Newbie Project - Tweaking the SoundBlaster Live! 24-bit

[J. R. Todd]

Greetings to one and all - this is my first post on the forums, though I've been lurking for some time. Apologies for any idiocies that follow...

I recently aquired, for a princely sum, the aforementioned sound card, and it certainly doesn't sound bad. Before any creative-bashing goes on (don't worry - I'll do that soon - see below) you must note that as far as I can tell the Chaintech AV-710, everyone's first choice on the cheap, is rather hard to aquire through retail channels in the UK.

Obviously, I'm interested in fiddling with the damned thing.

Does anyone have any particular experience upgrading sound cards?

Here's what I've come up with so far...

Changing the Op-Amps

This morning I performed a survey of the parts. Of all the op-amps mounted on the PCB...none of them have a slew rate greater than 7V/us! And the headphone output op-amp (JRC4556A) has a slew rate of 3V/us. All other things being equal, (which they are not)...no wonder people complain about the card having a 'sloppy' and or 'lifeless' sound. Am I correct in this assertion? Compare this to some of the op-amps of choice recommended by Warren Young's 'Notes on Audio Op-Amps', such as the AD8620, with a slew rate
of 50V/us. The recommended Burr-Browns also have similar slew specifications.

I know that surface mount soldering is difficult, but the little pins on these look just-about doable. Assuming I can find one that operates within the 4556A's specs, would it be worth replacing them with better ones? I guess so. Are there any issues I should be aware of?

Also, would it be worth stacking Op-Amps in the same way that DACs can be stacked? Speaking of which...

The DAC

The Cirrus Logic 4382

Apparently this is a fairly decent DAC, though not perfect. The prospect of DAC-stacking this surface mount beastie is certainly beyond my abilities...unless anyone has a technique for such things. The only thing I can think of doing is building a simple clock generator and tapping it into the master clock. Is this the only pin that needs to have the clock fed into it? Or would the creative controller chip need it too? (I know good clocks aren't 'cheap', but anything's probably better than Creative's effort, judging by the choice of op-amps, one can only wonder at the other high-performance components in there! )

Would I need to desolder the 'master clock' leg? Would this not work happily? Is it feasible?

If it's not, the only thing I can think of is upgrading the crystal itself to a more stable version, though I don't believe that this will result in a lower-jitter signal necessarily because of the oscillator circuit that surrounds it. Am I correct?

Other Ideas

The only other things I can think of is upgrading the regulator ICs to higher-performance ones for cleaner power, or even powering the entire card independently of the PCI bus (and thus, the PC's power supply) using batteries, or simply giving the DAC a clean, battery-fed power supply. It would also be quite simple to 'upgrade' the no doubt awfully cheap Jamicon capapcitors for even non-audiophile high quality caps, if this would help. Any comments?

Thanks in advance for your patience and ideas,

- Toddy.

PS. I have used the 'search' function, but couldn't truly find what I was after, and I'd rather bow to experience than charge out with my own odd experimentings. (At least for now.)

[demogorgon]

I'v been thinking of doing the same for quite some time on my audigy 2, but never got around to it, too much hazle involved.

though i wonder, are the opamps on your board dual?

about the dac soldering, you can use the "flood-and-suck" technique..
read here

oh, and welcome to the forum BTW

-Marius

[J. R. Todd]

Hey, demogorgon.

Thanks for your reply. With regards to the nature of the op-amps, I'd guess that they were. Certainly, the data sheet on the NJM4556A states (the primary output) that it's certainly dual, and I'd imagine the rest were, too.

The SMD soldering guide has been duly bookmarked. Cheers. The flood-suck method might well work on a stacked DAC chip, or stacked op-amps, and I suppose one could always cover over the pads that one wanted to tap into or out of with something heat-resistant and non-conductive.

For future reference, I'm hoping that I can turn this thread into a running reference on sound-card modification in general later on. I believe that the modification of sound cards is underrated. For example, if one were to build a lovely CMoy to power headphones with some nice high-slew op-amps, and take output from the soundcard, is there much point if the sound has already been turned sludgy beforehand by an op-amp that is ten times 'slower'?

Oh, and why use a nasty Live! 24-bit anyway? Well, it's pretty ghetto, if nothing else.

Am I correct? Anyone have any more advice before I begin my tinkerings, particularly with regard to the clock issues? I'll probably begin with the op-amps anyway, as it's the simplest.

-T.

[demogorgon]

J.R.Todd

Why dont i ever learn?
i should have stopped looking into post i know will eventually make me buy something..

I like the idea of creating a reference thread, andfor what its worth il join in on the action

opa2604 and some opa2134 are on their way as we speak.
about the dac, i dont know very much about dac's other than in general theory, i'm gonna have to do something about that soon..
perhaps i'l find one thats pin for pin compatibe with the one allready there? - something to look into.
the clock though looks like to much hazle for me, fideling with such high frequeny signals can very easy get more interesting than planed, i imagine. if someone with a scope would join in the thread, i think perhaps we least could find out a thing or two, and go from there.
though there arn't many people around with 100mz scopes of their own. (considering the pci bus is 66mhz, the scope would probably have to be that?)

-Marius

[demogorgon]

ok, here's the dac on my card atleast,
http://www.cirrus.com/en/pubs/proDat.../CS4362_F1.pdf
haven't found any replacement yet, but looking.
doesnt look too hard to do something about it though.

-edit
well, there's a cs4382A available, doesnt look like much of an improvement though. i'l be having to take a look at what's allready on my board.

what that codec thingy does however, i still wonder..
anyone able to afford an explanation?
the codec is the SigmaTEL STAC9721 AC'97 codec.

