Oscilloscope

Having a multimeter is not enough to build an amplifier. I need an oscilloscope.
Thanks to craigslist, I found a new challenge.
Tektronix-TDS544A. Cool 500MHz digital scope with 4 inputs. But there are some caveats...
Before buying I tried to google it and found that all these scopes have leaking SMD capacitors. Leakage leads to a number of different anomalies.
Seller of mine scope told me the scope powers up but he can't see a thing. Since it is all crap shooting I gave it a try.
As expected, a lot of capacitors have leaks.
The plan is:
1. remove them all
2. clean all the PCBs
3. clean again
4. clean one more time
5. solder new capacitors

Some leaks look very suspicious

The worst leak

let's clean it up

Class D?

Among all the passionate discussions taking place on audiophile sites I found that I need to find a sweet point between the money, effort I put in my project, the fun I can get working on it and result (in terms of sound quality) I can get at the end.
Since I'm just an ignorant hobbyist I don't see a point to invest too much in my first project. I want it to be both fun and challenging.

So my amp is going to be fully digital class D amp. No analog circuits at all.

The roadmap is:
1. Play music on a device which has a USB
2. Convert USB to I2S
3. Pass I2S to PWM modulator
4. Feed power stage with PWM from the modulator.
Seems not to be super extremely complex.

I found these nice chips from Texas Instruments:
-  PWM modulator TAS5548
- 300W/channel power stageTAS5631B
last one promises pretty good THD up to 100W, but I don't think I ever need that power, especially having active amplification.
TAS5548 can processes 8 separate channels (4 I2S stereo channels) at 96kHz, has two ASRCs onboard and 7 biquads per channel. So it is able to handle all active crossover filters! I like the idea.

So next step is to design a PCB.

Two speakers test

Well, two speakers sound much better than one.
After playing with miniDSP settings I found the most sweet crossover point at about 1800Hz 24db/oct Linquitz-Riley.
Acoustics in my room is far from ideal so it affects my experience. I wish I had more lows but for some reason I hear them much better in the other room. Polarity change doesn't help.
Also I've decided to go with 3-way, I feel 1800 Hz is not the best crossover point for both tweeter and 8" woofer.

Now it is the time to think about new amplifiers. Mine don't drive 4 ohm (XT25 are 4 ohm) and I don't want to put resistors in series with my tweeters. Some people say that is a bad idea and I would agree...

Welcome Home!

My family is about to get back from their trip.
I want to impress them.
Some el-wire, tape, and a poster board turned into this cool thing

UPD: They were really impressed! I rock!

The First Speaker Is Ready For Testing

Here is my first four feet baby box:

It sounds good. Way better than a crappy Pioneer speaker or a couple of Chinese Acoustic Art I have. But one speaker is not enough for a good listening test.
I think I need to build a Wallin's Jig to measure my room and drivers.

MiniDSP 2x4

I got my drivers and MiniDSP 2x4 kit.
MiniDSP has a nice looking crossover management software.

While I work on my boxes, drivers have time to warm up.

First enclosure is almost done

One of the enclosures is almost done!

Someone can ask me why I placed drivers too far from each other. Well, the only good answer I have is "what if I want to add a midrange later?"
MiniDSP should help with signal delays.