"The Wire" Ultra-High Performance Headphone Amplifier - PCB's - Page 153 - diyAudio
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Old 8th June 2012, 11:16 AM   #1521
regal is offline regal  United States
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Quote:
Originally Posted by IanAS View Post
It's not voltage but current that makes the voice coil in the headphone move back and forth according to Flemings rules for motors and generators.

The applied difference in potential across the load (aka the voltage) is merely a means of making some current flow. The current interacts with the fixed magnets causing a resultant mechanical deflection in a specific direction.

So the signal path is in reality the current path from one capacitor plate all the way to the other.

What an amplifier is doing is servo'ing a power supply across a load.

Depending on the size of the reservoir and the size of the loads current demand, the amplifier could be servo'ing the mains supply across the load.

In a dual rail single ended supplied system the path is earth referenced to the centre tap or earth star between the two capacitors, which discharge one at a time. But with balanced a more elegant solution is that the one capacitor discharges from both plates and the same time.

A disadvantage is that twice the voltage capacitor is required so for a high power class AB amplifier that's something a of a problem as they tend to stop at 100V. And for the The Wire Bal-Bal is a problem as the clean and fast sounding polymer caps have very small values above 16 volts and we need at least 30V.

I'm also still using all the stock values and parts on my Bal-Bal except I did tack on some Black Gates across the Nichicon polymers and they did what the always do which is give a big powerful slamming rocket bass that is a bit muddled and grainy. I did it because with the HD800's there was a very disappointing lack of bass with The Wire in place so I thought I give it a go to see what happened. Took about three minutes to fit them in situ at the back of the PC under the table, so if it had no effect I was not wasting much time.

My Bal-Bal is supplied by the 400 Watt SMPS the Seasonic X400 but through the motherboard, so that's probably not ideal. I had various ideas regarding feeding it direct using the wires that normally go to the Molex or SATA power feeds and traced some of the mobo to sound card connections in the PCI but there are a few and I have to reverse engineer it more extensively that I have so far.

I've not tried tacking on the Vishays yet. The sound card needs a different output stage first I think.
This is another reason why the smart choice is two SE-SE boards for balanced output (with separate power supplies) Owen mentioned this performance is superior to a single bal-bal at the get-go.
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Old 8th June 2012, 11:51 AM   #1522
IanAS is offline IanAS  England
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Well no, in the respect of what I just said separating the two output chips on separate boards means you can't use this simplified and better circuit and current path. On the Bal-Bal Owen has used the shortest path with the two 10uF X7R's butting up to each other through a via. With two single ended boards you have to take the current all the way through both ground planes and possibly interconnecting wires if the earth plane is not shared. That's opposite of ideal.

Unless I'm visualising this incorrectly in my head just now, I wrote it down last year sometime and have not looked at it again recently.

I do recall Own saying that the measured noise performance (or cross channel noise?) was better with the Bal-Bal if two supplies were used due to the two separate ground planes, or something. The Bal-Bal is effectively two separate boards, one for each channel, just both on the same sheet of Glass Reinforced Plastic.

Another difference is two LME49990 vs. one OPA1632. My guess is that it's better to use the integrated rather than two separates. More so if the two separates are on two separate boards or some way apart on the shared earth plane as the two receiving op-amps might have slight variance with the common mode and differential mode conditions. Would you not then be relying on the voice coil to cancel that rather than the integrated differential op-amp doing it?

Upon reflection the Bal-Bal seems to be in every way better; you're cancelling noise at the input, the receiver is perfectly balanced, the output current path is the shortest and most elegant. Both channels are separate.

Maybe it could have been even better if one 10uF could have joined the two pins, as mention above, instead of two butted in series and using a via and in the same way one 30 Volt polymer instead of two 16V. Not that they sell 30V 330uF or even 160uF...... Actually thy maybe do: 150u 35V PLV1V151MDL1TD Available from Digi-key: 493-3868-1-ND

Last edited by IanAS; 8th June 2012 at 12:21 PM.
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Old 8th June 2012, 12:07 PM   #1523
qusp is offline qusp  Australia
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i'm aware that current drives the voice coil, i'm not that dim, but i'm not sure that the indirect influence of current noise (less prone to capacitor differences/performance than voltage) modulated by the voltage will be a limiting factor over the voltage noise modulating it. the noise of this amp is so ridiculously low and the amount of material and components in the signal path of this design so ridiculously small, that I would find the idea of it having significant audible effect highly dubious. doesnt stop me tweaking, but its absolutely not reason to change to a ground referenced system

Ian, given the physical positioning of your amp and all the noise on the supply/ground and air surrounding it, dont you think you are tilting at windows a bit, worrying about the noise of 1 extra cap? the design does pretty well with a lower value and with very local power, just a 0.47uf np0 would be probably fine, I think the high grade ceramics are actually not that bad these days. hopefully they can start to produce higher values in the new thin film caps, awesomely linear, but not available in useful sizes for this purpose

