Direct Digital Power DAC (DDPD)

Thanks! Seems it started to work after switching to wasapi exclusive and asio for amanero, without osciloscope I wouldn't setup it up, this is osciloscope window at 5V volume on ddpd using 8ohm dummy load, measured on dummy load. I will show you soon results from Multitone after I figure out some things in relation to my aux filter which is probably not a very good, I must measure without and with using aux filter with attenuator, 23,25x attenuation is not a very good while measuring small signal, right now I have moved switches of the Cosmos to 1.7V, does it have any sense? Which setup you reccomend for measuring signal from attachment trought aux filter which attenuate it 23.25 times? Which setup to use in Multitone? Maybe better to switch Cosmos to 4.5Vrms or continue with 1.7Vrms? Maybe better to use without attenuator?


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Ok, here is some mesurements but I am unsure if everything is right setup, expecialy levels! I must consult somebody on my forum about it, probably I will try without attenuator and aux filter because Cosmos adc minimum Vrms can be set by switches to 1.7Vrms, if you take a look into osciloscope window I posted Vrms value from DDPD mini at 5V volume is 1.49Vrms which might be put directly to Cosmos adc using 1.7Vrms switch, than it will be close to full resolution. Right now ddpd signal of 1.49Vrms is attenuated by 23.25 times, thats what Multitone/Cosmos see right now, might be wrong setup? Right now I'm afraid this measurements is right! Even I am unsure about setup.


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I'm unsure! DDPD output measured at dummy load is 1.49Vrms, attenuator is the same as like on this simulated circuit picture


50V sine IN is 23.25 times attenuated so OUT sine is 2.15, if divide 50 with 2.15 result is 23.25, so attenuation is 23.25 , what mean -40dbFS inside Multitone, does that mean measured Multitone input signal? -40db doesn't looks like 1.49Vrms / 23.25 times atenuation or it does? 64mVrms need to be 23.88dbFS ! All that is an indication that something is not right here. I am using multitone for the first time : )
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Yes definitelly something is wrong here. This is measured between COLD and GND, its very close to simulation result 64mVrms, so atenuator is right here but something other is wrong definitely. Cosmos is set to 1.7Vrms and I don't think Cosmos is bad here, I'm afraid about Multitone setup! My attenuation is known right now, it is 22.71 times. : )


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Yes! Also I have disabled "set system volume level" in Multitone. Nevermind, I will wait my frontend, trought ct7302 I will be able to fine tune levels on ddpd and use Rew instead. CT7302 have very good noise level, I'm using it with success in another projects, sound very good.
  • SRC / ASRC THD+N better than 24 bits. (-174dB)
To be honest I no need to measure ddpd, I hear how it sound in comparation to other things I have, I'm ok with -90db if it sound right! : )
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You could use REW for just recording. So select some other input device at Multitone and use Cosmos ADC at REW.

Keep recording on REW running and start recording at Multitone. Increase FFT size and averages at Multitone so that Multitone recording lasts long enough.
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I will try tommorow! Multitone confuse me, for example whatever I set it displays as db which is confusing. dbc, dbv, dbFS can't be the same, but multiyotne show it laways as db, I want to see dbc levels. Rew also had bug in thd calculation in someearlier versions, hope it is fixed in newer one.
This time I have used Rew and generator was HQ Player, even I am unable to figure out why levels is wrong, everything checked and tried. Even without attenuator levels is wrong. So I got back to Multitone and back to aux with attenuator. I found out that 1.25V on DDPD gives the best thd result? Also I have found the most clean sine wave was while using dsd128. The rest of things, what is your opinion? What is an optimum for our DDPD?? Here is four pictures using diferent DDPD voume voltage and also dsd64 and dsd128. My opinion is dsd128 is an optimum for our power dac while volume level is 1.25V and dsd64 while volume level is 5V, what is your opinion? My osciloscope is an pocket version so it might be also not an optimal measurement system. What I can see is DC db value in Multitone seems not indicate an input value db because measurements show -22.3db while volume level is 1.25V but -40db while volume level is 5V which is strange, if it shows db level of the input db values must be vicewersa. What mean DC value in Multitone? Anybody have idea where I can see real db level from input?


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Attenuator was made for higher power class D measurement, I no want to modify it, insead I will need to make another one, need only aux filter which is by default with atenuation around 2x if attenuator is removed. I have tried without attenuator and aux, directly soldered 8ohm resistor to ddpd out, first step was osciloscope measurement so for example I have measured 1.49Vrms, those 1.49Vrms is sent to Cosmos adc, on Cosmos adc I have moved switch to 1.7Vrms position so now 1.7Vrms is full range scale. Booth multitone and Rew shows wrong db value, almost half the value I measured. Checked everything in relation to sound setting on my Win10. Tried booth Asio and FlexAsio, nothing helped. I realy have no idea if this is an Cosmos adc isue. It would be very helpfull having measurement system for fine tuning dead time on ddpd, but sadly I right now do not have working equipment for measurement. Checked XLr cable too, pinout is ok. Also checked Cosmos gnd pin if it is on the right position, yes, booth Cosmos input and xlr cable have ok pinout. So something is wrong in relation to my pc, or Cosmos, or something else, I have no idea. How can I check if Cosmos is working correctly?
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Joined 2003
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Most probable it is the DUT (device undre test)... no?

You ask "What is an optimum for our DDPD??" - should the amp not work for all levels... not just one?

Start with a basic 1kHz sinus -20dBfs and an 8 ohm resistive load. What is the anticipated RMS voltage out for this input?

Be aware of that connecting a scope probe might be a problem with earth if the output is not floating...