First(ish) Amplifier project

[TychoF]

Hi everybody!

This is my first post on this forum but I have been reading it quite allot. First of, this is the second time I have to write this, the last attempt failed as i was not logged in so bear with me as I'm impatiently rewriting everything now.

First off, the disclaimer: I tried searching and reading for similar projects and questions, but I either couldnt find them or didnt understand them. As I imagine threads like these might get tiresome after a while, especially if the questions are easy to google, I would like to emphesize that I did try all that. Anyways, to the point:

I am planning to make a class D amplifier with integrated passive/active pre-amplifier, power supply and tone control. For the amp i'm thinking about buying ucd180st from hypex, the rest i'd rather buy elsewhere out of budgetary concerns.

I have some prior experience: made my own boombox (like in the forum here), did some simple maintenance on speakers and amplifiers. And i do a technical study.

I will be using the following global diagram:

Does anybody have any comment about above diagram?

In any case, my questions:

1)
How important is the voltage supply for an Amp? Must it be very stable? Is the difference between a 30V supply or 40V supply big?

2)
Is the power supply in the diagram enough for the system? Would I need to buy something better, like an smps or will this suffice?

3)
Will a simple/cheap pot meter suffice for attenuation or are there better solutions?

4)
I would like to make the case from wood, what are the differences between metal and wood i should consider? E.g. grounding or cooling?

5)
How important is sepparating tones for e.g. the subwoofer?

6)
Is it easy to make your own tone balance circuit?

7)
Which parts are most critical for the final sound quality?

Thanks in advance for helping!

Tycho

[luka]

yea, I would change the volume before the amplifier, where signal is still low
1) well at least it has to hold the voltage at your power levels, apart from that, I have used few different ones... again, depends for what you are going, top of the top might be complex
2)yes
3) yes it will and yes there are almost always
4) with case you are probably safe what ever path you take, since you can make it grounded or not in both cases
5)sepparating how, from what?
6)depends on your soldering skills, for myself easy
7)Source! but depends on so many thing, that can go wrong and make things not as good as they could be

[nigelwright7557]

Your sensible going for a reayd made class d module.
Class d can be a minefield for the inexperienced in class d.
Decoupling and pcb layout are very important in class d.

[TychoF]

First of all, thanks for your answers! I apreciate it.

@Nigel,
Yeah, first i thought about doing. e.g. buying something from 41hz. But then I realized I'm too inexperienced for that.

Originally Posted by luka

yea, I would change the volume before the amplifier, where signal is still low

Alright, ill do that. I thought that would be better as it would avoid some S/N problems. But if it's to much of a hassle i'll do it before hand.

Originally Posted by luka

5)sepparating how, from what?

I read in a few places that people would use a lowpass filter for the subwoofer. Besides getting the flattest response possible, is this really needed?

And then a question i forgot last time: how important is matching voltages?
e.g.
The ready made module I want to buy is 180 watts and uses between 30~50V. I have 2 different kind of trafo's to choose from: 30V and 36V. Which is the better choice?

Furthermore, i would like to make a 2.1 system. But Trafo's only come with 2 energy outputs. Could i couple all the trafo's outputs together and then splitt them to the three amps? like this?

[luka]

Originally Posted by TychoF

First of all, thanks for your answers! I apreciate it.

@Nigel,
Yeah, first i thought about doing. e.g. buying something from 41hz. But then I realized I'm too inexperienced for that.


Alright, ill do that. I thought that would be better as it would avoid some S/N problems. But if it's to much of a hassle i'll do it before hand.


I read in a few places that people would use a lowpass filter for the subwoofer. Besides getting the flattest response possible, is this really needed?

And then a question i forgot last time: how important is matching voltages?
e.g.
The ready made module I want to buy is 180 watts and uses between 30~50V. I have 2 different kind of trafo's to choose from: 30V and 36V. Which is the better choice?

Furthermore, i would like to make a 2.1 system. But Trafo's only come with 2 energy outputs. Could i couple all the trafo's outputs together and then splitt them to the three amps? like this?

I would use LPF, since you can't let sub play more then 80Hz or so

Its not important to match voltages, it won't be a problem for you

I would use 36v one, if it is powerfull enough to hold the voltage, compared to 30v one. Every trafo has lower voltage under load, the bigger the trafo the less voltage drop you have at same power levels. Also 36v one means you have more peak power the deliver to the load, this is what you need in good dynamic song

Well I will say yes and no, while you can, but you can't ensure true current sharing of the two trafos
I would use one for one amp, the one that will need the most power (sub amp), and other trafo for lower power amp, the one fullrange (with lower power amp I don't mean it has to be lower power, but the one amps that will draw less power)