Extreme X-DAC v3 mods by sandyK

[dejanm]

SandyK,

I understand your point about transformers at the output. I do remember that you are not a fan of transformers at the signal path. Your explanation is a typical remark about it and it is not unreasonable. Actually it is absolutely true that it does not have the frequency throuput as some other solutions. But you know .... sometimes you have to lose on one side in order to get something else on the other. But let's not discuss it further ....

Thank you very much for your kind offer but it is really not necessary because I have some high resolution flac files. Also there are some that you can download (you have to pay for it) from Linn site and they are in 24/192 resolution. I heard them on a very good system (TAG + Audioplan where the PC was a source) and that is ... I do not know how to describe it ... somethinmg very special. Extraordinary reproduction.

Does DAC V3 receiver has the capability to receive 24/192 or is it limited to 24/96 ?

[Deleted]

Dejan
You may have also noticed that Robert has now also greatly widened the bandwidth of his SC HA ? His FB capacitor has now been reduced from 1,200pf to 33pf.
"I have opened the HF response using 33pf polystyrene's now arrives at an AV = 2 at ~ 3Mhz and gently slopes to unity way past radio Moscow on the short wave band "
Anyway, getting off that, the MF X-DAC V3 can only go up to 24/96 , althought it does upsample to 24/192
Alex

[dejanm]

Nov 1, 2009 9:20:58 GMT @sandyk said:

Dejan
You may have also noticed that Robert has now also greatly widened the bandwidth of his SC HA ? His FB capacitor has now been reduced from 1,200pf to 33pf.
"I have opened the HF response using 33pf polystyrene's now arrives at an AV = 2 at ~ 3Mhz and gently slopes to unity way past radio Moscow on the short wave band "
Anyway, getting off that, the MF X-DAC V3 can only go up to 24/96 , althought it does upsample to 24/192
Alex

Thanks for your kind answers ...

[robvanaalst]

Alex,

I just saw in photo 3 that you also replaced the bi-polars C111 and 211. What did you use?

Thanks,

Rob

[Deleted]

Rob
The output capacitors have been bypassed. Although the AD8065/AD8066 have a little higher DC offset than later types, it is quite easy to null the remaining small DC offset to a minute amount by fitting a VERY high value resistor in paralllel with the appropiate resistor out of R3 and R4 in fig.34 as shown in the DSD1792 data sheet, if need be.
Alex

[Deleted]

Mar 24, 2010 4:06:31 GMT @sandyk said:

Rob
The output capacitors have been bypassed. Although the AD8065/AD8066 have a little higher DC offset than later types, it is quite easy to null the remaining small DC offset to a minute amount by fitting a VERY high value resistor in paralllel with the appropiate resistor out of R3 and R4 in fig.34 as shown in the DSD1792 data sheet, if need be.
Alex

P.S.
replacing C19 and C20 with polypropylene types makes a further worthwhile improvement.(68nF and 8.2nF) They are part of the PLL filter circuit from pin 22 of the DIR1703E.
(This was a recent "flow on" finding from the SC DAC.)

[robvanaalst]

Thanks Sandy!

I had already bypassed the output caps... no audible noise on my system...

By the way, for the JLH PSRR I ended up tossing the 2x4700uF 10V caps. 8x1200uF 10V low ESR (Panasonic FM) per V-rail turns out to be overall cheaper and the ESR is much lower because of the parallel configuration. ESR is now 2mO per rail and it sounds great! PCB is a tat bigger...

[Deleted]

Mar 26, 2010 12:37:02 GMT robvanaalst said:

Thanks Sandy!

I had already bypassed the output caps... no audible noise on my system...

By the way, for the JLH PSRR I ended up tossing the 2x4700uF 10V caps. 8x1200uF 10V low ESR (Panasonic FM) per V-rail turns out to be overall cheaper and the ESR is much lower because of the parallel configuration. ESR is now 2mO per rail and it sounds great! PCB is a tat bigger...

