A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

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#3,521
mr_whocares said:
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 !
Click to expand...

At first, thank you for commenting my TVC question - your Sowter build sounds very interesting to me!

Do you perhaps have any photos, schematics, parts lists or the like that describe your build?

Moreover, where did you get the 26-position switches from? The "shalcos" referenced on the sowter page seem not to be available, so I could only use Seiden or ELMA, however, they only offer 24-position switches.

Is it true that there is a "burn-in" phase? At least the Promitheus guys write something about 400 hours burn in.

Best Regards,
Hermann

P.S.: You can also respond by E-Mail so that the forum is not flooded, if you like: hermann@qwer.tk
 
#3,523
dddac said:
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....
Click to expand...

Hi Doede, as I understand, some decoding needs to take place as DD/DTS is compressed (AC3), but it might be a fault with my source too (reading up on the Philips support forum).. . As it's a less critical (listening) feed, I'm thinking going suboptimal, analogue line-out -> ADC -> DDDAC, that will fix it.
 
#3,525
delivery's and trackingnr's

Hi guys, I noticed a lot of fuss about the delivery of the DAC's + tracking nr's and even someone accused us of taking quick money.

Look, we do all the best to deliver the DAC's through out the world. However, some countries are difficult and shipping may take some longer. Mostly caused by slow customs. We do all we can, to solve problems and all our packages are secured and must be signed for. We never lost a package and everyone is supplied at the end.

Our policy is to deliver all over the world, but when people keep nagging about shipping and delivery times, it is easy for us to exclude some countries for selling and shipping. It's your call.

Everyone who asks for tracking nr's are replied within two days. Also most of the technical problems are also solved within days. But I noticed that a lot of our mails end up in spamboxes...
So please, check your spambox first, before accusing us for not replying.

Marco,
Audio-Creative
 
#3,527
dr.knibbeling said:
Hi guys, I noticed a lot of fuss about the delivery of the DAC's + tracking nr's and even someone accused us of taking quick money.

Look, we do all the best to deliver the DAC's through out the world. However, some countries are difficult and shipping may take some longer. Mostly caused by slow customs. We do all we can, to solve problems and all our packages are secured and must be signed for. We never lost a package and everyone is supplied at the end.

Our policy is to deliver all over the world, but when people keep nagging about shipping and delivery times, it is easy for us to exclude some countries for selling and shipping. It's your call.

Everyone who asks for tracking nr's are replied within two days. Also most of the technical problems are also solved within days. But I noticed that a lot of our mails end up in spamboxes...
So please, check your spambox first, before accusing us for not replying.

Marco,
Audio-Creative
Click to expand...


Hi Marco

It was not my intention to start any type of "fuss" about shipping and the time it takes.

Over the years I have been shoppinga lot of hifi stuff on the net, and shipping to Norway have been max 2 weeks ( customs included ).

When i order the DDDAC from your shop I asked for a tracking number. When the order confirmation came there was no tracking nr. When I sendt you a mail and ask where my stuff was, you told me it could take up to 4 weeks. But still no tracking number from you.

I suggest you automaticly send the shipping info when you confirm that an order is beeing shipped. Then your customers know what's going on, and you don't have to answer unnecessary mails from your customers.

This post is written with the best intention from my side, and I realy hope your business is going well in the future.

Best
Tommy
 
#3,528
#3,529
Modding

carlsor said:
I started a new thread explaining the upgrades I made to my single board DDDAC.

http://www.diyaudio.com/forums/digi...ngle-board-pcm1794-nos-dddac.html#post4129467



The first Thread item I detailed was the CCS circuit which should answer your question.
Other Thread upgrade topics will be added as soon as I can.
Click to expand...

Hi Carlsor,

Thanks for taking the effort starting a seperate thread explaining your mods!

For sure I will contact you when I start rebuilding my two -deck DDDAC.
I wonder if a buffer could improve the double in the same way as the single one?
Doing the half clock mod is on the list, same for the pin 20 mod and swapping some of the caps.
Have the cinemags and tantallums from the start, six month ago or so...

Cheers!
Ed
 
#3,531
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Sent from my iPad using Tapatalk
 
#3,532
Hi

Ive installed jfet CCS on pin20 using 2sk208 R. Initial listening is proving positive but
a small problem emerged. I set both CCS to exactly 0.40ma but the bias voltage
measured 2.7V on the left 1794 but only 2.53V on the right. These voltages were
about the same when I refitted the 6K resistors so the CCS are not at fault. Vcc is 8.0V on both 1794s.

I assume that the bias voltage should be set as near as possible to 2.7V to maintain
equal pos and neg o/p voltage swings. Is it then correct to adjust the CCS on the right
channel to get the correct 2.7V?
 
Last edited:
#3,533
Zeta4 said:
Hi

Ive installed jfet CCS on pin20 using 2sk208 R. Initial listening is proving positive but
a small problem emerged. I set both CCS to exactly 0.40ma but the bias voltage
measured 2.7V on the left 1794 but only 2.53V on the right. These voltages were
about the same when I refitted the 6K resistors so the CCS are not at fault. Vcc is 8.0V on both 1794s.

I assume that the bias voltage should be set as near as possible to 2.7V to maintain
equal pos and neg o/p voltage swings. Is it then correct to adjust the CCS on the right
channel to get the correct 2.7V?
Click to expand...

correct! don't bother on 0.4mA... just make sure you have 2,7 Volt on POS and NEG terminal vs. GND Measured BETWEEN POS and NEG terminal you need to come as close as possible to 0mV DC. do not Play Music...
 
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