BUILD THREAD - A New Take on the Classic Pass Labs D1 with an ESS Dac - Page 61 - diyAudio
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Old 9th May 2013, 04:20 PM   #601
qusp is offline qusp  Australia
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Quote:
The reason is I want to avoid the above part..
why? because you dont know how to calculate what you need? thats a terrible reason to use a transformer. which will in one foul swoop kill the hard fought performance. yet again, better off not using the NTD1 at all (well maybe not that much worse off, depends on the transformer). Using a transformer does not absolve you from working out the correct capacitor value for the reflected secondary impedance

honestly, it really seems that a number of people did not think it through at all before deciding to build this design; especially given we have had this exact conversation a number of times reaching back to the first version boards.

Last edited by qusp; 9th May 2013 at 04:30 PM.
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Old 9th May 2013, 04:30 PM   #602
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Qusp, just a quick question for ya and I hope it is not a stupid one...

Since this is a fully balanced output, would the DC offset if any be nulled at the receiving end if omitting the output caps? What would be the end result doing so?

Thanks
Do
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Old 9th May 2013, 04:31 PM   #603
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I wont comment on the Broksie stage ...
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Old 9th May 2013, 04:38 PM   #604
qusp is offline qusp  Australia
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Quote:
Originally Posted by pinnocchio View Post
Qusp, just a quick question for ya and I hope it is not a stupid one...

Since this is a fully balanced output, would the DC offset if any be nulled at the receiving end if omitting the output caps? What would be the end result doing so?

Thanks
Do

haha not a stupid question, one better off asked than not. I already covered this long ago. the DC will cancel yes... somewhere ... but you need a crapload of headroom and a tough as nails amp. if its not cancelled before you add gain ... well ... think about how much DC that would mean after say 12-15db gain then you would need your amp to be perfectly matched phase to phase and a fully balanced crossover.

basically its not doable, unless you have a BAL-SE stage as the FE of your poweramp, so that the DC is cancelled there (with medium voltage devices, like to220 fets or something, small signal jfets wont cut it). otherwise you will add a heap of voltage and current gain, to end up with several hundred watts of common mode DC for the speaker to cancel, and thats IF you have that much headroom in your rails, which is a mighty big IF.

most amps will have their FE driven into clipping even before any gain is added.

Last edited by qusp; 9th May 2013 at 04:44 PM.
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Old 9th May 2013, 04:45 PM   #605
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Quote:
Originally Posted by qusp View Post
haha not a stupid question, one better off asked than not. I already covered this long ago. the DC will cancel yes... somewhere ... but you need a crapload of headroom and a tough as nails amp. if its not cancelled before you add gain ... well ... think about how much DC that would mean after say 12-15db gain then you would need your amp to be perfectly matched phase to phase and a fully balanced crossover.

basically its not doable, unless you have a BAL-SE stage as the FE of your poweramp, so that the DC is cancelled there. oitherwise you will add a heap of voltage and current gain, to end up with several hundred watts of common mode DC for the speaker to cancel, and thats IF you have that much headroom in your rails, which is a mighty big IF.
Ooooh! ok

A new day without learning something new is a wasted day. Now I can go to bed!

I plan on using it on my B24 amplifier but I might use a balanced Pre in front of the amp. Just not sure yet... I will try to find the formula to calculate the correct amount for the caps and buy them.

Thanks!
Do
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Old 9th May 2013, 04:58 PM   #606
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the B24 has a pretty large input impedance yeah? as it happens mate, I tried my NTD1 directly driving nattonrice's B24 and a set of revelator based Troelsgraven Ellam-98 2ways when I took it down for last years Sydney head-fi meet.

that build (AKD12P with first gen NTD1 and fifo) was using 4.7uf auricap || 0.47uf vcap cutf and I can tell you it was not lacking bass response. in fact those little 2 ways give out a surprising amount of tight bass.

why bother with a preamp?

these are his Ellams and his B24

Click the image to open in full size.

Last edited by qusp; 9th May 2013 at 05:01 PM.
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Old 9th May 2013, 05:12 PM   #607
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also, i'm not ashamed to admit Im a bit of a bassshead when it comes to my music, test albums were various Massive Attack, Shpongle, Tool, Trentmoller, NIN. because aside from liking such music on occasion I was specifically testing the revelators for bass response, to see if I should be planning a sub, as i'm building a slightly larger set of 2 ways using the 18W rather than the 15W. I left without any worries about the performance in that area.

Last edited by qusp; 9th May 2013 at 05:24 PM.
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Old 9th May 2013, 06:10 PM   #608
Nikitas is offline Nikitas  Greece
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Qusp in case no one told you before, or you' are not intelligent enough to realize by yourself, you are irritating. And insulting. You may not like what I' m typing but that that doesn' t give you the right to respond like that. Now, stop being an ars, say something productive, or please don' t respond to me.
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Old 9th May 2013, 06:49 PM   #609
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hahaha, you know whats irritating? having to answer the same bloody elementary questions over and over and over again in the same thread. questions you should have asked and answered for yourself before taking the build on.

if I let that irritation show, sorry i'm just human.

here, i'll post the calculator again

its an xls file, you'll have to add the extension, the forum doesnt let you attach .xls
Attached Files
File Type: zip impedance calc.zip (5.4 KB, 23 views)

Last edited by qusp; 9th May 2013 at 07:01 PM.
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Old 9th May 2013, 06:51 PM   #610
Nikitas is offline Nikitas  Greece
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Then DON'T!!

Who asked you specifically??? I didn't!! you stuck your nose.
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