Rob
Sorry, but I missed this reply. Originally, I used 4 x 1,000uF per rail for the same reason. Back then, low ESR caps were not available.
You need to be careful though that sibilance doesn't become a little worse when using so many low ESR caps in parallel.
Alex

UPDATE.
This morning I replaced the 24.576MHZ Oscillator module with a 1PPM TCXO version that I bought from ebay. Because the TCXO version is larger, (14 pin DIP instead of 8pin DIP) I needed to relocate the ceramic capacitor near pin 1 of the module to underneath the PCB. I didn't worry about trying to make an adaptor PCB, as this would have resulted in additional stray capacitance, but instead I extended the leads on pins 7 and 8 of the new module. The hardest part of the operation was removing the old oscillator module !
It sounds great! "Papa Doo Run Run-California Project" is the best that I have ever heard it. Everything is more 3 Dimensional , and the low end appears to have more impact as well.
Not too bad for around US$27.50 all up.

[leeda]

Hi:

I have just joined this great forum (having just purchased a X-DAC V3 with walwart PS - it arrives next week).

Jaycar kit
I have read through this mod thread but its not clear if anyone has actually built the regulated PS based on the plans & jaycar parts. Does the Jaycar kit come with a PCB board?

I am in the US (120V) and I noticed the recommended MT2086 toroidal transformer requires 240 V on input to get the 15V output. Any other suggestions? What am I missing here>

Big Computer Printer Walwart
What about using a much bigger and better walwart. I have an older computer printer walwart (the size of a brick) that would seem to be much better regulated that has +/- 12V DC (400ma) on the outputs. I could also use the 5VDC output on this bigger walwart to get rid of the cheapo walwart for my squeezebox player.

Is this a 95% solution to my problem? Your thoughts?

Regards,
Lee

[Deleted]

Apr 24, 2010 17:06:07 GMT leeda said:

Hi:

I have just joined this great forum (having just purchased a X-DAC V3 with walwart PS - it arrives next week).

Jaycar kit
I have read through this mod thread but its not clear if anyone has actually built the regulated PS based on the plans & jaycar parts. Does the Jaycar kit come with a PCB board?

I am in the US (120V) and I noticed the recommended MT2086 toroidal transformer requires 240 V on input to get the 15V output. Any other suggestions? What am I missing here>

Big Computer Printer Walwart
What about using a much bigger and better walwart. I have an older computer printer walwart (the size of a brick) that would seem to be much better regulated that has +/- 12V DC (400ma) on the outputs. I could also use the 5VDC output on this bigger walwart to get rid of the cheapo walwart for my squeezebox player.

Is this a 95% solution to my problem? Your thoughts?

Regards,
Lee

Lee
The PSU used is virtually the same as us used in the "Silicon Chip Headphone Amp Tweaks" thread.It uses a Jaycar KC5418 PSU kit, although other locally available PSU kits with +-15V DC output at 1A will be suitable.
www.jaycar.com.au/productView.asp?ID=KC5418&keywords=kc5418&form=KEYWORD
The Transformer that I used for a U.S.A. version was a dual primary Clairetronics toroidal transformer from RS Components. Due to their weight, it would be advisable to purchase a 30VA 15-0-15VAC toroidal transformer locally.(Forget Digitech!) If you use a dual primary version, you connect both primary windings in parallel. e.g. 117 + 117
Looking at the diagram printed on the transformer, the top of the 1st primary winding will connect to the top of the 2nd primary winding, and the bottom of the top primary winding will connect to the bottom of the 2nd primary winding.
The JLH as shown has now been upgraded to use 2 x 4,700uF 10V low ESR capacitors in parallel per supply rail instead of the original 2 x 2,200uF 10V low ESR per rail. PCBs for this MAY become available soon from RG.You can either fit a 3 pin socket to the power supply with a suitable home made lead going to a 3 pin DIN plug, or wire a captive 3 wire lead to a 3pin DIN plug. The centre pin of the 3 pin DIN plug MUST be the 0 volts or EARTH wire. In the unmodified X-DAC V3, this power will be then correctly steered via internal diodes.
Using the attached photo as a guide, the supply to the X-DAC V3 would come from the LHS of the JLH.With the PSU for the X-DAC V3, it would be better to turn the JLH around the other way.Any new JLH PCBs are likely to take screw connectors at both ends.
The transformer shown was used for testing before fitting a U.S.A. version with dual primary windings.




