AD831 Chinese mixer board - Page 1
Forum section: electronics / beginners

author: Amish_Fighter_Pilot
author_rank: Regular Contributor
timestamp: May 24, 2025, 10:36:15 am
content: It seems like these AD831 boards from China are everywhere now and yet I can't find a manual for one. I would really like to know what it can handle and is capable of. I have several different pages that all say different things about the frequency range these can handle. I need to mix things at lower frequencies. At least 1KHz minimum would be nice, but 500Hz would be even better. Can anyone definitively say what voltage these need? I have heard anywhere from 5V to 11V.

author: radiolistener
author_rank: Super Contributor
timestamp: May 24, 2025, 11:16:45 am
content: use search:https://www.eevblog.com/forum/rf-microwave/ad831-module-question/

author: Amish_Fighter_Pilot
author_rank: Regular Contributor
timestamp: May 25, 2025, 12:54:18 am
content: That is a great thread. Thanks. I'm not seeing anything there about low frequency though. I will check again.

author: shabaz
author_rank: Frequent Contributor
timestamp: May 25, 2025, 01:12:58 am
content: You can eyeball it, if you can visually see capacitors on the inputs of interest (e.g. the RF input or LO input)then that will limit the low frequencies. You could just try it to see what the limit is, but I doubt 1 kHz may have been tried all that often.Secondly, what's your actual end scenario/use-case, since it sounds like it may not be RF-related?

author: Amish_Fighter_Pilot
author_rank: Regular Contributor
timestamp: May 25, 2025, 07:49:30 am
content: Quote from: shabaz on May 25, 2025, 01:12:58 amThanks. My current project is an interference-as-music samples project. So it's RF related, but there's no modulated signal involved and transmission distances will be a matter of a few feet(a meter maybe?). Ideally I want to make directional antennas with a shielded side(or sides). It's inspired by RF material analysis. I have seen a few rigs on YouTube where people are using the AD831 and similar parts to my setup to do AM and FM radio setups; so I know I'm working with ideas that have been tested. I've only been learning signals for a few months as I have had spare time; so I have really had to do a sort of crash course and learn a lot of terms!

author: radiolistener
author_rank: Super Contributor
timestamp: May 25, 2025, 09:33:56 am
content: Quote from: Amish_Fighter_Pilot on May 25, 2025, 12:54:18 amAccording to datasheet, AD831 works from DC, and as I remember, I didn't seen issues at low frequencies like 5 kHz. For better performance I would prefer to use LO at MHz range (or even > 15 MHz), to avoid issues related to higher noise floor at low frequency.Regarding its use in audio path measurements, it is important to note that the AD831 has a 10.3 dB noise figure, which is relatively high if you intend to evaluate high-quality audio circuits. Therefore, you may need to use a ultra-low-noise amplifier at its input to prevent the AD831’s own noise from masking subtle noise characteristics of the audio path under test. In general, accurate measurement of ultra-low noise levels is a non-trivial task and goes beyond the scope of this discussion.

author: Amish_Fighter_Pilot
author_rank: Regular Contributor
timestamp: May 25, 2025, 09:52:51 am
content: The good news on the noise issue is that I do not need the audio to be "quality" in any traditional sense. My main purpose is to use materials to cause phase and frequency distortion for sampling so a little circuit noise probably won't even register relatively speaking.

author: Amish_Fighter_Pilot
author_rank: Regular Contributor
timestamp: May 26, 2025, 06:55:26 am
content: I did my first test of this board today. I had a Fnirsi scope/generator making signal on the LO and then I had my generic FG-200 function generator doing the antenna input. I then had the output line split to two wires which I clipped to my other Fnirsi pocket scope to monitor it. Then I took an old lead acid battery that was still reading 10.5V and hooked the power to the AD831. Instantly saw signals on my scope. I need to put a low pass filter on that output though because I was picking up a lot of higher frequencies that I don't want(I really want nothing over 1KHz to pass that output). It was clearly working though. So that's really encouraging. Does anyone know if I should be putting a heatsink on this thing? I have an IR gun; so what temperature do I have to reach before I realistically need to add passive cooling?I also made my first solder-on SMA cables using FG402 cable and it went well! I have done a lot of audio cable soldering in the past, but this is my first coaxial cable soldering job. I got these solder-on ends from Amazon that were so much nicer than I expected they would be. I mean they are genuinely heavy and nice. The cable is the same brand and it's excellent too. I usually expect way worse from those sites. I'm a careful shopper, but I've been lucky so far not to get any junk for this project. Then again I haven't tested the cheap amps I got so we'll see!