Only with the DAC output no white noise and no distortion.
With the preamp I have a lot white noise and also no distortion with preamp.
The right channel of my preamp is broken.
I connect the left preamp output with the Dx Blame MHIII Hx, de amplifier is playing now music (with the 8K2 resistor) and no hissssss.
There is quite what went wrong last week and that will definitely cause this problem.
The only thing I wanted to know now is what a good replacement 390R resistance for the Dx Blame MHIII Hx, then I can order this resistor.
Regards,
Rudy
I connect the left preamp output with the Dx Blame MHIII Hx, de amplifier is playing now music (with the 8K2 resistor) and no hissssss.
There is quite what went wrong last week and that will definitely cause this problem.
The only thing I wanted to know now is what a good replacement 390R resistance for the Dx Blame MHIII Hx, then I can order this resistor.
Regards,
Rudy
I have no idea, the only thing I mean the volume went up, and the emitter voltage also up to 200mv, the music went very loud.
I was also curious how hot the heat sinks are went, but they were lukewarm.
Here's an example, video now uploading:http://www.youtube.com/watch?v=s2g8mwdmJQ4
I have ordered also resistors for replacement of the 390R:
2x (REY25-340) - 1K2 0.25W TAKMAN Metal Film Resistors
2x (REY25-370) - 2K2 0.25W TAKMAN Metal Film Resistors
2x (REY25-390) - 3K3 0.25W TAKMAN Metal Film Resistors
2x (REY25-405) - 4K3 0.25W TAKMAN Metal Film Resistors
2x (REY25-420) - 5K6 0.25W TAKMAN Metal Film Resistors
Regards,
Rudy
I was also curious how hot the heat sinks are went, but they were lukewarm.
Here's an example, video now uploading:http://www.youtube.com/watch?v=s2g8mwdmJQ4
I have ordered also resistors for replacement of the 390R:
2x (REY25-340) - 1K2 0.25W TAKMAN Metal Film Resistors
2x (REY25-370) - 2K2 0.25W TAKMAN Metal Film Resistors
2x (REY25-390) - 3K3 0.25W TAKMAN Metal Film Resistors
2x (REY25-405) - 4K3 0.25W TAKMAN Metal Film Resistors
2x (REY25-420) - 5K6 0.25W TAKMAN Metal Film Resistors
Regards,
Rudy
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Bimmer, I'm not sure that you want to put resistors to drain the caps... It will not prevent the amp from making strange noises, it will only make the noises sooner/faster. It will also produce voltage ripple in your power source. I suggest you put a speaker protection circuit that disconnects the speakers when you shut off the switch, and let the caps drain at the actual rate, which is only dependant from the internal electrical consumption. That's what I did and I'm happy with the result.
DX provides a proctection circuit here:
http: // www nabucoeletronica com br/dx/files/spkprot-schematic.pdf
(please insert appropriate dots)
More information here:
http: // www dx kinghost net/ (same advice)
It lacks only a protection for short circuit in the output, which may damage your speakers.
The circuit will switch off speakers as soon as power is turned off; and inserts a delay during power-on.
Regards,
Max.
http: // www nabucoeletronica com br/dx/files/spkprot-schematic.pdf
(please insert appropriate dots)
More information here:
http: // www dx kinghost net/ (same advice)
It lacks only a protection for short circuit in the output, which may damage your speakers.
The circuit will switch off speakers as soon as power is turned off; and inserts a delay during power-on.
Regards,
Max.
I'm finished
Greetings all,
I just finished my DX Blame MKIII at 2:00 this morning. I know it sounds incredible that I just now finished, yet I’m the first person to get boards from my own North American group buy. I made a lot of mistakes. I mean a lot of mistakes. I got in a bit over my head with this one. This is the second piece of electronics I’ve built, the first being the LM3886 kit from ChipAmp.com. I also took a long break around Christmas & New Years.
Here is a list of things I did/learned which I think may be helpful to other builders – in case there are any builders who have not finished.
I got a lot of help from people on this forum, and certainly wouldn't have made it without you guys.
