DIY home theater audio system

[Nexo]

Hello everyone!
I'm here in order to ask about how to start building my own home theater audio system.
There is a lot of information out there and it's quite overwhelming so I rather ask you where should I begin.
Let me start: In one month I'll start my fifth semester of Electronics Engineering and I'll study a subject call Analog Electronics.
I got in touch with the teacher and asked him if I could present a Home theater made up merely off transistors and op-amps, that is, an utterly analog system and he said that it would be interesting so I decided to start doing right now.
I want to learn the theory behind it and make a really good project and I want to take advantage of the fact that I have a month before starting the semester and 3 more months to finish the project. The sooner, the better.

So... I want to ask you, dear EEVBlog fellas for directions.
I want to do it all myself, from the simulations on Symulink (Matlab) to build the enclosure for the speakers but, where should I begin?
I already know how diodes and transistors work but, how can I use that knowledge in order to accomplish such a task?

As I said before, there is a lot of info out there like: pre-amps, amps, power amps, woofer, sub-woofer, etc... I'm thirsty from knowledge but I'm overwhelmed by the amount of info and the lack of direction.

Any advice would be much appreciated.

Thanks in advance!

[JS]

Start with specs, how many channels, how much power? Into what load?

I guess you are starting with already made cabinets, as acoustics of small boxes is quite a can of worms... Most practical way to go about it would be a power IC with all you need inside, not what you want. Your next best bet would be to get a nice power module and then replicate, maybe a slightly different one for the sub as you could need higher power there.

If you are after a few watts you might get away using an opamp and a discrete buffer, like darlington or mosfet power stage and some biasing circuit, an opamp driving that stage. If you are short in voltage for such a setup (limited by opamp working rails) and you need a bit more power bridging is an option, just build twice as many power stages and drive high and low signals to the cabinets.

JS

[hayatepilot]

For power amplifiers there is the excellent Audio Power Amplifier Design Handbook.
The power of the amplifiers doesn't need to be very high 10-20Wrms per channel will usually give you more than enough volume. The subwoofer needs more power. The lower and louder it should play the more power you need. I'd say start with 200W.
As for the speakers themselves I would suggest you use one of the hundrets (if not thousands) of DIY speaker designs out there. I designed coaxial speakers for surround/Atmos myself. 

Since this is for analog electronics course I would focus on the electronics and not the speakers itself.

Greetings

[Nexo]

Great advice and resource!
@hayatepilot you are right about focusing on the electronics. I'll start reading the handbook you gave me but then again, what should be the first step? I mean, having in mind that I want a 5.1 audio system. Should I focus on filters in order to have a circuit for each interval of frequencies I want to have or what should I do?

Again, thank you very much!

[hayatepilot]

What you want is a basic 5-Channel power amplifier with a single volume knob. Don't bother with the full capabilities of a modern AV-Receiver.
This means that the source (a bluray player or a PC) will provide the signals for each channel. No filters are needed in hardware since this can all be done at the source.
This depends on your source and how flexible it is.

You could also use a off the shelf HDMI audio processor as the source of your amplifier such as this one: miniDSP nanoAVR HDA
This would take care of all the filtering, bass management, room correction and even volume control.

[Nitrousoxide]

A good way to start designing is to use high level (not so much for this case I suppose) and low-level block diagrams to give the problem a certain level of abstraction.
Block diagrams can really help with making the system seem less daunting.

Hopefully, you would end up with a pre-amp stage, differential stage (subtraction), and phase splitter/power stage. This is all assuming that the amplifier is operating as classes A/B/AB.  It is possible to design a discrete class D amplifier, it would give you better efficiency too.

Start by forming a single channel, you can then replicate it 6 times and attach it to the output of a filter bank, which can be designed last.

[b_force]

If you can get it covered by your study, get Loudspeaker handbook (Eargle), Loudspeaker and Headphone handbook (Borwick) and Sound Reproduction (Toole, must read)
(A few can be found in "some digital ways")

To start with, determine budget, size, aesthetics, SPL (loudness) and what is your lowest frequency.
Personal note, try to put energy in Class-D designs instead of analog amplifiers, since the future isn't gonna have a lot of analog amplifiers anymore.
Waste of energy otherwise imo

[Doctorandus_P]

You say: "I want to do it all myself", but the only way to do that is to start be re-inventing the universe.
Not very practical.

About amplifiers, Depending on the quality / power level required just designing a power amplifier can be several years of work. Do you see an audio amplifier as a block you want to buy, or as a challenge to develop yourself?

For a very "practical" approach there are a lot of audio amplifier boards on Ali / Ebay / China / etc.
Small to big Class D boards, analog A/B chip designs and analog discrete transistor kits.

A tip for multiple channel simultateous volume control: Use the PGA2311 or CS3310.

[+Mikie]

I can suggest a man named Douglas Self, he has a website with some of his designs published. Most if not all of them use only transistors.

Another one is Australian with a lots of his designs published on his site "Eliott Sound Products". including 400-odd wats discrete sub amplifier.

There was also an analog surround processor published by Electronics Australia quite some years ago. I'd think something like that would impress your teacher.

For speakers, another unusual solution would be a full-range driver in a transmission line. My personal opinion is that in terms of sound quality nothing else comes close.

If you're just starting with this hobby (and electronics education) I would assume nobody would expect you do design stuff from scratch, so it's ok to scour the net for ready-made designs and excell in putting it all together. Good luck.