cviller said:
Capacitance is great!
The third thermistor is for triggering the fail over protection (chassis -> thermistor -> earth).
Oh ok, I just saw TH1 in the corner. I didn't notice it before.
Well, I guess for a few bucks more it wouldn't hurt.
My power supply build without the transformers is ~ $113.32.
Re: R12 value - what is best?
brought up several times in this thread ;
Papa have gadget on his bench called "SuperGizmoMegaTronicInducingFunnyWaveFormsAndMeasuringPupuResidualsOnOutputOfNewestMegaGizmoMadeForDoingSomethingWithTheseFunnyWaveForms"
then he just connect gadget to F5 (both in and out) and looks on screen , tweedle with one's source resistor value , 'till FunnyWaveForms just looks funniest .
every amp is happy camper when upper and lower part of WF are the same .............
edit:
Papa - you were faster ........ just killed all Romance
rickmcinnis said:
brought up several times in this thread ;
Papa have gadget on his bench called "SuperGizmoMegaTronicInducingFunnyWaveFormsAndMeasuringPupuResidualsOnOutputOfNewestMegaGizmoMadeForDoingSomethingWithTheseFunnyWaveForms"
then he just connect gadget to F5 (both in and out) and looks on screen , tweedle with one's source resistor value , 'till FunnyWaveForms just looks funniest .
every amp is happy camper when upper and lower part of WF are the same .............
edit:
Papa - you were faster ........ just killed all Romance
labjr said:
You should be able to do it with a decent sound card and an FFT program -- by observing the 2nd harmonic -- I would suggest that you build a notch filter ahead of the sound card so that you don't over-load it. The notch doesn't have to be that deep, only some tens of a dB -- It is only necessary to know the level of the fundamental, not to look at it! Make sure to use a low noise opamp like the AD797 or LT1028.
Wobbly DC
Tuning up my second channel of F5 today. the last one I did is solid on 0v dc on the output ( well as good as my multimeter is ) however the seconds channel wobbles around from 0.00 to 0.12 . What would cause this and will it be a problem ? I havent listened to either channel yet.... Any advice appreciated.
dave
Tuning up my second channel of F5 today. the last one I did is solid on 0v dc on the output ( well as good as my multimeter is ) however the seconds channel wobbles around from 0.00 to 0.12 . What would cause this and will it be a problem ? I havent listened to either channel yet.... Any advice appreciated.
dave
Thanks, and another question(s)
Having never done this before ...
Would you recommend an FFT program?
I am assuming the low noise op-amp to be used within the recommended notch filter.?
Any particular frequency for this filter?
The filter is to be placed at the amp's input? (I am sure that sounds close to infantile but I want to be sure)
I am sorry if all of this has been answered before. I did look but the search function is not very specific. Thanks for the help which I suspect will be useful to many of us building amps with the new group buy boards.
Thanks, yet, again,
jackinnj said:
Having never done this before ...
Would you recommend an FFT program?
I am assuming the low noise op-amp to be used within the recommended notch filter.?
Any particular frequency for this filter?
The filter is to be placed at the amp's input? (I am sure that sounds close to infantile but I want to be sure)
I am sorry if all of this has been answered before. I did look but the search function is not very specific. Thanks for the help which I suspect will be useful to many of us building amps with the new group buy boards.
Thanks, yet, again,
Thermistors
For those who are interested -- I just examined 3 varieties of 4k7 thermistors from Digikey -- in comparison with a 4k7 metal film -- note that the cold resistance of the thermistor must be measured prior to testing -- in run set I used my AP Analyzer with an A-weighted filter in, in the second I used my HP 3581 Wave Analyzer at 1kHz with the 30Hz BW filter set in.
The thermal noise of the thermistors is no different from that which would be predicted from a resistor of similar value, at similar bandwidth.
I am using Denis Colin's noise amp which has a noise floor of 2nV -- slightly worse than than the noise floor he obtained using the AD797 (I use an LT1028).
For those who are interested -- I just examined 3 varieties of 4k7 thermistors from Digikey -- in comparison with a 4k7 metal film -- note that the cold resistance of the thermistor must be measured prior to testing -- in run set I used my AP Analyzer with an A-weighted filter in, in the second I used my HP 3581 Wave Analyzer at 1kHz with the 30Hz BW filter set in.
The thermal noise of the thermistors is no different from that which would be predicted from a resistor of similar value, at similar bandwidth.
I am using Denis Colin's noise amp which has a noise floor of 2nV -- slightly worse than than the noise floor he obtained using the AD797 (I use an LT1028).
Hi,
make up a couple of pairs of RCA plugs.
One pair with a wire link direct across the pole and barrel.
One pair with a resistor between pole and barrel. These resistore can mimic the source resistance of partner equipment or be 1k0 or even 10k if one wants to check noise sensitivity of the power amp. Or make up a variety of pairs for test purposes.
make up a couple of pairs of RCA plugs.
One pair with a wire link direct across the pole and barrel.
One pair with a resistor between pole and barrel. These resistore can mimic the source resistance of partner equipment or be 1k0 or even 10k if one wants to check noise sensitivity of the power amp. Or make up a variety of pairs for test purposes.