dddac said:
As far as I understand the value of the output C isn't critical. So why not put in a 100uF just to be sure... Or is this too simple?
Jan
dddac said:
Hi Doede,
Thanks for your postings.
It is very kind of you to offer me to check the dac for me!
But I am sure that now that we have found the problem, I will manage to get the thing working.🙂
Unfortunately (stressed by the lack of luck on that day), I had strifed plus and minus of the two 5 Volt supplies, last week, so I will almost certainly have to swap some parts now. I will start working on it after Christmas since work is keeping me extremely busy now (as is my 10 weeks old baby😉 )
Anyway, thanks again for you kind offer, and I look forward to hearing the DAC somewhere in January!
Regards,
Lucas.
P.S. I am always amazed to see how much experience and expretise can come together through such a forum. Without internet people like me could never have undertaken such projects as these...😎
I am spooked,
Perhaps I seeing things I should not looked for...
I still have an oscilation on the outputs! About 5Mhz, always. I have done:
- one dac (changed resistors to 2k2 and 1k5)
- 8 dacs
- changed voltage
- changed powersupply to 9.6V RC car battery pack
- changed C's up to 470uf
- changed all C's to a minimum of 100uf
- removed the clock circuit and changed to mode 2
- disconnected battery checker
- changed to a LM317
- removed and bypassed the complete 8.5V voltage source (LT1085) and put my variable power supply on 8V
HELP?
Edwin
Everyhing is working, both channels have normal output with this oscillation on top of it. I see the following image on the right and left output, which looks like an oscilation of about 5Mhz... Is this normal???
Snif
Perhaps I seeing things I should not looked for...
I still have an oscilation on the outputs! About 5Mhz, always. I have done:
- one dac (changed resistors to 2k2 and 1k5)
- 8 dacs
- changed voltage
- changed powersupply to 9.6V RC car battery pack
- changed C's up to 470uf
- changed all C's to a minimum of 100uf
- removed the clock circuit and changed to mode 2
- disconnected battery checker
- changed to a LM317
- removed and bypassed the complete 8.5V voltage source (LT1085) and put my variable power supply on 8V
HELP?
Edwin
Everyhing is working, both channels have normal output with this oscillation on top of it. I see the following image on the right and left output, which looks like an oscilation of about 5Mhz... Is this normal???
An externally hosted image should be here but it was not working when we last tested it.
Snif
I'm sorry I can't help but,
Edwin: what's your scope? The screen looks similar to mine. It's a Tek 2232. I got it second hand, and I'm looking for infos, manuals...
Can you help me?
Alex
Edwin: what's your scope? The screen looks similar to mine. It's a Tek 2232. I got it second hand, and I'm looking for infos, manuals...
Can you help me?
Alex
Hello,
It is indeed an Tek 2232. I bought it secondhand also, it is in perfect condition and a great help with these kind of problems! I have a manual with the schematics, however I can not help you with a copy because it is almost impossible to copy with all these fold out pages. However I can help you if you have a problems with the scope, please ask me question if you need any help with it!
Edwin
It is indeed an Tek 2232. I bought it secondhand also, it is in perfect condition and a great help with these kind of problems! I have a manual with the schematics, however I can not help you with a copy because it is almost impossible to copy with all these fold out pages. However I can help you if you have a problems with the scope, please ask me question if you need any help with it!
Edwin
Hi,
Does your manual explain how to connect it to a printer or a computer, to acquire data?
I'd like to know how to use the connectors on the left side.
Alex
Does your manual explain how to connect it to a printer or a computer, to acquire data?
I'd like to know how to use the connectors on the left side.
Alex
doede board sizes
Hi,
For those who have Doede PCBs, what are their sizes? is the PDF scale 1:1?
Looking for a suitable box on RS...
good luck with those oscillations.
Bricolo, have a look at http://www.slack.com/elec.html and http://www.slack.com/manavail.html#atek
Hi,
For those who have Doede PCBs, what are their sizes? is the PDF scale 1:1?
Looking for a suitable box on RS...
good luck with those oscillations.
Bricolo, have a look at http://www.slack.com/elec.html and http://www.slack.com/manavail.html#atek
I cannot see why you have the oscillations, but I assume from your info, you cannot hear them ?? I also doubt if it will do any thing bad to the music, but you might want to try to put a small Capacitor at the output of the dac (so parallel with Rload) Choose a corner freq of lets say 200kHz ?? 4,7nF with 270Ohm....
you can see if the oscillation goes away,
plan b is a RC at the output. lets say, 27 Ohm in series and then 47nF parallel.....
