Please tell me about single transistor audio amp
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Joined: Sep 2016
Posts: 2
newbie
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OP
newbie
Joined: Sep 2016
Posts: 2 |
Hello! I have drawn a schematic of 2N3904 2N3904. Here is a simple audio amplifier with an npn transistor. What should be the value of voltage source V2? How can I calculte it? output connects to a speaker and input can be pc or mp3 player. Could you teach me ? I'm new to audio and electronics.
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Re: Please tell me about single transistor audio amp
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Joined: Jan 2007
Posts: 10,490 Likes: 116
shareholder in the making
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shareholder in the making
Joined: Jan 2007
Posts: 10,490 Likes: 116 |
Dude, you're doing it all wrong!
2x6 will be around here soon to tell you 2N3904 should be a 12AE10. In that case, V2=160V.
House of the Rising Sone Out in the mid or far field Dedicated mid-woofers are over-rated
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Re: Please tell me about single transistor audio amp
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Joined: Aug 2004
Posts: 6,379 Likes: 7
axiomite
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axiomite
Joined: Aug 2004
Posts: 6,379 Likes: 7 |
OK, let's see... (it's been a lot of years so take this with a grain of salt): 1. I don't think this is going to be sufficiently powerful to drive a speaker, at least not with any noticeable volume. The transistor is a low power one, rated for well under a watt. Looks like more of a preamp stage than a speOther limits for the 2N3904 are 200mA current and 625mW power, so let's see...aker amp. 2. The transistor is rated for ~40V max, so that is the absolute highest, but this seems more like a circuit that would run on 12V or less to me. 3. R1 seems to be in an odd place, normally input resistors like that are connected to ground not to a power rail. EDIT - might have found the original source, or at least another instance of it. In the following link the author is using a 3v cell, which seems reasonable. http://hackaweek.com/hacks/?p=327In this article r1 is there because the circuit is being used as a microphone preamp. The author mentions an electret microphone but I didn't think electrets needed a bias voltage from the preamp. Oh well... Hope this helps. Good luck...
Last edited by bridgman; 09/08/16 12:27 AM.
M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39 M5HP, M40ti, Sierra-1 LFR1100 active, ADA1500-4 and -8
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Re: Please tell me about single transistor audio amp
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Joined: Aug 2004
Posts: 6,379 Likes: 7
axiomite
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axiomite
Joined: Aug 2004
Posts: 6,379 Likes: 7 |
1. I don't think this is going to be sufficiently powerful to drive a speaker, at least not with any noticeable volume. The transistor is a low power one, rated for well under a watt. Looks like more of a preamp stage than a speOther limits for the 2N3904 are 200mA current and 625mW power, so let's see...aker amp. Looks like a cat walked across the keyboard while I was copying and pasting. I don't have a cat though, so must be my fault. Should read: Looks like more of a preamp stage than a speaker amp. Another argument for this being a microphone preamp are the values of R3 and C2. R3 is going to limit current to the point where driving a speaker isn't likely to work, and same for C2 at audio frequencies. If I was going to try to drive a speaker with this kind of circuit I would make the following changes: - use a battery between 3 and 9V - remove R1 or (better yet) connect other end to ground instead of power - change R3 to lower value, between 1K (9V) and 220 ohms (3V)... that's probably still higher than needed but trying to be safe here - I think R2 needs to be scaled down accordingly, so keep it ~10x the value of R3 - replace C2 with something ~10x larger - if you don't already have the 2N3904, consider getting a higher power transistor instead Note that the real answer here would be to go with at least a two transistor circuit but assuming that experimentation & learning is one of the goals here (in which case starting with 1 transistor is good).
M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39 M5HP, M40ti, Sierra-1 LFR1100 active, ADA1500-4 and -8
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Re: Please tell me about single transistor audio amp
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Joined: Jan 2007
Posts: 10,490 Likes: 116
shareholder in the making
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shareholder in the making
Joined: Jan 2007
Posts: 10,490 Likes: 116 |
Circuit ignition, enabled by V2 connected to 120VAC, will certainly provide more enjoyment than listening to any audio through this amp.
House of the Rising Sone Out in the mid or far field Dedicated mid-woofers are over-rated
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