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Old 2nd June 2013, 02:12 PM   #11
qusp is offline qusp  Australia
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Sure, sometimes with other designs I have seen the same, but with people somehow assuming/claiming that their design will have the same high performance, just because the same parts and/or schematic are used. that isnt really what we see here, just a case of mistaken identity and seems pretty harmless.

I guess it just hurts my head that opamp+buffer = the wire, when really it had very little to do with the parts. as you say and as ive said in these cases before, the parts themselves, which is usually all the designs have in common (sometimes only vaguely), are pretty standard high performance ICs arranged in a fairly standard format. what makes it the wire is the performance, execution and OTT objective (ie. not frugal) design philosophy, all are missing here.

perhaps Owen wont even use the name for his commercial designs, it would be difficult now and thats a pity to not be able to leverage the well respected 'brand'. flattery doesnt pay the bills

of course it might help his cause if he was able to get them out this year too before another 5-10 copies are out there.

Last edited by qusp; 2nd June 2013 at 02:16 PM.
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Old 2nd June 2013, 02:15 PM   #12
qusp is offline qusp  Australia
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so anyway honestly Cyko500: I think you have a lot of work to do here on this design, i'll have a look tomorrow.

one thing I will say, just using a small value, low impedance capacitor type doesnt make for good HF decoupling, the enemy of proper HF decoupling is inductance and distance. inductance comes in the form of vias, thin, long traces and the package inductance, you have all of these on your decoupling caps

Last edited by qusp; 2nd June 2013 at 02:22 PM.
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Old 2nd June 2013, 03:08 PM   #13
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Here's mine,take a look...
Click the image to open in full size.

Specs:
Click the image to open in full size.

Last edited by GTrenchev; 2nd June 2013 at 03:12 PM.
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Old 3rd June 2013, 10:26 AM   #14
qusp is offline qusp  Australia
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right, so first of all congrats on a cute little amp and backing yourself with the measures, but its not even in the same ballpark sorry mate. Everything is significantly worse; noise is 60dB higher, crosstalk under load is pretty ordinary and ~24db worse, THD ~25-30dB worse, the channels are not matched, FR is something like 90-100x or more worse and the measurement only goes up to 15kHz so it probably gets more sketchy, while the wire is ruler flat, has a 0.002dB wiggle.

I wont go on, every single measure is like that, guess you are sharing a ground on the channels on the board to get crosstalk issues like that under load, or are using a mini/phono jack with bad crosstalk

noise may be better than the above, if the ADC you are using to test it with is limiting the measurement, but that seems unlikely, as most soundcards will have better spec than that.

Last edited by qusp; 3rd June 2013 at 10:33 AM.
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Old 3rd June 2013, 01:22 PM   #15
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"No Load" represents the exact specs of my soundcard in loopback.Sorry,I don't 10000$ AP.
Besides,I'm curious about the device that has -160 dbA noise floor?I measured the latest AP on Electronica 2012 exhibition,and it did -126 dbA.
Edit : I can confirm absolutely flat FR up to 10 Mhz.
I found the spectrum measurements:
Click the image to open in full size.
As you can see,it just repeats the soundcard output at any load.The card is Audiophile 2496.I don't think it's that bad,and I'm sure it will do better with better ADC.
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Last edited by GTrenchev; 3rd June 2013 at 01:39 PM.
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Old 3rd June 2013, 02:00 PM   #16
qusp is offline qusp  Australia
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it isnt close to flat up to 15khz ... how do you explain the huge difference in crosstalk with somewhat higher power? that 8Ω loading wont make any difference to the soundcard. if everything else there is your soundcard, that makes the measurements pointless except to show gross error and you cannot truthfully make the claim you have.

re 160dBa, the wire does I presume your DbA measure is at 1khz? should be the same as standard dB in that case. not sure what Owen used for that measurement, but given i've seen measures from Ap2, the AP above, an incredible HP analyser and knowing where he works, I tend to trust it.

edit: re -160dB, its probably done with a long FFT

you can go on thinking that perfboard with no ground plane and pretty red film decoupling caps is just as effective if you like, I disagree and without some meaningful evidence, we can only take your pretty crappy measurements above as evidence to the contrary

btw again, no worries cool little amp, but why the compulsion to make claims of objective performance that are just biased assumptions?

