Itsthemedication in the Adafruit forums writes -

I just put together the BB power supply, and only have 29 more to go. One reason for selecting this PS was for the adjustable voltage, i.e. I needed a STABLE 1.9 volts (don’t ask). Anyway, if anyone else is thinking about this excellent little board and needs a voltage greater than 3 I highly recommend ditching the single turn pot (very imprecise and possibly noisy as well) and replacing it with an 18 or 25 turn pot like Digikey 490-2914-ND (92 cents). The switched 3.3 and 5 volts work great by the way!

Adjustable breadboard power supply – v1.0 – This project details the design of a very low dropout adjustable power supply. A good power supply is essential to electronic projects. While there are many existing designs for adjustable power supplies, this one makes improvements that make it more useful for hobby designs.

• MIC2941 regulator has guaranteed 1.25A output
• Low dropout, only 40mV – 400mV compared to 1.25V – 2.0V for LM317. This means you can use a wider range of output voltages including generating 3.3V from as low as 3.7V (such as 3 AA’s or a lithium ion battery)!
• Short circuit and overheating protection
• Input diode to protect circuitry from negative voltages or AC power supplies.
• 2.1mm DC jack and terminal connector for voltage inputs
• Two indicator LEDs for high and low voltages
• Output selection switch to select from 3.3v, 5v and Adjustable
• Onboard potentiometer for adjusting voltage from 1.25V up to within 0.5V of the input voltage. (20V max)
• On/Off switch for entire board
• Heat sink included

Breadboard and battery clip or DC power supply is not included, you can use any DC power supply with 2.1mm plug (we have a nice one in the shop). For design documents, instructions, parts list, etc. Check out the project webpage!