Alex
P.S.
Your other idea is likely to give disappointing results as the voltage is too low, and the results may then be even worse than using the original supplied wall wart.

[Deleted]

The JLH as shown has now been upgraded to use 2 x 4,700uF 10V low ESR capacitors in parallel per supply rail instead of the original 2 x 2,200uF

Hi Alex

Is this now standard for JLHs or just in the X-DAC, I presume Suntans again?

Any point or problem using higher voltage so that only one stock of caps necessary? I haven't found Suntans anywhere but Australia.

Thanks, Syd

[Deleted]

Apr 29, 2010 12:55:54 GMT @juke said:

The JLH as shown has now been upgraded to use 2 x 4,700uF 10V low ESR capacitors in parallel per supply rail instead of the original 2 x 2,200uF

Hi Alex

Is this now standard for JLHs or just in the X-DAC, I presume Suntans again?

Any point or problem using higher voltage so that only one stock of caps necessary? I haven't found Suntans anywhere but Australia.
Thanks, Syd

Hi Syd
The difference is only small when changing to the 4,700uF, but I feel it is worthwhile,especially when using any JLH at a higher current than 100mA.
You can use 10V or 16V low ESR types. Even 25V may be O.K. these days, but make sure they aren't physically too large to fit the PCB. Stay clear of the so called "Audio" types, as they are usually less than neutral sounding.Samxon is another very good brand that I have tried.


Alex

[Deleted]

Thanks Alex, I googled around for Samxon but few results, non in UK.

So I've placed an order at Jaycar again, got some of 10V and 16V.

Syd

[robvanaalst]

Hi Alex,

Thanks for your tip to upgrade the TCXO. I found a 0.3ppm for the same price as a 1ppm and was a bit surprised to hear such an improvement over the stock 25ppm.

I recently replaced the four OPA2134 with the OPA1612 a friend gave me. Most noticeably improvements are in the low frequency's. The OPA1612 has extremely low noise and distortion combined with a high bandwith. I will also change out the AD8066 with this one once I get some more and see if it improves even more.

I also designed and built an integrated pcb for both a regulated power supply and the JLH ripple eater (adding the JLH is still the single biggest improvement in my opinion). I'm planning to have the digital circuitry separately fed from the analogue part with a additional power supply/JLH. Although I don't expect a huge improvement, because of the pretty well designed 5v power regulation on board, I still want to try it; I've been surprised before. Or did you already try this?

Rob

[Deleted]

Sorry, but i missed this reply.I must make sure I look further than the previous 20 posts all the time.

Hi Rob
Yes, the adding of the JLH makes a major contribution.
Did I mention that I am now using the metal can LM4562HA at the output? This change was recommended by a friend with a similarly modified X-DAC V3. It gets rid of the BB "house"sound.
Did you notice with the TCXO that it sounded pretty average, then after playing several songs after switch on, that you would suddenly be aware of a major improvement? The 5V area is well designed. Due to space constraints I didn't try a separate JLH preceded by a 7805. I did however try bypassing the series diode, and changing the big electros to 100uF , which I thought would give more benefit from the existing JLH. It sounded decidedly worse !
I am not game to further play around with the other I.C.s as the tracks are damn thin, and I didn't fit I.C. sockets when I replaced the 5532s. In any case, my modified version of the Silicon Chip magazine designed 24/96 DAC is now quite a bit better.Heaps of JLHs and 2 PSU PCBs in it , although both PSU PCBs are fed from a single transformer. My X-DAC V3 is now relegated to the PC, where it does a great job.
Regards
Alex

[robvanaalst]

Alex,

Yes, it was weird how the new TCXO "kicked in" after a couple of songs.

I like the idea of the metal cans...

