I've got it a month ago, went thru some modifications of design flaws, and now it sounds quite fine!
The best modifications:
- Swap the opamps for opa2134
- Trow some ceramic NP0 caps between each I/U output and ground - i've used 3.3n with great results. everything around 1-3n will work.
The first modification brings the details which were hidden by the NE opamps the original board had. Yet, you get the OPAs oscillated a bit - you'll hear too much crispiness, TSSS sound here and there on female vocals. The second mod kills the high frequency noise coming from DAC to the OPAMP's legs, and therefore limit it's input bandwidth - stopping the oscilliation and cleaning up high frequencies.
Then, i went for upgrading the overall PSU condition on the board - poor designed thing.
As you know, big caps on remote board connected with looong thin wires to the DAC board are worthless. You need thick wires, and major robust capacitance on the board.
Here comes the Panasonic FC and ELNA-for-audio caps i had, 470u/47u. The 47u went directly on the SMT ceramic bypass caps nearby the dac on analog-Vcc and bias legs, and the 470 gone to hold the overall +5V that came to IC.
The result was a bit more clean sound, nothing major as the opamps swap and additional filtering.
Overall, it's a fine DAC for cheap. I'm going to use 3 of these in 3-way active digital crossover simulation system.
Anyone got the schematics? If not, i can post it as i got it in the package
The best modifications:
- Swap the opamps for opa2134
- Trow some ceramic NP0 caps between each I/U output and ground - i've used 3.3n with great results. everything around 1-3n will work.
The first modification brings the details which were hidden by the NE opamps the original board had. Yet, you get the OPAs oscillated a bit - you'll hear too much crispiness, TSSS sound here and there on female vocals. The second mod kills the high frequency noise coming from DAC to the OPAMP's legs, and therefore limit it's input bandwidth - stopping the oscilliation and cleaning up high frequencies.
Then, i went for upgrading the overall PSU condition on the board - poor designed thing.
As you know, big caps on remote board connected with looong thin wires to the DAC board are worthless. You need thick wires, and major robust capacitance on the board.
Here comes the Panasonic FC and ELNA-for-audio caps i had, 470u/47u. The 47u went directly on the SMT ceramic bypass caps nearby the dac on analog-Vcc and bias legs, and the 470 gone to hold the overall +5V that came to IC.
The result was a bit more clean sound, nothing major as the opamps swap and additional filtering.
Overall, it's a fine DAC for cheap. I'm going to use 3 of these in 3-way active digital crossover simulation system.
Anyone got the schematics? If not, i can post it as i got it in the package
Ok, here is the schematics if anyone is looking for it:
http://img153.imageshack.us/img153/9063/dsc6604.jpg
I hope i haven't cut someone's copyright rights, as i've got it right from the seller.
I think that the addition of schematics is a must for DIYers, and will help selling these DACs + will help DIY community to implement them = WIN-WIN situation
http://img153.imageshack.us/img153/9063/dsc6604.jpg
I hope i haven't cut someone's copyright rights, as i've got it right from the seller.
I think that the addition of schematics is a must for DIYers, and will help selling these DACs + will help DIY community to implement them = WIN-WIN situation
Do you mean I/V output and ground? What pin are you using for that? Sorry, i'm pretty new to this and need to be walked through it like a child.
LOUT+
LOUT-
ROUT+
ROUT-
each of which to the ground via NP0 capacitor. Keep the leads short - scratch the PCB under the opamp, put some solder on the spot to get a place where you'll solder one of the leads of caps, then solder the caps in between of that spot and the opamp's lead.
The pins are 2 and 6 on each adjacent to DAC opamp. These are negative inputs of the opamps.
Some pics:
http://img685.imageshack.us/gal.php?g=dsc6593j.jpg
The pics are enourmously large and not informative - i threw too much caps under the opamps
Please disregard the big caps on the opamps themselves - i threw them just to check whether it will help anything - putting them rail-to-rail - well, nothing remarkable.
The red wires you'll see nearby DAC - my fail, the SMT electrolytics are hard to remove, and i've ruined the PCB traces during desoldering.
