Very low noise USB AD Converter

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
G

ginetto61

Member
Joined 2009
Paid Member
Hi ! i would like to know if anyone knows of a usb ad converter solution with very low noise to be used both for some noise measurements It could be also a kit but not smd of course ... i am a beginner. Possibly not that expensive. The option of external power supply and not rely only on USB voltage from the PC would be nice as well. Thank you so much.

P.S. if another thread treating this issue already exists please direct me there.
 
Last edited:
P

phofman

Member
Joined 2005
I have been looking at similar offering too. For boards/kits the selection is rather small. The boards offered for reasonable money do not have stellar parameters.

IMO your best option is a decent USB soundcard, pre-owned at best. For low-noise measurements you will need balanced inputs, I have not seen a USB ADC board with them (apart of some expensive evaluation boards).

As of SMD - it is a standard now, through-the-hole components are long gone in the low-signal world. Especially if low noise is required. I am afraid you will have to learn SMD techniques eventually if you want to go beyond pre-assembled boards.
 
G

ginetto61

Member
Joined 2009
Paid Member
schiirrn said:
What is "not that expensive" in your case?
You probably won't find a non SMD converter chip.
Click to expand...

Hi ! i was thinking below 200USD ... and sorry not having checked first. Yes you are right ... new chips come almost all in smd format.
So diy is out of my reach ...

phofman said:
I have been looking at similar offering too.
For boards/kits the selection is rather small.
The boards offered for reasonable money do not have stellar parameters.
IMO your best option is a decent USB soundcard, pre-owned at best.
Click to expand...

Hi ! thanks a lot for the very kind and valuable advice. Yes i would go that way

For low-noise measurements you will need balanced inputs, I have not seen a USB ADC board with them (apart of some expensive evaluation boards).
Click to expand...

Sorry ... could you explain me why balanced inputs are needed ? i see that scope probes are usually unbalanced if i am not wrong
I need some instructions on noise measurement procedure but i do not really know where to look for ...

As of SMD - it is a standard now, through-the-hole components are long gone in the low-signal world. Especially if low noise is required. I am afraid you will have to learn SMD techniques eventually if you want to go beyond pre-assembled boards
Click to expand...

i understand that the smd soldering stations are very expensive ... intended for pros i guess ... anyway good to know. It is a completely new field for me.
Thanks a lot again
Kind regards, gino
 
nigelwright7557

nigelwright7557

Member
Joined 2008
murtonpikesystems.co.uk
phofman said:
As of SMD - it is a standard now, through-the-hole components are long gone in the low-signal world. Especially if low noise is required. I am afraid you will have to learn SMD techniques eventually if you want to go beyond pre-assembled boards.
Click to expand...

When I design my mixed pcb's I add a row of vias next to each SMD IC so I can check for shorts between pins. Even though a SMD IC looks good you can sometimes get shorts out of sight.

I put a blob of flux paste on the pcb where the SMD IC goes and place the IC on top. This holds it in place while you solder first pin. I solder first pin by letting solder run up pad to IC. If you touch IC it can move.

I then put plenty of solder on all the pins and wick off excess with copper braid. Then I buzz the via's for shorts.

Any awkward shorts can sometimes be got rid of with quick dab of soldering with plenty of flux on pins.

Anyway, loads of SMD soldering tutorials on you-tube.
 
P

phofman

Member
Joined 2005
I am quite satisfied with KSGER V2.1S T12 Digital Temperature Controller Soldering Station Soldering Iron | eBay and 10pcs t12 soldering iron tips set for hakko fx951 fx952 Sale - Banggood.com . Very inexpensive and good to work with, in my limited experience.

To de-solder SMD stuff (and multiple-legs non-SMD) I occasionally use a low-cost alternative to ChipQuik Wood's metal (Bismuth, Lead, Tin, Cadmium alloy) 75 g. Wood Woods alloy | eBay , a very nasty stuff but works OK. I melted the pellets in syringe in boiling water and injected the metal into plastic straw to get a rod. I guess better would be non-cadmium Rose's metal 75g - Alloy Rose / Rose's metal / Roses metal (Lead, Bismuth, Tin alloy) | eBay but I have not tried one yet.
 
G

ginetto61

Member
Joined 2009
Paid Member
Mark Tillotson said:
Noise measurements for an A/D converter don't require measuring analog noise, you take the FFT of the output and do spectral noise density plot. You just need to short the input to get the intrisic noise of the converter
Click to expand...

Hi ! thanks for the helpful advice. I think that i will look at usb sound card with very low own noise.

There is another point mentioned that i do not really understand. i intend to measure preamps noise and are usually unbalanced. Why would i need a sound card with balanced inputs if my source of noise is unbalanced ?

altor said:
"Yes", if you need professional station like JBC, Metcal, etc. And "No", if you will go to EBay/AliExpress and by Bakon/Quick/Atten, etc. For ~50 euro you can buy the soldering station (with soldering iron), for ~100 - together with the hot air gun
Click to expand...

Hi ! i really did not know :eek: Thank you very much indeed for the very interesting advice. This will be, parkinson allowing (i am not sick now but it is a family issue), my retirement hobby for sure. I am mad at high fidelity ... i just love everything related to audio. I guess a firm hand is needed ... and i love smd parts ... and i am more intrigued by small signals units than power amps ... i will study about it seriously. Unfortunately i am too busy at the moment. I am still in the learning phase ...

phofman said:
I am quite satisfied with KSGER V2.1S T12 Digital Temperature Controller Soldering Station Soldering Iron | eBay and 10pcs t12 soldering iron tips set for hakko fx951 fx952 Sale - Banggood.com . Very inexpensive and good to work with, in my limited experience.

To de-solder SMD stuff (and multiple-legs non-SMD) I occasionally use a low-cost alternative to ChipQuik Wood's metal (Bismuth, Lead, Tin, Cadmium alloy) 75 g. Wood Woods alloy | eBay , a very nasty stuff but works OK. I melted the pellets in syringe in boiling water and injected the metal into plastic straw to get a rod. I guess better would be non-cadmium Rose's metal 75g - Alloy Rose / Rose's metal / Roses metal (Lead, Bismuth, Tin alloy) | eBay but I have not tried one yet.
Click to expand...

Hi ! thanks for the very valuable advice. As i said above i am scared by smd parts ... even if i understand their advantages ... I am still learning to evaluate and decide what to do
 
P

phofman

Member
Joined 2005
That re-purposing allows driving costs low. HDMI connectors and cables are well proven and inexpensive for the performance they provide. People often have spare HDMI cables at home, no need for another one. Ethernet cables were used the same way for the same purpose.
 
C

chris719

Member
Joined 2004
phofman said:
That re-purposing allows driving costs low. HDMI connectors and cables are well proven and inexpensive for the performance they provide. People often have spare HDMI cables at home, no need for another one. Ethernet cables were used the same way for the same purpose.
Click to expand...

Real HDMI carries audio well enough in its actual implementation.

Best to use BNC cables or some other agnostic controlled impedance interconnect for this purpose.

This is the same thing USB IF failed at with the USB Type C connector. It can be USB 2.0, 3.1 Gen 1/2, USB PD, or Thunderbolt 3 with barely any identification.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom