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Comment by dragontamer | Hacker News Reader

Chip costs are pretty low, all else considered. Yeah, AD is more expensive but I spend way less time reading documentation.

If you're a hobbyist like me, you don't really care about spending $5 on a chip instead of $2 on a chip... especially when you're paying multiples of that for the PCB and other parts of the equation.

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Part of the fun of hobby building is you can design your stuff any way you want. Maybe nobody will mass-produce an audio preamp with $20 opamps inside, but you can DIY one if you feel like it.

I built a digital audio interface with an ADI ultra-low-noise clock generator. It was a $20 part. That's a ridiculous price but it's also only $20.

Also especially for audio stuff it's not like all op amps have to be high spec. At the edge (input/output) components matter much more than inside the circuit, where levels and impedances can be designed in. A low-noise BiFET op amp makes a ton of sense for pre-amp, but as a generic buffer or whatever amplifier between stages, not so much. Even in 2020 a NE5532 is a fine choice in those places.

In general, you can always substitute a high-quality, expensive op-amp for a cheap op-amp.

From the perspective of a hobbyist with limited space: you want to minimize the SKUs that you stock in your personal shelves. Buying a higher-end op-amp and spamming it everywhere (even when its specs aren't needed) is far simpler than buying 10x different op-amps at the $0.50, $1, $1.50, $2, $3, $4, and $5 price points.

Just keep a supply of higher-quality $5 rail-to-rail low-bias op-amps at the voltage-level (3.3V for most Arduino projects).

Yeah, there's probably a $0.50 op-amp that does the job. But do you really want to keep another SKU on your shelf and keep track of it? There's simplicity in just buying over-specced parts for personal hobby projects.

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Well... maybe keep a stock of the $0.50 stuff too (EDIT: Ah right, LMV358. That's the cheap part I keep around). But I think you get my gist. Personal-supply closet management is certainly a problem for the personal hobbyist.

> In general, you can always substitute a high-quality, expensive op-amp for a cheap op-amp.

Yes, it will work in general. Unless the expensive opamp has a significantly wider bandwidth, then one must use with caution. Switching from a low bandwidth opamp to a high bandwidth opamp is especially problematic, the loop characteristics are different and it may need additional frequency compensation or bandwidth limiting, the original layout may become inadequate, etc. More often than not, a blind replacement make it oscillate like crazy.

Sometimes having a bunch of cheap opamps makes life easier.

And financially - your heart and wallet won't start bleeding when your $0.5 opamp is unexpectedly zapped by ESD, cooked in soldering, or fried in an overload. Killing a $10 ASIC is a big deal (just did that last week while prototyping an ASIC controller, but there isn't anything cheaper on the market).

Do you have any information on your digial audio interface you can share? Seems like an interesting project.

Not that exciting really. I built an instrument that could measure very small levels of harmonic distortion induced by converter phase noise. Then, being so equipped, I made a converter with immeasurable phase noise. The instrumentation was the exciting part, in all honesty. $1000 off-the-shelf pro converters now exceed its performance.

I feel like "Not that exciting really" is underselling it given that your hobby project is matching current $1000 pro equipment, but that could just be my own ignorance with the subject matter.

It's nice of you to say so. That's the nature of DIY. A hobbyist has some aesthetic or objective performance goals, but they have no economic goals, so the range of things that hobbyists build greatly exceeds the range of commercially available equipment.

I'm working on a pretty expensive piece of measurement equipment and the $12 AD7193 I'm using seems expensive until you see how crazy accurate this thing is. It's worth every penny.

Hobbyists don't make up even a tiny sliver of their revenue. And if you're a hobbyist and paying any money at all for Analog Devices (or other semiconductor manufacturer's parts) then you're kinda doing it wrong - most of them have free samples:

https://www.analog.com/en/support/customer-service-resources...

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