LOUT-
ROUT+
ROUT-
each of which to the ground via NP0 capacitor. Keep the leads short - scratch the PCB under the opamp, put some solder on the spot to get a place where you'll solder one of the leads of caps, then solder the caps in between of that spot and the opamp's lead.
The pins are 2 and 6 on each adjacent to DAC opamp. These are negative inputs of the opamps.
Some pics:
http://img685.imageshack.us/gal.php?g=dsc6593j.jpg
The pics are enourmously large and not informative - i threw too much caps under the opamps
Please disregard the big caps on the opamps themselves - i threw them just to check whether it will help anything - putting them rail-to-rail - well, nothing remarkable.
The red wires you'll see nearby DAC - my fail, the SMT electrolytics are hard to remove, and i've ruined the PCB traces during desoldering.
Thanks s3tup, that's very useful.
I was considering doing the Lampucera capacitor changes and then tube out. There are some differences between the DAC I received and the schematic, a couple of which might be important, a couple others I'm not sure on. You might have a different spin of the board from me.
Choke L1 for cleaning up the photodiode bias seems to have been replaced with a resistor.(!)
The +5VB and +5V supplies from the power connector are swapped, no impact I think.
The isolation transformer T1 for the coax isn't there I think, it looks like two shorting links. Could someone confirm please, I don't want to pass that ground into the DAC.
R13 is not a resistor, it's a capacitor as in the diagram.
The IoutL+ is connected to op-amp pin2 and IoutL- is connected to pin6. This is the reverse of the diagram, the right channels are per the schematic.
If you're considering the Lampucera capacitor upgrades for the previous DAC version, stay away from C30 and C31, they're part of a filter for the PLL. Also, probably best to leave C2 and C3 as they are, I think their RC charging is used to delay the enablement of the chips until the supplies have stabilised.
If I've got this wrong please let me know, I intend to be waving a soldering iron in the direction of this guy next weekend, I'd rather be told I'm an idiot than have a dead DAC!
I was considering doing the Lampucera capacitor changes and then tube out. There are some differences between the DAC I received and the schematic, a couple of which might be important, a couple others I'm not sure on. You might have a different spin of the board from me.
Choke L1 for cleaning up the photodiode bias seems to have been replaced with a resistor.(!)
The +5VB and +5V supplies from the power connector are swapped, no impact I think.
The isolation transformer T1 for the coax isn't there I think, it looks like two shorting links. Could someone confirm please, I don't want to pass that ground into the DAC.
R13 is not a resistor, it's a capacitor as in the diagram.
The IoutL+ is connected to op-amp pin2 and IoutL- is connected to pin6. This is the reverse of the diagram, the right channels are per the schematic.
If you're considering the Lampucera capacitor upgrades for the previous DAC version, stay away from C30 and C31, they're part of a filter for the PLL. Also, probably best to leave C2 and C3 as they are, I think their RC charging is used to delay the enablement of the chips until the supplies have stabilised.
If I've got this wrong please let me know, I intend to be waving a soldering iron in the direction of this guy next weekend, I'd rather be told I'm an idiot than have a dead DAC!
Yes, you are correct on all fronts concerning the design "flaws" - the transformer is pricey, so the best cost saving thing is just throwing 2 wires instead of it. Use toslink for isolation as a cheap method.
As for toslink choke - you mean that green fat "resistor" on the back of toslink receiver? It is choke.
The reversed input polarity on opamp... Are you shure? Weird Really weird - i'll check it tomorrow.
As for the Lampizator thing... I'm not that into low ESR caps hanging on their long legs, nor tube buffers directly on the DAC's outputs, tantalum caps et cetera. bypassing ceramics with film on long leads? What a cute resonant circuit up there! I bet it rings
You'll probably need a transformer instead of opamps to connect it to tubes.
CD DAC Lampucera lampizator
Stay away... imho
As for toslink choke - you mean that green fat "resistor" on the back of toslink receiver? It is choke.
The reversed input polarity on opamp... Are you shure?
Weird Really weird - i'll check it tomorrow.As for the Lampizator thing... I'm not that into low ESR caps hanging on their long legs, nor tube buffers directly on the DAC's outputs, tantalum caps et cetera. bypassing ceramics with film on long leads? What a cute resonant circuit up there! I bet it rings
You'll probably need a transformer instead of opamps to connect it to tubes.
