Thanks for the info. I actually already placed an order today for the active parts kit. I'll probably use the onsemi devices and see how that sounds.
Randy
What capacitors are you using across the mean well ska 30A-15?
What the problem appears to be is that without the caps, the dc-dc converter puts out a lot of ripple, per Jameco. They do not recommend the converter for audio for this reason. When I stated that the ripple should be able to be dealt with, they stated, yes possible with a cap. Since the ripple is 100khz, I need to figure out the best cap to bridge. I would suppose this would be across the pos and neg output.
What the problem appears to be is that without the caps, the dc-dc converter puts out a lot of ripple, per Jameco. They do not recommend the converter for audio for this reason. When I stated that the ripple should be able to be dealt with, they stated, yes possible with a cap. Since the ripple is 100khz, I need to figure out the best cap to bridge. I would suppose this would be across the pos and neg output.
I get 18.2 volts across pos and neg of the output of the dc-dc converter.
My modified Koss PortaPros sound very good with this. I haven't tried any of my "high end" phones yet but I have always like the PP's as they are great at what they do and a standard of low priced phones, outshine many costing much more.
After running for 20 minutes or so, the output devices are just warm. I haven't installed the heat sinks yet. I guess it depends upon the load but will install them for the draw of the bigger phones that require more juice.
My modified Koss PortaPros sound very good with this. I haven't tried any of my "high end" phones yet but I have always like the PP's as they are great at what they do and a standard of low priced phones, outshine many costing much more.
After running for 20 minutes or so, the output devices are just warm. I haven't installed the heat sinks yet. I guess it depends upon the load but will install them for the draw of the bigger phones that require more juice.
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I wish you could edit posts after 30 minutes.
Anyway, I am using the HE-560's right now. Sound pretty good. A little bright, which they aren't on other amps, including the Lyr 2 with Telefunken E88C's. But burn in is needed, I would think. Still need to resolve the hum but almost inaudible on the 560's with the output of the converter bypassed with 4300uF's of Black Gate.
Anyway, I am using the HE-560's right now. Sound pretty good. A little bright, which they aren't on other amps, including the Lyr 2 with Telefunken E88C's. But burn in is needed, I would think. Still need to resolve the hum but almost inaudible on the 560's with the output of the converter bypassed with 4300uF's of Black Gate.
Ok, but the ripple from the wall wart is negligible. I am not sure what you mean by eliminate the volume control pot on the input. So take it out of the circuit?
Right. Yes they are long right now, as I get it together, to be shortened when finished. And I agree with stripping it down and then building up again, to try and get at the root of the problem. The hum is equal on both right an left. I have had hum in system, that was eliminated by work but if in both channels, it was often more of a PS issue. the hum is substantially reduced with the 4200uF but seems very little should be there to begin with. I don't have much test equipment, cap checker, ohm meter, ESR test equipment, but if I eliminate the pot, to audibly hear if there is still hum . . .
Got the feed coming in from the WW totally away from the board, but no change. Moved the wires around for the pot but no change.
Do the jumpers change anything and which ones should and shouldn't be in place and where do you like to run all your grounds to? I like going back to the main PS cap as in star grounding but not sure about this board.
Also the sound is a little metallic, not sure if this changes with burn-in or this is an issue with the current hum problem and what is going on with the PS.
Do the jumpers change anything and which ones should and shouldn't be in place and where do you like to run all your grounds to? I like going back to the main PS cap as in star grounding but not sure about this board.
Also the sound is a little metallic, not sure if this changes with burn-in or this is an issue with the current hum problem and what is going on with the PS.
Ok, it was the wall wart. Go figure. I plugged in a battery supply I have that can run this fine to the converter and zero hum, even on my very sensitive phones. When I called Jameco the tech said that anything on the input side of the converter would not cross to the other side but somehow the WW, even though there is little ripple is doing something to the whole system. So there you go. I can get it together, button it up and enjoy the music.
The sound is also getting a little sweeter now, with the upper frequency tinniness going away and the overall presentation is smoother, very good dynamic contrasts, with a deep full bass.
Interestingly, the output devices are running hotter now, odd. I will put on the heat sinks but interesting that there must be a change in the current flow.
The sound is also getting a little sweeter now, with the upper frequency tinniness going away and the overall presentation is smoother, very good dynamic contrasts, with a deep full bass.
Interestingly, the output devices are running hotter now, odd. I will put on the heat sinks but interesting that there must be a change in the current flow.
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Everything working well on a battery. One thing, I have read that some report the output devices getting pretty warm, mine are running what I would call hot, much like most tube to touch. So how hot do these normally run? They are heat sinked now. I would be concerned closing them up in the Hammond case I bought.
You have to let the heat escape, elsewise you'll have charred bits everywhere.
Dick isn't particularly fond of using the chassis as a heat sink as it can couple noise into the amplifier, but in the first version I built I did exactly this.
With a 30 ohm load and +/-15V supplies, the output stages should dissipate ~0.5W
Dick isn't particularly fond of using the chassis as a heat sink as it can couple noise into the amplifier, but in the first version I built I did exactly this.
With a 30 ohm load and +/-15V supplies, the output stages should dissipate ~0.5W
Yes I realize that heat has to escape. I got the recommended Hammond case and that is an enclosure I am using, per the previous image. I use heat sinks on the devices not the chassis as a heat sink. So have you drilled holes in the case to allow heat to escape?