X-ACT DAC

[PinkFloyd]

Anyone familiar with the MF X-ACT Dac? I got one secondhand today and must admit I was pleasantly surprised when I went under the bonnet. Unlike some of the other X-Ponents this guy has a double sided PCB with through plated holes, very nice indeed!

She sounded a bit syrupy (but very listenable) so I've recapped her with a mix of starget, Pana FC / FM and a couple of nichicons here and there... burning in now and no apparent improvement as yet, will probably go in again and play about with a few different opamps, comes with philips NE5532 as stock. I must say for £70 it appears a bit of a bargain and looks highly tweakable... will add more to this thread as I progress with her.

More on it here (manual download is there) www.hifiengine.com/library_model.php?make=Musical%20Fidelity&selected_model=X-Act

[PinkFloyd]

a few pics

[rickcr42]

I have some damn where a lot of the original ad copy/factory specs/opinions for this DAC so if found will add some general content to this thread for prosperity.
Had gathered it while looking for a cheap DAC years ago to mate with my 50+1 Pioneer CD Jukebox that I loved for it ability to play for hours and hours (load it,set to random play,forget it) but was not happy with the sound of.The X-DAC was a finalist along with the DITB for El Chepo Dacko with the DITB winning by a nose

[rickcr42]

Tough question,tough answer Stefan

My present personal benchmark DAC is a very expensive to build "bastardization" of the Audionote Kit 1.1 digital section (DIY from the Audionote schema) and Yuri's "Retro DAC" analog section (ditto).

big,heavy,expensive,sounds great

I also have in system a tiny little Dac In The box (my DITB referenced here in threads many times) that is modded a bit to come damn close to the above for pennies in comparison.I call this my "DAC Sandwich" due to the original DITB being sandwiched in between a +/-8 VDC @ 2A per power supply box (bottom) and a new output/IV stage box (top) for a creating a 6x6x6 cube when stacked.

Tiny,cheap,sounds great

DAC #1 is a zero OS type,uses the ADI AD1865 DAC chips,has a triode output section

DAC #2 is 8X OS,uses the ADI AD1851 DAC chips and has a totally passive resistor/Sowter Transformer analog section (IV/line out) and is fed from a HagUSB clone with a couple of mods :

1-selection of USB/External power for home/portable use
2-SPDIF select so I can use a CDP "pass through" or the USB DAC to feed the above


I could live with either one with each having been tweaked to personal taste so sounding more alike than dissimiliar though there is a lot to be said for the smaller DAC due to the ability it has to swap out the power supply for battery operation combined with a small size that can fit anywhere-desk,rack,backpack (loses the external power box section goes to battery pack powering),etc.................

[rickcr42]

....upon further reflection (second cup of java ) if you are doing a DIY transport then I2S and "one box" would be your best solution as it eliminates a major source of jitter-the SPDIF interface.

Aftermarket add-on DACs are great for upgrading comprimised CDP digital sections but should be beat by a properly designed "it's in the box jerky" DAC because it eliminates any need for a digital transmitter or digital receiver there being nowhere to transmit TO.The strength of I2S is it has individual lines for digital signal and clock that in an SPDIF connection are kinda/sorta multiplexed into a single stream (spdif xmit) that is sent over a distance of cable to the DAC which has the demodulator part (spdif rcv).all of which are totally not needed when the transport digital and DAC sections are in close proximity as they would be in an all-in-one unit hence taking advantage of the strengths of I2S which is a better interface while avoiding its weaknesses which is transport to DAC connection length

[rickcr42]

something like this may be useful for a DIY Transport/DAC as a CDP

www.audiokit.ro/I2S.html

[PinkFloyd]

Hi Rick,

This one I have is not the X-DAC, it's the X-ACT. I believe the X-ACT was a slimmed down cheaper version of the X-DAC.

A quick look under the bonnet reveals Sanyo LC78835 18 bit digital filter and D/A convertor, Sanyo LC8900K digital audio interface receiver, ST M74HCU04 high speed complimentary metal oxide semiconductor (CMOS) and a Motorola MC74HC86N quad 2 - input exclusive OR gate..... oh, and a Philips NE5532.

