You mean the other way around right?
The supply is currently CLCLC (cap choke cap choke cap). Try removing the first pair of caps, making it LCLC instead, so the first thing after the transformer is a choke. That'll lower the output voltage a bit and lots of people prefer the sound that way. You can move the first caps to join some of the others if you like. Just have a listen and see what you prefer.
Does this mean your chokes survived their snap crackle and pop last week or are these new ones?
If you still need a lower voltage then try a lower value for the bleeder resistor, but beware it's going to get hot, so you might want to use a higher wattage metal bodied one you can heatsink or bolt to your chassis.
Also, your output voltage, is this with a test load resistor on to simulate the load of your dddac? That should bring it down too.
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Hi James yes the choke survived no problem with them at all🙂
Thanks for your advice just lashing it altogether now hopefully I should be done in 15 minutes........ Famous last words
Thanks for your advice just lashing it altogether now hopefully I should be done in 15 minutes........ Famous last words
Don't worry guys, converting PCM to DSD with decent player (Foobar, HQ Player), will sound GREAT through very good DSD DAC! After hearing Lampi DSD (chipless) DAC fed with true DSD and PCM converted to DSD, to me it's completely clear that's the way to go as future DAC. (for me it is)
I am REALLY curious what Doede will bring up, as the Lampi is quite expensive and I do like DIY.
Cheers,
Mark.
Well, 45 minutes later... The voltage is still above 19v, I'll have a play around over the weekend. What value bleed resister do you use James?
I have joined the PSU to my DDDAC foe a listen, I totally agree with Carlsor, it does add to the three dimentionality of the music, I really appreciate the eb and flow of the music more, and greater ease of listening.
choke input.
Hello,
Rectifier, choke, 2*3300 choke 2*2200 or 2*1000 or both with bleeder parallel.
You have a one board dac without shunts? Try to find a resistor that will give the same load as your circuit and see what voltage you are getting.
Always use a bleeder . 100 ohm will give you the minimum current needed to make it work like a choke input. If you put it across the first cap voltage will rise a little bit compared to putting it across the final cap
Greetings, eduard
Hello,
Rectifier, choke, 2*3300 choke 2*2200 or 2*1000 or both with bleeder parallel.
You have a one board dac without shunts? Try to find a resistor that will give the same load as your circuit and see what voltage you are getting.
Always use a bleeder . 100 ohm will give you the minimum current needed to make it work like a choke input. If you put it across the first cap voltage will rise a little bit compared to putting it across the final cap
Greetings, eduard
From my point of view, the pos/neg direct outs give the best sound. If you have accurate i/v resistors, the dc offset between them is practically zero. I keep the Cinemag output for if I'm connecting to someone else's solid state amp, but for my own kit I prefer to use the direct pos/neg these days.
Can you measure the voltage between gnd and the input and output of your chokes? You should see a voltage difference. I guess there's still a chance that your chokes have got hot enough to have fused the wires together inside and are acting as a piece of wire rather than a choke...
What voltage is your transformer?
And do you have 1 deck with shunts? Mine 1 deck with shunts with pulls 0.27a so I use a 47r resistor as a dummy load to simulate the DAC load when testing the supply and I use a 56r as my permanent bleeder resistor. I get about 11v output from my choke supply, but I only have a 12v transformer.
Thanks James / Edward
Thanks for the various pointers, I have a two board DAC with shunts.
I'll have a play around over the weekend, if I manage to get an hour of space ;-)
Thanks for the various pointers, I have a two board DAC with shunts.
I'll have a play around over the weekend, if I manage to get an hour of space ;-)
Ok, so that will probably pull somewhere around 0.5a
If you say your supply's going to be about 15v, then you do 15 / 0.5 = 30, so you need somewhere about 30ohm resistor to simulate the load of the DAC for testing purposes.
I'm using a 300va 15v transformer, but I don't understand how the voltage increases to 19v after the chokes and caps.
15v is the AC voltage. After you have rectified it and turned it to DC you can expect the voltage to be roughly 1.4 times that with no load applied.
this has been immensely helpful!!! be carefull to subtract the voltage drop of the bridge, or the diodes...
Transformer rectifier calculator
Transformer rectifier calculator
James it seems like a 12v transformer is enough as I don't see why we need to get so close to 12v DC as the 8v shunts don't need it. I'm I missing something here?
I asked Guido about the voltage overhead needed for the TentLabs shunt regs and he said 2v is fine, so in theory as long as you have over 10v at the 8v shunt input that's fine. Bear in mind the series resistors on each dac deck mean that 10v at the mainboard doesn't mean 10v at the shunt inputs.
But whether you can get away with a 12v transformer is going to come down to how many decks you have and what kind of load you're pulling as more decks will mean more voltage drop.
I'm fairly ok with a single deck and a 12v transformer. I think I have something like 10.6v at the shunt inputs.
I imagine 2 decks and a 12v transformer would be very borderline and 4 decks would mean that a 15v is needed.
Makes sense. I will have one deck like you so I feel 12v transformer will be enough.
Hi,
I currently upgrading the original 1794 motherboard (hosting 4 decks) by the new 1794S motherboard.
I have 2 questions:
a-/.In my original 1794 motherboard, the four Ra output resistors are 33R each, because I have 4 decks. The new 1794S is supplied with four 133R resistors, and I would like to get the confirmation that I should replace these 133R resistors by the four 33R resistors (as I assume that the output resistors should remain the same as long as the number of decks remains also the same...).
b-/.on the 1794S motherboard, I see a free location named "12MHz X-tal" with two 22nF capacitors: what is the utility of this ?
Thanks
I currently upgrading the original 1794 motherboard (hosting 4 decks) by the new 1794S motherboard.
I have 2 questions:
a-/.In my original 1794 motherboard, the four Ra output resistors are 33R each, because I have 4 decks. The new 1794S is supplied with four 133R resistors, and I would like to get the confirmation that I should replace these 133R resistors by the four 33R resistors (as I assume that the output resistors should remain the same as long as the number of decks remains also the same...).
b-/.on the 1794S motherboard, I see a free location named "12MHz X-tal" with two 22nF capacitors: what is the utility of this ?
Thanks
A) no those resistors are the same for both motherboards
B) the new blue motherboard now supports SPDIF input as well so that is a tent clock option you can use if you wish. Please go to Doede website and download the circuit diagrams and it should then be clear
B) the new blue motherboard now supports SPDIF input as well so that is a tent clock option you can use if you wish. Please go to Doede website and download the circuit diagrams and it should then be clear
So I was right, thanks !
I had downloaded the 1794S circuit diagrams a few weeks ago and found them back in my PC (not on the Doede website...): I see this Tentlabs clock option, but my 1794S has already one Tentlabs 12MHz included and soldered on the printed board .
So my question relates to the 2 holes named "12MHz X-tal" located close to the Wolfson WM8804G circuit, as shown on the following image : what are they used for ??
An externally hosted image should be here but it was not working when we last tested it.
Thanks
If you do not use the tent clock, you can install a 12MHZ Chrystal and the two ceramic capacitors there to form the clock. In this case, as the Tent clock is installed, they are not needed, so leave it unpopulated....