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"The Wire" Ultra-High Performance Headphone Amplifier - PCB's
"The Wire" Ultra-High Performance Headphone Amplifier - PCB's
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Old 13th February 2018, 06:21 PM   #2651
TypodCrow is offline TypodCrow
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@opc - I'm going to try to use this s a preamp going into a stax amp. The Stax amp has an input impedance of 50k.

Would you suggest any modifications/additions put behind a switch when using this in preamp mode into that sort of setup? i am exploring using either a constant gain and then the Stax amp volume pot for control vs the volume pot I already have on my Wire and leaving the stax amp at a reasonable constant gain.

I read online that with speaker amps, you usually want between 20-30 fold difference between the source's output impedance and the sink's input impedance. Can i just leave the stock impedance settings and use this safely + with full sound quality?
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Old 14th February 2018, 07:29 PM   #2652
TypodCrow is offline TypodCrow
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Also adding to the above question ^ I am listening to The Wire right now, and am noticing quite a bit of hum (sounds like AC noise), especially when the RCA on the back of the case are left floating. Any ideas for solutions? I still here the hum but it's much quieter when the RCA are wired to a dac.
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Old 16th February 2018, 07:00 PM   #2653
TypodCrow is offline TypodCrow
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Any thuoghts guys?

To summarize: I'm getting a lot of hum out of the amp on low impedance iem's. Occurs at all volume levels, getting louder as I increase volume.

Connecting the RCA out back to a DAC helps, but doesn't eliminate the hum. It feels like a grounding issue but I'm unsure of where it might be coming from.

Any help would be greatly appreciated.
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Old 16th February 2018, 08:42 PM   #2654
Detectit1 is offline Detectit1
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Could be a ground loop issue.

Here is a nice article with info to determine or not.

Ground Loops - Eliminating System Hum and Buzz | Audioholics
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Old 16th February 2018, 09:04 PM   #2655
TypodCrow is offline TypodCrow
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Alright well this would help to isolate the looping issue to the amp alone, am I correct? Ground loops arise when the ground of one component differs from the ground of another, thereby causing a hum defined by the difference between the two grounds?

The hum I'm getting is most prominent with no source attached whatsoever. Amp alone just hums as soon as I power it on. There shuold only be a single signal ground on the amp, which should be the amp's own signal ground. Hence my belief that this isn't a ground loop issue, but something else.

How would the absense of the rework defined here affect the performance of the amp (ie. if I had a rework/initial release board that hadn't been reworked, what would I expect to change compared to a correct board/reworked initial release board): "The Wire" Headphone Amp Build Wiki
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Old 21st February 2018, 07:13 AM   #2656
ulogin is offline ulogin
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Quote:
Originally Posted by TypodCrow View Post
Should I only expect optimal performance for a certain range of impedances? Or does is drive everything from sensitive IEM's to planar magnetics with the same quality?
I would like to know as well.

According to my friend, the "ability to drive down to 4 ohms with no load dependance" literally means the ability to drive sensitive headphones -- including BA-based in-ear-monitors -- without any hint of noise. He said if a built does not drive all in-ear-monitors -- and he has a few -- with a totally black ground, then it is no good.
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Old 21st February 2018, 07:20 AM   #2657
TypodCrow is offline TypodCrow
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Let's avoid the he - said she - said game here. My build I have purchased significantly hums with sensitive (anything less than or equal to 32ohms) gear, IEM's especially (since those are what I own that are more sensitive). Significant hum means that I cannot "drown out" the humming noise unless I crank my music to deafening levels, which are extremely unhealthy for listening. Other than that I can hear the noise loud enough on top of the music I'm playing.

With a heavier load (Mr. Speakers Alpha Prime, or an external amp plugged into the headphone out) I get almost no audible hum. It barely exists, but is drowned out by the audio

From what I understand about The Wire - and the numbers I've seen on The measurements - I should be hearing nothing at all, on both heavy loads and sensitive loads (greater than 8ohms at least) since the noise should be far below the audible range (at least -100db). Please correct me if in wrong.

Last edited by TypodCrow; 21st February 2018 at 07:27 AM.
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Old 21st February 2018, 02:10 PM   #2658
multisync is offline multisync  Canada
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I have a SE to SE version of the Wire. I have had it since the 1st version of the WIRE came out. I am using an external +/-15 volt, fet, series regulated power supply that I bought on ebay as a kit a few years ago. I use the head phone amp as a preamp with a voltage gain of 3x. The wire is powered on 24 hours a day. I listen to it almost every day. With my Sennheiser 598 head phones and the volume control at any position and all inputs disconnected I cannot hear any type of noise or hum with the wire powered on or off. There is absolutely no hum or hiss at all that I can hear. If you can hear hum or any type of noise you have a wiring problem, a grounding problem, a soldering problem, a component problem or perhaps a power supply problem. Try hooking the wire up with 2 nine volt batteries. If the hum goes away it may help you to isolate your issues. Is the hum 50/60 hz or 100/120hz?

The buffer chips in the wire can output 250 ma before current limiting cuts in. You can drive speakers with the wire headphone amp directly without danger of destroying the chips. I've done it. In fact I also have the wire's bigger brother, the wire power amp, 8 chips in parallel.
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Old 22nd February 2018, 04:59 AM   #2659
TypodCrow is offline TypodCrow
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Quote:
Originally Posted by multisync View Post
Is the hum 50/60 hz or 100/120hz?
The noise in 120hz (just checked against a generated tone on my phone). I've taken the amp apart. Here are some pictures.

The wire - Google Drive

It makes a little more hum every time I physically come in contact to the volume knob or heat sink or transformer. The build quality looks ok to me - PSU is running at +/-15v dc output. I will check the noise riding on the PSU DC output tomorrow with an oscilloscope if I can.

Is there anything in the build quality that leads you to think there might be a problem? I don't see anything jumping out at me.

Brown wires go to headphone out. White seems to be signal in and red/grey seem to be AC power from the wall. I've tried multiple outlets at home and work so I'm certain that it's not just my AC power input that's really REALLY noisy - it should be fairly clean.
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Old 22nd February 2018, 01:52 PM   #2660
multisync is offline multisync  Canada
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C32,C27,C23,C30 look a little suspect. I cant tell if they are actually soldered or cold solder joints or touching a nearby pad. More hum when touching a part usually means the part is not grounded. The shaft of the volume control is usually grounded through the metal case and there should be no hum when touching it. When you turn the Wire off is there a few seconds of silence before the filter capacitors discharge? Is the output voltage of the Wire buffer chips very close to 0 volts, within a few millivolts. Put your meter on the millivolt AC scale and measure the outputs of the power supply, again should be near 0Volts AC. Also check the AC power supply output voltage with different loads should be the same ie near 0VAC
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