X-ACT

[xerxes]

For an all in one box solution, how about this: www.tentlabs.com/Products/diycd/index.html

Mr Tent seems to know a fair bit about CD player design, so I reckon it should sound pretty good.

[rickcr42]

This one I have is not the X-DAC, it's the X-ACT. I believe the X-ACT was a slimmed down cheaper version of the X-DAC.

meant X-
act but for some reason X-DAC came off the keyboard ;D

A quick look under the bonnet reveals Sanyo LC78835 18 bit digital filter and D/A convertor, Sanyo LC8900K digital audio interface receiver,

Why I ended up with the DITB and not X-ACT.Even though at the time I knew very little about digital audio and in spite of the good reviews for the MF DAC I was not comfortable with a product that used such a non standard chipset,one found in no other product I could find.I went with the AA product using the AD1851 that looking back now armed with a bit more knowledge (not much but a bit ) would have instead gone one up in the lineup to their DAC using the AD1862 which was likely the best DAC chip ADI ever made yet is obsolete while the AD1851 succesor,the AD1861 is still being made......weird

Mr Tent seems to know a fair bit about CD player design, so I reckon it should sound pretty good.

Late to the party again Owen,I posted a link to that over a month ago ;D

and hell yes Mr.Tent knows a bit about CD Players having posted the most complete website on DAC design in existance with full "why i chose this way" years ago and the Tent Clocks are considered among (if not the) best available to modders

[jelosno]

interesting that Tent uses the I2S only in his CDP.

all the upgrade modules run the classical SPDIF if I understand that correctly...

VERY TEMPTING such a top loader CD transport..... 2100 Euros for the DCP kit and 1500 Euros for the Transport kit alone and that does not come with the I2S module...
All excl. VAT and shipment of course... ;D

found that link about a DIY DAC. I think it was linked from the Tentlabs site...

members.chello.nl/%7em.heijligers/DAChtml/dactop.htm

and the DIY CDP
www6.head-fi.org/forums/showthread.php?t=102583

[rickcr42]

interesting that Tent uses the I2S only in his CDP.

all the upgrade modules run the classical SPDIF if I understand that correctly...

ALL CD players is a direct interface that depending on the chipset will be either I2S or EIJ (probably misspelled that,fk it )

SPDIF is only used to get the signal OUT of the box and is a comprimised solution originally being designed to TEST digital.When the first aftermarket DACs began to appear there was a need to get from A to B (CDP to DAC) and it was the SPDIF interface that was chosen but this way before the effects of jitter were known.as with most things (RCA Jacks a good example) once a connection becomes a "standard" it does not matter if that standard is seriously flawed or not and whey with RCA we are still over fifty years out trying to improve on it and with SPDIF the same (spawned the market for jitter-reducers among other things )

why is SPDIF flawed ?

Because it takes the original individual raw digital DAT and CLK lines then combines them into a single stream (Transport ) that must be separated at the receiver end (DAC) back into individual lines.Think FM multiplex or modulator/demodulator to get a sense of it.
Any time you take a thing and convert it to make for economical signal transmission that must at the other end be "De-converted" you have added steps that can screw with the signal integrity and while digital audio does have error correction steps included in the original format they are not enough to correct the little things like jitter which is more of a distortion than an error.

So we can make great DACs but the problem is getting a good jitter free signal to them and that is no small feat considering how many areas there are for it to enter into the equation and why folks need to pay as close attention to the interface in their DIY efforts.

"it's all in the box jerkweed" CD Players can also have jitter but is more easily conquered being mostly mechanical in nature (chassis density/mass,rack isolation).Take care of the CD loading mechanism (why top loaders are better than drawer loaders),the laser to disc integrity then chassis to outside world coupling and if the circuits are good there should be little or no jitter in a CD Player

Adding the SPDIF transmitter,spdif cable toslink,coax,AES3),SPDIF receiver between the raw digital and digital to analog conversion process allows errors to enter that would otherwise not be there in the closed system

found that link about a DIY DAC. I think it was linked from the Tentlabs site...

that's the one.A good read.....

and the DIY CDP

One day I will go that route (DIY CDP) if I can ever find the time/focus to get 'er done.Digital is not my favorite format (I place it third after 15 IPS analog tape and vinyl playback ) but it is here and to stay so I have no choice but to make the best of it (some salt pepper and ketchup on my shit sandwich ) and the best of it is that route keeping my other "DAC" strictly for USB.

