Okay, so apparently, the ohm value of the transformer dictate the A load on the circuit. Kinda logical but now I don't know. I don't have the resistance of the Triad/Hammond double C core, or split bobbing as some call it, so I can't use that.
But, I changed it from 35ohm to 10ohm and that drove up the A. I also changed such that the inductor is now in parallel.
Ripple is still 0.02mV
I(L1) = 1,17A
I(R1) = 1.28A
I need to figure out the resistance thing in the transformer. The amount of information in order to work in PSUD2 is kinda slim .. .LOL
But, I changed it from 35ohm to 10ohm and that drove up the A. I also changed such that the inductor is now in parallel.
Ripple is still 0.02mV
I(L1) = 1,17A
I(R1) = 1.28A
I need to figure out the resistance thing in the transformer. The amount of information in order to work in PSUD2 is kinda slim .. .LOL
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Hello,
T1 will be something like 500mOhm i guess.
You need to simulate with a 2A current sink that will be similar to a DDDAC with 8 boards.
It could be necessary to *** a resistor in series with the LL2771 when used with choke input to get a regular voltage rise.
So use an LCRC with the right values and you will end up with a 1 millivolt which will be dealt with by the 7810 and the Tent shunt.
Greetings, eduard
T1 will be something like 500mOhm i guess.
You need to simulate with a 2A current sink that will be similar to a DDDAC with 8 boards.
It could be necessary to *** a resistor in series with the LL2771 when used with choke input to get a regular voltage rise.
So use an LCRC with the right values and you will end up with a 1 millivolt which will be dealt with by the 7810 and the Tent shunt.
Greetings, eduard
Hey Guys,
I was not finding my DDDAC to be giving me a high enough output. I went back to Cinemags 15/15B transformers. Technically, it should give a Vrms of 2.7V correct. But when I play any music, it doesn't sound very dynamic and the gain also seems subdued. Now, I had to find some other source/dac which had a similar Vrms and I found my SoulNote SC710 CDP which in the unbalanced mode gives out 2.5Vrms. Which I would consider almost as close as the DDDAC with Cinemags technically. Now when I play a CD and connect the CD's RCA output to my preamp as well as connect the spidf out from the CDP to DDDAC and then to preamp, I can change the source from CDP to DDDAC on the fly. When I do, here is what I observe, the gain and overall sound immediately becomes more forceful with the CD player's output and feels very dull with the DDDAC. It feels lifeless.
Now, I had already measured the DC voltages across the Pos, Neg and Common previously and shared with you and DD said, those looked within range and fine. But today I decided to measure the Vrms as well on the DDDAC.
Here is what I did and saw. I played 2 different 100hz tones using the USB connection from my Macbook to the DDDAC (Macbook's system volume kept at 100%). The measurements were as follows:
Vrms across Pos and Neg of both Right and Left channels: 1.66V
Vrms across Pos and Common of both Right and Left channels: 0.83V
Interestingly, when I measure the Vrms at the RCA output jacks of the DDDAC, i.e., after the Cinemags outputs, the readings on both left and right channels were coming only as 0.34Volts. No change was made to the system volume.
Here are my concerns:
1. Should the Vrms across Pos and Negative of both channels of the DDDAC not be 2.7Vrms and across Pos and Common 1.4Vrms or so? Meaning I am actually getting only half the Voltage RMS output from my 4 board dac?
What could I do to rectify this as I am really finding the dac to give a very dull output and it is pretty evident that if I am getting these low Vrms values, the gain has to be low and hence the performance has to seem this uninspiring.
Hi Kartick,
this definitely not correct. Playing a tone at 0dB (are you 200% sure your player is not doing any kind of volume control?) should give 1.2Veff between POS/COM and also between NEG/com. between POS/NEG 2.4 Veff
It looks there is something not ok if you put a load on the transformer.
only thing to clarify is, is it in the DAC or with the Transformer/load?
to do so you have to disconnect the Cinemag and measure again. than we know where to look further
this definitely not correct. Playing a tone at 0dB (are you 200% sure your player is not doing any kind of volume control?) should give 1.2Veff between POS/COM and also between NEG/com. between POS/NEG 2.4 Veff
It looks there is something not ok if you put a load on the transformer.
only thing to clarify is, is it in the DAC or with the Transformer/load?
to do so you have to disconnect the Cinemag and measure again. than we know where to look further
Hi DD, All,
One update. Further to my last message, I took a Windows laptop and downloaded some more tone samples at 0db - 100hz and 1Khz and repeated the Vac mesaurements.
Now I got this:
Vac at the dac's pos and neg: 2.34V on both R and L channels
Vac at the rca output: still 0.33V on both R and L channels
I went back to my MacBook and played these same samples and got the exact same Vac values.
Vac at the dac's pos and neg: 2.34V on both R and L channels
Vac at the rca output: still 0.33V on both R and L channels
Please note that these measurements were also taken while the primary wires of the Cinemags were still connected to the DDDAC. I am confused that I still did not disconnect the Cinemags and the Vac values reached closer to what the prescribed Vac of 2.4V should be there.
- Should I still disconnect the primaries of the Cinemags from the pos and neg and repeat the measurements?
- Why am I getting so low Vac across the RCA or at Cinemag's secondary? Here is how I have wired the cinemags secondary at the RCA jacks:
Yellow wire to RCA's Hot pin
Orange & Black to RCA's Ground pin
White wire is not connected anywhere (floating)
One update. Further to my last message, I took a Windows laptop and downloaded some more tone samples at 0db - 100hz and 1Khz and repeated the Vac mesaurements.
Now I got this:
Vac at the dac's pos and neg: 2.34V on both R and L channels
Vac at the rca output: still 0.33V on both R and L channels
I went back to my MacBook and played these same samples and got the exact same Vac values.
Vac at the dac's pos and neg: 2.34V on both R and L channels
Vac at the rca output: still 0.33V on both R and L channels
Please note that these measurements were also taken while the primary wires of the Cinemags were still connected to the DDDAC. I am confused that I still did not disconnect the Cinemags and the Vac values reached closer to what the prescribed Vac of 2.4V should be there.
- Should I still disconnect the primaries of the Cinemags from the pos and neg and repeat the measurements?
- Why am I getting so low Vac across the RCA or at Cinemag's secondary? Here is how I have wired the cinemags secondary at the RCA jacks:
Yellow wire to RCA's Hot pin
Orange & Black to RCA's Ground pin
White wire is not connected anywhere (floating)
Hey, dug out all the old posts which gave out the Cinemag wiring details and coincidentally rewired the secondary exactly as you now mentioned, i.e., by also removing the previously connected black wire.
Another development to the Vac ratings - Now when I measure the same test tone at the DAC's pos and neg, I get 2.34V something and then from the inside of the RCA jacks (by connecting the cinemag's secondary as I just mentioned - removing black wire), I am getting 2.34V here as well.
But very interestingly, when I take the probes of my DMM and measure the same Vac from the other side of the RCA connectors, that is by inserting one of the probes insider the rca (hot) and touching the other probe to the ground, I am still getting that weird 0.33Vac something reading.
What does this mean, that my RCA jack material is making me lose voltage due to the way it is constructed or is it that the probes of the DMM dont make as proper a contact like they do when touching the rca from the opposite side (internal side)?
Another question - say hypothetically that my cinemag trafos were magnetized. What would be an audible way to judge that? I asked a local amplifier designer friend here and he said I should have heard distortion when listening to audio. But that is not the case. I am getting very clean sound, of course it is different to using capacitors but nonetheless it is clean.
typically at loud bass tones the sound will distort. if you have a clean sound there is nothing to worry about magnitism
The problem is that the bass impression isn't as loud as some of the capacitors, let alone bass distorting. No distortion whatsoever, I am assuming my cinemag pair is not magnetized. I have removed the black wire and reconnected everything last night, if I hear anything untoward, will report back.
Well yes, either that or the DMM probes don't make a proper contact to get the correct readings. I had recently changed all cinches but point taken DD, will try to replace another one and see what happens.
