A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 157 - diyAudio
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Old 2nd January 2013, 04:46 PM   #1561
qusp is offline qusp  Australia
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ahh nope apparently ground pin currents at 1A are 6.1mA, hmm so if thats the case and we use the external ground for the return, then the reg output will still be seeing the full 45v till the output caps charge.

haha beaten to the reply. yes I was thinking of the GND pin being used for return currents instead of simply a means to measure the reference, ie not a convoluted '2 terminal device'

head failing... except it isnt seeing the full voltage, only the difference, erase ground pin from thinking, not ground.

Last edited by qusp; 2nd January 2013 at 04:57 PM.
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Old 2nd January 2013, 04:52 PM   #1562
opc is offline opc  Canada
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nope... you're still thinking about it a little backwards. Every pin on the TPS that used to be connected to GND will now be connected to some arbitrary voltage, let's call it VREF for fun. If VREF is connected to the true circuit GND (eg the GND of the unregulated supply feeding the reg) then the input to GND and output to GND voltages are exactly as they appear.

If you elevate VREF with a zener by 24V then all that the TPS sees is the differential voltage between Vin and VREF and Vout and VREF. The TPS shouldn't care what the true input and output voltages are relative to the actual circuit GND.

The sense pin should be connected directly to the load as one would usually do.

Cheers,
Owen
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Old 2nd January 2013, 04:58 PM   #1563
qusp is offline qusp  Australia
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yeah see edit =) its really not a ground pin even at normal voltages
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Old 2nd January 2013, 05:03 PM   #1564
qusp is offline qusp  Australia
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you know how I get at this time of night, I spew my thought process out onto the screen and use copious edits.

its a ground sense pin, not a ground return pin. it sources current for the reference only, not the load. just as an opamp does

Last edited by qusp; 2nd January 2013 at 05:06 PM.
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Old 2nd January 2013, 05:07 PM   #1565
opc is offline opc  Canada
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Tada!



It's the middle of the day here, and I've had a very big coffee, so I'm running at peak capacity

Go to bed!

Cheers,
Owen
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Old 2nd January 2013, 05:19 PM   #1566
qusp is offline qusp  Australia
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Quote:
Originally Posted by opc View Post
Tada!



It's the middle of the day here, and I've had a very big coffee, so I'm running at peak capacity

Go to bed!

Cheers,
Owen
haha OK I might just do that, I just need to go run the DPS600 load testing first







kidding

been staring at a wifi/blutooth ES9016 dac layout i'm working on for the last few hours too, diptrace functionality is great, but it has some idiosyncrasies that hurt my head too, especially since it runs in emulation in wine on mac.b I decided further caffeine was not productive a couple hours ago, fading
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Old 3rd January 2013, 04:37 PM   #1567
Rolle is offline Rolle  Denmark
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Hi

I need your advise on heatsink - I was looking at these 2, as they available in my country:
https://www.elfa.se/elfa3~eu_en/elfa...+49%2F200%2FSA

https://www.elfa.se/elfa3~eu_en/elfa...+49%2F150%2FSA

will they be ok? thermal resistance is 0,5K/W and 0,6K/W respectively

Thanks for your advice
Rolle
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Old 3rd January 2013, 05:27 PM   #1568
qusp is offline qusp  Australia
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the second one is borderline, first one seems ok, depends, will you be using it for heatsinking other power supplies too? will it be exposed to the air or inside the case? what will the orientation be?
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Old 3rd January 2013, 06:34 PM   #1569
Rolle is offline Rolle  Denmark
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Hi qusb

Actually I was thinking something similar like you did with the nicely tapped heatsink you got from Conrad heatsink back in 2011:

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

It will be in a vented wooden enclosure in a desk - backside of the desk removed for better air circulation. I have separate heatsink for a Paul Hynes PR3 reg used for powering the buffalo dac. So no additional power supplies on the heatsink besides the board from OPC

Will I be ok or you think I should look for bigger heatsink than the one rated at 0,5K/W?

Thanks
Rolle
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Old 3rd January 2013, 07:09 PM   #1570
qusp is offline qusp  Australia
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OK well the heatsink we got, is just comfortable with it inside a case, it does run a little toasty in summer but its still OK. do you know what temp that heatsink rating is given at? heatsinks get more efficient as they get hotter believe it or not; the hotter they get, the more heat they can get rid of. so its important how theyve rated them.

the first one is basically the same dimensions as the conrad unit, but with a thinner base and the depth of the fins is not as much, so for me I would avoid that one if you are mounting in a desk, the wood wont take any heat away from the heatsink either like it does with my current chassis. the heatsinks we have are 0.36C/W for an 80C rise, which translates to ~0.45C/W for the temps i'm running them, which is only about hmm maybe 25C rise above ambient, meaning the heatsink can get up to 65-70C on our hottest days. for an air temp inside the chassis of ~50-60C

so really to be safe I would take the next size up if I were you
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