BUILD THREAD - A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 46 - diyAudio
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Old 4th July 2012, 09:06 AM   #451
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It is probably my bad english. I sense an aggresive tone here, and i really didnt mean to upset anyone. I am full of admiration for this beautiful project, and all the work you and owen had put into it!!!

I basically just wanted to learn more. I coulndt find much information or performance parameters concerning the smd caps. The only information seems to be wether the cap is X7R, c0g etc. Nothing about esr, esl etc.

I did read the BOM. But i am probably not ordering from digikey. And mouser and RSonline didnt have the BOM components. So i needed other components, and i didnt just want to take whatever showed up.
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Old 4th July 2012, 11:38 AM   #452
opc is offline opc  Canada
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Hi pedefede,

I certainly didn't mean any anger or aggression on my side... perhaps I misunderstood the intention of your original post. I was just trying to clarify a common misunderstanding about SMD parts.

I'll give you a few pointers on picking the right ones later today, as I'm off to work right now.

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Old 4th July 2012, 11:43 AM   #453
qusp is offline qusp  Australia
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no aggression here either, pretty much ditto opc. I tried to clear that up in my last post as well as giving further info, but perhaps you took it as further aggression? your wording in the post sounded like you were caught up in the all too common mistake of thinking that SMD are somehow inferior for audio. funny thing is, most times 'audio grade' parts are in fact lower spec parts than the industrial grade.

the bafflingly common mods of replacing SMD parts with leaded audiophile approved parts for decoupling HF continue to this day.

it seems we both misread you in the same way; my apologies for the misunderstanding, but your meaning was not conveyed as intended; at least from my reading.

I also gave my opinion on where I feel the only tweakable positions are, as well as asking where you had bought the zfoils for; twice …

I myself, as you may know use tx220Z zfoil resistors for the power resistors in place of the caddocks and I use OTT VCAP CuTF bypassing Auricaps on the output, but I feel these as well as matched mosfets and perhaps playing with the power supply are the only areas there is any point upgrading and thats only personal taste

Last edited by qusp; 4th July 2012 at 11:56 AM.
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Old 4th July 2012, 01:17 PM   #454
hirez69 is offline hirez69  Europe
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Default Tx200Z

Hi qusp,

can you help me to understand how to replace 200R Caddock resistors that are rated for 30W with TX220Z Texas (ZFoil) that are certified up to 8W?

In this post, replacement is recommended for Ohmite 400R

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

What is your final hint?

I know your opinion about in the supply of matched fets: alternatively, do you have any tips for finding required matched mosfets?

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File Type: pdf tx220z.pdf (65.1 KB, 46 views)
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Old 4th July 2012, 01:40 PM   #455
qusp is offline qusp  Australia
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because its not dissipating more than 8W… besides they told me unofficially 8W is a pretty safe rating and they would deal with 12W if well heatsinked. i've been using them for well over a year now.

Owen would never recommend a $50 resistor, regardless of whether its the better part or not, you'll find hes using the zfoil though, as we gifted some to him as a surprise, I hope he is anyway lol. I ran a small group buy and got the price down a bit, but its still not cheap. the ohmite are not always in stock either, he recommended the thin film ohmite, not the thick film that is more often stocked

sorry i'm not going to explain the matching process again, every couple of months I get asked to explain it, I even started a thread about it. Owen and I both posted instructions, mine a bit more involved, as I didnt have such high quality measurement gear so I had to augment it with a measurement amp. there are no tips for finding them, you have to buy a heap and measure them all, 3 measurements per fet at operating point; then grading. to supply the whole number being asked for in this thread, I would estimate at least 200-300 fets would need to be measured, 600-900 measurements, sorry guys, not going to happen.

Last edited by qusp; 4th July 2012 at 01:42 PM.
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Old 4th July 2012, 02:08 PM   #456
hirez69 is offline hirez69  Europe
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Thank you qusp,

then I can replace both sets, 200R and 400R, with Texas TX220Z? Please, can you confirm?

I absolutely want you to stay sane, so do not ask you to perform 900 measurements!
The matching problem is not so the procedure, rather than the availability of a generous number of MOSFETs to be measured.
Could you give a value to the matched fets on the final result?

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Old 4th July 2012, 03:47 PM   #457
qusp is offline qusp  Australia
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at +/-45vdc supply each 200R is dissipating 2.72W, each 400R is dissipating 5.44W the fets are dissipating a couple of watts each and the whole board sans power supply is dissipating ~42W

so yes you can use for both, I presume opc only recommended upgrading the 400R as the 200R ohmite thin film is almost impossible to find, while the 400R is only difficult to find.

I sold the sets for 50-70 depending on how tight the matches were. its certainly one of those 'dont quit your day job' things. you would be looking at months of time and the initial cost, to do it properly. each fet needs to reach operating temp, lets be frugal and give 15mins per fet whether it makes the grade or not. 225hrs plus sorting, packing, shipping. you might be able to do it quicker if you did several at once, but that would mean a more involved test rig to build

I dont want to discourage people, but I also want whoever does it to go in eyes open. unlike myself. if you have high grade test gear you could probably cut that measurement time in half. I had to research the circuits to get the right results and fail a few times so my time was more than 15mins a fet I can tell you

Last edited by qusp; 4th July 2012 at 04:02 PM.
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Old 8th August 2012, 11:12 AM   #458
CeeVee is offline CeeVee  Portugal
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Hi Guys,

I picked up my DAC to finish it now and came up with the issue of the wrong orientation of the input protection zeners.

So ...decided to put up a picture with the schematic corrected if it's ok with you owen ?

Official schematic at beginning of thread should be updated i guess, leads to continuous confusion for some.
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File Type: jpg Schematic Channel A CORRECTED.jpg (156.6 KB, 591 views)

Last edited by CeeVee; 8th August 2012 at 11:15 AM.
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Old 9th August 2012, 12:44 PM   #459
marce is offline marce  United Kingdom
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For SMD decoupling capsuse X7R, by AVX Kemet Panasonic etc. For decoupling digital circuitry they are the best, use a low value COG with larger value X7R for oscillators, the COGs in this position do have some advantages, but for elsewhere X7R in the smallest package size for a given valueare adequate (and the best solution due to their size and minimum parasitic inductance). The practice of replaceing small SMD caps with leaded "audiophile caps" is one of the most uneducated and silly mods I have seen done, it does not improve anything and would make matters worse.
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Old 11th August 2012, 02:20 AM   #460
qusp is offline qusp  Australia
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Hey CeeVee, this has been covered a number of times, there was a mistake on the PCB, you need to make little zener tipis to make back to back zeners. there are pics in this thread as well as the other one. i'll see if I can track it down. they go on pads Z1, Z2, Z7, Z8 putting them on all the pads of course wouldnt actually protect that well, they need to be back to back as in the schematic.

Last edited by qusp; 11th August 2012 at 02:23 AM.
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