[ROBSCIX]

Quote:

Originally Posted by ManuLM /img/forum/go_quote.gif EMI is produced indeed, but I wonder why you bring it to the equation of a dirty power supply. Dirty environment yes, very strong EM like TX antennas (like in a cell phone transmitting some datas) , local oscillators / clocks, thermal noise, crosstalk sources on the PCB level are generating/catching noise but I do not see it as specific nor critical from the supply source perspective, thus my question.

When I think of the word "dirty" in relation to electronics I think of ANY additional signal that is not wanted nor intentional created. EMI can "infect" any signal including power and some common "dirt" in a PSU is high frequency noise that can be induced from EMI or RFI....just plain interference. This also depends on what type of PSU we are talking about of course.
I see what your saying though....I guess we just have a different way of looking at things.
Quote:

Originally Posted by ManuLM /img/forum/go_quote.gif As for PSRR, for me the simplest way of looking at it is to see how we measure it. As said before, a ripple is injected on the supply source, and measured on the output signal. The attenuation gives the PSRR, which is in some nice datasheets given as a function of the ripple frequency. I remember there is a detailed description on an app note from TI, will post it here if I can put my hands on it. EDIT: here it is http://focus.ti.com/lit/an/slyt202/slyt202.pdf

Again, I see what your saying but I don't consider ripple as "dirt"..LOL if you get what I mean. Thanks for the info. No sense in dragging out this topic as we just a different view point on the same subject.

 

[ROBSCIX]

Quote:

Originally Posted by ManuLM /img/forum/go_quote.gif Okay, managed to get all parts, dig out where my solder iron was hidden, and get going. Soldering is easy thanks to your picture earfanatic, and the pins are spaced enough for an easy soldering. I did apply exactly the same parts as you did. I've chosen 1% 0.6W resistors to be on the safe side. But most important, how does it sound. I quickly tested on my speakers and more on my K701 amplified by the Heed Canamp, both connected to the line out of the HD2. Mmmm, what a PRAT, it really kicks ass... It really impresses me on the K701. Now I understand the buzz about the LT1028ANC you guy make. I specially like the high drums, very sharp, very fast. A lot of dynamism. Thanks a million

Good stuff, you got it all modded up and it gives you some good sound!
LT has quite a few good chips, the 1028 is a great chip but can be very tricky to use in some circuits. Well unless you have the know how to mod them to accomadate the chip. I like modding soundcards, glad it all worked out for you. Are you planning any other mods for this source?

 

[earfanatic]

Quote:

Originally Posted by ManuLM /img/forum/go_quote.gif Okay, managed to get all parts, dig out where my solder iron was hidden, and get going. Soldering is easy thanks to your picture earfanatic, and the pins are spaced enough for an easy soldering. I did apply exactly the same parts as you did. I've chosen 1% 0.6W resistors to be on the safe side.

That's great.

 

[ManuLM]

Quote:

Originally Posted by leeperry /img/forum/go_quote.gif humm, you really wanna use the same chips(same model/batch) for each channel polarity, what's up w/ the third chip on the right hand? and 797B has a higher PSRR(and a "fuller" SQ) than 797A apparently you could have also used high grade gold plated sockets..or solder the opamps directly to get a cleaner signal.

I actually wanted to test first on 797A since I could get them easily. Now that I'm onvinced of the combo I will order the adapter to SOIC and solder them.
The black sheep AD797A is a guy made in USA while all the others come from Malaysia, so it is definitely not the same batch. To be sure you get a single batch you've to order a 50pcs ribbon since packaging happens in the fab... I do not want to setup a shop

No plans for further modifications so far, unless you guys have other good ideas

Edit: I can only solder directly the I&V. Next to the final buffer there is a cap that I believe whould prevent the adapter to go deep enough in the vias.

 

[ROBSCIX]

Unless you want to start changing out some of the caps with some higher quality units.
You may be getting to the point of diminishing returns. Have you done any mods on your STX BTW?

 

[ManuLM]

Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif Unless you want to start changing out some of the caps with some higher quality units. You may be getting to the point of diminishing returns. Have you done any mods on your STX BTW?

I also tend to think the next steps may not be as rewarding...

not yet played with the STX. Looking at the mods so far, I've not been convinced also, but maybe it's just lazyness (or lack of time). What's your take on this ? Specially looking at the final buffer ?

 

[earfanatic]

In my case the mod's are over for a while.
Next step for me would be a Burson set but those cost a lot. Next Year maybe.
(I hope my family don't listen now

)

 

[ROBSCIX]

Quote:

Originally Posted by ManuLM /img/forum/go_quote.gif I also tend to think the next steps may not be as rewarding... not yet played with the STX. Looking at the mods so far, I've not been convinced also, but maybe it's just lazyness (or lack of time). What's your take on this ? Specially looking at the final buffer ?

Yes, that is what I mean. Your going to start hitting the limits of what that card can produce. It will take alot of money to get small sonic gains.
Many of the mods mentioned around here for the STX/ST are just generic modifications that produce better sound on many soundcards. Removing the coupling caps, improving the feedback circuit...using higher grade opamps.
Do you mean your single ended buffer, the AD797?
There are other opamps I prefer more, like dual LME49710HA.
Almost any soundcard will have cut corners, places the engineers sacrificed some sound quality for price. They usually try and give you the best signature they can for the budget the set out by the company. Which is usually much less then what the MSRP is for the source. It only makes sense to go back and improve what they neglected and modify what you can if you're planning on keeping the source for awhile. Provided you have the skills and understanding to perform the modifications without damaging your source/card.

 

[leeperry]

Quote:

Originally Posted by ManuLM /img/forum/go_quote.gif Next to the final buffer there is a cap that I believe whould prevent the adapter to go deep enough in the vias.

you might as well grab a bunch of AD797BN

where the LT1028A keeps amazing me is its low end bass percussion...instant head nodder!

I'll try to score some LME49710HA soon, to see if it can compete...but I don't think it could match it SS-wise

you might as well desolder that pesky red wima cap, and put it at the back of the board.

 

[earfanatic]

I forgot one little mod to do... the RCA output's are crap. Just meassure the resistance between it's ground and the card's ground. It has a hudge difference between left and right RCA on my card. As I recently payed a fortune for RCA cables it deserves proper golden RCA connectors too.

 

[ROBSCIX]

Quote:

Originally Posted by earfanatic /img/forum/go_quote.gif I forgot one little mod to do... the RCA output's are crap. Just meassure the resistance between it's ground and the card's ground. It has a hudge difference between left and right RCA on my card. As I recently payed a fortune for RCA cables it deserves proper golden RCA connectors too.

Yes, connectors are another part that companies can skimp out on. Are you going with some high quality golden RCA jacks?

 

[ManuLM]

I wonder if the amplification stage is ground referenced (bipolar), or if we have AC coupling caps just before the RCA. If ground referenced, then I would expect the ground to be virtual and therefore not give a direct link to the ground, explaining strange impedances.

 

[ROBSCIX]

Trace out the circuit.

 

[earfanatic]

Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif Yes, connectors are another part that companies can skimp out on. Are you going with some high quality golden RCA jacks?

Not too expensive ones... There is a brand here with high quality audio cables and connectors called Kácsa audió. From they high quality line I think this is maybe compatible with the ones on the HD2:

"24K gold plated PCB mount professional RCA jack with teflon insulation, right angle solder pins and fixing rods, with red or black color code ring and 24K gold plated front-side fixing nut."

And looks cool too. Its € 6.73.

 

[ROBSCIX]

Thats is reasonble for quality connectors. Is this the model your going with for this card?