A New Take on the Classic Pass Labs D1 with an ESS Dac

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what i want to know is: why did he not order kits for those who wanted kits and boards for those who wanted boards? i mean if i wanted a kit i had to want a board, right?

and let me just say i m not angry at all :), just in case anyone would think so

i m just confused :) .
 
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ooh I dunno, maybe because it was easier to just order sets of everything so that when people just drop out without arranging someone to take their place, which lets just say is not unusual, he would not be stuck with just a set of parts, or just a board to find a home for. I really do not think that there are any grounds for questioning someone who put 2000 out of his own pocket to cover this for everyone. then of course the time spent on design, testing and now support.
 
the above wasnt meant to sound as harsh as what it reads, and not directed at anyone in particular, but lets just say I get why people arent always that keen to get involved. most were excellent, so its not a sweeping statement and I do get that **** happens, just guys, leaving things to the last minute is not fair given the amount of warning

BTW I found the heatsinks needed at conrad if anyone is keen on adding them, it will increase shipping costs a bit, but the sink itself is pretty reasonable.
 
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Rail voltage and current draw

Is 45VDC regulated still true in the final circuit? What is the current draw of the I/V rails at this DC voltage? Thanks!
Nic
Hi Guys,
- Transformers from Antek:
Antek - AN-0240
They're $11 each - 2 x 38.4VAC with 480mA current draw, which should give about 53.5VDC. I'm using +/- 45VDC regulated which is about perfect. You could probably get away with +/-50VDC as well. They're 25VA, and the circuit needs about 21VA. I don't like over-sizing transformers for low level circuitry, so I'd rather be at 84% capacity with a 25VA than 42% with a 50VA. Any comments here are welcome, and there is a 50VA version for $13 if people prefer that.
 
haha my only comment is i'm glad I got chunky heatsinks coming. I specified the 90va center tapped +/-45vac secondary for mine to allow me to use it with other circuits if need be. so i'll be running +/-50v again. I got a custom potted sumR trannie with 2 x center tapped 25vac secondaries @ 1A and the center tapped 45vac @2A for a total of 140va.

its a bit of a monster for a DAC. Richard was kind enough to put 18AWG solid core copper leadouts on it for my own peace of mind.

so going by the above the new design layout is roughly the same, except i'll have more current to burn as I dont need to account for so many regulators voltage drop. although i'm sure my minigold isnt anywhere near as efficient as the ICs.

apparently my salas shunts are on the way also :cool:
 
haha my only comment is i'm glad I got chunky heatsinks coming. I specified the 90va center tapped +/-45vac secondary for mine to allow me to use it with other circuits if need be. so i'll be running +/-50v again. I got a custom potted sumR trannie with 2 x center tapped 25vac secondaries @ 1A and the center tapped 45vac @2A for a total of 140va.

its a bit of a monster for a DAC. Richard was kind enough to put 18AWG solid core copper leadouts on it for my own peace of mind.

so going by the above the new design layout is roughly the same, except i'll have more current to burn as I dont need to account for so many regulators voltage drop. although i'm sure my minigold isnt anywhere near as efficient as the ICs.

apparently my salas shunts are on the way also :cool:

Do you plan to power the buffalo with the Salas shunt ?

D.
 

opc

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Hi Guys,

Well, the additional caps arrived yesterday, and I finished the kits late last night. I'll start shipping this evening, so the first 10-20 people who paid should see their board ship today.

pidesd:

I made an announcement several pages back that because there was an equal number of boards and kits (I wrongly assumed that everyone with a board wanted a kit to go with it) it would be easier to just sell them as a set.

I actually have no idea what you would want with just the SMD parts? The only use I can see would be if you're etching your own board with exactly the same layout. If that's the case, then take it from someone who has etched dozens of his own boards: it's easier, cheaper, and better to just get them made professionally. I can promise you that making your own will cost you significantly more than $20.

Anyhow, unless someone here wants just a board without parts, then I'm not willing to separate them. I'll ask those on the waiting list, and we'll see what happens.

NicMac:

My plan is to use +/-45VDC, and that's more or less what the board is designed for. You can use up to +/-50VDC, or down to whatever voltage you want. I saw a steady decrease in distortion as voltage was increased, but distortion started to increase again above +/-45VDC. Performance was slightly worse at +/-50VDC, and when you factor in the added dissipation, I see no reason to use anything other than +/-45V unless power dissipation is a problem and you're willing to give up performance in exchange for running lower rails. I posted some THD+N curves at different voltage levels to show this somewhere earlier in the thread. +/-45VDC is what Nelson would call "The sweet spot" for this particular circuit.

