Breadboard Hi-Fi noise reduction techniques - Page 1
Forum section: electronics / projects

author: ThatElectronicsGuy
author_rank: Newbie
timestamp: September 30, 2025, 04:36:21 pm
content: Hi, I'll keep it short.I am building audio project and I've stepped into prototyping phase. I have played first circuits and the ideas work perfectly but the noise is so huge that I cannot get anything worth even taking look at. I aim to get prototype on breadboard with as low noise as possible. I know about a lot of techniques but I am brainstorming now. Can you share your proved tips, techniques and ideas for that? For example 100nF cap to decouple power rails of opamp and bulk electrolytic are something but now questions are posing themselves:Why 100nF? On THD legs are longer, thus SRF is going to be much lower, thus maybe there is better known value for this? Should I decouple only positive rail or both positive and negative?This type of things are hanging there in my mind. I am using hi fi opamps if you were wondering (opa2134pa). High pass filtering? Where in the circuit? Maybe many times? Decoupling? Yes, but is 10uF-10k(tantalum) a good combo or maybe it's better to hop on lower resistor and film cap? Maybe everywhere lower resistors than 1k are good option? Or maybe it's not going to make such a difference? On the other hand higher current mean more power - amps might get too hot.Let me know your thoughts.

author: tggzzz
author_rank: Super Contributor
timestamp: September 30, 2025, 05:42:42 pm
content: Quote from: ThatElectronicsGuy on September 30, 2025, 04:36:21 pmThere are too many sources of noise for it to be possible to give a useful answer on the basis of that information. Whole books have been written on the subject, and people have made careers out of "noise reduction".Jumping to conclusions is unlikely to be beneficial; methodical experimentation is necessary.Define your ideas which work perfectly but which you cannot get anything worth looking at.Define "huge noise". Voltage-vs-time, voltage-vs-frequency. Numbers, not adjectives.Show a schematic, and a photo of your implementation.Define how you have attempted to locate the source of the noise.Note that a Tek 2465B is not a low noise instrument in the context of audio circuits.You may findthisandthathelp you to get an answer to your question.

author: Vovk_Z
author_rank: Super Contributor
timestamp: September 30, 2025, 06:21:28 pm
content: 0.1 uF ceramic cap under or near the opamp (0805, 1206 etc) is good enough for audio frequencies opamp. You have to start worry a bit about it if you use some really fast opamps like ADSL-drivers, fast current-feedback opamps etc.And 10-100 uF general use electrolytic type capacitor near the power supply connector (for every supply rail) is just fine.Audio circuit can be quite low noise with 2k ... 10 k resistors in signal path.

author: TimFox
author_rank: Super Contributor
timestamp: September 30, 2025, 06:28:18 pm
content: In the good old days of phonography, RIAA preamplifiers for magnetic phono cartridges (10 mV or even lower) required careful engineering to reduce noise.It's hard to hear the noise of a decent amplifier that starts from 1 V signal levels.What is your application?

author: Benta
author_rank: Super Contributor
timestamp: September 30, 2025, 07:18:01 pm
content: Don't use plug-in breadboards, they're a big noise catcher/source themselves.Use perfboard (and soldered parts) instead and plan your layout first.

author: Benta
author_rank: Super Contributor
timestamp: September 30, 2025, 07:21:50 pm
content: Quote from: TimFox on September 30, 2025, 06:28:18 pmNot to forget moving-coil pickups which required special transformers or super-low noise preamps before the RIAA preamp.But had brilliant sound quality.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: October 01, 2025, 12:16:17 pm
content: Let's also definenoise. I don't like to lump 60 and 120 Hz (50 and 100 Hz) in with the word noise because it gets confusing if not continuously specified. Usehuminstead. Next, numbers describing noise are only meaningful if they also specify ameasurement bandwidth. And, ideally, themeasurement floorof the test system.That said, the methods to reduce hum are almost always different than the methods used to reduce noise. Hum will involve common current loops, ground locations, shielding and proximity. Reducing noise will require addressing gain distribution (structure) actual semiconductor devices used and things contributing Johnson noise. Impedance may determine how well you can do. Surprisingly, capacitors rarely enter into it unless the circuit is oscillating and you don't realize it. Paralleling capacitors rarely accomplishes anything in the audio world, in spite of immense verbiage to the contrary, though it can be useful in RF designs.So, vastly more info, including a schematic and maybe a photo, is needed to suggest even a place to start.

author: ThatElectronicsGuy
author_rank: Newbie
timestamp: October 04, 2025, 03:34:29 pm
content: So I managed to get satisfying results (sorry for not answering I've just moved on). It turned out I had dead opamp screaming in the circuit. I also added couple other things like decoupling caps, low pass filter. I've used instrumentation amplifier in the circuit and as well differential amplifier after so now results are good for breadboard. I don't want to dive into details of the schematic right now. I'll show you my project when I finish. The circuit is working on breadboard so you can assume that topology is alright.But now I have put the same circuit on perfboard to see and compare if it's going to stand better in noise/hum terms and it turns out it doesn't work. I mean I suspect that my socket from Ali express might be bleeding voltages after heating, but am not sure. Do you think that perfboard itself can 'bleed' voltage on the holes around? I observe very weird offsets on pins next to supply rails. Also I checked with diode test in between these and I have around 2/3 volts (depends on pair of holes, did it with socket).Also I have used other type of sockets which are DIP-8 and on these ones I see no issues like this. That's why I suspect the other one (DIP-14) .What do you think?

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: October 04, 2025, 09:01:53 pm
content: I wouldn't expect those sorts of problems with good quality parts, including plug-in proto boards. OTOH, anything is possible with the cheap stuff. You should be able to test yourself with (powered down) an ohmmeter, or (powered up) looking for voltage adjacent to power points with your DVM. When I have those sorts of problems it's usually not anything exotic, I've just put the circuit together wrong or something's floating.