Scope Cleaning

All capacitors were removed with "twisting" method. I don't have hot tweezers to desolder large SMD capacitors and I'm afraid I would damage more pads if I used a single soldering iron. Almost all the traces left in place, I lifted just two pads which is not bad having almost hundred caps and all these leakages which could damage everything around.

After all capacitors were removed I had to clean all the acid residue. I found a lot of PCB cleaning stories. Seems that most popular way is to use Simple Green general purpose cleaner.
Simple Green + toothbrush + baking oven at about 150F made it virgin clean.

All capacitors are replaced with new low ESR leaded ones.

Before caps replacement

After all the caps are replaced. Still have Acquisition board fail...

Error log shows a mysterious error

I still have failed acquisition test, but scope seems to be working. 

Unfortunately I couldn't find where the problem can be. The only suspicious area is around U1602, where were a lot of corrosion. I replaced this opamp with a new one but could not find where one of the legs connected. Seems to be a broken trace. I would be happy to fix it but could not find where to connect it. Need to try to find out...

It  looked not very nice...

But I think I can live with non-calibrated scope.

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.

Woodworking

Time to have some fun with MDF and tools!

MDF sheet didn't fit into my car so I had to cut it in store. Both Lowes and Home Depo have the same crappy saws and I was afraid they can't cut it precise enough. Well, I ws absolutely right.
Thanks my colleague Mike - he has a table saw and he helped me to trim all the pieces to be the same width.

After I had all the pieces cut and holes routed I could start to glue it all together. I decided not to use any screws because if I veneer it later screw heads can be visible even covered with putty.

Don't think I would make a sandwich like this next time. It is really hard to position parts right

Drivers fit pretty well:

I'm going to reassemble speakers many times so I put some effort and used t-nuts. I like the result.

By the way, Harbor Freight clamps did the job but I would not recommend them for any professional work. They are very cheaply made, but no one can beat the price.

Turntable got a new needle and a new belt. Now it works. Want to show to my kid how we used to listen music

It is going to be 2-way design with XT25 tweeters and HiVi M8a woofers, XT25 can be crossed pretty low with 4th order crossover.
MiniDSP 2x4 will do the job well I hope.

My wife and kid are going to have a long trip to visit all the grandparents so I'll finally can do a lot!

What a huge amount of information I have to digest!

Passive filter design scares me a lot. Especially the price for good quality components. I'll go with with active amplification, it will give me much more flexibility

There will be new speakers

Speakers

Not so far I bought some used Onkyo gear on a garage sale. LP, preamplifier, amplifier, FM tuner, cassette deck, surround amp, two tower speakers - all for 50 bucks. Great deal. But speakers were just burned down. Initially i just wanted to repair speakers, but it was just a beginning of a new adventure... Speakers design was quite questionable - 3.5 feet tall speakers made of 0.25” panels, not properly sealed. 1st-order crossovers made from crappy components. So I had a dilemma - buy new drivers and get renewed pair of shitty speakers or build my own new speakers out of nice solid ¾” MDF…
I chose the second way.

I had a little previous experience with building speakers, but it was not really serious.

Almost every step on this way seems to be a new experience for me and I expect myself making stupid mistakes. I have to buy all the tools and materials needed and having not too much free time the whole process is going to take a while. I better be patient (I hope my wife will be patient too)...

So I started to recall all the knowledge I through the years trying to find some good recipes. Wise people on the Internet keep saying “for your first speakers choose a proven 2-way design” and bla-bla-bla. But who listen to a wisdom nowadays? Let's see...

And what a surprise! I picked up another Pioneer speaker at a dumpster. It works!
It seems to be the same design but I don't care, I'll use it as a test load for my experiments.