@regal
2 x SE is not a balanced output, its a bridged output, 2 different things that are unfortunately often confused. me I much prefer balanced and I see the above as a very minor (my words would be meaningless) side effect of the ADVANTAGE of truly balanced systems. Owen said the noise (maybe thd too?) performance of a single SE-SE amp was slightly better (obviously, its only one amp) and if you needed the voltage swing 2 amps would be better, as youve always been banging on about swing. but add 2 amps together and you double the noise (as well as the issues mentioned by ian above), unless you need the voltage I see little advantage and only pitfalls. totally personal taste but I see no reason to bring ground directly into the signal path at the end of a balanced system

Last edited by qusp; 8th June 2012 at 12:23 PM.
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Old 8th June 2012, 12:15 PM   #1524
qusp is offline qusp  Australia
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Ian, yeah I use dual PSU's, bipolar LDO's on battery power, indeed it is 2 completely separate amps, you can see it just looking at the board
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Old 8th June 2012, 01:43 PM   #1525
IanAS is offline IanAS  England
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Originally Posted by qusp View Post
tilting at windows a bit
I haven't heard that phrase but yes I probably am a bit. A pal says I'm 'gilding the lilly'. But it does get results. Another pal said we should stop where we were back in 1994 as he could imagine no further improvement was possible. If course it was though and I didn't stop.

It's not noise I think we could get an improvement with by doing this. I've heard the effect of more and of less solder joints and of copper track. It can be easy to hear on a revealing system. A general degradation of the sound. So by missing out another two joints, a via and two capacitor end plates, by previous experience, it will make the sound clearer and better even if by just half the width of a gnats knacker.

Or is that two times two joints, etc. I've come over tired. Maybe it's that speciality beer I had after feeling inspired by the other thread to try more varieties of it.

Last edited by IanAS; 8th June 2012 at 01:50 PM.
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Old 8th June 2012, 02:20 PM   #1526
qusp is offline qusp  Australia
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haha no wonder you havent heard of this saying, it doesnt exist; its 'tilting at windmills' now i'm getting tired. how perfectly ridiculous and deliciously ironic, that I would make an intellectual/literary reference and make a typo

oh hey i've got my own audio demons I like to chase, that may or may not be that meaningful in the big picture, but they are all part of that picture and its an individual picture. yes less components for the same job is always a good thing provided they do the job at least as well, only Owen can tell us why he chose that arrangement in particular.

I was just saying there might be bigger fish to fry in your setup. I know you hate solder more than most; I too have sometimes wondered about the possibility of using teflon or ceramic substrate and welding the parts on with jewellers solder before the actives go on, but i'm pretty happy with having as little parts in the signal as I do, particularly as I use sabres volume.

One day, probably not too far away, we as individuals in our homes; will be able to program in a design such as the wire and fabricate an integrated circuit from it from mostly pure copper and dielectric/thin film, all in one piece with no solder joints and I will be right there with you grinning from ear to ear

one thing is for sure, its a superb little amp with a deft touch and a knock out punch

Last edited by qusp; 8th June 2012 at 02:26 PM.
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Old 12th June 2012, 05:14 PM   #1527
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This is an open message for Owen or any other interested party.

Seeing as all the boards have been sold and Owen does not seem to be planning
on doing any more runs and there still seems to be some interest...

Would there be any interest (or opposition) to getting another run of boards done,
by myself or someone else either with or without the original Gerbers?
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Old 12th June 2012, 05:18 PM   #1528
qusp is offline qusp  Australia
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hes running a fully commercial venture with the LPUHP now mate, if he doesnt object to getting another board run of the headamps fine, but if you run something too similar, particularly leveraging the name, youde want to watch your back =) not good form to copy it without the gerbers either.
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Old 12th June 2012, 05:55 PM   #1529
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Thats why I'm being open and up front...


Quote:
Originally Posted by qusp View Post
hes running a fully commercial venture with the LPUHP now mate, if he doesnt object to getting another board run of the headamps fine, but if you run something too similar, particularly leveraging the name, youde want to watch your back =) not good form to copy it without the gerbers either.
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Old 12th June 2012, 06:10 PM   #1530
jtktam is offline jtktam  Canada
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Quote:
Originally Posted by qusp View Post
hes running a fully commercial venture with the LPUHP now mate, if he doesnt object to getting another board run of the headamps fine, but if you run something too similar, particularly leveraging the name, youde want to watch your back =) not good form to copy it without the gerbers either.
i missed the LPUHP groupbuy a while back.. where did you see him go fully commercial? i will get it there

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