Trying to amplify signal

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I'm trying to make a simple signal tracer amplifier

So the first thing I did was connect the signal generator leads straight to an 8 ohm speaker 🔇 to prove that there would be no sound because it needed to be amplified 

Unfortunately it came through loud and clear 

Alright well my little cobbled up one transistor will just make it LOUDER

Unfortunately it did not.

Now there's probably a million things wrong with my circuit but that's kinda the reason I set out like this without looking up a recipe

So this seems to work but it's not as loud as just a direct connection

Also I made the circuit without looking anything up the resistors were arbitrarily chosen and I remembered seems like the base resistor is always a large value

Also the capacitors were arbitrarily chosen

I do get forward bias on base to emitter

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And obviously yes I'm gonna have to crack open some books and try to see what's up

For instance right now I'm kinda wondering hmm what do I need to make it louder CURRENT GAIN

OR VOLTAGE GAIN

I'm pretty excited to get through this part because next I want to take a look at complimentary pair and then also I want to use some 8 DIP amplifiers

And here's one old lady that's glad the storm is gone 

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[J M Fahey]

Well, good intentions but a couple problems.
1) you are injecting signal on the +V rail.
That may have 10-15V DC on it  but it is Audio ground, so you are shorting your signal.

2) same thing, speaker is connected to same +V Audio grounded rail.
Nothing audio there except maybe some hum or ripple.   

3) get a tutorial on how to design a single transistor gain stage.
Values are not random.

4) even if, an 8 ohm speaker has way too low impedance to be driven by a humble small transistor.
Back in the day, Student circuit examples used a very high impedance crystal headphone (almost unobtanium today) o a 2 k ohm magnetic headphone (same thing)

If you want simple, use a small IC such as LM386



Full article:
https://electronics-diy.com/electronic_schematic.php?id=1047

My only disagreement is them using a 10k input pot.
Audio 100k would be much better.

It easily drives a small speaker, 2" plastic type is fine, or standard walkman/phone earphones

[g1]

Like JM said, the input and output are going to wrong places.  Even if the transistor were set up with correct resistor values, the input cap would connect to the other side of that base resistor.  The output cap would connect to the other side of that collector resistor.

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Thanks guys I appreciate it as stated before this is a great place 

I'm gonna go back and do an autopsy on this circuit I'm particularly interested in the voltage at the collector

It's a target 🎯 rich environment for me learning 

I'm essentially trying to build an aircraft with people from NASA looking on 

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Ok I went back and constructed the circuit and took some readings

About the V+ value I think I just wanted enough to get the Vbe I needed

Anyhow

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Seems like I remember the emitter and current should be about the same but that doesn't mean the resistors are the same.  In fact all those little circuits I made I don't recall that being the case.

Seems like I do need the collector voltage more positive than the base voltage and I'm pleased with that 

I better do something so maybe I'll increase the value of the collector resistor 

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And one problem that needs to be worked out and I had noticed this before

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And as the input signal is turned up it gets worse (base gets more negative)

I have the positive terminal of the electrolytic facing the circuit

Probably something simple doh 

[saturated]

Ok yeah the signal (at least half of it) thinks the V+ is ground

Anyway I went back and read some stuff here and decided to heed their advice and add a base resistor to ground

Which I did and it helped but I had to accommodate both V+ and the ground resistor thinking about voltage drops.

I saw where there was a threshold where Vbe would hold up then start to decrease to head south and that coincides with the onset of clipping of the output.

That said I don't expect anyone to make heads or tails of this nonsense I'm gonna have to keep working on it for a while.

Thinking out loud I guess the base voltage needs to exceed the input signal voltage so maybe increase the value of the base to ground resistor

 

So yeah I'm getting my rear end handed to me that's a good thing 

[J M Fahey]

Try 1M Base to collector and 3k3 collector to +V and get ready to ride.

Inject 100 mV into Base through a 1 or 10 uF cap, positive end towards Base and scope collector.

You´ll have so much gain that probably signal clips, go figure.

Attenuate signal drive and tell us how many mV it takes to reach clipping.
Gain will be HUGE.

This is a basic gain stage around which I built many projects, from signal boosters to 8 channel mixers back in the 80s, published in Music Magazines, Argentine Musicians built tons of those and used them live .

Google says:
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Overview created by AI
"Project Primavera" was a famous electronics and audio project DIY (do it yourself) published by the renowned Argentine technician and manufacturer Juan Manuel Fahey in the pages of the mythical national magazine El Musiquero in the late 80's.
The project consisted of design and step-by-step schemes to build a home or studio audio mixer console.
Project Details

    The Author: Juan Manuel Fahey, an eminence in the manufacture of national audio amplifiers (much remembered for equipping bass players like Ricardo Iorio), was part of the staff of the magazine providing their knowledge in technical sections.
    The Publication: It was distributed in the form of monthly deliveries or fascicles within El Musiquero, allowing musicians and enthusiasts of the time to buy the components in electronics houses (such as those on Paraná Street in Buenos Aires) to assemble their own console.
    The Legacy: Today it is a cult project between vintage audio technicians, music lovers and nostalgic Argentine analog electronics.

Are you looking for the electrical schematics or the list of components of a specific module of the Primavera console, or are you interested in knowing what exact numbers of the magazine was published?
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