I have built the default version of the P1 Preamp. It works well. I use a pair of Sennheiser 650 headphones when critical listening to line gear. The preamp is very neutral, adding no color that I can detect. The tone controls are subtle but appropriate. I used Alpha pots with center detents for the tone controls. This is a very inexpensive project to build. The circuit measured flat within a half dB when they were centered. Noise performance and distortion are near the limits of my bench gear. However if you were to revisit the layout I would suggest that you put a little more space between the components as some are tight. That could be done without increasing the size of the PCB. And if it were me I would swap the physical placement of the overall volume and channel trim controls. When I reach for the volume I always end up at the wrong end! The usual convention is to have the volume control to the right. Also I recommend that you combine the channel trim controls into a dual pot (flipping the left channel) converting your trims into a balance control. I also am toying with the idea of ordering a GoldPoint attenuator to put in place of the volume control. I will most likely make these mods to the 2nd PCB that you sent me and put the results in a nice case. Over the upcoming holidays I plan to swap out the OPA2134s for some 'so called audiophile parts' that I have on hand and see if I can hear a difference. Hopefully I should have time during the holidays to take some PICs as well. And please be certain to not take my comments as critical. On the overall your design shows well. My suggestions are just that. Please discount them at will. 

Jul 03,2019
254 viewsReport item
  • Comments(1)
  • Likes(2)
You can only upload 1 files in total. Each file cannot exceed 2MB. Supports JPG, JPEG, GIF, PNG, BMP
    View More
    VOTING 2 votes
    • Engineer from
      • 10
        design
      • 10
        usability
      • 10
        creativity
      • 10
        content
      10.00
    • bobo from INDONESIA
      I'm ordinary staff, my hobby creating bulid audio amplifier and digital electronic stuff.
      • 10
        design
      • 10
        usability
      • 10
        creativity
      • 10
        content
      10.00
    View More