Sorry, sorry, you are right, I measured my XR+DAC and D50, they both are around 2Vrms, probably the same as other sources I have, since I did not hear any difference while switching sources. I probably slipped the decimal point and forgot about it.
Now with that error on my part behind us, how is that going to be a problem for +-5V, even +-4.75V rails? 2Vrms barely reaches 3V peak.
As for your other suggestion, it is easily possible to do a slight mod in the schematics to use 7806 instead 7805 before converting it to +-5V rails, on the same pcb. I don't think there will be an audible and measurable difference though, I will test when the needed parts arrive.
Now with that error on my part behind us, how is that going to be a problem for +-5V, even +-4.75V rails? 2Vrms barely reaches 3V peak.
As for your other suggestion, it is easily possible to do a slight mod in the schematics to use 7806 instead 7805 before converting it to +-5V rails, on the same pcb. I don't think there will be an audible and measurable difference though, I will test when the needed parts arrive.
Just because designing with absolute minimum supply voltages is not good design practice as specifications might not be met completely when the +/-4.75V are in reality +4.70 and -4.65V..... Also that famous 2V rms standard is often higher than 2Vrms....So the situation is in some aspects too tight but I explained that before so no need to repeat. There should be room to breathe.
The device needs a symmetric PSU to solve matters 100%. A switcher operating in the audible range is best omitted.
"2Vrms barely reaches 3V peak". True but please think of opamps that have outputs that have a maximum output voltage swing way below rail voltages... +/- 5V only works when IC's are specifically designed for these voltages like the PGA.
Essentially +/- 5V will work OK in your design but as written before, the design misses a few things so it can be better.
The device needs a symmetric PSU to solve matters 100%. A switcher operating in the audible range is best omitted.
"2Vrms barely reaches 3V peak". True but please think of opamps that have outputs that have a maximum output voltage swing way below rail voltages... +/- 5V only works when IC's are specifically designed for these voltages like the PGA.
Essentially +/- 5V will work OK in your design but as written before, the design misses a few things so it can be better.
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TPS60402 used here is not operating in audible range, it's running on 50KHz. Preamp is absolutely silent to my ears, I will do some measurements later on to verify this.
Yes, it is better to have symmetric power supply, but idea here is to have a compact preamp running on single PS.
Yes, it is better to have symmetric power supply, but idea here is to have a compact preamp running on single PS.
OK your BOM says TPS60401 which runs in the audible range. The predescribed limitation of a single power supply is what causes all the annoyances 😀 This while almost any small transformer has 2 secondary windings. Just a small 2 x 7V 7VA Talema (standard voltage in their toroid range) or Rcore and it is solved. If LDO regs are used a 2 x 6V might work out OK.
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Lets not try to solve a problem before it reveals itself🙂 These are the measurements through my Scarlet 2i2 external sound card.
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I see now why MUSES 72320 did not post THD on the very first page of datasheet:
Total Harmonic Distortion 1 THD1 f=1kHz,VIN=1Vrms
BW=400Hz-30kHz - 0.0005 - %
PGA2311:
0.0002% THD+N at 1 kHz (A-Grade)
I can't, I don't have 72320 to test. I can only compare to LDR Pre MkII, so we will see how it goes when I get chance to do that.
I see that there was lot of trashing on PGA series, probably due to poor chinese or other questionable implementation. I also see that people even reported lock ups and volume bursts. I experienced none of the above so far in my setup, and it has been heavily abused for at least two weeks.
I see that there was lot of trashing on PGA series, probably due to poor chinese or other questionable implementation. I also see that people even reported lock ups and volume bursts. I experienced none of the above so far in my setup, and it has been heavily abused for at least two weeks.
Questionable implementation like lack of buffer opamps and omitted AC coupling often is seen in the cheap Chinese designs. That is true. However, it can depend on the sources a user connects to the device. A good design should therefor be equiped with the in practice proven necessities.
Good thing is that the cheap designs do use symmetric +/- 5V power supplies 😀
Good thing is that the cheap designs do use symmetric +/- 5V power supplies 😀
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I have AC coupling and OPAMP buffer at the output of all my sources. Same goes for input at my power amp. So duplicating it up "just in case" is simply unnecessary degradation of the signal path IMHO.
New firmware will be posted soon, with proper interrupt handling for both encoders, and with interrupt disable during write cycles to PGA2311.
Lovely Design Love it, would it be possible to change the Display to a Graphical LCD, As I find procuring the display used by you is a little difficult down here in India, and I did find one, not sure if it will match.
We easily get - Buy 12868B V2.0 Graphic Blue Backlight LCD Display Module Online
We easily get - Buy 12868B V2.0 Graphic Blue Backlight LCD Display Module Online
oh well, then could you help with finding the display you used, what library was used so it will help me find... the right display