You can listen to music if you prefer one or the other or no filter at all.
good luck,
doede
you can see if the oscillation goes away,
plan b is a RC at the output. lets say, 27 Ohm in series and then 47nF parallel.....
You can listen to music if you prefer one or the other or no filter at all.
good luck,
doede
rbroer said:Pssssttt,
A clue, 128*Fs
That's is what I though 128 * 44Khz = about 5.6Mhz ! Which is my oscillation. And that's why I was starting to think it is not 'my' problem but a more generic design problem (or done on purpose because of the lack of filtering) of the DAC .
However why am I the only one seeing and mentioning this behavoir ???
Edwin
Edwin, I am not sure whether I am about to say is correct since I have not designed a DAC chip before. My understanding is that many multi-bit DAC chips have an osc inside locked to the external reference clock through PLL. This osc can run 128X or even higher and is used to control the current source switching.
What you have seen is the switching noise. In a tradtional DAC design, the LPF will block it out yet this is not the case here. As far as your amp, and especially the speaker tweeter can handle it, nothing to worry about. Not sure whether it is a good idea to add a RC filter to output end. This seems to contradict the idea of a filter-less DAC design. Plus most amps will serve as the filter for you anyway.
What you have seen is the switching noise. In a tradtional DAC design, the LPF will block it out yet this is not the case here. As far as your amp, and especially the speaker tweeter can handle it, nothing to worry about. Not sure whether it is a good idea to add a RC filter to output end. This seems to contradict the idea of a filter-less DAC design. Plus most amps will serve as the filter for you anyway.
Slowly creeping out of the mud...
After swapping parts, fitting Blackgates BG-N 33u, and exchanging the lt1085 for a 317, I still had the same problem...
Then I had to do what I didn't want to do: desoldering the DacTower with the 8 pieces of TDA 1543...😡
Then I put in one TDA without heatsink. For the first time I could hear undistorted sound coming from the dac...🙄
The sound I heard was indeed lively in the midrange. The bass was somewhat lacking in dynamics. The treble however was harsh and undetailed. Not smooth at all, and without any sophistication...
Compared to my already heavily modified Philips DVD 963 SACD this sound wasn't very promising...
I must add however that only ONE TDA was running at its nominal 5 Volt (because of lack of heatsinking), that there hasn't been any break in period, and that the output caps were not a Blackgate N in super-e configuration like it is in the DVD 963 SA.
So maybe it will all improve dramatically.
Now I must consider building a new DacTower, or start a new pcb with 8 pieces of TDA sitting in a rectangular shape with a heatsink on top of them. We'll see...😀
After swapping parts, fitting Blackgates BG-N 33u, and exchanging the lt1085 for a 317, I still had the same problem...
Then I had to do what I didn't want to do: desoldering the DacTower with the 8 pieces of TDA 1543...😡
Then I put in one TDA without heatsink. For the first time I could hear undistorted sound coming from the dac...🙄
The sound I heard was indeed lively in the midrange. The bass was somewhat lacking in dynamics. The treble however was harsh and undetailed. Not smooth at all, and without any sophistication...
Compared to my already heavily modified Philips DVD 963 SACD this sound wasn't very promising...
I must add however that only ONE TDA was running at its nominal 5 Volt (because of lack of heatsinking), that there hasn't been any break in period, and that the output caps were not a Blackgate N in super-e configuration like it is in the DVD 963 SA.
So maybe it will all improve dramatically.
Now I must consider building a new DacTower, or start a new pcb with 8 pieces of TDA sitting in a rectangular shape with a heatsink on top of them. We'll see...😀
Attachments
Re: Slowly creeping out of the mud...
I had 100% the same!
One dac is working, 8 not, even with a LM317 it did not work... You only get to 2.7V output on the Lm317 of LT and lots and lots of oscillation. The only way for me to get it working with 8, is to have an extra 220uf on the + and - power rail very close to the LT1085 it self. I soldered it on the + and - power rails pins parallel to the + and - 12V wires from the battery. I also raised the output C to about 100uf !
This way it works at my place!
Ok, two with the same problem, hardly a coincedence.
E.
Lucas_G said:After swapping parts, fitting Blackgates BG-N 33u, and exchanging the lt1085 for a 317, I still had the same problem...
Then I put in one TDA without heatsink. For the first time I could hear undistorted sound coming from the dac...🙄
I had 100% the same!
One dac is working, 8 not, even with a LM317 it did not work... You only get to 2.7V output on the Lm317 of LT and lots and lots of oscillation. The only way for me to get it working with 8, is to have an extra 220uf on the + and - power rail very close to the LT1085 it self. I soldered it on the + and - power rails pins parallel to the + and - 12V wires from the battery. I also raised the output C to about 100uf !
