[Shredicus]

So I got one of these bad boys as an upgrade from my Magni 3. There is a greater noise floor from the A-100 (it is an 8 Ohm output impedance after all) so I'm thinking of keeping my Magni 3 as a pre-amp to the A-100 (to help moderate the extreme volume potential of the A-100 from my computer) and then so I can use the Magni 3 with any lower-impedance headphones I come into. Does anyone know of any drawbacks to using the Magni 3 as a pre-amp to the A-100?

As for impressions; the difference in dynamics between the two is quite palpable -- after volume matching and quickly A/Bing between the two (while using the Magni 3 as a pre-amp -- not sure if that would skew the sound or not, I can't admit to telling a difference straight from source); on my K7xx, bass is much more authoritative, meatier, the Magni 3 sounds shallow in comparison. On my HD600 everything is cleaned up, instrument separation is stronger; on ruckus-y tracks where the snare would get lost on the Magni 3, it punches right through the noise on the A-100. On my Ether Flow C's, bass slaps haaard compared to the Magni 3, and the mids (my biggest beef with the Ether Flow C's is they sounded a little hollow) have much more body and weight to them.

I'm also considering selling my Magni 3 and EL DAC for a DAC/amp that can output RCA, so if anyone has any good suggestions for a product that fits that bill for around, I dunno, $250, it'd be much appreciated! (I was thinking, maybe the Aune X1s...)

Actually the with the jumpers installed output impedance is near zero according to Keith from Emotiva. It's 220ohms with the 220ohm resistors unbypassed.

 

[kdoof]

Actually the with the jumpers installed output impedance is near zero according to Keith from Emotiva. It's 220ohms with the 220ohm resistors unbypassed.

Ah, this is great to know! The box was missing the jumpers so I have to wait a bit to install them. Hopefully that's the case and I can sell off my Magni 3's and not worry about it.

 

[kdoof]

Actually the with the jumpers installed output impedance is near zero according to Keith from Emotiva. It's 220ohms with the 220ohm resistors unbypassed.

Where's he say this? I've been poking around but all I've seen is people reporting greater noise floor with the jumpers in, compared to without.

 

[Shredicus]

Where's he say this? I've been poking around but all I've seen is people reporting greater noise floor with the jumpers in, compared to without.

On page 16 of this thread:

https://www.head-fi.org/threads/emotiva-a-100.825970/page-16#post-14062849

Note that noise floor and output impedance are not directly correlated. Damping factor is determined by output impedance

 

[kdoof]

The A-100 started out as a small integrated amp for driving speakers (the original Mini-X A-100 didn;t even have a headphone output).
When it became clear that people were using "speaker amps" (including the A-100) to run certain low efficiency planar headphones...
As well as certain high impedance headphones that need a lot of voltage...
And that many people preferred the way a lot of vintage equipment sounded (running their headphones from the main outputs via dropping resistors)...
We made a few modifications to allow the A-100 to fulfill those particular requirements.

As I said, I don't have all the details yet, but the new amp is going to be more like a "traditional high-end headphone amp".
It will have quite a lot of power - but not as much as the A-100 (it won't be designed to handle speakers).
I expect it to have adjustable or selectable gain, balanced and unbalanced outputs, and be able to drive any current planars and high impedance phones really well.
It will also be quiet enough to drive high-efficiency IEMs (and normal headphones) very well.

(Most modern planar headphones, while they benefit from a powerful amplifier, don't require as much power as certain few early "super inefficient" models.)

Do you guys happen to have any idea as to approximate price point yet?

 

[kdoof]

On page 16 of this thread:

https://www.head-fi.org/threads/emotiva-a-100.825970/page-16#post-14062849

Note that noise floor and output impedance are not directly correlated. Damping factor is determined by output impedance

Interesting, thanks for hunting this down. Yeah so far I love the quality of the sound other than the noise floor, which is a bit high and detracts from the overall experience. Disappointing to hear that it'll get even higher with the jumpers in place.