So thanks goes out to everyone who posted. I always keep meticulous records of items bought and money spent on projects, so in a few days I’ll put together a final list of parts and post it. I hope this does some other people some good.
-Byron
Also: I would love to post lost of photos, but I can't right now. I'll explain that in another post.
Greetings all,
I just finished my DX Blame MKIII at 2:00 this morning. I know it sounds incredible that I just now finished, yet I’m the first person to get boards from my own North American group buy. I made a lot of mistakes. I mean a lot of mistakes. I got in a bit over my head with this one. This is the second piece of electronics I’ve built, the first being the LM3886 kit from ChipAmp.com. I also took a long break around Christmas & New Years.
Here is a list of things I did/learned which I think may be helpful to other builders – in case there are any builders who have not finished.
- I was not able to adjust the offset voltage using the 1K trimmer. When I turned the little knob, the offset voltage would change briefly, then move back to about 0.4r to 0.5R. Because I had no way of knowing what the trimmer was set at, I replaced each one with a 550R ¼ W resistor. I found the temperature of the transistors in the middle of the board did have an effect on offset voltage. They would get warm, and if I blew cool air across them, the offset voltage would change. My solution was to put large heatsinks on them, then put a fan in the bottom of the chassis blowing directly on the heatsinks. In the case with fans on, offset is ~300mV.
- Mounting the TO-220 case resistors (the 3 in the middle-top of the board) to the big heatsinks was tricky. I drilled and tapped holes in the heatsink for them, but even using nylon screws, I would get intermittent contact between the back of the transistors and the heatsink (which is grounded, as they’re part of the chassis). I ended up covering the holes with my insulating material and using a bar to clamp down the transistors.
- I did not use the lifted ground, but installed a jumper in place of the optional 10W resistor. It works just fine.
- I’m using the SoftStart from Elliott Sound Products (ESP). It’s simple to build, small, and I can recommend it to anyone.
- The board Alex mm designed seems to be designed for a 3 rack unit chassis. When the transistors on top are bent parallel to the board, and the board is parallel to the heatsink, it fits just perfectly in a 3-rack unit case.
- Alex included exposed tracks on the bottom of the board to builders to tin. I went one step further and soldered 18AWG wire to the high current-carrying tracks. This caused the board to bend upward in the middle, putting a stress on the leads to the transistors mounted to the heatsink. They were already mounted to the bottom of the board, and now the board was pulling away from them, ripping the tracks off of the board. If I were to build this again, I don’t think I would do this.
- Lastly, when I first had problems with my board, Carlos sent me a link to a U-tube video in which he explained how to troubleshhoot a board. The gist of it was not to try to diagnose your problem with measurements and thinking. The circuits are far too complicated. Just check and check again. If necessary, remove any component which might me bad, and test it outside the board if you can. After having spent a lot of time troubleshooting mistakes, I’m in absolute agreement. When measuring voltages or resistances, I would get one value the first time, then check again and get a different value, then a third time and get different values. I was unable to figure out anything. Every time, the way fixed a problem was to re-solder any joints which didn’t look perfect, or replace every component which I guessed might be bad.
I got a lot of help from people on this forum, and certainly wouldn't have made it without you guys.
So thanks goes out to everyone who posted. I always keep meticulous records of items bought and money spent on projects, so in a few days I’ll put together a final list of parts and post it. I hope this does some other people some good.-Byron
Also: I would love to post lost of photos, but I can't right now. I'll explain that in another post.
Rudy ,
Thanks for the info, may i suggest clamping the board to a flat surface before soldering the traces i would also suggest 24g wire ....
Why would you need one, many amplifiers don't make noise on startup or shutdown, why would his or your DX amp be doing this....?
If not faulty caps, must be a lot of DC drift on shut down ....
Thanks for the info, may i suggest clamping the board to a flat surface before soldering the traces i would also suggest 24g wire ....
Why would you need one, many amplifiers don't make noise on startup or shutdown, why would his or your DX amp be doing this....?
If not faulty caps, must be a lot of DC drift on shut down ....
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