Author Topic: "What the hell is this, and why do I need one?"  (Read 6457 times)

Offline alexm

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Re: "What the hell is this, and why do I need one?"
« Reply #15 on: July 29, 2019, 07:35:04 AM »
Today I've received a parcel at the post office. Looks stunning. Thank you!

Offline Analog

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Re: "What the hell is this, and why do I need one?"
« Reply #16 on: July 29, 2019, 03:53:15 PM »
Forget how it looks!

Put it in something, and tell us how it works!

Offline alexm

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Re: "What the hell is this, and why do I need one?"
« Reply #17 on: July 29, 2019, 04:13:26 PM »
Oh, it will take some time since I haven't finished my DAC project yet, but I'll do (I have a good gut feelings for the improvements brought by this device). Thank you again!

Offline Analog

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Re: "What the hell is this, and why do I need one?"
« Reply #18 on: June 01, 2020, 10:26:33 AM »
Working on a new version that will:

Have 2 inputs. (It is designed to drop into that ancient DAC we made in a previous lifetime.)

Work on either 3.3V or 5V logic designs.

The first version is up and running, but there are a few things that probably need to be changed. Originally, it was basically taking 2 of the above PCBs, and placing them side-by-side, with the switching in the middle. Looks like the 2 inputs don't like being that close together, so they are both oriented horizontally, which makes for an odd-looking really long PCB.

Stay tuned..........................

Offline drmike

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Re: "What the hell is this, and why do I need one?"
« Reply #19 on: June 05, 2020, 07:28:38 AM »
hey pat,
would this work with my legato? would i have to retro fit it to my dac?
thanks,
drmike

Offline Analog

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Re: "What the hell is this, and why do I need one?"
« Reply #20 on: June 05, 2020, 09:15:25 AM »
It is only for a DAC.

The input stage, for ANY DAC, that uses the CS8412/4/6 RX chips needs major help. It uses a Schmitt trigger, hung directly on the line, which is probably the worst thing that you can possibly do.

The idea was to introduce some hysteresis, to keep the input stage from bouncing around. A good idea, but putting it right on the line is dreadfully bad idea. So, this acts as a buffer, to that, and does some other "signal conditioning".

The guys who make the DACs copy the circuit in the datasheet, and it is the worst one imaginable. (Yeah, I know...................how can it be so bad, and why would they do it if it was that bad? Because they don't know any better.) It also has that nasty transformer everyone has been told is so damn good. (There are tons of rantings, by myself and the rest of the gang down here, on lots of forums, on how bad that transformer is and why.)

So, this fixes both problems at one time, for both channels.

The DAC we made, way back when, did not have a transformer-coupled input, so this adds that feature. The switching was done, with a relay, ahead of the active circuitry, as that took up less space (way back then) than making 2 active stages, and switching it digitally. Plus, the chips back then were sooooooooooooooo big!

The whole thing now is all SMT, so it doesn't need a lot of space. We have chip families that will work on both 3.3V and 5V, so we can use it for old designs that use the CS8412, and ones that use the CS8416. Each stage is "self-contained", with their own regulators. Again, thanks to modern SMT chips, we can get regulators for both voltages with the same footprint. The only drawback, if you want to call it that, is each channel needs its own transformer. (And the first attempt they seemed to talk to each other, up above 80 MHz or so.)

Anyway, probably more info than you wanted, but that is what it does and why it does it.

Offline drmike

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Re: "What the hell is this, and why do I need one?"
« Reply #21 on: June 05, 2020, 11:35:23 AM »
so if my dac had this gizmo retrofitted, my dac has a bnc coax jack, would it work connected to the legato? this way over my head?

Offline Analog

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Re: "What the hell is this, and why do I need one?"
« Reply #22 on: June 05, 2020, 03:17:57 PM »
If you only have ONE input jack, you would buy the PCB that is shown.

If your DAC has two input jacks, this might work, but only if the holes, for the 2 input jacks, line up.

And they probably won't................

Then you have to know how your DAC works, in order to wire it in. Find the supply voltage.................know where the output wire goes............if you need the selector version, where to pick up that control wire.

Yeah, might not be for you............

Offline drmike

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Re: "What the hell is this, and why do I need one?"
« Reply #23 on: June 06, 2020, 05:32:36 AM »
you're right!