 

[Th3Drizzl3]

The A-100 started out as a small integrated amp for driving speakers (the original Mini-X A-100 didn;t even have a headphone output).
When it became clear that people were using "speaker amps" (including the A-100) to run certain low efficiency planar headphones...
As well as certain high impedance headphones that need a lot of voltage...
And that many people preferred the way a lot of vintage equipment sounded (running their headphones from the main outputs via dropping resistors)...
We made a few modifications to allow the A-100 to fulfill those particular requirements.

As I said, I don't have all the details yet, but the new amp is going to be more like a "traditional high-end headphone amp".
It will have quite a lot of power - but not as much as the A-100 (it won't be designed to handle speakers).
I expect it to have adjustable or selectable gain, balanced and unbalanced outputs, and be able to drive any current planars and high impedance phones really well.
It will also be quiet enough to drive high-efficiency IEMs (and normal headphones) very well.

(Most modern planar headphones, while they benefit from a powerful amplifier, don't require as much power as certain few early "super inefficient" models.)

Count me in im!!! happy to buy a unit. love my a100 and im guessing it will be relegated to speaker use in the kids room or my other office it depends on the output power of the new model. please keep us posted

 

[KeithEmo]

The headphone output on the A-100 is derived from the main amplifier outputs.

With the jumpers OUT (the default), there is a dropping resistor between each output and your headphone.
With the jumpers IN, those resistors are bypassed.

This means that, in general, the noise floor will be slightly higher with the jumpers in place.
However, whether that difference is slight or noticeable depends on the particular characteristics of your phones.
There may also occasionally be very unusual situations where the opposite is true.
(I would expect the increase in noise to be more significant with lower impedance headphones that are also relatively high efficiency.)

On page 16 of this thread:

https://www.head-fi.org/threads/emotiva-a-100.825970/page-16#post-14062849

Note that noise floor and output impedance are not directly correlated. Damping factor is determined by output impedance

 

[lambdastorm]

Hey Keith,

Long time A100 user reporting in. Still pretty satisfied with what I get for $229 but I've got a new problem. A100 uses 2-prong power plug so technically it's not grounded. Not a problem for my HD600 and HD650, since as long as I turn the music up a bit it drowns out the slight hum. However my ABYSS hums loudly whenever I touch its aluminum frame. I suppose that has something to do with the headphone itself since its full aluminum construction makes the headphone conductive no matter where you touch it. But the day before yesterday I brought one of my friends over to let him try his HE6 on my A100 and to my bewilderment, HE6 hums too when I touch the headphone cup, and its not even metal, its plastic. The hum completely goes away when I put my hand on the amp, and goes back when I don't touch it.

At this point I think its a grounding issue which would be remedied by using a 'proper' 3-prong power plug.

 

[Shredicus]

Hey Keith,

Long time A100 user reporting in. Still pretty satisfied with what I get for $229 but I've got a new problem. A100 uses 2-prong power plug so technically it's not grounded. Not a problem for my HD600 and HD650, since as long as I turn the music up a bit it drowns out the slight hum. However my ABYSS hums loudly whenever I touch its aluminum frame. I suppose that has something to do with the headphone itself since its full aluminum construction makes the headphone conductive no matter where you touch it. But the day before yesterday I brought one of my friends over to let him try his HE6 on my A100 and to my bewilderment, HE6 hums too when I touch the headphone cup, and its not even metal, its plastic. The hum completely goes away when I put my hand on the amp, and goes back when I don't touch it.

At this point I think its a grounding issue which would be remedied by using a 'proper' 3-prong power plug.

Interesting. I wonder if something like this would realize any sort of improvements with this amp:
https://www.amazon.com/Pangea-Audio-AC-14-Powercord-Meter/dp/B0030ERI1W/

 

[KeithEmo]

The audio circuitry in the A-100 is grounded through the analog ground - the ground connection on the RCA connectors.
This arrangement provides excellent noise performance with most systems.

(The amplifier itself is fully insulated and does not require a power safety ground.)
The chassis is actually connected to the signal ground through a resistor... so that ground is sensitive to the ground provided by your source equipment.