CD DAC Lampucera lampizator
Stay away... imho
Last edited:
That's great s3tup, I couldn't understand the colour bars on the toslink "resistor", that explains it.
I'm heading headfirst into the tube output, I have no idea how tube output can avoid the high frequency components of the DAC output though, all op-amp designs are designed to filter this. But..... Lampizator's enthusiasm has convinced me to give it a go. One thing that's really nice about this current output DAC is that changes can be totally reversible. Pull out the I/V op-amps, insert leads into the op-amp sockets and off to the tube stage. Don't like it, remove leads and op-amps back in! Hey-presto. A second nice thing is that the SRPP tube stage needs only one capacitor, for me this appeals as much as omitting the op-amps. Whether my ears can tell the difference of course, time will tell.
I'm heading headfirst into the tube output, I have no idea how tube output can avoid the high frequency components of the DAC output though, all op-amp designs are designed to filter this. But..... Lampizator's enthusiasm has convinced me to give it a go. One thing that's really nice about this current output DAC is that changes can be totally reversible. Pull out the I/V op-amps, insert leads into the op-amp sockets and off to the tube stage. Don't like it, remove leads and op-amps back in! Hey-presto. A second nice thing is that the SRPP tube stage needs only one capacitor, for me this appeals as much as omitting the op-amps. Whether my ears can tell the difference of course, time will tell.
help me help me please
problem with the left channel.
no music no noise, nothing.
the opamp after 3 second the DAC put ON is pratically untouchable: very very very HOT
!!!
the other opamp(right channel) are normally tepid.
no modding on the DAC board neither on the power supply board.
transformer 12-0-12.
only the imput transformer put in.
the supply is +/- 12v.
thanx a todos for help.
problem with the left channel.
no music no noise, nothing.
the opamp after 3 second the DAC put ON is pratically untouchable: very very very HOT
!!!the other opamp(right channel) are normally tepid.
no modding on the DAC board neither on the power supply board.
transformer 12-0-12.
only the imput transformer put in.
the supply is +/- 12v.
thanx a todos for help.
Any news on this?The reversed input polarity on opamp... Are you shure?
Hi Grael
I'm not sure it makes any difference, except maybe if you want to remove some of the SMD components. As my board is, the -ve current outputs are by the edge so easier to lift if I do so.
The Lampizator tube stage is working now, hideous 50 Hz hum initially, mostly resolved but not completely yet. DAC sounds great with tube but painful if you don't know what you're doing (like me). The experience has increased my interest in inductors!
I'm not sure it makes any difference, except maybe if you want to remove some of the SMD components. As my board is, the -ve current outputs are by the edge so easier to lift if I do so.
The Lampizator tube stage is working now, hideous 50 Hz hum initially, mostly resolved but not completely yet. DAC sounds great with tube but painful if you don't know what you're doing (like me). The experience has increased my interest in inductors!
Regarding tube output of the DAC: I've fixed the mains hum problem I had and the fix was trivial and well-known, just follow the instructions on this link on how to make a star ground.
http://www.geofex.com/article_folders/stargnd/stargnd.htm
Now that it's running quietly I definitely recommend it, the basic circuit is here
http://www.lampizator.eu/LAMPIZATOR/REFERENCES/SATCH/IMG_5501.jpg
I didn't use exactly the HV supply in the above link, I think I have about 170 V biasing the tube anode, and I use a LM317HV regulated 12.6 V DC supply for the heaters in series. I will be trying the HV bias circuit by Thorsten Loesch on the link below to see if any difference is audible to me.
http://www.fortunecity.com/rivendell/xentar/1179/theory/vasfda/vasfda.html
Regarding the SRPP circuit, I usually see the output capacitor connected to the upper tube cathode, here it is connected to the lower tube anode. Both work, is one preferred over the other in some circumstances?
