. This may also explain why i prefer the PLL - it probably has superior psrr.
6h5c said:
I thought it interesting that the Flea made more of a difference than swapping the Abacon XO to a Tent XO😀
Yeah, I hope so! I did listen to it with the Abracon XO mounted on the Flea. Lets say it was very hard to determine a difference when the Tent was fitted 😀. But to squeeze everything out of the design I used a Tent XO 😀
Ray
Ray
6h5c said:
Sorry, don't know how that happened. I'll put together a flea. Busy listening to the ezdac minus the SRC at present
analog_sa said:
Don't be sorry, I'm glad you posted the results, I'm now thinking about giving that PLL a try, at the end of the day its the listening results that count 🙂
Will you be trying the SRC? I wish I tried mine without it first before fitting it to see what effect it had, its good to try these things out
analog, I'm not sure I understand your setup. You said you're using I2S from a USB receiver? And you're bypassing the ASRC? So, the I2S is connected directly to the DAC? Did you mount the crystek part when the ASRC was in or out? The PLL1705 is a clock generator, so that is a very different beast from a canned XO or the crystek smd part. It would be helpful if you could provide a schematic showing the different setups you've used.
Hi Ezkcdude
"a schematic showing the different setups you've used"
oh, my. i'll be spending the day drawing schematics then 🙂 like it's not enough i skipped gym already
1. I2S from 2707 USB feeding SRC4192. With either canned oscillator or PLL2705.
2. I2S from 2707 + masterclock (11.289MHz) feeding PCM1798 (SRC is desoldered)
3. Same as 1. only with AD1896
Does this make it clearer?
"a schematic showing the different setups you've used"
oh, my. i'll be spending the day drawing schematics then 🙂 like it's not enough i skipped gym already
1. I2S from 2707 USB feeding SRC4192. With either canned oscillator or PLL2705.
2. I2S from 2707 + masterclock (11.289MHz) feeding PCM1798 (SRC is desoldered)
3. Same as 1. only with AD1896
Does this make it clearer?
Well, i'm done with the assessment. Obviously i had some prejudices about the entire issue of ASRC and it's interesting how it all resolved in practice.
A great "rundown" of dac technologies can be read at the asylum. My conclusion is quite similar but due to different tastes i seem to enjoy ASRC.
First of all, the minor differences. The TI and AD chip sound very, very similar to me. Might have a minor preference for the AD chip but these differences are completely swamped by the difference in clocks per example.
The obvious effect of the ASRC is that practically any music gets a lot of added get up and go. Subjectively it also sounds louder, more dramatic, with greater dynamics and better bass. The soundstage is very stable irrespective of volume. Peaks are handled with ease.
Downside? Timbral accuracy is not so great. Quite noticeable on piano. If classic music was my main preference i might prefer simple oversampling.
An easy analogy is to compare ASRC to an active preamp and OS to a passive. Over the last couple of years my prefences have moved towards the healthier, although less transparent sound of actives. The ASRC adds more of the same.
It would be amusing to put together an ultraflexible version of Ezdac. One that can completly bypass the ASRC and have an option for multiple regulators and sharp/slow filtering.
I guess bypassing the ASRC is not as easy as using the inbuilt function. What would be a good analogue switch to use? Relays?
So far i've had a really great time with this project 🙂
A great "rundown" of dac technologies can be read at the asylum. My conclusion is quite similar but due to different tastes i seem to enjoy ASRC.
First of all, the minor differences. The TI and AD chip sound very, very similar to me. Might have a minor preference for the AD chip but these differences are completely swamped by the difference in clocks per example.
The obvious effect of the ASRC is that practically any music gets a lot of added get up and go. Subjectively it also sounds louder, more dramatic, with greater dynamics and better bass. The soundstage is very stable irrespective of volume. Peaks are handled with ease.
Downside? Timbral accuracy is not so great. Quite noticeable on piano. If classic music was my main preference i might prefer simple oversampling.
An easy analogy is to compare ASRC to an active preamp and OS to a passive. Over the last couple of years my prefences have moved towards the healthier, although less transparent sound of actives. The ASRC adds more of the same.
It would be amusing to put together an ultraflexible version of Ezdac. One that can completly bypass the ASRC and have an option for multiple regulators and sharp/slow filtering.
I guess bypassing the ASRC is not as easy as using the inbuilt function. What would be a good analogue switch to use? Relays?
So far i've had a really great time with this project 🙂
Thanks, for your thorough description. I think these ideas would be useful ultimately for a v.2.0.
analog_sa said:
Sorry, do you mean you use the system clock of the PCM2707 (pin FUNC2) or an external masterclock ?
Is the PCM2707 running with a quartz or a clock ?
Thanks 🙂
Thank you Analogue_sa, good post and description!
Having the option to bypass the ASRC would be brilliant and something I wanted since building the first Ezdac.
Some form of switch would be very convenient IMO
Having the option to bypass the ASRC would be brilliant and something I wanted since building the first Ezdac.
Some form of switch would be very convenient IMO
00940 said:
The system clock from the 2707. For the 12MHz it uses a Kwak 7. Made quite a difference.
analog_sa said:
Thanks 😱
Now... if you could play with different I/V stages, different PS, we'd know all we need to know about the possibilities of those chips
00940 said:
Thanks 😱
Now... if you could play with different I/V stages, different PS, we'd know all we need to know about the possibilities of those chips
Not really. You'd just have another subjective opinion...
But since you're asking 🙂 I tried separating the analog and digital supplies on my AD1852 dac with very good results. Used an ALW Jung for the analog side.
IV conversion effects have been examined in detail many times. Ezdac's solution seems to work very well and is pleasingly minimalistic.
I guess a tube diff amp following the same concept will work just as well and probably better if you'd be willing to deal with heat, additional PS and coupling caps.
t. said:
Note that he used an Abracon smt XO. It seems to have worse jitter specs than the Crystek part that I specified in the XO. However, I may not be comparing apples-to-apples. The crystek part specifies 12kHz-80MHz at 0.5 ps typical, 1 ps Max. The Abracon part gives period jitter at one sigma (1 std dev?) as +/- 25 ps Max. It's like they do this on purpose to make it difficult to compare parts.
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