Advice/Help sought for modding a Digital Link III

[James G]

Hello dac gurus! I have a DL3 dac that I'm looking to tinker around with. My goal is to be able to do is crank the bejezzus out of it without the ear bleed syndrome. I must have girl ears or something because I'm really sensitive to harshness. So I want to start with the dac since I am using multiple sources. Eventually everything will get attention, but it will take some time.

My thoughts are to incorporate some of the mods that the mod houses like Cullen and RAM are doing but maybe using different parts, as well as some other ideas you guys might have. I have no doubt their work would sound better than anything I could accomplish, but the shipping from Japan to US and back would cost more than the sum of all the parts I'd need to do it myself, and I'm a tightwad. That and I'm addicted to filling my pea brain with any bits and bytes I can get a hold of. I'm thinking as long as I'm not using other's ideas to make a profit nobody's gonna get upset. This is just for my own personal enjoyment and I have little ego about it.

But since I'm new to DIY audio I need a lot guidance as to what areas I need to focus on, and which are a complete waste of time. So far I have increased the power supply caps from 48,000uF to 115,000uF with a decent effect of tidying up the sound a bit (the 48,000uF went into my transport). I've also ordered a Audiocom Superclock4 to replace the 27MHz crystal feeding the PLL chip and hopefully I'll get that in a couple more weeks or so. We'll see if it helps the PLL chip do it's job. Cullen and RAM seem to disagree on this.

So, I'll have a bunch of questions I'm hoping you guys can help me out with.

QUESTION#1
According the PS Audio the DL3 uses a discrete output stage but there is an opamp employed apparently to eliminate feedback issues. All this is over my head. This is a snip from the PS Audio website:

<snip>
99% of every DAC on the planet uses an op-amp to convert the output of the DAC to a voltage. We learned years ago that this is the worst thing you can do for the sound, because op-amps all have two major problems when used for this function: feedback and speed issues.

Without getting too technical, the greatest opportunity for a bright and edgy “digital” sound is caused by op-amp based current to voltage converters (IV converters) because the high speed of the DAC’s output causes transient or slewing induced distortion in the op-amps (SID). SID is a combination of feedback and transient response issues that some exotic high-speed op amps can come close to handling, but all have a problem with it.

PS Audio’s engineers avoid the SID harshness by eliminating the feedback of the IV stage. We do this by a unique single transistor IV converter with no feedback. Speed issues and SID issues are completely eliminated with this technique.
</snip>

The part is a "Texas Instruments TL082C JFET Input Operational Amplifier". Whitepaper is here:
http://focus.ti.com/lit/ds/symlink/tl081a.pdf

Do you think there would be any improvements to be had by changing it out for an "exotic high-speed op-amp"? Any recommendations?




QUESTION#2
In the Cullen Mod there are 2 caps connected to this op-amp. From what I can tell, they seem connected to these holes that already exist on the PCB which connect to: pin 3(1 IN+), pin 4(VCC-), pin 5(2 IN+), and pin 8(VCC+). I could be mistaken though. What are the purpose and recommended values of these caps?

Also what do you think of the Dale resistors? Any other recommendations? I like detail, but not so much that it becomes unrealistic. What I like better is the "sweeter" sound.




QUESTION#3
The pre-regulators are 3-terminal 78/79xx types. What do you think about replacing these with discrete drop in replacement types like Paul Hynes or the like? Worth the trouble?


QUESTION#4
The main regulators (at least that's that I think these are) are National Semiconductor LM317LM SOIC-8. Any better drop-ins to be had?
http://octopart.com/lm317lm-national+semiconductor-9152




Well, that's all I can think of for now. I hope it's not too many questions.

Please give me any other ideas you might have but I want to address the components first before I get into the tweaky stuff. The purpose of this thread is only to improve this dac's performance tuned for my ears and nothing else. Not I need to move my speakers, isolation, bass traps, cables, etc etc. Thanks!

[James G]

No takers huh? What gives?
That's OK I'll just keep talking to myself, I'm used to it.

On the floors of Tokyo
Down in London town's a go go
With the record selection,
And the mirror's reflection,
I'm a dancin' with myself

Please enjoy these photos of my cap and clock mods so far.
I still wanna play some more later.

I more than doubled the smoothing caps capacity.
The Nichicons were added in parallel just because I had them laying around with nothing to do.
No real agenda to that.










The photos don't do it any justice, but the Audiocom Superclock 4 is a little work of art.
Right now I just have it's power connected to one of the supply caps (15v).
Once I get familiar with that sound, I might try moving it to the regulated output.
If that shows any improvement I might try feeding it with a dedicated power supply. Who knows?
It's only been up and running for about an hour or so.













Any suggestions???

[Puffin]

Hi James

I suspect that you may not have had any replies if people are not familiar with your Dac. I have not heard of it, although you have not given the makers name.

It seems that what you have done so far is probably as much as most of us would do by way of mods.

If you prefer talking with yourself have a listen to this! A great summer tune IMO

http://www.youtube.com/watch?v=jgNCC...eature=related

Rob.

[James G]

Sorry Rob, I guess this dac is less popular than I thought. It's a PS Audio Digital Link III. The link to the manufacturer's website is in my sig below.

I was kidding about talking to myself just so I could have an excuse to post those lyrics up.

Hey that link you sent is pretty good (played of course via USB out to my newly clocked dac). I listen to Groove Salad a lot when I'm milling about the house or playing on the internet.

[leo]

I don't know this dac internally so can't really offer much help, tbh I'd rather try mods myself first before recommending them.

