Thanks, muting is also a good idea and easier to implement.
In order to have the encoder switch functioning before the preamp is on, would require a different circuit to be live already to accept the push signal. I've already considered having a 'standby' Arduino/ATtiny circuit to monitor IR remote signals for exactly that purpose when the preamp is off. Therefore it would be possible to connect the encoder switch to it as well, should I decide to stick with my encoder knob on/off idea.
However, your mute-idea sounds good too. Is that how commercial preamps work?
In order to have the encoder switch functioning before the preamp is on, would require a different circuit to be live already to accept the push signal. I've already considered having a 'standby' Arduino/ATtiny circuit to monitor IR remote signals for exactly that purpose when the preamp is off. Therefore it would be possible to connect the encoder switch to it as well, should I decide to stick with my encoder knob on/off idea.
However, your mute-idea sounds good too. Is that how commercial preamps work?
Thanks for the warning. I don't get any noise from a Waveshare 2.4" TFT LCD screen, but I'll check again. It is not a touch screen, if that maybe makes a difference.
Nice. I may use that.
It's easy to add a filter if the noise is caused by a PSU, but the screen is not causing any noise when running off USB cable power or a battery + DC-DC converter.
It's rewarding to work on the project with Muses + hi-res LCD screen. I haven't seen any offerings online that does the same. So, are we raising the bar, or what? 😆
This sample screen shows the quality of the display and smoothness of the font. Btw. I can use just about any TrueType font on the screen. The big font used here is Calibri.
This sample screen shows the quality of the display and smoothness of the font. Btw. I can use just about any TrueType font on the screen. The big font used here is Calibri.
Beautiful! I had bad experience with a dc converter on a cheap (but nice) OLED display being extremely noisy (at high volume settings). The display (and MCU) had an extra PSU, GND was not shared with analog ground, and still it made the preamp noisy. But yes, I got rid of it by filtering it with CRCL (4700uF/10R/4700uF/small ferrite toroid with 32 turns of wire).
EDIT: pushing the encoder button mutes my preamp, so if I change input I let it first mute and than switch the input. That way we are at low volume after the new input is selected.
Question: will you switch GND with inputs in your preamp? Or will GND stay connected with all inputs?
EDIT: pushing the encoder button mutes my preamp, so if I change input I let it first mute and than switch the input. That way we are at low volume after the new input is selected.
Question: will you switch GND with inputs in your preamp? Or will GND stay connected with all inputs?
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Thanks. It can display other colours too. See pics below. The screen looks so much better in real life. The camera doesn't do it justice.
I will also mute when changing inputs. But my code saves all settings on the MCU, so I can return to the same volume level after changing inputs. I may let it ramp up from a lower level, though. It's all refinements that can be added afterwards. Right now I'm concentrating on designing the attenuator board in Kicad. A secondary board will follow and that one will handle standby-mode with probably an ATtiny as MCU.
I'm not there yet, but I will use the input relays on the Iron Pre PCB. I'm not sure if GND is switched, but you can check on the schematics in that thread.
It's a full colour screen, but I prefer white on black. Colours will be selectable by the user from a settings menu. There is also a function that fades the screen after a certain amount of time has elapsed; The time interval and fade amount is selectable from the settings menu. I did the coding for this while I impatiently waited for the Iron Pre kit to be released.
Btw. I like the volume readout to be a percentage from 0 to 100. Obviously, it can be changed to -dB, but I prefer 0 - 100.
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Thanks IAIMH. Hopefully it will be good enough to go inside the Iron Pre which you had such a big hand in making a reality. I'll forever be thankful. Now I get to listen to the Iron Pre while I'm working on this attenuator although it's still on the breadboard. Bliss!
Great solution to use eeprom to store settings. I connect a voltage divider to a free analog pin and monitor the supply voltage so that if it drops I can automatically update the eeprom before everything goes off. That saves me from writing to the eeprom at every change because I need to update the eeprom only at power down.
EDIT: the downside is you can't send the MCU that tracks the supply voltage to deep sleep unless you use an external part that fires an interrupt and wakes up the MCU.
BTW I wouldn't use a standby PSU to enable mains on/off by remote control, I think a hard switch at the back of the preamp suffices.
Finally the Muses72323 is in stock at Mouser!
EDIT: the downside is you can't send the MCU that tracks the supply voltage to deep sleep unless you use an external part that fires an interrupt and wakes up the MCU.
BTW I wouldn't use a standby PSU to enable mains on/off by remote control, I think a hard switch at the back of the preamp suffices.
Finally the Muses72323 is in stock at Mouser!
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You can certainly hear it if the input GND is switched! Few professional amplifiers or preamps have this feature.
Yes, I know that you can hear it - but what about the possible ground loops when multiple sources are connected to the preamp?
It is precisely this, that the GND points of the inputs are not permanently connected to the unit (Iron Pre or whatever) that eliminates the ground loop, I think.
Does that also count for the very first batch where ZM gave directions on how to alter the PCB? I have one of those first SE PCBs.
^ I can never be 100% certain...
The easiest way to check, IMO, is to beep test the board. If all the GND pads for the inputs share the same trace, then you know they're all connected. For all the versions (about 5) that I've had on my bench Pin 1 for all the balanced boards are connected ... and all the GND pads for the SE boards are connected. It would surprise me if yours was any different, but I'd still take 30 seconds to give it a quick check.
The easiest way to check, IMO, is to beep test the board. If all the GND pads for the inputs share the same trace, then you know they're all connected. For all the versions (about 5) that I've had on my bench Pin 1 for all the balanced boards are connected ... and all the GND pads for the SE boards are connected. It would surprise me if yours was any different, but I'd still take 30 seconds to give it a quick check.
And also note the recommendation from that fella above me re: make before break / break before make switching accordingly for mechanical switches.... can help with POP! or not when switching.
How that's handled for electrically engaging / disengaging relays... dunno... may not apply, but it might be worth a thought.
How that's handled for electrically engaging / disengaging relays... dunno... may not apply, but it might be worth a thought.