Last edited by qusp; 3rd June 2013 at 02:13 PM.
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Old 3rd June 2013, 02:57 PM   #17
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@qusp,I think we have a misunderstanding.I'm not pushing anything,in fact,I had even read your posts on the previous page before posting photos and specs of the amp.That post was generally appointed to the thread,not to you.I just wanted to represent some good practices with this kind of designing and building,as I acquired them with experience.
When I was building this amp 2 years ago(I started before "The Wire" appeared),I had about -60dB crosstalk without load.I was told by many "specialists",that this is the limit a perfboard can go,so I should leave it that way.Later I've build a second version with larger decoupling caps,and went to -85 dB,then I was told that the problem is with stereo jacks.My third version(above) has better grounding and does -94 dB with headphones on.Of course,at 8 Ohm it's much worse,but that's over the roof anyway.At since it repeats the performance of a professional soundcard,I can honestly say that perfborads are not that bad for a single project(which,I presume,is what the author aims at).
I'd ask how you measured 160db with AP's "24-bit Analog Devices ADC",but I don't think that's necessary.I'm sorry for loading the thread with useless posts.Have a nice day!
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Last edited by GTrenchev; 3rd June 2013 at 03:00 PM.
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Old 4th June 2013, 02:44 PM   #18
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Been busy with work, but to sum up: Read thread. Tried again. This time entirely through hole. Tell me what's wrong if you like.

And sorry, being a noob to the forum I cannot edit the thread title or my posts it seems.

Thanks for the help.
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Old 5th June 2013, 10:33 PM   #19
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Quote:
Originally Posted by qusp View Post
edit: re -160dB, its probably done with a long FFT
Definitely a case of FFT gain, yes. Remember it's pretty healthy, 30+ dB even for N=16384.

In The Wire SE-SE, noise is resistor-limited, with a bit of extra current noise contribution (the LME49990 has in=2.8 pA/sqrt(Hz)!). When fed from a noiseless 0-ohm source, effective input voltage noise works out to about 6 nV/sqrt(Hz). Good, but not particularly close to what the LME49990 could do (en<1 nV/sqrt(Hz)). Noise would be the same with a LM4562 or NJM2068. At unity gain, dynamic range does remain very high though (about 127 dB for a 2 Vrms signal @ 20 kHz BW, or around 140 dB at the maximum of about 9 Vrms, certainly distortion limited at this point). Nobody's gonna hear sub-1V noise, that's for sure.

I'm just wondering what people are supposed to drive the thing with while not compromising noise or distortion or both. Maybe that's the point of calling it "The Wire". But you're still missing a gain stage and volume control.

@GTrenchev, what sort of opamp are you using in there? Even if the LME49990 were available in DIP (it isn't), I'd assume a 100+ MHz GBW opamp at near unity gain wouldn't take kindly to sockets and a perfboard layout. Almost 80 dB of chsep driving 8 ohms is quite impressive though. That has to be power amp territory, in spite of a shared ground.

Last edited by sgrossklass; 5th June 2013 at 10:43 PM.
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Old 7th June 2013, 03:53 AM   #20
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Quote:
I'm just wondering what people are supposed to drive the thing with while not compromising noise or distortion or both. Maybe that's the point of calling it "The Wire".
thats not the point, the point is to have it so that it doesnt leave any finger prints on what you feed it. I said nothing about the performance being necessary, I simply objected to the baseless claim of equal performance with perf

Quote:
But you're still missing a gain stage and volume control.
only if you actually NEED gain and a volume control.

unity gain is more than enough for most headphones with many modern sources, which also often have digital volume control, which is why the design is how it is.
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