• ROHM 2SB737, PNP NOS Transistors, Low rbb, Low Noise, Qty 2
Buy two "new old stock" ROHM 2SB737 TO-92 transistors. 2SB737 data sheet.

The 2SB737 available here are new old stock that were purchased for the John Roberts P10 preamplifier featured in the March 1981 Popular Electronics article "Build A High Performance Phono Preamplifier."

Note that our tests show that these devices measure in the "Q" Hfe range of 120-270 and although they are genuine 2SB737 with known history and measurably low noise they may have been mis-marked by ROhm. Devices from another lot and provider from the 1980s era marked "S" also measure in the "Q" Hfe range.

John misplaced his stash of the highly sought-after 2SB737S and recently found them. John tells the story of the "Lost 2SB737" here:

"Back in the 70s I had an interest in low noise design (I was doing some consulting for Loft Modular Devices a studio effects/console company better known for their Loft 440 delay line/Flanger). I saw the 2SB737/2SD786 low noise complementary pair written up in an IEEE journal article. Perhaps odd that a college drop out like me was reading the IEEE journals but I got Rudy Bozak (the Rudy Bozak from the speaker company of the same name) to sponsor my IEEE membership while I was consulting for him.

Back to the low noise devices, I contacted ROHM who was representing them in the US… IIRC they were developed by a small Japanese company for MC head amps and ROHM ended up buying that small Japanese company. Because the PNP was slightly lower noise than the NPN, I used the PNP in all my designs (before Peavey). The “S” in 2SB737-S stands for a graded high beta (hfe) part, good for low noise applications.

Back in the early 80s I recall reading an article in Studio Sound written by some big dog UK console designer declaring that transistors that quiet were impossible or unlikely to ever be made. I popped a few in the mail to him to blow his mind (it worked). :-)

Later in the mid 80s’ when I went to work for Peavey, they already had the NPN complement (2SD786) in their system so I just used that for my low noise applications while designing inside Peavey. The small difference between PNP and NPN did not justify me bringing in another similar part.

I first used these inside mic preamps for use in Loft Consoles. Almost as a "by the way," when I published my P-10 phono preamp kit, I offered a MC version using these devices. The P-10 topology involved a flat gain stage front end before an active RIAA EQ stage. It was simple to swap in a higher gain, low Z gain stage for the MC and use JFET devices at lower gain for MM. I got a rave from Peter Aczel publisher of the Audio Critic (an audiophool rag), when a friend of mine shared my P-10 MC preamp with him. I ended up trading him a preamp for a nice pair of two-way time aligned loud speakers "Fourier" that my friend designed and Aczel was promoting.

The proliferation of serviceable IC mic preamps around the turn of the century (that did not suck), made these low noise discrete bipolar devices less attractive to large scale audio manufacturers. ROHM ended up obsoleting them.

Fast forward to this century I had what was left over from a large purchase back during my kit business/console consulting days stashed in my back lab. For some extra drama I misplaced this stash and couldn’t put my hands of them for almost 10 years. Last week while looking for some missing microphones to build more drum tuners I found my long missing stash of 2SB737s devices wedged into the back of an empty parts bin compartment (I still haven’t found those mics).

I shared low noise devices with Wayne so they can be put to better use than sitting in my back lab."

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ROHM 2SB737, PNP NOS Transistors, Low rbb, Low Noise, Qty 2

  • $9.95