kevin gilmore Posted July 9, 2013 Author Report Posted July 9, 2013 (edited) ebay is your friend for stuff like this. get a 100mhz scope to go with it. if you have a Tektronix power supply frame already, these are great http://www.ebay.com/itm/Tektronix-FG-502-Plug-In-Function-Generator-Rack-/111110966177?pt=LH_DefaultDomain_0&hash=item19debacba1 if you don't have the bias set right, its probably not going to sound right. Edited July 9, 2013 by kevin gilmore
trident900fi Posted July 9, 2013 Report Posted July 9, 2013 ebay is your friend for stuff like this. get a 100mhz scope to go with it. if you have a Tektronix power supply frame already, these are great http://www.ebay.com/itm/Tektronix-FG-502-Plug-In-Function-Generator-Rack-/111110966177?pt=LH_DefaultDomain_0&hash=item19debacba1 if you don't have the bias set right, its probably not going to sound right. I have a old generator that I've built when I was young ! I have a good scope too... A better generator can't be bad ! When I plug the generator to the amp, the input signal is getting bad I raise the supply voltage to 29V, and he always clip to earlier... Bias is set to 80mV over the 2R resistor.
kevin gilmore Posted July 9, 2013 Author Report Posted July 9, 2013 This is going to end poorly. most likely!
Emooze Posted July 10, 2013 Report Posted July 10, 2013 I want to know what kind of CD player you have.
holland Posted July 10, 2013 Report Posted July 10, 2013 In the absence of a function generator, you can use your computer's sound card and download some test tones. You can also double check each resistor is actually the correct value, and diode test all transistors. Brute force works. If it sounds bad, why are you running it for 5 hours? Something's broken.
RudeWolf Posted July 10, 2013 Report Posted July 10, 2013 If there's something broken a simple EMU-0404 ADC/DAC card will do nicely. You just have to whip up test loads and most importantly- know what to look for. Software wise there is more than plenty to use. Just be sure to calibrate everything properly.
trident900fi Posted July 10, 2013 Report Posted July 10, 2013 I want to know what kind of CD player you have. I was using a old completely tweak Marantz CD-67 SE-MKII... He actually sound better than the Krell...
trident900fi Posted July 10, 2013 Report Posted July 10, 2013 In the absence of a function generator, you can use your computer's sound card and download some test tones. You can also double check each resistor is actually the correct value, and diode test all transistors. Brute force works. If it sounds bad, why are you running it for 5 hours? Something's broken. Thank for the tip with the sound card, I didn't think about it ! I check many time and everything is right... The amp work at low level without problem. It's only when you like to raise the volume, that it doesn't run correctly and rapidly distor ! At the beginning, the sound was awful ! But with time, he is getting far better. Just found someting strange. When I put 0.51V in the input, I have 0.56V at the output, and when I put 0.92V in the input, I have 1.00V at the output !
spritzer Posted July 10, 2013 Report Posted July 10, 2013 There is nothing that would make the amp sound better over time. Broken is broken so just do a simple loop through test on the computer and see what is going on. I also don't see the benefits of running higher rail voltages like that. The amp was designed for a fixed point so I'd stick to it.
trident900fi Posted July 10, 2013 Report Posted July 10, 2013 I found the mistake ! He is not broken ! I have two headphones plug, one standard and one for symetric headphone. There was a mix in the output !!! That why it sound so bad and quickly go into cliping... It's much better now and he sound a lot better than my old CD player Thanks to Kevin for for his beautiful cloning !
kevin gilmore Posted July 10, 2013 Author Report Posted July 10, 2013 those are 150 watt switchers?? 24 volts at 6.5 amps ?? they are certainly running under their minimum power specs and are going to be too noisy at such low power... amp only pulls about 400 ma
trident900fi Posted July 10, 2013 Report Posted July 10, 2013 (edited) Yes it's 150W, 24V and 6.5A ! And there is no noise at all. I measure less than 1 mV RMS AC residue per rail... The amp is dead quiet I have this power supply from a previous project, I try it and there were just fine ... Edited July 10, 2013 by trident900fi
jwzhan Posted July 10, 2013 Report Posted July 10, 2013 Those are very large switchers.... why not just go linear like sigma 22... or the original PSU. You certainly have the room for that...
kevin gilmore Posted July 10, 2013 Author Report Posted July 10, 2013 I would eventually get the Krell Klone power supply and build an Off board balanced dynahi and crank the bias to 1.2 amps per Chanel And use those supplies for that.
trident900fi Posted July 10, 2013 Report Posted July 10, 2013 Those are very large switchers.... why not just go linear like sigma 22... or the original PSU. You certainly have the room for that... Like said before, I have this supply at home from a previous project. I give her a try and they make the job in the right way ! I listening to the amp since 3 hours, and he is really damn good !! Absolutely no background noise, as might suggest the power supply I used... This is clearly oversized, but he accommodates well
kevin gilmore Posted July 11, 2013 Author Report Posted July 11, 2013 (edited) its not that those switchers are necessarily the wrong thing, i'll be that there is ultrasonic noise coming out of them that takes special equipment to see, its that the thing is enormously big for no reason. The original 2 box solution seems more rational. All the electrolytics likely get rid of any of the ultra high frequency noise. Now i'm certainly not one to pick on someone for excessive overkill but mine is going to look as close to the original just because I can. Complete with the rounded corners and the massively thick and machined front plate. Anodized two tone. The build job is still very nice, and the 4 pin headphone jack is what I intended. Edited July 11, 2013 by kevin gilmore 1
RudeWolf Posted July 11, 2013 Report Posted July 11, 2013 (edited) Don't listen to them Trident, they're just jealous! 1. Pad the walls of the enclosure with large resistors. 2. Hook them up to the PSU's to get rated power consumption. 3. ? ? ? 4. Profit! Edited July 11, 2013 by RudeWolf
trident900fi Posted July 11, 2013 Report Posted July 11, 2013 To avoid the high frequency, I can add an inductor in every rail, to make a low pass filter ! The power supply doens't cost me anything, that why I use it ) If I don't have this at house, I already built the Krell one ! Build job was done by hand, I do not have specialized tools for this kind of work...
fordgtlover Posted July 12, 2013 Report Posted July 12, 2013 Now i'm certainly not one to pick on someone for excessive overkill but mine is going to look as close to the original just because I can. Complete with the rounded corners and the massively thick and machined front plate. Anodized two tone. The build job is still very nice, and the 4 pin headphone jack is what I intended. I plan to build mine in the same vein out of respect for the amazing original. I can't wait to see your build.
fordgtlover Posted July 28, 2013 Report Posted July 28, 2013 With this amp only drawing ~400mA, is there any need for a transformer bigger than 50VA?
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