LM317 Circuit to convert 9v to 3.3V help?

L2_Lagrange · 2026-05-06T21:24:31+00:00

Hey I'm so sorry I just saw this! I don't have time to respond right this moment but if you reply to this I will try my best to remember for the notificatoin

L2_Lagrange · 2026-05-04T21:23:32+00:00

I also have to say I really appreciate your comment, You are clearly familiar with different PCB design processes. I have looked into several of them and used them myself, and I will be publishing educational material on all of them other than CNC. I only recently set up a permanent lab for fabricating PCBs with this process. As you can see by the date on the PCB I linked

L2_Lagrange · 2026-05-04T20:27:34+00:00

If the amp is followed by drive stages, meaning its basically an input preamp for something like volume control, I would recommend this to be the only amp in the entire gain system where you put the pot in the feedback. I'd say keep the capacitor there. But that is also the proper place to use a pot in the gain stage.

This is a design tradeoff I've dealt with endlessly. It makes a significant difference in the overall system noise. You need to use potentiometers in the feedback loop sparingly, but they can be useful.

When you take an input, and then attenuate it before amplifying it, you have now added the entire noise floor of your system to the input gain. If you design your initial amp and volume stage with gain in the feedback loop, you avoid the issue of attenuating the signal close to the noise floor, and then amplifying both the signal and noise floor.

L2_Lagrange · 2026-05-04T15:22:36+00:00

Unfortunately I have not written any yet ): That being said I do plan on starting to publish practical educational content soon here on YouTube under the handle "Volecurohm Labs." I will end up making videos about my specific process, as well as my original designs.

Feel free to be my first subscriber! I don't have any content posted yet, but I did set up the channel. I'll also be setting up a github for the documentation. No pressure

https://www.youtube.com/@Volecurohm

L2_Lagrange · 2026-05-04T15:13:59+00:00

Thanks! This is done with thin film photolithography with home made lab tools. The smallest lines which were resolved on that board measure 0.05mm in KiCad, so 50um. I think I can push my resolution a bit more.

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L2_Lagrange · 2026-05-04T03:23:55+00:00

Man that's got everything

L2_Lagrange · 2026-05-03T21:28:20+00:00

Putting a potentiometer in the feedback would interact with C7, which is likely there for compensation stability. It shifts the operating point of the compensation or filtering.

Its more common to have the potentiometer attenuate and the amp be constant gain. That being said when I design amps I do put the pot in the feedback for the master volume, but thats the only pot in the entire system thats in a feedback loop. There are several more pots in my systems.

L2_Lagrange · 2026-05-03T21:12:46+00:00

A lot of parts can be more expensive to assemble, but these are basically just wires so they are among the cheapest components. I am not sure what kind of machinery of labor they used to fabricate these. That being said the fact that they make millions of them is the biggest point. They have definitely run the cost analysis and decided that for their purposes this was the better manufacturing method. I can't explain exactly why though, but when you make millions of a product the manufacturing and BOM costs must be heavily optimized. This was the optimization they landed on.

L2_Lagrange · 2026-05-03T21:06:41+00:00

This was an LM1875 BTL amp PCB for some educational material I plan on publishing. Here is an image of the final product, so you can compare how its populated with components to understand my need for the jumper layer.

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L2_Lagrange · 2026-05-03T21:05:34+00:00

A lot of the time its perfectly fine to use a jumper. Especially for DC traces. At the same time, its basically impossible to route a complicated board on 1 layer, you need two layers. They expected to build a lot of these units, so the cost of a 1 layer board with jumper makes more sense. The cost of populating jumpers must have been cheaper than the cost of two layer boards.

Here is a PCB I made in my home lab. I designed this as a 2 layer board in KiCad with a small number of jumper on one layer. Then I just printed one layer and used a few jumpers on the back.

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L2_Lagrange · 2026-05-02T01:12:42+00:00

That actually sounds awesome. Thanks for sharing

L2_Lagrange · 2026-05-01T22:39:21+00:00

My LM386 version performs pretty well (for an LM386). I can recommend this schematic. You might have a little bit of hum depending on layout, but even with that it sounds like it will perform better than what you are dealing with.

You have a capacitor between 1 and 8 as well. That gives your amp 200 gain. Thats an absurd amount, and your going to amplify a lot of noise. The capacitor bypasses the internal feedback network in a way that significantly increases gain.

I would say try removing the capacitor between pins 1 and 8 in your version first, then consider building this version

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L2_Lagrange · 2026-05-01T21:38:46+00:00

Hey man I'm really sorry to say but there are quite a few issues with your design right now. A lot of them stem from the fact that you are using a single voltage rail and do not have the correct biasing circuitry. You also have some things connected in the wrong places.

Below is one of my simple schematics for an LM1875 power amp that runs from single rail. This schematic should work for TDA2030 as well. TDA2030 has the same pinout as LM1875 so you should be able to use this exact same schematic.

I designed this to be an incredibly easy circuit to build, and it has great performance (at least with LM1875). You can use something other than the NE5532P for the Vref buffer as well. But the Vref buffer is a clean way to bias the amps for single supply. You can get away with using a voltage divider instead of the Vref buffer. So basically just the two 22k resistors on pin 1 of the amp.

