Elliott Sound Products NAB/IEC preamp

SeleniumFalcon
SeleniumFalcon Posts: 3,760
in DIY, Mods & Tweaks
I'm always trying to improve on the way open reel tapes sound, they have great potential but it's not always realized mostly due to limitations on the playback electronics. Elliott Sound Products' Rod Elliott has taken his ESP P06 phono preamp and changed the feedback components so it could be used with NAB and IEC (American and European) transports. Up to this point external tape preamps were very expensive and aimed at well healed enthusiasts.
I decided to use two heavy gauge steel (#20 gauge) enclosures from Hammond Industries, one for the power supply and the second for the main circuit board with connections.

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Comments

  • SCompRacer
    SCompRacer Posts: 8,491
    Wow, nice work! You got me thinking about it....


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  • SeleniumFalcon
    SeleniumFalcon Posts: 3,760
    Since this is the first project that used integrated circuit operational amplifiers (opamps) as the main devices I wanted to find a way to test them during troubleshooting. I found a very nifty product from MidZoo, a test platform that shows "good/no good" status on single and double opamps. Here is one that tested "no good":

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    One that checked out:

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  • SeleniumFalcon
    SeleniumFalcon Posts: 3,760
    I wanted to see how close the playback curve for NAB 7.5 and 15 inches per second measured to the ideal. I plotted frequency versus output on this graph the black trace in the center is the ideal response plotted with 500Hz as the "0" dB point. The red trace is with the LM5532AP opamp, a very popular choice for audio applications. As you can see the trace is 2dB down at the low end compared to the ideal response. The blue trace slightly above is done with two different opamps, one the OPA162 an FET input opamp that is only available on a surface mount format and the LM4562NA a very low noise audio purpose opamp. As you can see the low end response is slightly elevated beginning around 50Hz and reaching about 1.5dB over the ideal. Want to bet that's the response I'll like the most?

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