This way it works at my place!
Ok, two with the same problem, hardly a coincedence.
E.
Re: Re: Slowly creeping out of the mud...
Hi Edwin,
In my case I could easily reach 8.5 Volt though.
I was thinking whether these DacTowers were so badly prone to oscillations... Maybe it is because the distance from the upper TDA on to the capacitor is some 6 cm. In my case the tower is even a bit taller because I put 2 mm thick aluminium between each tda for better cooling. This makes the tower somewhat taller than that of Doede...😕
I think I will try it again with an extra cap soldered on the upper (ultimate) tda. See whether that helps.
Regards,
Lucas
Edwin Dorre said:
I had 100% the same!
One dac is working, 8 not, even with a LM317 it did not work... You only get to 2.7V output on the Lm317 of LT and lots and lots of oscillation. The only way for me to get it working with 8, is to have an extra 220uf on the + and - power rail very close to the LT1085 it self. I soldered it on the + and - power rails pins parallel to the + and - 12V wires from the battery. I also raised the output C to about 100uf !
This way it works at my place!
Ok, two with the same problem, hardly a coincedence.
E.
Hi Edwin,
In my case I could easily reach 8.5 Volt though.
I was thinking whether these DacTowers were so badly prone to oscillations... Maybe it is because the distance from the upper TDA on to the capacitor is some 6 cm. In my case the tower is even a bit taller because I put 2 mm thick aluminium between each tda for better cooling. This makes the tower somewhat taller than that of Doede...😕
I think I will try it again with an extra cap soldered on the upper (ultimate) tda. See whether that helps.
Regards,
Lucas
Re: Re: Re: Slowly creeping out of the mud...
I did not solder an extra cap on the tower. I put it were you connect the 12v from the battery for the dac power. So the cap is in front of the LT1085...
E.
Lucas_G said:
I did not solder an extra cap on the tower. I put it were you connect the 12v from the battery for the dac power. So the cap is in front of the LT1085...
E.
First flight...
I had ordered some new TDA 1543 chips, so I finally decided to build a new Dac-tower...
And indeed, it had been the old DAC-Tower that prevented this Doede Dac to work from the start. Maybe one of the TDAs has been faulty
For the first time I could hear this design with 8 paralell TDAs.
The sound is indeed much better than with one TDA.
I found the sound with 5 Volt supply quite relaxed, but also a bit less controlled in the treble.
Then I upped the voltage to 8 Volt. It does alter the sound quite heavily. There is more definition, but it becomes also a bit leaner and with less ambience in the midrange.
I do like its dynamics in the midrange, but the treble is still way more primitive than with my modded Philips 963
Still not a bad DAC. I will fix it into its new enclosure and use better cabling. I will also try various output capacitors and finetrim the output reference by listening to it. Let's see how much improvement can be made to it. I don't think it will ever beat the 963 DAC, but I will give it a chance.
Regards, and thanks to Doede!
Lucas
I had ordered some new TDA 1543 chips, so I finally decided to build a new Dac-tower...
And indeed, it had been the old DAC-Tower that prevented this Doede Dac to work from the start. Maybe one of the TDAs has been faulty
For the first time I could hear this design with 8 paralell TDAs.
The sound is indeed much better than with one TDA.
I found the sound with 5 Volt supply quite relaxed, but also a bit less controlled in the treble.
Then I upped the voltage to 8 Volt. It does alter the sound quite heavily. There is more definition, but it becomes also a bit leaner and with less ambience in the midrange.
I do like its dynamics in the midrange, but the treble is still way more primitive than with my modded Philips 963
Still not a bad DAC. I will fix it into its new enclosure and use better cabling. I will also try various output capacitors and finetrim the output reference by listening to it. Let's see how much improvement can be made to it. I don't think it will ever beat the 963 DAC, but I will give it a chance.
Regards, and thanks to Doede!
Lucas
Hi Lucas,
Have you tried the Wildmonkeysects loop filter mod yet?
Tonight I am going to test my Doede dac...hope it works...
But I am allready starting to look at possible mods...the wildmonkeysects one looks promising..
as a preventive measure I have also added little 20R resistors as stoppers for pin 1, 2 and 3 of the 1543. And 100R after the clock signal of guido tent's oscillator.
Regards,
Bas
Have you tried the Wildmonkeysects loop filter mod yet?
Tonight I am going to test my Doede dac...hope it works...
But I am allready starting to look at possible mods...the wildmonkeysects one looks promising..
as a preventive measure I have also added little 20R resistors as stoppers for pin 1, 2 and 3 of the 1543. And 100R after the clock signal of guido tent's oscillator.
Regards,
Bas
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