[rickcr42]

BTW Stefan,here is a DIY project article that I personally have always thought would be nice as the DAC section in a DIY CD Player.

www.geocities.com/agalavotti/zerodac.htm

[rickcr42]

www.werple.net.au/~gnb/mac-cdis/index.html

[jelosno]

would be nice as the DAC section in a DIY CD Player.

hmmm, with enough patience and reading I might be able to complete something like this. No timeframe mentioned here of course. ;D

compared to this one
www.pedjarogic.com/1541a/rev1.htm
as used in the DIY DCP mentioned above it seems relativly simple. Note the use of the words 'seems' and 'relatively'.

I actually like the sound of my CDP. Might be due to the tube output buffer stage used. The Pro2 drive and the use of the I2S signal/protocol, the advanced clocks.... all sooooo tempting..... It is just so easy to talk oneself into believing that dynamics, resolution, space and everything will increase dramatically - isn't it??

Stefan

[rickcr42]

It is just so easy to talk oneself into believing that dynamics, resolution, space and everything will increase dramatically - isn't it??

has created a serious industry in aftermarket parts,some with merit,some not so they make up for it with an abundance of words to confuse while nailing home certain phrases you know mean it is good but would be hard pressed to say exactly why

Pedja's DAC has been somewheat superceded by another version that is specific to a dedicated "Yahoo Groups" page.If interested I can send the link but you will need to sign up to see the files

[rickcr42]

tech.groups.yahoo.com/group/tda1541a_dac/?yguid=175486106

actually not a whole lot there in the files section but the threads are full of info that when combined with the original site flesh out the DACs design.

[jelosno]

That is why I linked to his 'number two' or 'the revised one'.

Just wanted to highlight the complexity.

He mentions on his site that he will not publish his new design because it was not only picked up by the DIY community. I guess that it went - in whatever implementation - into commercial equipment.

On his homepage there is the link to his company where he will market his new design.

AFAIK the stand alone DAC only works with SPDIF and USB input since the interconnects from the digital sourche to the DAC itself is rather long.

I2s will - according to what I have read so far - only work over very short distances like withing a CDP.

I have found supplies of the TDA1541 (correct?) for about EUR 9 and the 'A' version Pedja is using for EUR 17.
Is the A-version a double 16 bit unit while the non-A is a single one?
Anyway, very hypothetical this all since I will never be able to design a DAC until I will study this for a couple of years ;D

I wouldn't mind to build a kit one that has won its merits already. I am in no situation to judge from the layout whether the DAC might be promising or not.

The clock replacement of Tentlabs seems to be a accepted way to improve things though.

Rick, have you put something like a secret message (like the backwards recorded stuff on LPs) or a spell onto this board?

Me being the mister stainless steel box is thinking of wooden front panels to be put on to existing and upcoming equipment. VERY strange that!

Stefan

[rickcr42]

He mentions on his site that he will not publish his new design because it was not only picked up by the DIY community. I guess that it went - in whatever implementation - into commercial equipment.

On his homepage there is the link to his company

did not know that.I do try to keep on top of such things being an information junky but being one guy and getting a bit old I do have periodic slips (hard as that may be to beleive for some )

If the product is going commercial I say "about damn time" and glad to hear it considering how many have made their name/fortune,their "look what I designed" using the content on that site.Content that is very detailed,well thought out,explained in detail and that has been an evolution over years.

I remember the original threads (a Gainclone forum ) in which the Scott Nixon DAC was designed with the design being a group effort of sorts in the very beginning but as soon as he had a viable pc board went straight to sales and a supporting site ! No fkn around there !

Like with the Gainclone being an attempt to re-create the 47 Labs Gain Card the "Clone DAC" was a try at recreating the Kusunoki inspired 47 Labs Non-OS DAC.The first actual viable pcb design to come out of the discussion was the one shown here at the RJM site

www.geocities.com/rjm003.geo/rjmaudio/diy_dac.html

still a viable design,very simple to build and having more in common with the Nixon DAC that the Pedja DAC which has been evolving over time from simple/basic to fully engineered DAC (though which sounds better ? I think i would go with ultra simple being me but use the Pedja/Jocko spdif section,possibly reclocking.......)

