Jack, so I am at a loss to get this to run cooler. The board was sent tested. I have checked all the wiring and gone ahead and used the jumpers for the grounding. The voltages are correct, it is very simple and straightforward to hook up and I have music with no hiss and now no hum at all but the output devices are running hot. I would really like to button this up, use it and move on. Oh the hum was because my supply did not put out enough current so the converter was being starved. Steve helped on that.
Any ideas?
Any ideas?
Ah, yes. I had to do the same thing with a dac that I built. On it, running one more diode did sound better but also shortened the life of the dac chip quite a bit so I went back down in current.
Thanks! will try this right now. I really want to get this done and move one. Loving the sound!
Ok, bypassed. The sound was hollow then I looked down and the input was partially out. lol Plugged in and the hollow sound, which I am familiar with, having worked on amps a lot and had this happen in the past, only to realize I had not inserted the plug all the way.
Will get back to impression as to sound. My amp can not be burned in yet/caps formed etc, so now I can run it and keep it on and see where the sound goes but in comparing it to other amps I have, it is doing very well. Very dynamic, good contrast to types of sound and great detail retrieval without being etched or sterile. Bass response goes deep with a quality of being tuneful rather than one noted. I am using the Fostex TH900 right now. Earlier the HE-560's. Will have to try out the LCD's. All phones relabels with gold/silver cable by Whiplash Audio.
The output devices are now running just warm and most likely don't need heat sinks.
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Worked great.
I have a 20Ah battery that is flat (about 12mm), about 80% the size of the top of the case I am use and would provide around 20 hours of music. So the amp is also a nice transportable unit. Cool. Letting the Black Gates burn in.
. Enjoy 
Well, as you might guess, the noise of power transistors (low Rbb) is pretty good and the more current thru these, the lower the noise --->
The noise analyzer isnt made for power devices. It only goes to 30 milliAmps and 30 volts dc. But at 24v and 30mA, the noise of the pnp is <3nV/srtHz from 10 to 100KHz. 2nV at 1Khz and 0.5nv at 10KHz. Didnt check the other transistor yet but it will typically be a little bit higher for npn's. These op transistors dont contribute any audible noise to the over-all amp.
THx-RNMarsh
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Well that was short lived. My right channel burned out. Turned on the amp, and in a few minutes the acrid smell of electronics. I opened it up and R27 and 31 are charred and the other resistors on the output of the L channel, the 4 others look like they got hot. Strange as the headphones work fine and nothing was out of place. I get normal sound from the L channel and sound from the R but heavy static and some sound, which is understandable as the resistors are shot.
Not sure what caused this heavy current draw. this was a tested stuffed board. The power supply tests out fine as well.
Not sure what caused this heavy current draw. this was a tested stuffed board. The power supply tests out fine as well.
Would you say that if you got a flat and someone told you to stop driving?
Really? Well I have done this since I was 8 and now I am 65. I served 4 years in the military as a radioman and worked on equipment and had 2 tours of duty in a war and was able to make it so using a pre stuffed amp board to listen to music shouldn't be a real stretch.
A solution to the matter would be a better solution.
Nothing had changed on the pre stuffed board. the voltage was correct, grounding was as it should be, the headphones work fine and everything was secure. The output devices on the board were different from the ones on the left channel nomenclature. I have been busy and haven't taken the time to look them up but they are also hard to read.
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I don't believe so. The board came tested. I bought one board for me and one for a friend. I enjoy doing the work but was offered the pretested board so went ahead with that. The resistors are too badly burnt to tell what they were. The other side is correct.
I am pretty sure they are all 4.7ohm as the one I can read are 4r7 1 watt. A DKA30A 15 supplies the board and all in all, everything is pretty simple to do. The main thing at first was to realize I was using too low a ampere supply for the dc-dc converter, which can happen and that the transistors were running too hot, which eliminating one diode fixed by bringing down the bias.
I was kidding -- this was what my Mom told me the third time I failed the CW (code portion) of the ham radio test.
The 4.7R resistors dissipate less than 0.02W, and they are cousins of the ones that Nelson uses in his amplifiers.
There must be a short to ground -- when I ran this amp out it was only taking 110mA on each side.
What is odd is, with nothing changed, why would it physically get a ground? I checked the grounding and for shorts but will check again. I agree, that there would be very little heat dissipation from the resistors. I would agree, the first thing that came to mind was a short to ground, that is the only thing to me, that can explain this type of draw.
I was a code specialist in the military. Often in Vietnam we couldn't get out and so everything would be encrypted and I would do a skip to Guam and even hit Long Beach, Calif. sometimes. Loved using the bug.
I was a code specialist in the military. Often in Vietnam we couldn't get out and so everything would be encrypted and I would do a skip to Guam and even hit Long Beach, Calif. sometimes. Loved using the bug.