Figure 3: rbb’ = 2Ω of 2SB I’ve found the same 2Ω value in Douglas Self’s new book “Small signal audio design”. Although the. 2SB Rohm data sheet. 2SB Silicon PNP transistor Components datasheet pdf data sheet FREE from Datasheet (data sheet) search for integrated circuits (ic). 2SB Low rbb Low Noise Amp Components datasheet pdf data sheet FREE from Datasheet (data sheet) search for integrated circuits (ic).
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June 06, No simple fix to avoid the scratchy noise with gain changes due to small DC offsets, but you might want to experiment with cap quality there.
2SB Datasheet – Transistors, Bipolar, Si PNP Low-Power from ROHM Co.
First increasing current there, will decrease input signal swing before saturation, unless you change other values, but more importantly, I suspect the newer replacement devices are higher Rbb and happier at lower current density. February 18, There are some newer substitutes that aren’t as low R’bb but are acceptable in general microphone preamps. Those are super low Rbb transistors for low Z input stages. Regular transistors will be noisy in this application; I don’t know the NTE part, but I doubt it is a super low Rbb part.
The original Rohm transistors are discontinued; if you can’t source any, try the 2SA or, not quite as low noise but still pretty good, 2N Change both transistors in the input stage. Looking forward to some results!
Very nice that Mr. A am wondering what Adtasheet is using or their XL42 preamp now. Perhaps they 22sb737 protecting against some latch up condition. March 29, They were using truck loads of the 2sd NPN version. Started by jrmintz The Lab. Rossi Member Germany Posts: You can buy small quantities on the web I still have some back in my lab. The 85 looks identical except for higher breakdown voltage than 84 so no problem with either.
It will work but you’ll have more noise.
I usually added clamp diodes backwards across the be junction of the low noise devices to make sure they never zener if reversed, as that can make them noisy.
(PDF) 2SB737 Datasheet download
If you sprinkle when you tinkle, please be neat and wipe the seat. Low noise devices are generally graded for beta, as in the more beta the better for low dztasheet applications. April 01, Transistor substitution in GAR I don’t remember what transistor Peavey switched to. You are about to become the voice of Interplanetary Parliament. As we all know the 2SB has practically become extinct so I thought I’d follow Rossi’s ddatasheet and have them replaced by 2SA actually 2SA which I can get at daatsheet local dealer.
My stash of s datashet from my design work back in the ’70s, before I worked at Peavey. One weak link sonically for that design is the uF cap in the gain leg But I wouldn’t change it here for two reasons. Maybe he, or another ilumanted 2sb37 of this forum can bring some other substitutes! Maybe they have REAL much in stock. Roberts joins the thread!
Yup, they have been obsolete for years. Is there anything to consider changing resistor values etc. Bookkeeper Member Czech Republic Posts: Also on this forum are some threads about this part, but no conclusion what to use instead.
I typically would have run the 2sb at a little higher current density. I was already off the reservation when Peavey made their lifetime buy on that. The 2SA from Toshiba is an excellent super low Rbb transistor, but it has become scarce.
Rossi 2zb737 knows more than I do about what folks are using these days. Started by maxime The Lab. The original 2sb and 2sD were designed for moving coil head amps with ohm nominal source impedance, so arguably better than needed for ohm source impedance microphones. Started by abby normal The Lab.
So I’d drop them in and see how it works. The 2SA Hitachi that I pointed out earlier is a popular replacement used in quite a few preamp stages that previously had the 2SB But look at the data sheets for NF datasheer impedance curves, for something that doesn’t suck into ohms. You tell me whar a man gits his corn pone, en I’ll tell you what his ‘pinions is. In the schematic there are 2 2sb