Pedja who also was involved in those threads (among others who would be recognised) continued to explore and experiment with all the details freely posted while the sales for the Nixon DAC racked up so he deserves to get something back other than glory.bill gotta be paid no matter who you are ;D

I2s will - according to what I have read so far - only work over very short distances like withing a CDP

Probably what held it back from becoming the standard.Complexity/transmission distance without adding more circuitry

I2S=Inter-IC Sound

Developed by Phillips while as far as i know SPDIF was developed by Sony

www.nxp.com/acrobat_download/various/I2SBUS.pdf

"One chip in the I2S Bus system generates a Master clock, while all other devices derive their internal clocks from this reference. Standard clock rates include: 32KHz, 44.1KHz, or 48KHz [or multiples of these]. Data may be sent MSB first or LSB first. The word length is adjustable up to 28 bits. Synchronization with the data words may also be set to either the rising or falling edge of the clock. "


.There was a time when it was a near miss on that with a couple of companies,noteably Audio alchemy,having I2S connectors for interconnecting their digital audio products that it seeems worked quite well but we are talking about consumer audio where cost is the determining factor and with the lowly RCA jack spdif connector (mostly not even properly terminated) as the competition with a complex interface with higher parts count there never really was much of a chance for it to succeed.
A shame considering the possibilities of having access to individual lines for digital buss interfaces (DSP devices,microprocessor control,jitter reduction in software,buffering the signal in SRAM and clocking out of THAT instead of using the raw stream directly....)

I am no expert by a long shot but I do know a good thing when I see it and this had potential that by now would have been fully realised as viable had that path been taken early on.

If AA had lasted or if some of the other companies using the format stuck with it maybe things would be different and we would have not only one standard but a fully matured technology where we could just add in parts to the digital signal path as the need/desire arose.Sadly there IS NO STANDARD and that alone will kill the goose laying even golden eggs.

www.audioasylum.com/audio/digital/messages/123609.html

AFAIK the stand alone DAC only works with SPDIF and USB input since the interconnects from the digital sourche to the DAC itself is rather long.

in order of cable transmission length from least to most :

1-I2S
2-coax
3-USB (can be extended with repeaters)
4-Optical

Anyway, very hypothetical this all since I will never be able to design a DAC until I will study this for a couple of years

by that time we may all have implants directly to XM Radio

Rick, have you put something like a secret message (like the backwards recorded stuff on LPs) or a spell onto this board?
Me being the mister stainless steel box is thinking of wooden front panels to be put on to existing and upcoming equipment. VERY strange that!

Subliminal.Before you know it I will have you barking at the moon naked wondering what the hell happened and just when it was you went whacko

[rickcr42]

BTW-an example of using the I2S buss for all things digital audio

www.analog.com/UploadedFiles/Application_Notes/217090061AN_21065L_I2S.pdf

[jelosno]

did not know that

that is what i have read 'between the lines'. He is not clear about this. To my understandig it is what he's referring to.

I had a look on the other designs. What I liked about the TNT one was that it had no PCB. So doing one of those requires the parts only. Nice.

What I don't like is that it uses SPDIF.

For the DIY CDP I think I will go the following route:

• Top loader.
  
• This will be the Philips PRO drive.
  
• Pro drive provides I2S out.
  
• TDA1541A or nonA will accept I2S dircetly.
  
• A TDA1541A per channel is agreed by most to be better than a single unit handling left and right channel

I will use it for CD playback only so

• the DAC can be inside the CD transport chassis
  
• there is no need to make provisions for SPDIF
  
  
  
  
• The clock is very important.
  
• Tentlabs makes a excellent clock, at least what I did find on the internet in that regard.
  
  
• Output buffer will be tubes.
  
• Power supply seems to be very important and can hardly be oversized.

YUP, looks like a Tentlab CDP but their price for the complete kit unit is somewhat prohibitive.

