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  • #16
    Originally posted by tomzarbo View Post
    ...thinking that another of the isolated DC to DC converters will be needed to reduce/eliminate noise to the amp.
    ​Not necessarily, but you will probably need an isolator. The problem is due to digital noise, particularly from a Bluetooth or WiFi radio, that shares the same ground path as the analog signal. You can tell whether you need a DC/DC isolator by tracing the current flow from the supply back to "ground". If that path shares any part of an audio signal ground, you will probably need an isolator, either on the signal or on the DC supply. The chances of needing an isolator increase when you have a preamp module without separate digital and analog grounds and whenever you have a radio component on the circuit.. Of course, you only have the noise problem when you try to power everything from a single power supply.

    ​That 3W isolator is a good size, and the wide input range makes it easy to use.
    Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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    • #17
      Originally posted by neildavis View Post

      ​Not necessarily, but you will probably need an isolator. The problem is due to digital noise, particularly from a Bluetooth or WiFi radio, that shares the same ground path as the analog signal. You can tell whether you need a DC/DC isolator by tracing the current flow from the supply back to "ground". If that path shares any part of an audio signal ground, you will probably need an isolator, either on the signal or on the DC supply. The chances of needing an isolator increase when you have a preamp module without separate digital and analog grounds and whenever you have a radio component on the circuit.. Of course, you only have the noise problem when you try to power everything from a single power supply.

      ​That 3W isolator is a good size, and the wide input range makes it easy to use.
      Thanks for the info Neil.
      I'm hoping to do a lot of audio-related things this weekend, one of which is to try the same amp board I used with the other radio at a higher voltage this time...(15-16V), and patch it to this new LCD faceplate preamp. I want to see if it has the guts to push the Bantams to full volume, and also to see if there is a noise issue with this LCD Preamp. I'll have to get the voltage down to 5v anyway, so I may as well just use the isolated convertor to do the job and avoid possible issues. I'm relieved to hear that you think it is a good candidate.

      I also am still working on ideas to mount everything and get the buttons 'pushable' so to speak. I'm also trying to figure out if I need a glass panel over the LCD screen to protect it. I think yes on that one. Hopefully I can have a "Bantam" table radio in the works by May or June. This radio will be a LOT harder than the other one on account of the interface will need to be engineered/designed by me, where the other one was cut a hole and mount with four screws... but I'm actually looking forward to the challenge, it's fun.

      Thanks again for the input, I always appreciate it.

      TomZ
      *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
      *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

      *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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