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

according to the resistor structure/design and the data sheet var and vta series should be non-inductive / non-capacitive over a wide range.
http://www.partsconnexion.com/prod_pdf/vishay_var.pdf

Hi Mr_Whocares,

Are these Vishay "var" resistors, the same than the Vishay Bulk Foil TX-2575 ? (also named Charcroft ?). If not, where have you ordered them from ? They are rated 0.4W: is it enough ?...

For the others, I have started the building from the end (!) waiting the receive the dddac power supplies, meaning that I have adapted the Arduino program shown earlier in this post, to display the sample rate and the voltages (delivered by both the +12V and +5V power supplies of the dddac) on a LCD display.

It works, but the displayed voltage value varies +/-0.75V whereas the multi-meter indicates a stable voltage around 4.82V !?!... It seems that the loop delay (set as 200) affects the displayed value, or maybe the Arduino is not confortable in measuring its own +5V power source on its analog input ?? (that I have used for this test as I have not yet received the dddac P.S.)...
 
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Hi Mr_Whocares,

Are these Vishay "var" resistors, the same than the Vishay Bulk Foil TX-2575 ? (also named Charcroft ?). If not, where have you ordered them from ? They are rated 0.4W: is it enough ?...

yes, i think they are the same type.
as far as i know, they are available in 3 different tolerances : 1%, 0.1% and 0.01% . you can order them at many distributors/reseller (if on stock ;-) ) such as parts connextion (Vishay VAR-Series "naked" Z-FOIL RESISTOR), farnell (Y0706100R000T9L - VISHAY FOIL RESISTORS / VPG - WIDERSTANDAUDIOPRAEZISION,100R | Farnell Deutschland) , etc.

the rated power of 0.4w should be more than enough; i have been testing them for days and they do not get even warm in this application.
 
Hi,

I have been experimenting with resistors from my junk box. First I tried audio note tantalum, i did however not have the rigth value so I used 47 instead of 33 ohms. This does not work, the values are very picky, I had clipping issues.

I did however find some old stock allen bradly wich I could combine parrallal to get 33,6ohms, within 0,02 ohms matched. DC measured was 0,01v so this would work with my direct coupled output to the tube amps.

And then the sound: these are a bunch better than the dale! More natural, more openness, and most important; more colour :rolleyes:

In comparison the dale is more grey sounding. If you know what I mean................

Regards,
 
I´ve built the 4 DAC version. Does it make sense to remove all 3,3V and 8V regs and interconnect all boards for 3,3 and 8v (L and R separately of course) and connect the 3,3V directly to a LiFePO battery? For 8V a shunt-reg like tentlabs or belleson? It´s 4x cheaper! or..?

apoo
 
DSD and so on......

G'day All,

Looking very seriously at this, question I have is thus, have emailed Doede regards DSD, asking about the GTG they had comparing the dac's etc where DSD/ISO files were played, he replied mentioning the blog post(not his) was a little misleading, they were not played direct but converted to PCM before play. I have an Alix 2D2, MPDpup OS, both the WaveIO(yet to be updated) and the Amanero. If someone happens to have the same sort of setup, can you try a test for me please? Only as I have new bub on the way and need to be very concious of the dollar spend, I don't want to hassle Doede and hope you fellas can shed some light on this for me.
I know mpd can play DoP(DSD over PCM), can one of you please try it through the DDDAC and let me know if it plays? I would appreciate it no end!
Love the enthusiasm you guys have, enjoyed reading this thread, hope to hear from you soon!
Thanks,
Drew.
 
You need DSD1794 (not PCM1794) to play DSD directly instead of DSD->PCM conversion, with DSD the DAC portion is disabled internally only filter is working and it supports DSD256 as well.

DSD1794 needs I2C to set the registry, and a demux switch to feed PCM and DSD separately as DSD1794 doesn't detect DSD/PCM automatically, sometime its hard to switch between PCM/DSD if there is signal on both input PINs.



G'day All,

Looking very seriously at this, question I have is thus, have emailed Doede regards DSD, asking about the GTG they had comparing the dac's etc where DSD/ISO files were played, he replied mentioning the blog post(not his) was a little misleading, they were not played direct but converted to PCM before play. I have an Alix 2D2, MPDpup OS, both the WaveIO(yet to be updated) and the Amanero. If someone happens to have the same sort of setup, can you try a test for me please? Only as I have new bub on the way and need to be very concious of the dollar spend, I don't want to hassle Doede and hope you fellas can shed some light on this for me.
I know mpd can play DoP(DSD over PCM), can one of you please try it through the DDDAC and let me know if it plays? I would appreciate it no end!
Love the enthusiasm you guys have, enjoyed reading this thread, hope to hear from you soon!
Thanks,
Drew.
 
I/V and transformer

Here is a low cost combination, diy wirewound resistor with ISOTAN non-magnetic resistance wire and lundahl LL1527 transformer, LL1527 is warm at low-middle, with a bit loss at high for transparency, isotan has signature similar to TX2575 (airy), IMHO they match pretty well. (My speaker doesn't go lower than 50hz, probably that's restriction as well).
Also I felt the benefit of combining +/- of balanced output instead of using a single side is great even with a general purpose audio transformer (may also act as LPF).
 
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Thanks Muchly, tis what I feared, that integration may be a bit beyond me I think at this stage. Anyone you know who does a kit for these?
Had looked at Datasheets for both chips and noted the pin changes too. will see what I can imagine up......thanks again for the response.
Cheers
Drew.
 
Hi

I've just placed an order for a dongle board kit, and am now looking for a suitable enclosure. I font want to tule out upgrading, to maybe a 4 stack, so could anyone with a 4 stack advise what internal height I'd need to accommodate them please. Also any recommendations for suitable enclosures would be great. Would need to house, two psus, main board, spdif and waveio modules, and have room for sowthers in the future.

Many thanks, can't wait to get building!
 
dumb question

okay so i have my board but i am confused about the resistors for the main board. i have 1 module so the resistors are 133 are they soldered into RLoad Ra on both right and left?

the completed board shows 8 resistors soldered into position on both Ra and Rb hence my confusion......
 
okay so i have my board but i am confused about the resistors for the main board. i have 1 module so the resistors are 133 are they soldered into RLoad Ra on both right and left?

the completed board shows 8 resistors soldered into position on both Ra and Rb hence my confusion......

For a single DAC board you should solder the 133 resistors to all four Ra connecting points.

Some people use parallel connected resistors hence the reason why you see 8 resistors on some boards.
 
so here is my completed dddac.

internal.jpg


external.jpg


i had 4 led bezels which i salvaged off some other stuff and used. i was going to put some decals on but i am not sure i can be bothered now. i always did like minimalism....


bog standard at the moment as you can see, i have just ordered some clarity caps (m r) so am itching to try them.

am thinking about switching the main board round so that i can connect the caps directly from board to rca. any thoughts on whether this is a good way to go? this will mean i have to get some longer cable to run between the wave and the main board. i know nothing about the cable, does it have a special name and where can i get short runs with the necessary plug attached? if i do this it would mean having to increase the length of led cables too.

anyhow my thoughts on the dac itself. i was pleased that everything worked perfectly first time ie software etc. so often the interface between comp and dac goes tits up. so switch on, install drivers and music straight away. 2 days in and i am impressed, it has been steadily improving. whilst i thought it was a bit lightweight with regards to bass this seems to have become more noticeable and the highs have gained an incisive edge but without becoming strident.