However, depending on how your source equipment is grounded, you can end up in the situation you describe.
If so, you could try connecting a wire between the chassis of the A-100 and some other ground.
- you could try grounding the A-100's chassis to earth ground
- you could ground the A-100's chassis to the chassis of your source component
- you could try more securely grounding the chassis of your source component to Earth ground
None of these is specifically "the most right way to do it" - but any of them may reduce or eliminate your problem.

What's basically happening in your case is that the metal of the headphones is acting as an antenna - and picking up the hum field from the air.
In different situations, the hum could get better or worse when you touch the metal, and add your body to the antenna circuit.
(Presumably, deliberately or incidentally, the shell of the headphones is electrically connected to their ground wire, or to their signal line through a capacitor.)

Hey Keith,

Long time A100 user reporting in. Still pretty satisfied with what I get for $229 but I've got a new problem. A100 uses 2-prong power plug so technically it's not grounded. Not a problem for my HD600 and HD650, since as long as I turn the music up a bit it drowns out the slight hum. However my ABYSS hums loudly whenever I touch its aluminum frame. I suppose that has something to do with the headphone itself since its full aluminum construction makes the headphone conductive no matter where you touch it. But the day before yesterday I brought one of my friends over to let him try his HE6 on my A100 and to my bewilderment, HE6 hums too when I touch the headphone cup, and its not even metal, its plastic. The hum completely goes away when I put my hand on the amp, and goes back when I don't touch it.

At this point I think its a grounding issue which would be remedied by using a 'proper' 3-prong power plug.

 

[KeithEmo]

We're not big fans of expecting power cables to make our equipment sound different.

However, if you look at the back of the A-100, you will see that it has a standard two-wire IEC power inlet - so that one simply won't fit.

Interesting. I wonder if something like this would realize any sort of improvements with this amp:
https://www.amazon.com/Pangea-Audio-AC-14-Powercord-Meter/dp/B0030ERI1W/

 

[Shredicus]

We're not big fans of expecting power cables to make our equipment sound different.

However, if you look at the back of the A-100, you will see that it has a standard two-wire IEC power inlet - so that one simply won't fit.

Oops, linked the wrong one:
Pangea Audio - AC-14 - Power Cable 1.0 Meter - C7 https://www.amazon.com/dp/B003LYCZYG/ref=cm_sw_r_cp_apa_i_xQ-hBbVAR49H3

But I see your point. Cables are a pretty contentious thing in these circles

 

[lambdastorm]

The audio circuitry in the A-100 is grounded through the analog ground - the ground connection on the RCA connectors.
This arrangement provides excellent noise performance with most systems.

(The amplifier itself is fully insulated and does not require a power safety ground.)
The chassis is actually connected to the signal ground through a resistor... so that ground is sensitive to the ground provided by your source equipment.

However, depending on how your source equipment is grounded, you can end up in the situation you describe.
If so, you could try connecting a wire between the chassis of the A-100 and some other ground.
- you could try grounding the A-100's chassis to earth ground
- you could ground the A-100's chassis to the chassis of your source component
- you could try more securely grounding the chassis of your source component to Earth ground
None of these is specifically "the most right way to do it" - but any of them may reduce or eliminate your problem.

What's basically happening in your case is that the metal of the headphones is acting as an antenna - and picking up the hum field from the air.
In different situations, the hum could get better or worse when you touch the metal, and add your body to the antenna circuit.
(Presumably, deliberately or incidentally, the shell of the headphones is electrically connected to their ground wire, or to their signal line through a capacitor.)

Thanks a lot for the detailed response. I tried disconnecting the source gear today and my headphone still hums when I touch its shell, albeit not as loud. I'll take your advice and ground A100's chassis, as well as the DAC's chassis to earth ground.

I think both the A100 and the source gear are at fault here. Right now I'm using an ifi portable DAC and its clearly not grounded: Tried plugging my ABYSS in and it hums as well. I guess the designer doesn't have low-efficiency planars in mind when he designed this DAC, cuz IEMs with plastic shell have no such problem.

Right now I'm on a family trip outside the US, and the only cable I brought is the stock one. I've got a 14AWG 2-prong cable with floating ground back home. