OK. What's that attenuator? Potentiometer? TVC?
Also, the PDF link does not work. Can you upload the file?
The attenuator is this one: intact audio
and the amp's schematic here: http://www.kisfamily.net/HP/Hifi/Schema.PNG
With a sinus signal, I measure 200mV after the coupling cap and 20mV after the attenuator (I don't use the last connection).
and the amp's schematic here: http://www.kisfamily.net/HP/Hifi/Schema.PNG
With a sinus signal, I measure 200mV after the coupling cap and 20mV after the attenuator (I don't use the last connection).
I did it, with a 10K, it is the same. I have checked the manual, it seems that I should have 1.25V after the cap, instead of 200mV measured, maybe the problemcomes from here 😕
Also, I note there is no gridstopper on the input tube, the RC circuit is a bass cut/high pass at around 20Hz, be interested to see what comes of this.
The common is connected to ground on the das pcb
So effectively you connect th NEG to GND by doing this which is not a good idea regardless of any other problems
Hi All,
Absolutely loving the DDDAC 1794, Im addicted to just sitting and listening to music again 🙂
Just some questions if anyone has any knowledge / experience:
1) I am using Cinemags for my output. I am feeding a Hypex NC400 amp with an input impedance of 104k. I am there using load resistors of 15k on the Cinemag outputs (giving me a total of 13k load). At the moment I am just using very cheap ebay resistors for this task. Does the quality of the resistor affect the output at all? I mean from an electronic perspective, does that load resistor affect the quality of the analog signal?
2) I have 4 decks with an output impedance of 34ohm, which is great as the amp's input is 104k. However, I saw some nice looking Diamond Buffer boards (Sjöström Audio - SSB01 Sjöström Super Buffer - Diamond buffer)
Would I benefit (sound-wise) from building these buffers between the DDDAC and the Cinemags? When is the best situation to use diamond buffers?
Thanks all!
Absolutely loving the DDDAC 1794, Im addicted to just sitting and listening to music again 🙂
Just some questions if anyone has any knowledge / experience:
1) I am using Cinemags for my output. I am feeding a Hypex NC400 amp with an input impedance of 104k. I am there using load resistors of 15k on the Cinemag outputs (giving me a total of 13k load). At the moment I am just using very cheap ebay resistors for this task. Does the quality of the resistor affect the output at all? I mean from an electronic perspective, does that load resistor affect the quality of the analog signal?
2) I have 4 decks with an output impedance of 34ohm, which is great as the amp's input is 104k. However, I saw some nice looking Diamond Buffer boards (Sjöström Audio - SSB01 Sjöström Super Buffer - Diamond buffer)
Would I benefit (sound-wise) from building these buffers between the DDDAC and the Cinemags? When is the best situation to use diamond buffers?
Thanks all!
Yes, I made a mistake on my drawing, in reality, I connected it between POS and COMMON, sorry !
I have try to remove the Slagle autoformer and measure the voltage on the resistor of 100K between ground and output cap, I still have 200mV RMS instead of 1.2V indicated in the DDDAC's manual.
I have try to connect the dac to an HEGEL H80, it work also but I notive that I can increase the volume almost to the max despite the 75W of the amplifier and the 97dB/m of my speaker, something is strange.
Can you measure the voltage after your output cap please ? 🙂
What voltage are you referring to? DC should be zero (due to the cap), so I guess you're looking at some AC voltag. But what kind of signal are you looking at (wave shape, frequency, etc.)? Do you have a scope? If you measure the AC voltage with a DVM (common garden type), this might give wrong readings if you're using something else than a sine signal at around 50-60 Hz.
Start testing with the amp disconnected from the DDDAC. Measure the signal at the POS output of the DDDAC board (relative to COMMON). Then measure the signal after the capacitor (again, relative to COMMON).
Then repeat the measurements with the amplifier connected to the DDDAC.
I tired with 315Hz sine wave. I use a Fluke 123 Industrial ScopeMeter, it is not perfect but it is better than a common garden type... I hope 😛 I will take a real scope tomorrow.
Anyway, I try to measure with a 1 kHz sine wave, it is better, around 3V RMS between POS and COMMON and 0.9V after the cap and COMMON.
I don't know where the difference between frequencies comes from, I'll make others tests tomorrow with the scope 🙂
A question, I build my DDDAC on a wood board, is it a problem ?
How I have to connect the ground of the Lundahl choke as they are wired in common rejection mode ? I just connected the last cap's neg leg on my ground star (which is connected to GND on the DAC board).
Thank you for your help !
Anyway, I try to measure with a 1 kHz sine wave, it is better, around 3V RMS between POS and COMMON and 0.9V after the cap and COMMON.
I don't know where the difference between frequencies comes from, I'll make others tests tomorrow with the scope 🙂
A question, I build my DDDAC on a wood board, is it a problem ?
How I have to connect the ground of the Lundahl choke as they are wired in common rejection mode ? I just connected the last cap's neg leg on my ground star (which is connected to GND on the DAC board).
Thank you for your help !
Is this with the autoformer in place? Just to be sure, remove the autoformer and just leave the cap and the load resistor, then measure again.
Also, did you block the DC in your measurement of the voltage from POS to COMMON?
It is what I did, I have the same results, autoformer connected or not 😉
Without the DC, I find almost the same issue results.
Is there anywhere a list of checking points ?
I have a question about NOS DAC.
I guess the primary benefit of NOS DAC is it does away with brick wall filter affects, and if I’m correct, I wonder if I can find any benefit using 192K NOS DAC for 44.1K REDBOOK data, since the mirror image is still there even after up-sampled to 192K or 176.4K.
Can we still hear the difference between NOS and OS Delta Sigma in this situation? And why?
I guess the primary benefit of NOS DAC is it does away with brick wall filter affects, and if I’m correct, I wonder if I can find any benefit using 192K NOS DAC for 44.1K REDBOOK data, since the mirror image is still there even after up-sampled to 192K or 176.4K.
Can we still hear the difference between NOS and OS Delta Sigma in this situation? And why?
Here are the measurements, sine 1kHz, scope in DC coupling (same result in AC), between cap and COMMON:
Autoformer connected:
Autoformer not connected:
Pretty the same but it's not beautiful 🙁
Autoformer connected:
An externally hosted image should be here but it was not working when we last tested it.
Autoformer not connected:
An externally hosted image should be here but it was not working when we last tested it.
Pretty the same but it's not beautiful 🙁
1kHz square wave:
An externally hosted image should be here but it was not working when we last tested it.
A picture of my dac, if it could help...
An externally hosted image should be here but it was not working when we last tested it.
Can you provide both measurements POS to COMMON and CAP-OUT to COMMON side by side for comparison (without the autoformer)?
The photo shows the analog PSU connected directly to the DAC boards (red wire). Shouldn't this go to the mainboard, where the regulators are?