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I/V conversion and opamps - sorting fact from fiction

Mnyb

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Yes DAC is very often the best performer in your whole audio system and are aviable for not much money at all.
And the relatively cheap SOTA DAC’s you can buy is very close the limits of physics. So even better regulation of some voltage to nano volt performance will just hit the limits of physics.

Just the thermal noise in a passive resistor due to quantum physics set some limits.

And the board layout itself is an art form , to get anywhere you must probably do multilayer circuit board with smd components very close to each other ?

I would do this for learning and fun .

And you must get some measurement equipment otherwise you don’t know what’s your doing.
 

kemmler3D

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Personally, I'd never use concrete as I hate the stuff. I'd more likely go for epoxy-granite or a polymer acrylic resin (like Corian), or something I can thermoform.
Makes sense to me, and personally I'm the same way, if I could make the same $$ I make now building speakers, I'd do it in a second. :D

I think any material or process that has an audible benefit and is a poor fit for mass production is viable for DIY SOTA speakers. Personally I would mess with concrete because I would be 3D printing the cabinet, which is easy to make watertight, but lacks stiffness. Cement / concrete can add that in a fairly straightforward way - I think?

Anyway, a little off topic here but best of luck on the DIY SOTA DAC. I have seen some folks on DIYAudio do R2R but I'm not sure if there is much point to that.
 
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Here2Learn

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And you must get some measurement equipment otherwise you don’t know what’s your doing.
In this respect, I was thinking a Rigol MSO5074 seems apt, but analog voltmeter resolution is only 500uV. For most uses, even this scope would be overkill, but it we're postulating a SOTA PSU with noise in the hundreds of nV, then I probably would end up needing something else. Not really looking to spend too much in this realm, since it needs to be cost effective relative to purchasing any SOTA DAC unit. Do you know of any scope with suitable voltmeter resolution that doesn't cost the earth?
 
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Here2Learn

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Cement / concrete can add that in a fairly straightforward way - I think?

.... I have seen some folks on DIYAudio do R2R but I'm not sure if there is much point to that.
You'll get great stiffness with cement. Adding a small amount of graphene powder makes it even stiffer (and virtually eliminates the potential cracking of the concrete due to shrinkage/aging). One then has to figure out how to best damp the inside. Just as there are a myriad of materials that can be used to chase ultimate stiffness, there are a plethora of techniques one can use to attenuate sound energy inside the enclosure other than just types of stuffing.

Back on topic: R2R is possible if one can make super accurate PSU as previously discussed, but there's a lot of other problems (I think). R values for least significant bits, and having them trimmed to match in each channel for instance.
 

solderdude

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In this respect, I was thinking a Rigol MSO5074 seems apt, but analog voltmeter resolution is only 500uV. For most uses, even this scope would be overkill, but it we're postulating a SOTA PSU with noise in the hundreds of nV, then I probably would end up needing something else. Not really looking to spend too much in this realm, since it needs to be cost effective relative to purchasing any SOTA DAC unit. Do you know of any scope with suitable voltmeter resolution that doesn't cost the earth?

Use a soundcard (192/24), add an attenuator if needed and calibrate with a known voltage (say a DAC playing a 0dBFS signal).
Convert dB to mV/uV
 

radix

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You need to figure out your test & measurement. Can you even measure a SOTA DAC? The noise floor in your gear is likely way above SOTA, so you couldn't even tell if you built it.

It's not too hard to make nice opamp circuits for good audio. Just follow the manufacturer guides with decent filtered power supply. Once you have a measured baseline, you are then in a position to see what effects different power supply or buffers make. You need to keep fixing the biggest effect, not chasing the little things. That means you also need to know how to measure all the various aspects of an audio circuit.

A lot of work goes into the bells and whistles around the circuit, like temperature stability, part noise, part matching (or making the circuit less sensitive to mismatched), design for testing, proper power-on, no pops, etc. Then there's all the software that goes on the microcontrollers.

Anyway, good luck. I think it's fun to build things and making a DAC should be challenging and a lot to learn. You should be able to get something good, but it won't be SOTA. It takes more than gluing a few components together to make SOTA.
 

kemmler3D

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One then has to figure out how to best damp the inside.
So for that I'm thinking a good bit of absorptive material inside the cabinet, but also a layer of sand before the cement. And in between/around those layers, you can use all sorts of shapes to add damping via flex and/or transmission losses. No penalty for complex design when it comes to 3D printing. :)

It may be heavy AF when I'm done, but I could use the exercise.
 
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