MDAC First Listen (part 00110011)

[JohnW]

The ph5 gain is moderately low at 57db, i'd expect 64db for a MC stage, 40-44for MM stage. Noise is stated as 76db below 1mv at 1khz input. It is quite low output voltage though.

If you want a proper MC stage, just say the word.

Everyone has good words about your phono stage - so yes it be brilliant if I could use as a reference for the FDAC's internal stage

At least having a known good phono stage removes the preamp from the equation in my quest to solve the SQ issues with my Vinyl front end...

You dont now where I can source an inverse RIAA EQ filter do you? - I guess I'll have to build one - the only issue is sourcing the odd capacitor values...

 

[sam_cat]

I thought they said Zion before Christmas

The same was said of the FDac......

 

[ChrisPa]

I thought they said Zion before Christmas

The same was said of the FDac......

No! Really?

 

[sam_cat]

No! Really?

Ah, missed your (browsing ghost mode at work, black and white, no images etc)

 

[misterdog]

I thought they said Zion before Christmas

They all have day jobs also.

 

[sq225917]

Tell me the cap values John, I can source decent styrenes if needed.

 

[JohnW]

One point why use transformers I can understand in a valve stage

WRT Tube noise this is a question I needed answered for the VFET front end, so I measured a simple 20dB gain stage with 1mV input.

NE5532 (for Baseline measurements) 64dB Awtd SNR

6n17b 53dB

6111WA 56.5dB

JJ E88CC 50dB

6922 61dB

6n23 62.98dB(THD 0.0003%)

So it looks like we will be using the 6n23 for the VFET input stage - its only a couple of dB worst then a NE5532 in my tests.

I have 800 or so 6111WA's in the basement which I had planned to use for the VFFET / TDAC... but it looks like I'll be using 6n23's...

6n17b

https://dl.dropboxusercontent.com/u/86116171/6n17b.JPG

6n23

https://dl.dropboxusercontent.com/u/86116171/6n23.JPG

 

[jirij]

Just make sure you don't accidentally order the Russian 6b12 or 6b23.

(Do they have to name everything like this?)

 

[BigDog]

I just asked our PSU vendor for a couple of 110V samples, so I'll ship you one of these.

Scouting around a bit on this side of the pond for a 9V / 1A LPS for 120V AC mains.

Would this, other than 2.5mm plug size, be what you would be considering?

<http://www.jameco.com/z/MT12-Y090100-A1-Arndt-9-Volt-1-Amp-9-Watt-Regulated-Linear-Wall-Adapter_2227428.html>

How important is the quality of the DC to the optimum operation of the DETOX?

 

[LarsS]

That sounds great John. Looking forward to listening to them on my MDAC2. Hopefully I can pickup that up from you in the next Munich show? It's 162 days away so you have plenty of time:

http://www.highendsociety.de/index.php/en/high-end.html

Hope you can make it. I am buying the drinks if you have my MDAC2 otherwise you are buying. Deal?

I'll join you both in Munich, no matter what's the project status I'll treat you for beers (since we're in beers homeland).

Only been on this roadtrip for 1190 days / 3 years, 3 months, 3 days since first joined, so what's another year ... ;-)

 

[jadidih101]

I'll join you both in Munich, no matter what's the project status I'll treat you for beers (since we're in beers homeland).

Only been on this roadtrip for 1190 days / 3 years, 3 months, 3 days since first joined, so what's another year ... ;-)

That sounds great. Looking forward to it. Warning: John does not like beer. He seem to only like hard liquor and lousy tea.

 

[LarsS]

That sounds great. Looking forward to it. Warning: John does not like beer. He seem to only like hard liquor and lousy tea.

... ... let's teach him how great a good beer can be

 

[iansr]

... ... let's teach him how great a good beer can be

The beer in Munich is very good, but I think you are forgetting where John lives! Czech beer is very very good. Nearly as good as Timothy Taylor's in fact. . . .&#128513;

 

[JohnW]

Scouting around a bit on this side of the pond for a 9V / 1A LPS for 120V AC mains.