Hard to believe your Silicon Chip magazine designed 24/96 DAC is even better than the X-DAC (which sounds superb now).

I'm very interested in building this unit... Do you have an overview of all your final mods posted somewhere?

Thanks a bunch,

Rob

[Deleted]

Oct 19, 2010 11:11:54 GMT robvanaalst said:

Alex,

Yes, it was weird how the new TCXO "kicked in" after a couple of songs.

I like the idea of the metal cans...

Hard to believe your Silicon Chip magazine designed 24/96 DAC is even better than the X-DAC (which sounds superb now).

I'm very interested in building this unit... Do you have an overview of all your final mods posted somewhere?

Thanks a bunch,

Rob

Hi Rob
I wouldn't say final mods as yet, but the last post at the link gives pretty well the current state of play, although the photo is not up to date. The vast majority of the changes have been verified as improvements by several other RG members.
A couple of the expensive Paul Hynes 3.3V series regulators could be a future option. A friend of mine in Sydney bought one of the last few of the remaining complete kits from Altronics last Saturday.
I do not know the current availability of the Jaycar short form kits.Both vendors kits come with the DIR9001 and DAC already mounted, so no fiddly SM work is required.

Alex

rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=5237&page=2

P.S.
Greg Erskine has heard mine, and is also building one.

[Deleted]

Alex



My new oscillator has arrived. I saw in your post that you mention various pin numbers, I only have 4! I haven't started this mod yet, will this one be OK? Its about 17x10x7.

Thanks,

Syd

[Deleted]

Nov 2, 2010 19:12:07 GMT @juke said:

Alex



My new oscillator has arrived. I saw in your post that you mention various pin numbers, I only have 4! I haven't started this mod yet, will this one be OK? Its about 17x10x7.

Thanks,

Syd

Syd
That will be fine.
The pinout is the same, but because the oscillator is longer, you will need to extend 2 of the leads by cutting the leads off a surplus resistor or something, and then gently bend them back towards the centre , and sleeve the leads.You will need to relocate a capacitor (C40) at one end to under the PCB to fit it in due to the longer length.The hard part is removing C40 !
Alex

[Deleted]

Job done! That turned out a lot easier than I had feared. It has made a really noticeable improvement. Even more detail than previously and the bass is going much deeper. For such a simple mod its a massive return

Thanks again Alex, surely there can't be anything more to come from this little box???

Syd

[Deleted]

Nov 3, 2010 0:22:36 GMT @juke said:

Job done! That turned out a lot easier than I had feared. It has made a really noticeable improvement. Even more detail than previously and the bass is going much deeper. For such a simple mod its a massive return

Thanks again Alex, surely there can't be anything more to come from this little box???

Syd

Syd
Good work !
Did you notice that it took several minutes to reach it's best, then "lock in." ?
When I get sick of fiddling around with the SC DAC, I will have another look at the X-DAC V3.
I think you will agree that it's performance is a far cry now , from the original stock unit ? The JLH in the external PSU can take quite a bit of the credit too.
Regards
Alex

[robvanaalst]

After all the mods, including the metal can opamps and the 0.3ppm OSC, I considered building the SC DAC. Looking at the DAC chip I found that the chip in my X-DAC has a better S/N ratio, and further not much different. Why then the claim that the SC DAC sounds so much better? Looking at Sandy's scheme, I saw a lot of JLH's... Might that be the difference? So I chose to hook everything in my X-DAX up to separate shunt regulated power supplies with separate torroids.

1x-15-0+15 for the opamps, one 5.5 volt for the analog part of the dac chip, one 5v for the digital part and one 3.3 for the the I/O board (yes, 4 regulators + 4 torroids). I restored the opamp rails back to 15V, and lowered the 2 100uF elco's to 36.

(I used the twisted pear Placids for shunt regulators)

I would say the improvement is VERY, VERY substantial.

