# Converting DAC voltage to eurorack voltage

I've connected a DAC to a Raspberry Pi. The DAC gives a voltage between 0V and 3.3V.

I would like to convert this to an eurorack voltage between -5V and +5V.

Using the op amp calculator at masteringelectronicsdesign.com and circuitjs I found that this should work:

As an editable schematic: (circuitjs)

In reality though, this doesn't work. I put it on a breadboard and measured with an oscilloscope and the output is between -2.5V and +2.5V. Note that I power the op amp with -5V and +5V. The op amp is an MCP6001.

What is wrong with this schematic? Am I right that I can't rely on circuitjs and masteringelectronicsdesign.com for this, or is my breadboard setup more likely to be incorrect?

*** UPDATE ***

Conclusion:

1. I misunderstood op amps: they have a maximum difference between their Vss and Vcc (NOT neccessarily between 0V and Vcc) which can be fairly low like 6V

2. I misunderstood my function generator: 1.65Vpp means from -0.825 to +0.825 (NOT -1.65...+1.65V)

3. After replacing the op amp by a TL072, I indeed get a wave between -5V and +5V (almost, slightly less - suggestions for a better DIP op amp are welcome!)

4. I should use the -12/+12V from the eurorack power supply to feed the op amp

• How are you powering your opamp? Jul 26, 2022 at 9:37
• Circuit seems correct. The op-amp you're using has a rail-to-rail input and output, so +/-5V supply should be fine. Jul 26, 2022 at 9:44
• @WesleyLee I power the op amp with -5V and +5V Jul 26, 2022 at 9:44
• Wait, hang on, that op-amp uses a unipolar supply with max 6V rating. If you are feeding it with a -5V power rail connected to the $V_{ss}$ pin, with +5V connected to $V_{dd}$, then you are also exceeding its supply capabilities of max 6V $V_{dd}-V_{ss}$. Jul 26, 2022 at 9:47
• @TomCarpenter ah I did not know that. Somehow I was thinking that was relative to 0V. Jul 26, 2022 at 10:19