I can say nice choice with the clock, The Audiocom Superclock4 is a great product imo!
I have tried those Dale resistors although it was in another unit, they are sonically much smoother sounding than your typical metal film resistor , I've known some SMD reistors to sound pretty harsh so if the stock SMD types was a little hot in the high's going to the Dales would have quite an effect . The Dale RN60 maybe a little big so the smaller ones maybe better suited, might be RN55 can't remember from the top of my head the part numbers.

Upgrading regulation can bring huge gains in performance depending on the circuit , if your circuit has poor PSRR going from bog standard three pin regulators to something like Paul Hynes shunts or series regs can be a real ear opener I was extremely impressed with these when used in my Sabre based dac.

The I/V stage is very important with current out dacs , normally older op-amps used was poor but they have improved over the years although discrete can be better if done correctly .
Regarding the op-amp you see in your dac, without seeing a schematic we can't be 100% sure what its doing, could be a servo ? basically servo's are used instead of signal coupling caps. If it is a servo the type of op-amp used still has some influence on the sound, best to use the lowest noise types so to inject the least amount of crap back into the circuit as possible (those green caps added may be there to help clean the crap up? ).
If it is a servo and you want to replace it make sure you fit a jfet input type.

Again, without seeing schematics we can only guess

[James G]

Hi Leo. Thanks for your reply. You've given me quite a lot to thing about.
I wanted to throw something new into the mix on The Drawing Board, but just realized that since this is a US dac there might not even be a UK version of it. Haven't looked into it.

I totally endorse your not wanting to recommend mods without trying them yourself first. Heck, at this point when I try something it's about 95% guessing anyway. Which is part of the fun of it for me.

The Audiocom clock is a nice piece of gear, isn't it? Every CD player should have one of these! I have less than 24 hours constant run-in with it and already very pleased. Only the first hour was a little rough. I'd have to say everything people are saying about it is true. Some people are a little too enthusiastic for my tastes, but digital music does make more sense with it in the circuit. And this is with it running in it's most simple configuration (drawing power from the PS supply cap)! When I get 300 hours on it I want to start experimenting with feeding it cleaner juice. After it and my dac became good friends I found myself digging out CDs I had not listened to in a while. Last night (to my wife's dismay) I was jamming the Metallica Black album, bobbing my head and playing air guitar, reliving my teenage days.
In contrast, this morning I'm listening to baroque and thinking, "Damn, baroque sounds good!".

On to your second tip, I'm happy to hear your impressions about the Dale resistors. I do think the top is a little dry when the volume goes up and would love to find out if the Dales could sweeten the pot (after the clock run-in of course, but it was dry before any mods so I think this might be a signature of the output stage). It would need to be the RN55's because the SMDs they use in this dac are TINY! Good thing about that is that they'll come off without a big fight, and yesterday I found out the landing pads are not as small as I thought they would be. I figure neatly trim the leads, brush a little liquid flux on each end, and with a dab of solder on the tip of the iron it will be 'psst-psst' and I'm done. At least I hope it will be that easy.

About your third tip, good clean power supply is probably the most crucial point to first address in digital music playback, isn't it? Even my elementary approach to ripple rejection with the supply caps yielded results. I'm thinking the next easy step would be to try replacing the standard 3-pin 78/79xx pre-regulators with the Paul Hynes drop-in replacements and let the LM317LM's be for now. If you or anyone else has any experience with these please let me know your impressions.

As for the jfet cap mod, I guess it will be best not to mess with it. If I remember correctly they might trace back to the regs underneath the pcb. You are probably right about their use as cleaning. I have no idea what else they might have going on under there in the mod. It's over my head though. All I know is part swaps.

Well, I have to leave the country in a couple of weeks so I'll have to put this project on hold until September. I'll continue to update this thread with my successes, failures and impressions thereof in the event that it may be of benefit to someone in the future.

Until then I will put on my thinking cap!!







Thanks again Leo. You are an ace in my book.

[John]

You can get the digital link III here its a nice DAC but cannot advise aound mods My own experience was it responded well to good mains in my system so I imagiine that upgrading caps etc will really help this unit

[James G]

You can get the digital link III here its a nice DAC but cannot advise aound mods My own experience was it responded well to good mains in my system so I imagiine that upgrading caps etc will really help this unit

You are right on the money there John. It's responded well to what I've done so far and I feel like there's more to be had from wiping away what compromises had to be made for manufacturing.

I've seen some of the surface-mount aluminum caps replaced for higher grades. Do you know of an easy way to remove those things? They are a royal pain in my ass. On my CDP, I've tried to wick the solder away, suck the solder away, and lift one side at at time but they are really stubborn.

Does anyone know a good method for taking these off without cooking the traces? I have searched the internet on several different occasions and can't find the answer to this specific issue. One guy mentioned to just bounce back and forth from side to side, which works great for SMD resistors, but the bigger caps suck the heat away so quickly I think you'd have to have the speed and dexterity of Bishop from the movie Aliens for this to actually work.

Does anyone know an easy way to take these off? Thanks!

[James G]

Well, I thought I could wait 2 weeks before opening the dac again, but I gave in to temptation! After being quite pleased with the performance of the Superclock4 with it running for 7 days strait I was ready to experiment some more.

I moved the power wire from the supply cap to the output of the 7815 regulator. I did notice a slight difference in the performance. It was as if the timing of the music became more accurate. There is a feeling of a faster rendering speed, if that makes any sense in audio terms. Also maybe a slight increase in front-to-back depth. The clock seemed to be doing what it does better, so I'll want to put a quality power supply on it at some time.

I'm ready to see what the Dale RN55D resistors will do for the analog stage now. It's gonna be a real headache messing with those tiny SMDs and fitting the Dales so it better be worth it!

[John]

Keep us posted I am sure the work you doing it will really take it up a few steps