I am using the sowter TVC (9335) directly connected to the balanced output of the DDDAC (single deck !) without any coupling caps going to a pair of mono blocks power amps (300b) at an input impedance of 100k ohm. This combination works very fine for me. I have tested the TVC with an isolation transformer (3575) as well and found out there is no need for that! The 9335 is an excellent TVC and I could even not measure any resonance from 20Hz up to 100KHz !!! ; almost a flat response ;-)
The recommendation of coupling caps in front of the TVC is to make sure there is no DC available at the input of the TVC that could damage it (core magnetizing issue). But the balanced output of the DDDAC is almost DC free so you should not have problem with that configuration (but measure it just to be sure ;-) ) .
I have also tested the LDR solution (even battery driven!!) and found out that they do not come close to a good TVC.
Promitheus TVC are still manufactured (at least until 6 months ago) and have good reputation. Music First Audio (Stevens & Billington) suppose to be one of the best but also one of the most expensive one. I am very happy with my Sowters... Also an alternative could be a special TVC version of the Doede's output transformers . I remember to have seen them some where ... Just ask Doede !
Of course no resonance with no series capacitance to the inductive shunt..
I'd be interested to see how long this works for you, and the only reason I mention is that I've blown up OPA861 stages, twice, by loading them this way. Having said that, I'm not sure of the output stage of the DDDAC.. but if its open loop opamp, inductively loaded.. I find they work for a while.. and then don't
Hi,
I just recently got the 4 tier dddac built up and it's sounding really great though I dare not use it yet because of one issue. It seemed that DAC is not behaving normally even though there's music coming out from the output. I am measuring a voltage of 2.7v potential difference between the positive and common pins right before the output cap when music is not playing. Of course after the 2.2uF coupling caps it measured 0v. Doesn't look right to me so need the experts help here.
Other than that it sounded great actually.
Thanks!
I just recently got the 4 tier dddac built up and it's sounding really great though I dare not use it yet because of one issue. It seemed that DAC is not behaving normally even though there's music coming out from the output. I am measuring a voltage of 2.7v potential difference between the positive and common pins right before the output cap when music is not playing. Of course after the 2.2uF coupling caps it measured 0v. Doesn't look right to me so need the experts help here.
Other than that it sounded great actually.
Thanks!
What do you expect a voltage out DAC chipto do. That i why you need cap. or a traffo
Thanks all for the reassurance. Really needed it for music therapy.
Direct out from DAC is something new to me. My past experiences in building digital doesn't have this "built in dc offset" as there's always a gain stage that will address the DC offset (some of which even utilize some form of servo feedback). As I understand, the resistors are functioning as the I/V converter, so does this mean that even when there's no feeding of information from the I2S DATA line, the DAC is outputting some current to result in potential difference? I guess it's time for me to read the 1794 datasheet in more detail.
Direct out from DAC is something new to me. My past experiences in building digital doesn't have this "built in dc offset" as there's always a gain stage that will address the DC offset (some of which even utilize some form of servo feedback). As I understand, the resistors are functioning as the I/V converter, so does this mean that even when there's no feeding of information from the I2S DATA line, the DAC is outputting some current to result in potential difference? I guess it's time for me to read the 1794 datasheet in more detail.
Or read my website, it is all there
Gosh ... I did read your website... I must have really had a bad day and missed it....
Now I see it. Thanks! So indeed that there's current out at zero signal. This is a new learning for me. Appreciate it.
Will post some pics later to share with folks here my version of DDDAC.
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I am in the US and got a blue mainboard in two weeks.
Is NORWAY being punished for not being a full-fledged member of the EU? Does your package have to go through the German post office on its way to you?
(that will teach you ...)
As longs as it is 2 channel feed this should work, not if it 7.1 or 5.1
Not sure how that should work....
Norwegian customs are not the fastest I know. But check the tracking nr I would say, so you know where it is.... My experience is that indeed something's Europe could take three to four weeks, sometimes three days.... Hard to say
The problem is that I have no tracking number.
I guess you are right about the Norwegian customs.
Time will tell.
Susumu RG Rload Resistors
I replaced 120 ohm tantalum Rload resistors with pairs of 270 ohm Susumu RG SMD resistors on my second single board DDDAC setup. See pic.
Sounds great! More clarity without becoming analytical or losing musicality. To me the Susumu already sounds better than the Tantalum.
I've done considerable research on various audio forums regarding the Susumu RG resistors. They always beat the Dale RNxx resistors in clarity. One person compared the Susumu with all the standard and premium audio resistors and found it to be exceeded only by the TX2575 in sq.
Best of all, this is a CHEAP upgrade from the Dales. A dozen 270 ohm RG Susumu resistors cost less than $5usd from Mouser which is much less than the cost of ONE TX2575 or Rhopoint resistor. There is a substantial price break for 10 or more Susumu resistors. Also, it is easy to lose or fry apart these little buggers. These Susumu's have a 0.1% tolerance and rated at 25ppm/C.
The RG3216 sized SMDs are rated conservatively at 0.125 watts so a pair is rated at 0.250 watts for 0.054 watts of current load from one PCM1794 per differential output leg. I'm sure there is a creative way to gang a bunch of these at the proper values to be able to handle 0.216 watts generated from 80ma coming from a 4 board stack.
I replaced 120 ohm tantalum Rload resistors with pairs of 270 ohm Susumu RG SMD resistors on my second single board DDDAC setup. See pic.
Sounds great! More clarity without becoming analytical or losing musicality. To me the Susumu already sounds better than the Tantalum.
I've done considerable research on various audio forums regarding the Susumu RG resistors. They always beat the Dale RNxx resistors in clarity. One person compared the Susumu with all the standard and premium audio resistors and found it to be exceeded only by the TX2575 in sq.
Best of all, this is a CHEAP upgrade from the Dales. A dozen 270 ohm RG Susumu resistors cost less than $5usd from Mouser which is much less than the cost of ONE TX2575 or Rhopoint resistor. There is a substantial price break for 10 or more Susumu resistors. Also, it is easy to lose or fry apart these little buggers. These Susumu's have a 0.1% tolerance and rated at 25ppm/C.
The RG3216 sized SMDs are rated conservatively at 0.125 watts so a pair is rated at 0.250 watts for 0.054 watts of current load from one PCM1794 per differential output leg. I'm sure there is a creative way to gang a bunch of these at the proper values to be able to handle 0.216 watts generated from 80ma coming from a 4 board stack.
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