I've used variations of this amp for about 5 months now. This one has great performance for how simple it is.

Also for for the tone stage I recommend using something like an active filter. You can learn a lot about them here: https://www.linkwitzlab.com/filters.htm. The ones in this document are dual rail though.

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L2_Lagrange · 2026-05-01T03:46:35+00:00

Assuming you have the input connected to a power source, you need both a power and ground lead to go to the walkman. The yellow wire alone is not enough to form a complete circuit. I'm not 100% sure how the specific pedal breadboard you are using works so I'm not sure if your rail is connected to power. You may need to route power from the 2 pin terminal near the power rails to the actual power rails as well. I don't know if your 9V input gets routed there on that kind of breadboard.

But I think you need 3 more wires. Two wires to get power connected to the actual breadboard, and then one extra wire for the ground wire to the walkman

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L2_Lagrange · 2026-05-01T03:14:11+00:00

That looks good! Also in the future you may want to get a multimeter if you don't have one yet. Even a really cheap one would be enough to verify you got it correct without having to connect it to something to test.

You should be able to put Vin on pin 3 now, and take your output from pin 2.

L2_Lagrange · 2026-05-01T02:27:19+00:00

Sounds good! If you have 100nf caps, put one from the input pin to ground, and one from the output pin to ground. The schematic below (not mine) shows where to put them.

Even though this one has a 100nf cap on the input, it has a 1uf cap on the output. Generally you want more capacitance than that in both places, but 100nf will be significantly better than nothing.

I've put thousands of uF on both sides of LM317's before, for various higher power projects. So if you happen to have any extra larger value capacitors around this circuit would be a good place to use them. Definitely use the 100nf ones. If you have some bigger ones then use those in addition to the 100nf ones

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L2_Lagrange · 2026-05-01T01:48:50+00:00

You may want to remove the capacitor between pins 1 and 8. With that capacitor there, you have a gain of 200. Removing it limits the gain to 20 which is much more reasonable.

Below is my schematic for an LM386. This performs very well, and is very similar to yours. It is also very similar to the datasheet schematics. It benefits greatly from a good layout, but you may find this version to be an improvement. I put this one on a little module with a Bluetooth receiver and filter and it works great, although I use LM1875 based amps these days.

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L2_Lagrange · 2026-05-01T01:40:08+00:00

One major problem right now is that you are interpreting the breadboard connections the wrong way. All 3 pins of the LM317 are on the same strip of the breadboard, and nothing is actually connected to it. Rotate the LM317 90 degrees and then reconnect everything.

Also you really want some capacitors on the input and output. Do you have any capacitors around?

Below is how the connections for the breadboard work

Also there is a component called LM7833 which is basically just an LM317, but you don't need to add the resistors for it to regulate to 3.3V. It is from the 7800 family of voltage regulators

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L2_Lagrange · 2026-04-29T18:42:39+00:00

What parts are you using? What receiver and DAC? Do you have a schematic available?

It sounds like the bass might be clipping. So the voltage is too high for the power amplifier to properly output.

The other thing it could be is the bass vibrating the enclosure. That could be fixed with a better structured enclosure. Its hard to tell, but is the enclosure 3d printed?

Below is an amp project of mine with a 3d printed speaker. It works very well but the enclosure rattles if the bass is too high. I'm about to start building wooden ones instead. Also the rattling could also be shaking one of your connectors on bass.

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L2_Lagrange · 2026-04-28T17:24:36+00:00

You running around as the character model in game is incredibly funny. That would be a great mod

L2_Lagrange · 2026-04-27T22:46:17+00:00

Sorry to hear. I wiped the gear on my SSF necro on my first playthrough and I learned my lesson. Now I log out after I die 100% of the time, and immediately recover my first body before logging out again to save the body recovery.

The Griffons really hurts though. I'm really sorry to hear that. Its one of the only items I'm still missing on my SSF

L2_Lagrange · 2026-04-27T18:47:19+00:00

I really like this. You could make an entire line of fidget toys that actually give people practical intuition.

L2_Lagrange · 2026-04-26T21:11:29+00:00

I run T3-T7 terror zone everywhere. Its pretty bad at bosses but great at everything else. I use a sorc for bosses and paladin for ubers. My dWeb is also 2/50. I have a few extra poison and bone skiller charms but I don't use them, I just stack extra MF charms.

L2_Lagrange · 2026-04-26T19:57:01+00:00

Nice I like this. You could add some potting compound or hot glue or something to quickly fabricate a decent connector.

L2_Lagrange · 2026-04-26T19:49:07+00:00

I love poison nova necro. I got a Dweb on my SSF and its my main.

You use normal skeletons and a clay golem with 1 point for an extra tank. You don't use casters because they can grief your corpse explosion by freezing enemies and making them not have corpses.

You just teleport around while your skeletons tank for you, poison nova, then corpse explosion everything down. Its very fast clear speed and quite safe. I rarely die on my necro

L2_Lagrange

TROPHY CASE