I might order some TDA1541(A)s in the near future just to be on the safe side since they are a discontinued item.

Stefan

[xerxes]

I've been thinking about a USB DAC so I can compare uncompressed, EAC ripped WAV files to original CDs.

TentLabs mentions that the their CD PLayer will later include an optional SPDIF and USB input module, making it a one box CD player and external DAC that would allow me to compare USB input to original CDs very easily.

If I prefer the USB input, I could copy my favourite CDs to hard drive, but to save space use the internal CD drive for those CDs which I only listen to very infrequently. On the other hand, if I prefer the sound of the internal CD drive, I could still store some CDs on a hard drive and use them with the USB input when I want the convenience of making up a playlist. Either way the TentLabs player will be useful and neither part of it wasted.

I reckon the TentLabs CD player/DAC will be pretty good, probably equal to or better than many more expensive "ready made" products and as such, while it's fairly expensive, it probably represents good value for money. Once the SPDIF/USB input module becomes available I'd be very interested in this player and may well save up some pennies for it, so if you get one I'd be very interested to hear your impressions, not only of the sound, but also the general details about the kit, how it is to build etc.

[rickcr42]

I might order some TDA1541(A)s in the near future just to be on the safe side since they are a discontinued item.

years ago

the surprising thing is just how many are still kicking around

looks like a Tentlab CDP but their price for the complete kit unit is somewhat prohibitive

Expensive yes if just looked at as a DIY project.Overpriced ?I woud say no considering the source which say completed design and fully engineered rather than just some hobbyist coming u with an idea and trying to cash in.
Tent Labs will not be going anywhere (like off to college with loot made at the kitchen table workshop ) so there will be support networks in place and someone at the other end of the phone/email.

When you buy from a hobbyist they are selling you parts.From an engineer a product that took many hours on the bench to get right then set up parts suppliers to make sure the shipments flow without interupption AND spend up front to have enough stock to sell the product withgout the "will be a while before it gets to you,waiting for the parts".Such folks are in it for a means to make a living rather than as a hobby/means to make a couple of bucks so you know it will WORK and without weeks of asking questions in forum hoping you get the right answer. ;D

Having said that I am a really cheap bastard and like to wing it more often than not-gathering my own parts to build my own "cobbled" designs-and because of that my projects can take MONTHS to complete due to all the various sourcing problems like no single outlet for all things or the dreaded "out of stock" which usually leads to dust gathering due to loss of interest or just not enough time to pull it together.

Must be ten (or more ;D ) unfinished projects on the bench as I type this.Start one.wait for parts,while waiting start something else,wait for parts again,staret another project to pass the time,look at the bench and realise I am buried in halfsies then walk away totally until my attitude is better

the DAC can be inside the CD transport chassis

best way all thing considered

there is no need to make provisions for SPDIF

could be added later if you leave room inside the box for a SPDIF transmitter.Never hurts to have access to the outside worldf for future "unforseens".Could also add an I2S connector

The clock is very important

.

yes.as is the power source TO the clock

Tentlabs makes a excellent clock, at least what I did find on the internet in that regard.

again a completed design rather than open ended project and means less hassle getting it up and running

Output buffer will be tubes

OF COURSE !

You need also consider how you get there.what the IV section will be,what filtering,what gain...........

Power supply seems to be very important and can hardly be oversized.

Again yes.That and isolating each stage from other stages

[rickcr42]

If I prefer the USB input, I could copy my favourite CDs to hard drive, but to save space use the internal CD drive for those CDs which I only listen to very infrequently. On the other hand, if I prefer the sound of the internal CD drive, I could still store some CDs on a hard drive and use them with the USB input when I want the convenience of making up a playlist. Either way the TentLabs player will be useful and neither part of it wasted.

or just as a convenient feed to the hi end system from the computer for whatever (internet radio for one).By using a single DAC for all things with proper interfaces (USB,I2S,SPDIF) you eliminate system bloat plus can actually compare sources head to head because the "guts" are the same for all.

Full integration is a plus if done to a high standard,will be far better than any affordable commercial option with standards as high and is never a bad idea to leave access points in ANY device (extra inputs/outputs) to accomodate future possibilities/new technologies