Would this, other than 2.5mm plug size, be what you would be considering?

<http://www.jameco.com/z/MT12-Y090100-A1-Arndt-9-Volt-1-Amp-9-Watt-Regulated-Linear-Wall-Adapter_2227428.html>

How important is the quality of the DC to the optimum operation of the DETOX?

"Output connector: 2.5mm x 5.5mm, centre positive female barrel plug"

Detox uses a 2mm centre positive female barrel plug

Looking at the picture of the PSU and its looks like a Switching supply as its relatively thin and narrow.

With audio, every improvement in PSU seems to bring a positive change - that said the linear supply we are recommending for the Detox is only a simple linear unregulated DC output.

 

[Jason_PFM]

Apparently USB 2.0 galvanic isolation is now possible:
http://intona.eu/en/products
http://www.tnt-audio.com/accessories/intona_usb_isolator_e.html

As I understood, the Detox will only have galvanic isolation on the USB 1.0 output, but not the USB 2.0 output ?

They also seem to attenuate the packet noise by modulating the frequencies in a spread spectrum fashion.

Wonder how easy it would be to start using the new semiconductors in the Detox ?

 

[MattN]

Apparently USB 2.0 galvanic isolation is now possible:
http://intona.eu/en/products
http://www.tnt-audio.com/accessories/intona_usb_isolator_e.html

As I understood, the Detox will only have galvanic isolation on the USB 1.0 output, but not the USB 2.0 output ?

They also seem to attenuate the packet noise by modulating the frequencies in a spread spectrum fashion.

Wonder how easy it would be to start using the new semiconductors in the Detox ?

Even got the intona in a pretty box here...

http://jplay.eu/ml_post_slider/jcat-usb-isolator/

 

[GWM]

WRT Tube noise this is a question I needed answered for the VFET front end, so I measured a simple 20dB gain stage with 1mV input.

NE5532 (for Baseline measurements) 64dB Awtd SNR

6n17b 53dB

6111WA 56.5dB

JJ E88CC 50dB

6922 61dB

6n23 62.98dB(THD 0.0003%)

So it looks like we will be using the 6n23 for the VFET input stage - its only a couple of dB worst then a NE5532 in my tests.

I have 800 or so 6111WA's in the basement which I had planned to use for the VFFET / TDAC... but it looks like I'll be using 6n23's...

6n17b

https://dl.dropboxusercontent.com/u/86116171/6n17b.JPG

6n23

https://dl.dropboxusercontent.com/u/86116171/6n23.JPG

Interesting I use 5751 valves in my stage they are the best I have tried from a subjective point.

 

[JohnW]

Apparently USB 2.0 galvanic isolation is now possible:
http://intona.eu/en/products
http://www.tnt-audio.com/accessories/intona_usb_isolator_e.html

As I understood, the Detox will only have galvanic isolation on the USB 1.0 output, but not the USB 2.0 output ?

Yes detos only offers a isolated USB1.1 which is perfect for MDAC, and FDAC / MDAC2 have islaoted USB2.0 inputs so external isolation is not required.

You can think of "isolation" as attenuation in the real world as 100% isolation is not possible - so added extra isolation is not a bad thing

They also seem to attenuate the packet noise by modulating the frequencies in a spread spectrum fashion.

I don't see any mention of the spread spectrum, but looking at the PCB and they are not performing the same process as Detox.

This would work well between the USB host and Detox as extra signal "cleaning" is always helpful - but for those DAC's that are powered via the USB this unit does not offer the lowest noise - although substantially lower then from your typical PC / USB host.

 

[JohnW]

reat the MC stage as the best mic preamp you can come up with.

What Gain do Mic's need? I would have thought your typical MC gain would be too much - for some reason have I just presumed Mic's would be good with MM type gain of 40dB to 50dB?

 

[JohnW]

Interesting I use 5751 valves in my stage they are the best I have tried from a subjective point.

Interesting as people say that the GE 5751 sounds similar to the 6DJ8 (aka 6922)