You'll see between 110 and 120mA of current draw from each leg with +/-45VDC. That means each channel will draw about 230mA total from the regs.

Nikon1975:

I know this thread has become a little unruly (I should have split the GB stuff into a separate thread) but all you really need to do is read the first 15-20 pages or so.

The balanced vs. SE question has been asked and answered at least a dozen times, and there are even measurements to show you what you can expect.

As for dual mono, it would certainly be possible, but you'll need four BAL/SE converters, one for each output on two boards. Then you'd get dual mono balanced output.

One thing I forgot to mention, and that I noticed the other day, is that if you use this circuit in SE mode by just taking the positive output to ground, then you WILL get clicks and pops on power up and power down. The circuit relies on the CMRR of the next stage to reduce clicks and pops on power up/power down.

I tested it plugged directly into an Anthem A2 amplifier (balanced input with 36dB of gain) and there was very minimal clicks on power up, and nothing on power down. With just a SE RCA output though, there was a very significant pop on startup and shutdown. For this reason, I strongly suggest a proper BAL/SE converter which is what I've been saying all along.

Regards,
Owen
 
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Oh and I meant to post this last night, but the iPhone was giving me the ***** on the forum. But someone was asking whether I was using salas with the buff. For one, I'm nit using the buff, I'm using ackodac and 2 the ackodac already has high end linear low noise ad797brz based regs For all main supplies for the sabre. I'll prob give the salas a go with the ackodac and I'll probably release the buff from it's cramped portable home for a head to head, but it's home is in a portable a123 LiFePo4 powered balanced headpphone amp for my iems :D
 
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Hi Owen,
Thank you for the concise information and for the very well "mastered" circuit and group buy. Top notch.
Nic

Hi Guys,
NicMac:

My plan is to use +/-45VDC, and that's more or less what the board is designed for. You can use up to +/-50VDC, or down to whatever voltage you want. I saw a steady decrease in distortion as voltage was increased, but distortion started to increase again above +/-45VDC. Performance was slightly worse at +/-50VDC, and when you factor in the added dissipation, I see no reason to use anything other than +/-45V unless power dissipation is a problem and you're willing to give up performance in exchange for running lower rails. I posted some THD+N curves at different voltage levels to show this somewhere earlier in the thread. +/-45VDC is what Nelson would call "The sweet spot" for this particular circuit.

You'll see between 110 and 120mA of current draw from each leg with +/-45VDC. That means each channel will draw about 230mA total from the regs.

Regards,
Owen
 
ok thanks for the explanation opc. i just cant argue with you. you already gave so much that in the end i can only be grateful.

in fact, i would not use the smds on any pro pcb, just a regular pad per hole board. the reason i wanted the kit was because it would save me some space and make the design more compact. also, because i would only use a couple of the smd parts for the build (like caps) and use the rest for other things, it wouldnt make the whole thing too akward. and lets just say that, taking everything elase out of the equation,for the price , you get a pretty nice little bunch of parts.
 
protection diodes

They say a little knowledge is a dangerous thing. In researching parts, v regs in particular I was struck by the recommendation that with >25 volt output and > 10UF capacitance an output protection diode be included from the adjustment pin to the output pin. Was this an oversight or is there a good reason that this isn't needed in this circuit? The input protection diodes are there so I am guessing that I am missing something, and that makes me dangerous.

On a different matter Newark in the US (97K5040) or Farnel have a (MHP35201F) 200 ohm thin film R rated for 35 watts and a 50 ppm tempco. Similar price to a Caddock thick film. Ought to go well with those other $$$ Rs.

Another place to upgrade is the digital isolation transformer. Scientific Conversion part number SC947-02LF looks like the best out there. It is a 1:1 so it can work with SPDIF or AESEBU. It is surface mount and $17 but if we can get interest for 50 pieces it drops to $12. I would even be willing to set up a group buy if there is sufficient interest. I know I want 4 right away.
 

opc

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Hi Guys,

pidesd:

I'll keep an eye on what parts I have left, and I'll get in touch with you when the dust settles. If I have enough parts to make an SMD only kit for you, then I'll do my best to get one together.

Hang tight for now, and we'll see where we are in a week when everything is shipped out.

stephen1212:

You are indeed correct that two diodes are often used, one for the bypass and one for the output to input. Because the bypass capacitor is small (10uF) there isn't really a need for any protection on that node. Some people do like to put massive values there, and that diode is more intended for that sort of application (IMHO). I have never used one with 10uF bypass caps, and I've never seen a reg fail as a result (or ever really for that matter, they're pretty bomb proof).

Just the same, a small SOD23 can be soldered across the 240R resistors if you are concerned. I don't see a need for it though.

Cheers,
Owen
 
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