[Deleted]

Nov 11, 2010 20:32:06 GMT robvanaalst said:

After all the mods, including the metal can opamps and the 0.3ppm OSC, I considered building the SC DAC. Looking at the DAC chip I found that the chip in my X-DAC has a better S/N ratio, and further not much different. Why then the claim that the SC DAC sounds so much better? Looking at Sandy's scheme, I saw a lot of JLH's... Might that be the difference? So I chose to hook everything in my X-DAX up to separate shunt regulated power supplies with separate torroids.

1x-15-0+15 for the opamps, one 5.5 volt for the analog part of the dac chip, one 5v for the digital part and one 3.3 for the the I/O board (yes, 4 regulators + 4 torroids). I restored the opamp rails back to 15V, and lowered the 2 100uF elco's to 36.

(I used the twisted pear Placids for shunt regulators)

I would say the improvement is VERY, VERY substantial.

Hi Rob
A friend of mine actually has his X-DAC V3 fitted in a 1U rack case in order to get the PSU closer to the PCB.
If any SC DAC builder is adventurous and capable, the 1792 DAC as used in the X-DAC V3 can also be fitted to the SC DAC with further improved results, and only a few minor resistance value changes.
Power supply is everything,whether with a DAC, a preamp, or an amplifier.
To me, the main advantage of the SC DAC, is the nice wide open layout. I have a feeling that your verion of the X-DAC V3 would give the Buffalo 11 a real run for the money.Even those monsters with all the PH regs and transformers !
Are you able to take some photos and post them ?
Regards
Alex

[robvanaalst]

I couldn't embed the pics, so here are the hyperlinks:

1) Replacing the four OPA2134 with the OPA1612. Most noticeably improvements are in the low frequency's. The OPA1612 has extremely low noise and distortion combined with a high bandwith. Using the metal can LM4562HA at the output for further improvement. All opamps are soldered to DIP8 converters and pushed into the dip8 sockets.
picasaweb.google.com/lh/photo/4yG84K3zGNNxrMfCQDwU7w?feat=directlink

2) Replacing all relevant bypassing caps around the opamps with polypropylene 2% tolerance or better. The the biggies are soldered under the board.
picasaweb.google.com/lh/photo/w6YNfQ0og3R_v3ZUkyEb2g?feat=directlink

3) 4 separate regulated power supplies (I used the twisted pear Placids for shunt regulators) 1x -15-0+15 for the opamps (see pic 1.), one 5.5 volt for the analog part of the dac chip, one 5v for the digital part and one 3.3 for the the I/O board (yes, 4 regulators + 4 torroids). I restored the opamp rails back to 15V, and lowered the 2 100uF elco's to 36.
picasaweb.google.com/lh/photo/0401mpQv9Q38TM6zWHj8jQ?feat=directlink

4) cramming the 14 pin 0.3ppm OSC in a 8 pin place and the replacing the 68nF and 8.2nF by 2% tolerance polyprops (the grey one under the board (see pic 3.), the orange one on top.
picasaweb.google.com/lh/photo/eWDvdZjf0NemLmG7pjc0wQ?feat=directlink

[XTRProf]

Nov 11, 2010 20:32:06 GMT robvanaalst said:

After all the mods, including the metal can opamps and the 0.3ppm OSC, I considered building the SC DAC. Looking at the DAC chip I found that the chip in my X-DAC has a better S/N ratio, and further not much different. Why then the claim that the SC DAC sounds so much better? Looking at Sandy's scheme, I saw a lot of JLH's... Might that be the difference? So I chose to hook everything in my X-DAX up to separate shunt regulated power supplies with separate torroids.

1x-15-0+15 for the opamps, one 5.5 volt for the analog part of the dac chip, one 5v for the digital part and one 3.3 for the the I/O board (yes, 4 regulators + 4 torroids). I restored the opamp rails back to 15V, and lowered the 2 100uF elco's to 36.

(I used the twisted pear Placids for shunt regulators)

I would say the improvement is VERY, VERY substantial.

Yup, some photos (especially the 4 toroids with shunt regulators and where you cut copper traces ) please as I'm sure that will "murder" the SC Dac big time. I had been wanting to do that for a long time but no time.

Thanks.