The TDA1545 DAC is nearing completion. I'm trying, for once, to make a nice product, somewhat operational by a simple human being. The DAC has gotten a new 5 channel input selector. This is basicly 5 SMD relays (mounted on the solderside), the CS8412 receiver, and a basic cap filtered PSU. The TDA1545 DAC board fits on top, this way, when finished, everything is firmly attached to the receiver board. I will post the PCB layout, and schematics, when the last bugs have been squashed, and the values of some components have been optimized.

Let me just say, that this is a big step for me, as it is the first of my HIFI projects in 5 years, that is actually in feature freeze, and will reach a final and generally usable state.

I have been looking for a way to simulate an inverse RIAA network in spice, After using a passive discrete simulation for a while, i found this: How to calculate RIAA correctly?

Using the ELAPLACE part in OrCAD PSpice, changing the XFORM paramter to this

(1+3180u*s)*(1+75u*s)/((1+318u*s)*(1+3.18u*s))*

And everything works like a charm.

As noted earlier, I had some trouble with C7 blowing the chips. I am no closer to being sure what the problem was, but I am beginning to suspect a bad batch of chips, anyhow the original value is according to Phlips datasheet, way to high. I have now settled for a 2.2uF WIMA cap, and everything is playing nicely.

I had some help with my troubles at diyhifi.org, the thread is here:

TDA1545 Vref cap and the death of several DAC chips

I have just finished testing a prototyping board I have designed for the PIC18F2550, that I will be using in a project I am doing for a friend. The board is designed to interface with the PICKit 2, programmer/debugger, has an on board 5 Volt regulator, and pads for a serial port through the MAX232 line driver/receiver. This is not rocket science, just a nice PIC18F2550 to breadboard converter.


 

Cadsoft Eagle project files: uc-proto.zip

Finally after a thousand cups of coffee (for me that is) it is actually playing music again. This time through the last TDA1545 DAC chip that I haven't destroyed. This is a clone of the "Monica" DAC. I can not comment that much on the sound, since it has been a while since the TDA1543 DAC, was playing, but it sounds nice, and definitely different. If you have some spare chips and time, try it for yourself.

In the final version, R1 is 33k, and C7 has been omitted. C7 seemed to be the part causing the 2 DAC chips to die, I'm not sure why, and I'm not sure the final solution is to leave it out, but since I'm at my last chip, It'll stay that way for a while. Also check the output from the current source between R4 and D1, if above 6V, short out D1, D4, and D7.

TDA1545 NONOS DAC Cadsoft eagle project files

TDA1545 Datasheet

Damn that horse! I have spend much of the day building a TDA1545 version of my DAC, but with no success. The CS8412 SPDIF -> I2S/EIAJ converter locks to the signal, but only noise comes out from the DAC. Maybe I will have to resurrect the TDA1543 board, to make sure everything in front of the DAC, still works.

For a couple of weeks now my backspace key has only been working sporadicly, being frightened that I might hammer they key to atoms, I decided to try and clean it. First I found the service manual of my Dell Inspiron 1300, and pulled out the whole keyboard, only to realize, that I was unable to tear it apart like a normal keyboard. The plastic parts had some pins going through the metal baseplate, these had then been melted flat to keep the thing together. If I pulled these "weldings" apart, I would never be able to assemble the thing again.

In this case google wasn't a friend, since it was only concerned with "sticky" keys, and I do not use sugar in my coffee.

In the end I took the button off, like I had done once before to make sure I hadn't missed anything.
 

I proceeded to take of the plastic piece over the rubber that contains the conducting "drop" in the middle.
 

I thought it seemed like there were two holes on the rubber, and began thinking of using what I call "contact clean". I tried spraying a little onto the rubber, and I could see it underneath. I then massaged it gently with a finger, through the rubber (still talking about my keyboard), for a while.
 

I had an editor running, so that I could see the key, slowly began working. I then replaced the plastic part, and the button, and it is working again!

Generated on 2018-05-03 01:14:21.839924