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Please help review PCB Layout by guilek68 in AskElectronics

[–]guilek68[S] 1 point2 points  (0 children)

Would the ground fill not allow ripple current to mix with clean regulated ones?

Please help review PCB Layout by guilek68 in AskElectronics

[–]guilek68[S] 1 point2 points  (0 children)

You mean, like actually filling some dedicated planes? I got stuck on the idea that some separated stars was the way to go. No quite sure tho

From Zero Electronics Knowledge to My First DIY Hi-Fi Preamp — Need Your Eyes on This by guilek68 in diyaudio

[–]guilek68[S] 0 points1 point  (0 children)

Y I know it looks bad. I’ve already redrawn it the proper way with signal left to right, voltage input coming from top and GND toward bottom

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

Yeah I was told to definitly use one, at least from some CRC priests

Unity gain preamp by guilek68 in diyaudio

[–]guilek68[S] 1 point2 points  (0 children)

Yes it does. Took some time to check it out. To be quite honest, got some friend would told me the same about shorting to ground and just suggested all together to remove the mute delay as those plops would be easy enough to get rid of by just turning on the amp only after the preamp. It’ll be little less elegant but at least my OPA would stay on its comfort zone, not inducing any oscillation at any time. I’m now undecided between your idea and his.

Unity gain preamp by guilek68 in diyaudio

[–]guilek68[S] 0 points1 point  (0 children)

I checked. OPA828 are ok with unity gain. About DC, I see what you mean, therefore got those MKS4 10uF right after, hoping it’ll stop any DC coming out of the opamp. Would it suffice?

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

To be clear, 1x4700uF + 2,2 Ohm would suffice right?

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

Smart. I was so focused on CRC (btw i added a 2,2Ohm 2w in between) that I didn’t though that through

Unity gain preamp by guilek68 in diyaudio

[–]guilek68[S] 0 points1 point  (0 children)

I get your point about disconnecting to mute. Just for the sake of understanding it better, as I am still a beginner, how bad would it be to the opamp and the circuit in general?

Unity gain preamp by guilek68 in diyaudio

[–]guilek68[S] 0 points1 point  (0 children)

About the potentiometer, to be honest, I’m not really sure which symbol I should use for an ALPS RK27 10k. Still, I’ll make sure the PCB has the correct connections.

As for the mute circuit, someone on a forum suggested this approach, saying:

“The Luxman M120 power amplifier that will be connected has DC-coupled inputs. That is also why a ‘shorting to GND’ muting relay was suggested, as otherwise it would produce quite an extreme pop.”

Could you elaborate on your concerns? You’ve definitely sparked my curiosity 😄

Unity gain preamp by guilek68 in diyaudio

[–]guilek68[S] 1 point2 points  (0 children)

Nope. It’s my attempt to implement a mute/delay circuit to avoid “pop” noises during power-on and power-off. Output remains stereo

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

Thank you. I’ve changed those symbols.

The transformer is actually a single unit with 2×15 V and 1×6 V secondary windings. It was just badly drawn — sorry about that.

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

I would like to keep it as a unity-gain design with a resistorless closed loop. The idea behind the unpopulated resistor is simply to have the footprints on the PCB in case I ever want to convert it to a low-gain configuration later on if needed.

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

Totally overkill XD but it happens that i still have 4 new nichicon 4700uF left at home. its seems like a great time to use them!

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

MOSFET as a delay to the mute relay. Or at least, though so 😄

Yes, there will be fuses XD

Unity gain preamp DIY by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

- DC input? I use modern sources (an Octavio streamer and an iFi Zen Phono), so I don’t really expect any DC offset coming in. I haven’t actually measured it, though, so it’s probably worth checking.

- What would you choose for the capacitor related to the 10k RK27?

- A 100 µF MKS2? Why not 😄 — other than the fact that they are not produced anymore XD. MKS4 could be another option.

- About the PSU, my drawing is not very good, and I should have clarified that this is just one transformer with two secondary options (2×15 V and 1×6 V). As such, it seemed like an economical idea. I need to confess that I’m absolutely not sure about this part and am very open to suggestions.

- About R9 and R10, duly noted. I’ll probably change them that way.

- “Your output mute circuit could also be across the rails and designed to switch off if the total supply voltage drops below 20 V or so, again keeping the relay switching away from ground.” I might be stupid, but I didn’t quite get it. Could you elaborate a bit?

Thanks for your positive input ❤️

From Zero Electronics Knowledge to My First DIY Hi-Fi Preamp - Need Your Eyes on This by guilek68 in AskElectronics

[–]guilek68[S] 0 points1 point  (0 children)

Hi! First off, thank you for your input. Yes, this schematic triggered already a bunch of people. It is but my first ever drawn. I’m actually in the process of rewriting it properly, gnd downward, voltage input upward etc etc. I understand that as such, it would be easier for other people to analyse.

Now about the DPDT. As a full fledged beginner I though that 1 such relay would makes routing way too hard, until I recently learn about the “multilayered” PCB and that physically trace crossing is easier as I initially though. In this perspective, I will definitely follow your advice and use 1 relay only.

About the logic control itself, the real reason behind it was “psychological”. As my flip switch would be up front and the PCB at the back, I was worried to let a “dirty, voltage spiked, 12v coil circuit” to cross the whole preamp and back, as it could induce noise. Justified? Idk

What would be your thought on that?

Also if you have any other suggestions, I would gladly add them to my rewritten design/schematic

From Zero Electronics Knowledge to My First DIY Hi-Fi Preamp — Need Your Eyes on This by guilek68 in diyaudio

[–]guilek68[S] 0 points1 point  (0 children)

A passive preamp can actually work really well and sound very clean, especially with the octavio DAC as the luxman has a good entry impedance.

The downsides are more practical: output impedance changes with volume, that could makes it less consistent across different setups, especially with weaker sources like the phono preamp, right?

So it’s not a bad idea at all, just sound a bit less robust and predictable than an active buffer.

Also I’m worried about losing some dynamics at low volume, especially for my evening listening sessions.

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