Transistor differences

[electricteeth]

Howdy! I am VERY new to this forum. I thought I would do some lurking around before I made this post. So, I built the three beginner projects in order to get up to speed. I know a little about electronics and soldering so it was tough but I made it through and they work and sound great. The Compression OP-Amp was the hardest to understand. There is so much stuff on this forum that confuses me but as time goes on I will start to get the picture.
So, with that said I am going to attempt a bass fuzz or boost. The biggest thing I have noticed about the beginner projects is that they are not as bass friendly as I thought they would be. They sound good with my bass but when i turn them on it cuts out alot of the low end and there are slight amounts of buzz (increasing as I dial in more gain). I have a few specific questions that may help me get on my way and maybe you seasoned pros can help:

1)I understand that caps pass more or less frequencies depending on size. Larger values pass more frequencies and lower value pass less? What is a good value for bass and at what value does it stop making a difference? Does a higher value equal higher noise?

2) I was getting alot of different tones from messing with the resistor values from V+ of the transistors and ic's in the beginner projects but little success with low end rumble. Are there specific transistors/ic's which have better bass response or should I just keep messing with voltages? What about fets and mosfets? I hear those have a more "tube" like response. What does this mean?

3) What is a good and maybe more simple circuit that I can play with to learn more about getting those low end frequencies beefed up without losing all of my attack? (i also built a clone of a popular bass boost and while it does boost bass it cuts treble and doesn't distort well).

Maybe I can be helped and maybe I can't. If there is any useful info that I am missing could I be pointed in the correct direction? Thanks!

[R.G.]

Howdy! I am VERY new to this forum. I thought I would do some lurking around before I made this post. So, I built the three beginner projects in order to get up to speed. I know a little about electronics and soldering so it was tough but I made it through and they work and sound great. The Compression OP-Amp was the hardest to understand. There is so much stuff on this forum that confuses me but as time goes on I will start to get the picture.

That is absolutely the right attitude. What many people fail to understand is that, like sex, the vast majority of electronics building goes on in your brain. It's a fundamentally mental exercise. If you can get to where you enjoy the learning, your progress takes off like a rocket.

1)I understand that caps pass more or less frequencies depending on size. Larger values pass more frequencies and lower value pass less? What is a good value for bass and at what value does it stop making a difference? Does a higher value equal higher noise?

You're right at a point where it starts to get slippery. Capacitors are like frequency-variable resistors in a way. They all have an infinite (ideally) resistance at DC, completely blocking it. But as frequency goes up, they block it less - their "resistance" to current flow goes down as frequency goes up. The bigger the capacitance rating, the faster their ability to impede current flow decreases.

So EVERY capacitor completely blocks DC, and EVERY capacitor lets through twice the current if you double the frequency. And a 2uF cap lets through twice the current that a 1uF cap does at ALL frequencies that are not DC.

But a capacitor does not *select* frequencies on its own. To be frequency selective, it must be paired with a resistor (or an inductor, but don't go there yet). In almost every circuit you see where a capacitor makes a frequency difference, it's paired with one or more resistors. In fact, there are always resistors there, but sometimes they're hidden inside other parts, like the resistance of a transistor collector or base.

There is a huge amount more that I won't confuse you with right now. I'll simplify it for you so you can get more addicted...  ... To get an octave lower bass, double the capacitance values of the series capacitors. This lets through twice the AC current, and reacts with the already-there resistors to lower the frequencies where the resistors and caps interact. Notice that this is a gross oversimplification and that there will be places it does not work well, but for what I think you're asking, it's a good start.

And to your original question, there is no capacitance value which lets more bass through on its own. It only has meaning when it's combined with the other resistances. It's possible to make the same pass-frequency with a 0.001uF cap as a 1uF cap by changing the resistors around them.

A higher capacitor value does make for more noise, but not in the way you mean it, so set that aside for the moment until you get to studying noise in the future. It's not simple.

2) I was getting alot of different tones from messing with the resistor values from V+ of the transistors and ic's in the beginner projects but little success with low end rumble. Are there specific transistors/ic's which have better bass response or should I just keep messing with voltages?

Hmmm. That's the wrong question. It's a lot like "Do you like bananas more than swimming?" They're not opposed quantities; they never touch.
All transistors and ICs respond in some way all the way down to DC. It's the circuits around them that limit and shape their low frequency response, so no, you can't sub in a different transistor to the same circuit and get more bass. You have to modify the circuits around them to get more bass. This is not true at the high end, and different transistors and ICs do have different high frequency responses because of the imperfections inside, but that generally happens above audio frequencies.

Yes, you should continue messing with voltages instead of subbing in different transistors and ICs, but even better is to go read about how resistors and caps interact to cause filtering.

What about fets and mosfets? I hear those have a more "tube" like response. What does this mean?

First off, it's not true. It's an electronic myth that FETs of any/all kinds are "just like a tube", or the watered-down version "more tube like" in the way it's generally used, suggesting that just using a FET of some kind will make for a tube sound. In general it means that either the person that says it does not understand what they're saying, or that they want to sell you something.

Maybe I can be helped and maybe I can't.

You personally control that issue, 100%. Really wanting to understand is the key. It's like the old joke - how many psychologists does it take to change a light bulb? Only one - but the light bulb has to really want to change.

If there is any useful info that I am missing could I be pointed in the correct direction?

What would help you most is to read about resistor-capacitor filters. It's in most basic electronics tutorials.

Then ask questions.