An old question, with a new twist (I believe)...
I will use an active line stage (preamp) with balanced inputs. I will therefore use the balanced outputs from the DDDAC 1794 chips.
What is the better coupling option: capacitors or transformers? Why?
Caveats:
I will use an active line stage (preamp) with balanced inputs. I will therefore use the balanced outputs from the DDDAC 1794 chips.
What is the better coupling option: capacitors or transformers? Why?
Caveats:
- So far all comparisons between caps and transformers were for SE output using caps and BAL output using transformers. It's not surprising that BAL sounded better due to the stronger drive and the partial cancellation of non-linearities.
- I am not (yet) asking for specific parts (caps or trannies). I am interested on the principle techniques.
- I don't need the voltage gain that would be possible with transformers, so that's not a 'pro' argument for transformers in my case.
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If it's a real balanced preamplifier, then as I recall, nothing needs to be applied to the DDDAC output. So direct connection is possible. The 2.7V DC present at the outputs will be canceled as common mode at the input of the preamplifier. If the preamp has a potentiometer at the input, then this cannot be applied as DC current will flow through the potentiometer. Otherwise, in my experience, a transformer sounds better than a capacitor at the output, but not every one. Some are even worse than cheap capacitors.
I have a problem ... 
No sound from DDDAC-output after blown fuse in the PSU (the lower voltage one) ... Where can I start to look for problems? So far I have verified that amp is working (vinyl), and that my BBB-streamer is working (I can hear very faint sound comming out from speakers ...) Any takes?
No sound from DDDAC-output after blown fuse in the PSU (the lower voltage one) ... Where can I start to look for problems? So far I have verified that amp is working (vinyl), and that my BBB-streamer is working (I can hear very faint sound comming out from speakers ...) Any takes?
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I asked the manufacturer of the preamp, and they recommended to block the DC.
Just to be sure: did you mean "a capacitor" (single ended), or two capacitorS (balanced)? Did you compare caps and transformers both in balanced configuration?
If you have to block DC on the balanced outputs, you need two transformers or four capacitors. I haven't tried balanced out because I don't have any balanced audio devices, but my friend has and it works (4 capacitors). No one I know has tried it directly.
With capacitors, each balanced output should be bridged to signal GND with a 150-200k resistor to charge and discharge the capacitors to 2.7VDC. When I had capacitors, I bridged it with 4 resistors 150k on a balanced connector, and the RCA connector was just connected in parallel to the plus output and signal GND. With a transformer, bridging output with resistor to GND is not necessary. If the transformer requires compensation on the secondary, plus and minus outputs are connected usually with 1k5-2k5 ohms for 600:600 ohms transformers (one resistor at each secondary winding).
With capacitors, each balanced output should be bridged to signal GND with a 150-200k resistor to charge and discharge the capacitors to 2.7VDC. When I had capacitors, I bridged it with 4 resistors 150k on a balanced connector, and the RCA connector was just connected in parallel to the plus output and signal GND. With a transformer, bridging output with resistor to GND is not necessary. If the transformer requires compensation on the secondary, plus and minus outputs are connected usually with 1k5-2k5 ohms for 600:600 ohms transformers (one resistor at each secondary winding).
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Ok.
I have a good understanding of the BAL and SE connections. Your description of using caps for BAL output is intriguing:
1. Why did you use FOUR caps although you used SE instead of BAL connections?
2. What do you mean by signal GND? There is no such thing with a BAL connection.
You didn't understand me well.
I put four capacitors in order to have DC isolated balanced outputs, even if I didn't use them. We usually exchange audio equipment with each other, some have a balanced system. To charge the capacitors, they should be connected to a signal GND over 150k, so that you don't hear a crack when you select the input with DDDAC on the preamplifier. It does not affect the operation of the balanced connection in any way.
The SE output is made by taking the plus output from the balanced connector to the hot output of the RCA connector, and the cold output of the RCA connector must be connected to the signal GND on the motherboard.
Doede explained it all long ago.
