Buffers from the past…

A design from some of my earliest encounters with the audio DIY hobby that I have always wanted to try is Eldon Pawliw’s headphone buffer. This is based on an original article called “Aunt Corey’s Buffered Passive Preamp” by Stereophile reviewer Corey Greenberg. The original article appeared in Stereophile in 1991 and is still available at Stereophile online – go and have a look!. Aside: While reading it, note a few funny references that make you realise how different the world was back then (looking in databooks for parts information, sending SAEs for information, not a single mention of websites, emails or Goggle anywhere etc. 🙂 )

The design for this circuit is exceedingly simple as there is just one active part per channel – the BUF03 closed-loop buffer IC by Analog Devices. The “closed-loop” part is important, because it means it can be connected outside the feedback loop of an opamp: Nesting the buffer in the feedback loop s what you’d have to do with newer buffer ICs such as the BUF634 or the LME49600. The BUF03s have been discontinued for ages (mine have 1991 date codes…), but are now starting to show up on ebay as NOS or pulls from scrapped equipment. I bought mine as NOS a couple of years ago from a diyaudio.com member but haven’t done anything with them until now.

To try out the design I made a board layout for a stereo buffer. I stuck to the original design but decided to change the bypass scheme a bit. The BUF03 is a fairly wideband device, so I thought that using 100nF ceramics as the first stage bypass was better than the 1uF electrolytic used in the article. The other bypass caps are Elna Cerafine 220uFs (because I had them). The board is two layers and measures 36x65mm.

The boards worked fine during my quick tests 🙂 The BUF03s are internally biased to class A and run very hot. In fact so hot that I need to find some small heatsinks for them I think. This also means there is a risk of thermal drift in the offset, so that will have to be adjusted later on. This also means I haven’t got any detailed listening impressions yet, but I am looking forward to trying the buffers out for real – hopefully very soon 😀

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4 Responses to Buffers from the past…

  1. Pingback: Project files: BUF-03 stereo buffer | theslowdiyer

  2. DaveR says:

    hi, have you had a chance to compare your buf-03 buffer to the B1? I’m very interested in these options for my own preamp plans. Thx

    • theslowdiyer says:

      Hi Dave,

      No I haven’t sorry. My current setup doesn’t even need a preamp as I have a DAC with volume control so the BUF-03s have been mainly driving headphones and the B1 will not do that.

      /U.

  3. Pingback: Project files: BUF-03 revisited | theslowdiyer

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