-Marius

[Spartacus]

Hi,

The 4556 op-amp is rated for 70mA and is used for driving headphones. If you don't intend to use headphones you could simply bypass it. Replacing the 4558s with AD8620s sounds a good idea, but remember that faster op-amps need better HF decoupling, so you should consider making sure their supply pins are bypassed with small value film caps. Also the DC specs of the 8620s are much better than the stock devices, so you should be able to replace any DC blocking caps with a wire link or solder bridge.

As for the clock, simply remove the crystal and associated resistor/caps and apply the new oscillator.

One thing to keep in mind: simple mods like swapping op-amps are worthwhile, but there comes a point with upgrading sound cards where it becomes more practical to vuild an external DAC. Your decision of course.

[J. R. Todd]

My sincere apologies, chap.

The 'on their way' thing sounds familliar - an AD8620 is being delivered courtesy of the Analog Devices samples department. Other than that, you might have to take the lead on the first replacement, as I'm woefully underequipped to do any type of electronics work. There's still tools to aquire...and the Electronics department doesn't allow non-students to use their facilities.

With regard to the DAC, they're far less industry-standard than op-amps and so finding a drop-in superior replacement will be very difficult, which is why I thought it best to concentrate on reclocking the beast. We do share the same DAC, though, so at least we can collaborate on this a little, I hope.

The PCI bus, bog standard, I believe functions on 33Mhz, with various variations. Though I don't think one can seriously 'reclock' the master PCI bus clock!

http://en.wikipedia.org/wiki/PCI

I was hoping to, at some point, simply get a good, clean master clock signal into the DAC...but I don't know if the Creative controller chip will also need to be reclocked.

Best of luck with your endeavours, chap.

-T.

For the curious, here's the components list of my Live! 24-bit, with a diagram.

ST Microelectronics (ST) 33078 - Low noise op-amp, presumably for microphone input. (#1)
Japan Radio Corp (JRC) 4556A - Headphone (primary) line-out. (#2)
ST Microelectronics (ST) 4558C - Other line-out op-amps. (#3)

Cirrus Logic (CS) 4382 - 24-bit 96kHz DAC. (#4)
Wolfson Microelectronics (WM) 24-bit 96kHz ADC. (#7)

24.576Mhz generic crystal. (#5)

Various regulators, bus buffers, etc.

As for #6...yeah...what is this?

[demogorgon]

J.R, offcource the PCI is 33mhz, i was confusing it with AGP.
And i was conserned the bus frequency was the same as the pci bus itself, as the card would already have that clock available..

I think i have some 8620's, but they are dip i seem to recall, i'v been in contact with their sample department as well

We do have the option of testing the A V the non A cs4382.
i hear there are differences between pieces with different suffixes on other dac's. worth a shot.

and as you say, finding a BETTER dac, is a chalenge in itself, finding a drop-in is impossible it would think.

your electronics department sound like the same kind of bozos the mechanical department here are.
but hey, if you have problems getting it done yourselv, postage isn't much over the pond anyways, so perhaps we can work something out.
i have experience with smd soldering, and good equipment.

good luck to you as well
-Marius

[J. R. Todd]

'lo all.

Demogorgon - It appears that I might've rushed my post. We don't, indeed, share the same DAC, but it appears to be at least in the right series (43xx) so I'm sure its at least similar. I hope.

Originally posted by Spartacus

The 4556 op-amp is rated for 70mA and is used for driving headphones. If you don't intend to use headphones you could simply bypass it.

Mmm. Well, I don't know about Demogorgon, but for me, it's all about the headphones, though placing a little bypass switch on the backplate of the card for a 'pure' lineout sounds like an interesting modification project.

Replacing the 4558s with AD8620s sounds a good idea, but remember that faster op-amps need better HF decoupling, so you should consider making sure their supply pins are bypassed with small value film caps. Also the DC specs of the 8620s are much better than the stock devices, so you should be able to replace any DC blocking caps with a wire link or solder bridge.

Mm...I've read up on the need for this...but I'm not sure on how to implement it. And there appears to be a whole, ghastly array of SMD capacitors and resistors in place already around the op-amps, so they may be decopled already. I think it's a 'solder and see' scenario.

As for the clock, simply remove the crystal and associated resistor/caps and apply the new oscillator.

The question is - does the oscillator only generate the clock for the DAC and ADC, or does it drive the Creative on-board chip as well? Or does it run from the PCI bus clock?

If the former is true, it's going to be hard to find it without a 20+Mhz scope and some time. It's hard to trace a signal on such tiny pins (inside an operating computer, mind).

I presume that the DAC runs on a 24.576Mhz master clock signal, as it's a supported frequency in the data sheet, and the crystal runs at the same speed. Can I simply put a new 24.576Mhz (or other supported speed) master clock signal into the MCLK leg of the DAC (see attatchment) and leave the L/R signalling leg (which presumably comes from the creative controller chip?

There are a plethora of other clocks, too.

One thing to keep in mind: simple mods like swapping op-amps are worthwhile, but there comes a point with upgrading sound cards where it becomes more practical to vuild an external DAC. Your decision of course.

Indeed, indeed. Though I think the modification of a sound card is more helpful for neophytes such as myself because you don't have to worry so much about the power suppy, surrounding components, etc. and replacing the existing components, hopefully, have the same support componentry arround them.

-T.

[FLECOM]

be careful with DAC's with letters at the end, a lot of time the difference will indicate the type of input they accept... ex TDA1543 is i2s while the TDA1543A is EIAJ etc