I put four capacitors in order to have DC isolated balanced outputs, even if I didn't use them. We usually exchange audio equipment with each other, some have a balanced system. To charge the capacitors, they should be connected to a signal GND over 150k, so that you don't hear a crack when you select the input with DDDAC on the preamplifier. It does not affect the operation of the balanced connection in any way.
The SE output is made by taking the plus output from the balanced connector to the hot output of the RCA connector, and the cold output of the RCA connector must be connected to the signal GND on the motherboard.
Doede explained it all long ago.
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So, regarding this one, I am still stuck. I suspect it might be the cinemags that are blown, so I though I should try with the old caps to check if that gives any sound. Only I'm not sure how to wire this. Is it as simple as couple it between pos and neg?I have a problem ...
1. Disconnect DDDAC from PSUI have a problem ...
2. Replace fuse
3. Turn on PSU
Does the fuse blow again?
If you get the correct voltage at the PSU out:
1. Turn off
2. Reconnect PSU to DDDAC
3. Turn on
4. If fuse is happy and there is no smoke etc., try to follow the supply voltage on the DDDAC using a DVM.
5. If supply voltages are ok: do you get the expected voltage drop on the output load resistors (approx. 2.4 V)?
If this is all ok: play some music on the DDDAC and check if the audio signal appears at the load resistors (use a scope, or a DVM in AC setting, or a headphone/loudspeaker hooked across the POS & NEG outputs).
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Alreight... I gave this a try. My setup is as follows: DDDAC balanced out --> Pass XP 12 (balanced input into MUSES/stepped-resistor volume control) --> USSA5 power amp --> Open Source Monkey Coffin loudspeakers. I compared the DDDAC balanced output with (i) my Sowter 9335 transformer vs (ii) DC blocking capacitors (Wima MKP 4.7 μF). Both options don't provide any voltage gain, so no worries about different signal levels.
The Wima MKP caps are good no-nonsense parts. According to my experience, such parts are perfectly transparent and do not affect the sound at all as long as we're talking about DC blocking of low-power signals (yes, capacitor "sound" may be a thing in loudspeaker x-overs, where real current/power is involved -- a very different story).
Of course, by using the balanced outputs of the DAC chips, the partial cancellation of the non-linearities of the DAC chips works in the same way as with a transformer. As expected, the caps are totally transparent. In contrast, the transformer does add a tiny little bit of it's sonic signature. Brass instruments get a slightly fatter, sexier sound, and female voices may have a wee bit of "bloat". I wouldn't say that these effects are good or bad in an objective view. However, my subjective ears prefer the caps.
After reading the capacitor tests by Cyrill Bateman (a highly recommended read!) I may also try some 4.7 μF Wima FKP caps, which use a proper metal foil, not just a flimsy layer of a metal-vapour deposit. To be honest, though, I don't expect to hear a difference.
Conclusion: if you don't need any voltage gain in front of your (pre-)amp, and if your (pre-)amp accepts balanced connections: use the DDDAC balanced output!
All you need is four capacitors.
It seems ok as far as I can tell, but there is just a very faint sound of music in the background ... I think I should try to bypass the transformers and instead try the caps that I used to have there. It would be nice to get a refresher on the wiring on that, though ... Pos and com with a certain resistor inbetween? I'll see if I can find it on the dddac website if no one happens to have it already here ...
Hi DDDAC lovers and everyone interested. The last years we spent a lot of time on (expensive sometimes) upgrades and tweaks. So much and after so many years we might forget about how simple the dddac can be setup in it basic form for a very reasonable budget. Dick from Audio Creative wrote a very nice article / blog on the original basic setup of the DDDAC.
It is in Dutch, but there is a button to to translate the text in any other language…..
In my own office, I still use a very basic dddac with a small 40 watt amplifier and a few small B&W speakers. Always enjoy it
Article on back to basics
It is in Dutch, but there is a button to to translate the text in any other language…..
In my own office, I still use a very basic dddac with a small 40 watt amplifier and a few small B&W speakers. Always enjoy it
Article on back to basics