ah-luo-ko-ko said: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
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!
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.
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.
johnm said: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.
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
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
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
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
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
An externally hosted image should be here but it was not working when we last tested it.
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
Kevin Wood said:
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 !
Segran said:
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!
For the price, together with a publicity design's being gaining, publishing basic PCB layout would be great marketing move. I wasn't really after the gerber files - just to see if the PCB layout in general is any good. Not making them available (schematics and PCB layout) at least in their basic block-diagram form, could be good enough reason for suspicion...
Boky
luxury54 said: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
An externally hosted image should be here but it was not working when we last tested it.
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
Since you have a soft spot for tube output, give fast switching soft recovery diodes a go, in particular in DC filament supply...
Boky
To tell the truth I haven't asked for the layout. Might be worth while to as Lawrence for the silkscreen print, showing the components.
There are labels for the resistors as well - under the components... And showing the resistance value, not the number...
I can agree that the solder used is bad, I used the same method to clean the holes (removing components, filling fith new good solder and sucking the holes clean).
If you don't feel up to modding this board for what ever reason, have a look at this:http://www.beis.de/Elektronik/ADDA24QS/ADDA24QS.html
The DA24QS as a kit is twice the cost of the BIG DAC. You can buy bare PCB's if you want as well. It even comes in a balanced output version. I haven't tried this DAC myself, but it seems to be very well engineered. Component values for the analog filter looks a bit strange but does the job. The only problem I can see is a 0,4-0,5 VDC offset on the output of the first OP, but changing the components according to AN-84 will solve that (same as on BIG DAC). All components are thru hole (except the chips from Crystal and the PLD) so modding would be easy. You still need to be "semi-pro" with the soldering iron as the Crystal chip's are TSSOP footprint.
I'm happy with the BIG DAC after the mod's I've put in, so I'll stick with it. At least for now. And for the price of it, I regard it as good value.
luxury54 said:
Hi,how do you like the sound characteristic of AD826?
it is a very fast opamp with 350V/uS slew rate compared to only 20 of LM4562 ,and in this place after DAC it is imperative to have such a good slew rate and wide frequency capability, that's why also tubes sound great because they have a very high slew rate never masking the microdetails (it is a video opamp linear up to a few GHZ,so is perfect in audio and will not oscillate easily)
i don't like transformers,i have the feeling they are more mellower and laid back than tubes kind of compressing and leaving only macrodinamycs ,masking the small micro details, it's about lazy rise times,so another slew rate thing...
I don't want to offend you but it seems that 'theory' is really more important for you than anything else.
First
A very fast op amp doesn't gives ANY garantee of good sound. Again perhaps on paper. Try a LM7162 and give me your results. Video op amps were NOT designed for audio. BTW LM4562 doesn't have bass and don't play well if they are not broken in.
Tubes have a very high slew rate ? Not sure, really not for most of them
The slew rate is measured by using a square wave and calculating the number of volts that the square wave rises vertically on the Y axis, over the amount of time it takes for this voltage rise to occur, on the X axis. If the slew rate is high, the sound will tend to be "crisp" with a bit of "edge" to it, while a low slew rate gives a sound that has less of these characteristics to it.
Look at the square waves of tube gear and transistor gear and tell me which ones 'often' have better squares waves. Musicality is still another thing but we can't measure this parameter
So you don't like transformers
Again your feeling like you wrote is based on what ? Mediocre vintage transformers that rolls off highs ? Come on TRY real things so you could change your minds. Lundahl transformers (and probably some others) on my dac doesn't sound slow, laid back etc like your description.
Like I wrote on a previous message Heat your soldering station, experiment and listen instead of reading specs.
dear legarem,in this place the opamp is only a sumator between the + and - alternances of the DAC amplifying only the differences between alternances and masking all that is in common (any kind of digital or supply noise) so this is a must to have a high slew rate here for being able to follow and reproduce all the low level details...
you don't think that tubes have a high slew rate?
then what about electrons heated up by the filament that have the capability of the speed of light in vacuum,because it is really vacuum inside
you don't think that tubes have a high slew rate?
then what about electrons heated up by the filament that have the capability of the speed of light in vacuum,because it is really vacuum inside
Right, a couple of photos I took while updating the filter components:
Filter area with components removed. The four blue 1nf capacitors are correct for the new design so they stay. The rest go.
Note that all four resistors on the left hand side in each channel labelled 22k or 36k (22k fitted in all cases) are changed to 13.7k. The two resistors labelled 6k8 in each channel are replaced by 3.32k resistors. The caps near these two resistors labelled 56p and 102 are repaced by 220pf. The resistors marked 1k are in series with the first Op Amp stage outputs. I replaced these with 75 ohm resistors. The two missing caps on the right hand side, where the yellow wire is attached, used to sit between the two stages. I'm now taking the output from here and have junked the second Op Amp stage.
Note also that the 4 electrolytics on the left hand side between the DAC and Op Amp stage are gone.
New filter components in place. This photo was timestamped 1 hour and 40 minutes after the previous one. That's how much fun I had soldering in the new components!
Some power supply decoupling under the Op Amp and one of the 220pf caps had to go on the underside.
The four decoupling capacitors were bypassed by a solder bridge on the underside of the board.
I hope this is helpful for anyone making these changes. I will try to draw a schematic of this part of the board and also annotate one of these photos so we can see what components are where.
Kevin
An externally hosted image should be here but it was not working when we last tested it.
Filter area with components removed. The four blue 1nf capacitors are correct for the new design so they stay. The rest go.
Note that all four resistors on the left hand side in each channel labelled 22k or 36k (22k fitted in all cases) are changed to 13.7k. The two resistors labelled 6k8 in each channel are replaced by 3.32k resistors. The caps near these two resistors labelled 56p and 102 are repaced by 220pf. The resistors marked 1k are in series with the first Op Amp stage outputs. I replaced these with 75 ohm resistors. The two missing caps on the right hand side, where the yellow wire is attached, used to sit between the two stages. I'm now taking the output from here and have junked the second Op Amp stage.
Note also that the 4 electrolytics on the left hand side between the DAC and Op Amp stage are gone.
An externally hosted image should be here but it was not working when we last tested it.
New filter components in place. This photo was timestamped 1 hour and 40 minutes after the previous one. That's how much fun I had soldering in the new components!
An externally hosted image should be here but it was not working when we last tested it.
Some power supply decoupling under the Op Amp and one of the 220pf caps had to go on the underside.
An externally hosted image should be here but it was not working when we last tested it.
The four decoupling capacitors were bypassed by a solder bridge on the underside of the board.
I hope this is helpful for anyone making these changes. I will try to draw a schematic of this part of the board and also annotate one of these photos so we can see what components are where.
Kevin