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Are these transistors interchangable?
Are these transistors interchangable?
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Old 21st September 2019, 03:08 PM   #1
Lysergium is offline Lysergium
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Default Are these transistors interchangable?

I'm building a diy preamp for my diy amp. all component values ilustrated.
Click the image to open in full size.

accidentaly broke off all the legs of one of the BC547 transistors.
https://www.sparkfun.com/datasheets/...ents/BC546.pdf

i have one 2SD2375, could i used it?
2SD2375 npn transistor complementary pnp, replacement, pinout, pin configuration, substitute, marking D2375, equivalent, datasheet

emmiter-base voltage 6v for both, collect-base difference of 30v, collect-emmiter difference of 15.

as long as it doesn't completely mess up the signal, and just changes the parameters of the preamp a bit, im fine with that.

Nomimal voltage: 12V

Current consumption: 1.2mA

Voltage gain: 50-55

Maximum input signal level: 150 mV p/p

Maximum output signal level: 8 V p/p

Frequency response: 20 Hz to 200 KHz
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Old 21st September 2019, 03:13 PM   #2
maton00 is offline maton00  Mexico
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It will work but you are sending a truck for a bicicle work, also take in count the pin distribution the transistor you have is a TO-220 and the original is a small signal low noise transistor, it will certainly work but it will be sub optimal
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Old 21st September 2019, 03:35 PM   #3
Lysergium is offline Lysergium
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Can the draw backs be predicted? distortion? buzz? or something weirder?
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Old 22nd September 2019, 12:38 PM   #4
Lysergium is offline Lysergium
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http://www.farnell.com/datasheets/727135.pdf

This one should be basicaly the same, right? emmiter-base voltage 5v (1v lower), other values same.
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Old 22nd September 2019, 12:41 PM   #5
Lysergium is offline Lysergium
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or would this be better?
BC33725 pdf, BC33725 description, BC33725 datasheets, BC33725 view ::: ALLDATASHEET :::

Trying to use only scrap parts i have for this project.
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Old 23rd September 2019, 02:31 AM   #6
indianajo is offline indianajo  United States
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Transistors with too much input capacitance can filter the highs off a signal. Imagine a 600 pf capacitor parallel with the base of your TR1. Datasheets mostly don't show that, Cib, but you can go some by the size of the case. TO220 is pretty big , TO92 is pretty small. Not even going to look at your bc33725 datasheet, alldata versions of datasheets are pretty stripped down from the real thing. Try datasheetcatalog.com for some full featured datasheets.
emitter base voltage is a very basic measurement, not having much to do with capability for music.
Some indication is given by some transistors Ft spec. I just changed the drivers of my amp from 3 mhz TIP41c/42c to 30 Mhz MJE15028/29 and the highs really cleaned up.
If your signal is mellow guitars and human voice, those signals don't have any highs. So don't worry about it. I was testing with top octave solo piano, and that really shows up a circuit with bad high frequency response. (Peter Nero, Young & Warm & Wonderful dynatrack LP). Speakers were 14 khz capable, as are my ears. Steinway calibrator for what a top octave piano is supposed to sound like is in the next room from the speakers. If you don't have one, go to a concert that has one and listen carefully, particularly to the low & high frequencies. Tough sound source to reproduce.
Fast transistors for front ends don't have to be expensive. I find them occasionally for $.02 to $.08 on closeout at newark (farnell US) when they hit the end of the bin & want rid of them. I'll buy a hundred then, cheaper than the $9 freight on the box usually. BC639/640 BCE were bargains recently, in previous years I've scored MPS8099/8599 with the more usual EBC pinout. If you want the classic 2n5401/5551 or BC546/556 you'll pay more like $.35 each because that is what project sheets require.
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Last edited by indianajo; 23rd September 2019 at 02:42 AM.
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Old 23rd September 2019, 03:57 AM   #7
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by Lysergium View Post
or would this be better?
BC33725 pdf, BC33725 description, BC33725 datasheets, BC33725 view ::: ALLDATASHEET :::

Trying to use only scrap parts i have for this project.
The time you are wasting here trying to use improper parts is worth more than getting the proper parts.

Just order a dozen BC547 and keep extras for future projects.
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Old 23rd September 2019, 09:30 AM   #8
Lysergium is offline Lysergium
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I've built the preamp, using BC550C transistors.
Improved the volume quite a bit, maybe to the upper limit of my small speakers. Some cool distortion with the volume all the way up, clean signal with the volume down a little bit.
Will still try your recomended circuit today. Probably will be better.

The thing is, that the original BC547 transistors i had, were from a device, identical to the one i got the C33725 and BC550.
So they probably are.
Or I might just go buy the 547's, i'm not that lazy. maybe a little bit.
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Old 23rd September 2019, 09:37 AM   #9
Lysergium is offline Lysergium
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"The absolute maximum current this transistor can handle is 100 mA. This is the DC current rating. The peak current rating is 200 mA."

Might be a dumb question, but if my power source is 2.5A, all that current doesn't go throught the transistor, right? otherwise my preamp should have fried by now
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Old 23rd September 2019, 10:21 AM   #10
indianajo is offline indianajo  United States
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Current is limited by R3, R4, R7 & R8.
Read a transistor tutorial online. This circuit is a common emitter version of a bipolar junction transistor (BJT).
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