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Old 13th March 2009, 11:08 PM   #121
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Location: Sydney
Quote:
Originally posted by Kevin Wood
Well, I made the changes to the filter components yesterday to the values from the Cirrus application note:

R8, R14, R15, R16 = 13k7
R10, R11 = 3k32
C36,C37 = 1nF
C32, C34 = 220pF

I also changed the Op Amp to an AD826 and added some decoupling to its' power supply.

Took a few photos but haven't had time to post them up yet and also haven't had time for any serious listening. Those boards are indeed a pain to rework. Very difficult to solder in places because the heat is conducted straight into the ground plane.

Frequency response now measures absolutely flat from DC to 20KHz and about 4 mV of DC offset on the worst of the outputs.

Kevin
So, how does it sound with 826 and filter values above? My guess would be just a tad bright?

Regards,
Boky
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Old 13th March 2009, 11:11 PM   #122
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Quote:
Originally posted by ah-luo-ko-ko
All .. suggest stick to the DAC mod for this thread .. let try different things, document the mods for those who are not as handy ..

Listening is somewhat "subjective" -- eye of the beholder ;-)

I have buddies who are into the very high-end stuff. But whenever after having listened to their systems, I always like my system 'better' which are made up of mostly modified/DIY components. In fact, a buddy who owns a system based on B&W 801 driven by Bryton mono amps system is somewhat surprised (presently) when he listens to my system.

My wife and I visited a high-end store just two weeks ago and listened to a system using the limited edition Dynaudio 30th anniversary speaker (retailed for 20+K just for the loudspeaker). When we walked out of the store, both my wife and I think that that 'system' is 'thin sounding' and 'artificial' :-))))

The fun with DIY is the mod challenge, try to get the 'best' by building from scratch or mod a low price kit, share the experience and have fun ..

Let's continue trying the different mods and share your experience.javascript:smilie('')

Cheers.
Dynaudios are the best available out there..... maybe it was the other components and room acoustics to blame....

Regards,
Boky
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Old 13th March 2009, 11:12 PM   #123
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Does anyone have any info on PCB layout or schematics for this DAC design?

Boky
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Old 13th March 2009, 11:56 PM   #124
Segran is offline Segran  Sweden
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Quote:
Does anyone have any info on PCB layout or schematics for this DAC design?
You get a schematic from the guy selling the DAC if you ask for it - at least I did, after buying it!

Unfortunately the schematic is a bit "schetchy" and some component values don't match what's actually put in the PCB.

I haven't asked for the PCB layout, but if I was selling this DAC and trying to make a living from it I wouldn't give away the layout!

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Old 14th March 2009, 11:22 AM   #125
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Quote:
So, how does it sound with 826 and filter values above? My guess would be just a tad bright?
I'm impressed, actually. The treble is smooth and accurate, and certainly doesn't dominate things. It sounds good all-round from the few hours of listening I've had so far.

Kevin
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Old 14th March 2009, 01:14 PM   #126
johnm is offline johnm  United Kingdom
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Excellent - looking forward to doing the filter mods on mine once the final resistor values arrive. Was hoping today but looks like Monday now - grrrr! I take it low wattage resistors are fine here? Mine are only 0.25w I think...

I'm just a bit concerned with desoldering the components. I have a 50w Weller soldering iron with a small-ish tip, and a 25w Weller with a pencil tip. I'm guessing I'll have to use the 50w because of those large psu/earth traces and wriggle the leads out carefully. Last time I tried this I lifted the through-plated hole so can't say it's something I'm looking forward too

Have to say though to those that are unsure whether to mod or not my DAC sounds pretty impressive already just with the filter caps removed, and running the op-amp directly to the output phonos (though your pre-amp MUST have DC blocking caps installed to do this). Looking forward to seeing how much better the proper datasheet filter mod sounds.
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Old 14th March 2009, 03:10 PM   #127
hafp is offline hafp  United States
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[QUOTE]Originally posted by johnm

I'm just a bit concerned with desoldering the components. I have a 50w Weller soldering iron with a small-ish tip, and a 25w Weller with a pencil tip. I'm guessing I'll have to use the 50w because of those large psu/earth traces and wriggle the leads out carefully. Last time I tried this I lifted the through-plated hole so can't say it's something I'm looking forward too


Hi johnm,
1/4 watt resistors should work in the signal path; there is much debate on the sound of resistors as well...

As for the desoldering process on this board, take the advice of the other guy who said that changing parts on this DAC board takes time and effort.
You will need a pretty hot iron with a small chisel tip which will heat the lead holes very fast; use a thin braid solder wick to help take some of the solder away.
Be careful not to try and pull the parts out unless the pad is hot enough to keep the solder melted, otherwise it is pretty easy to lift the trace lead pads.
You may need to clear the holes as the other guy explains.

Good luck with your mods.
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Old 14th March 2009, 03:59 PM   #128
Mush is offline Mush  United States
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Default CS4397 vs CS4398

My DAC just arrived yesterday with a CS4398. Lawrence will sell me a CS4397 unit for $35. Is the difference great enough that I sould get the CS4397?

Warning to those that are thinking about this board. Nothing is labeled except for capacitor values that seem to be wrong. The board is thick and parts are tight so desoldering looks like a headache. I'm looking at it and thinking that I just don't have time to deal with determining the layout and desoldering.

I don't have all that much time to experiment so I am considering either a 6n6 tube buffer output (I can build one in about 30 minutes) or interstage transformers. I have a set of UTC A-20 and am not really sure if they will work.

I'm no expert in this realm and your suggestions are greatly appreciated.

Thanks and I hope all are doing well -- Mint
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Old 14th March 2009, 04:35 PM   #129
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if it is not much trouble for you to build the tube output stage then don't bother with any of these operational amplifiers and analog stage modding...
i used this schematic after trying various cathode followers and stuff...this will wipe the floor in a comparison with any of yours or your friend's expensive cd-players

Click the image to open in full size.

for good results you must use 6,3v stabilised DC on the filament (not AC),and all grounds connected in a star fashion
(DAC Gnd + pin9 on tube socket + the "-" of the filament + the "-" of anode supply + RCA out Gnd)
also remember to take signal directly from L- and R- of the DAC since this schematic inverts the phase
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Old 14th March 2009, 04:47 PM   #130
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Quote:
Originally posted by Kevin Wood


I'm impressed, actually. The treble is smooth and accurate, and certainly doesn't dominate things. It sounds good all-round from the few hours of listening I've had so far.

Kevin
after listening to the AD826 and if you would swap it now with a LM4562 you would observe lack of focus and details on HF signals and a weak bass response (more punchy and more focused on the midrange than the smooth low detail and brilliant highs of AD826)
I have both of them and took out all the LMs from all the audio stuff i've modded till now (it is also a matter of taste)

regarding the desoldering process,i think these chinese guys used the lowest quality solder they put their hands on...
it's very hard to suck out the solder,but i had positive results adding some good quality solder on the joints,mixing it with the poor quality one,and after heating them up i managed to suck out the whole solder without damaging the holes
good luck !
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