For the sound, I loved the stock op-amp version, and used it nearly exclusively with my tube amp. Since the addition of tube out on the DAC, I've switched nearly 100% to my LM3886 monoblocks from chipamp.com. I built these but never warmed to them, but with this DAC they sound super, I really appreciate the detail and separation they give. I do find that I'm listening a bit less to vocal music (Isabelle Antena, Terry Callier) and more to electronic music (Trentemoller, mixes from Resident Advisor). For my next project I'll build a pair of tube amps (Oddblocks), this modification makes me feel more confident about completing that successfully.
http://www.geofex.com/article_folders/stargnd/stargnd.htm
Now that it's running quietly I definitely recommend it, the basic circuit is here
http://www.lampizator.eu/LAMPIZATOR/REFERENCES/SATCH/IMG_5501.jpg
I didn't use exactly the HV supply in the above link, I think I have about 170 V biasing the tube anode, and I use a LM317HV regulated 12.6 V DC supply for the heaters in series. I will be trying the HV bias circuit by Thorsten Loesch on the link below to see if any difference is audible to me.
http://www.fortunecity.com/rivendell/xentar/1179/theory/vasfda/vasfda.html
Regarding the SRPP circuit, I usually see the output capacitor connected to the upper tube cathode, here it is connected to the lower tube anode. Both work, is one preferred over the other in some circumstances?
For the sound, I loved the stock op-amp version, and used it nearly exclusively with my tube amp. Since the addition of tube out on the DAC, I've switched nearly 100% to my LM3886 monoblocks from chipamp.com. I built these but never warmed to them, but with this DAC they sound super, I really appreciate the detail and separation they give. I do find that I'm listening a bit less to vocal music (Isabelle Antena, Terry Callier) and more to electronic music (Trentemoller, mixes from Resident Advisor). For my next project I'll build a pair of tube amps (Oddblocks), this modification makes me feel more confident about completing that successfully.
Ok, I checked, you were right, highfieldrebel!The reversed input polarity on opamp... Are you shure?
So, it's better to know this to avoid that left and right channels have different phase...
Good job on your tube output!
But far too complicated (and dangerous) for me and my pitiful soldering skill!
oh #%@$!
Now i've done it. Nevermind the beating i took on the stock market today, i thought i'd tweak a little with my Gigawork board... I was hearing some clipping/distortion so i decided to do some op amp swapping on the last one and replaced it with a OPA627 dual, but 180deg the wrong way. There was a bit of smoke and the op amp was very hot & smelly, so i replaced it but now only have RT channel audio. Swapped around the I/V's with others and still no go. I don't see any evidence of traces or anything else fried, but does anyone have any ideas? I'm only equipped with a DMM, fwiw.
now i'm beating myself up for double stupidity... tech stocks and tech swaps. oy vey.
Now i've done it. Nevermind the beating i took on the stock market today, i thought i'd tweak a little with my Gigawork board... I was hearing some clipping/distortion so i decided to do some op amp swapping on the last one and replaced it with a OPA627 dual, but 180deg the wrong way. There was a bit of smoke and the op amp was very hot & smelly, so i replaced it but now only have RT channel audio. Swapped around the I/V's with others and still no go. I don't see any evidence of traces or anything else fried, but does anyone have any ideas? I'm only equipped with a DMM, fwiw.
now i'm beating myself up for double stupidity... tech stocks and tech swaps. oy vey.
also...
Is there any way to measure the L/R +/- out of the PCM1798 to determine if this could be fixed or a candidate for Lampucera or Trafo stage?
Is there any way to measure the L/R +/- out of the PCM1798 to determine if this could be fixed or a candidate for Lampucera or Trafo stage?
Mootzeroni, I think you have the right idea on how to identify the problem.Is there any way to measure the L/R +/- out of the PCM1798 to determine if this could be fixed or a candidate for Lampucera or Trafo stage?
Pull the left op-amp (U11) on the schematic, and put a 100 ohm resistor between sockets 2 and 3, and another 100 ohm resistor between 5 and 6. Have input running, the louder the better probably and measure the AC voltages across pins 2 and 3, and across 5 and 6. If you don't get a clear result, do the same on the right op-amp (U12) to compare. We're looking for about 10 to 100 mV of signal is my guess.
Good luck, and take a bit of care placing your DMM probe tips, lots of ICs get dead with one of these slipping and shorting something unfortunate!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.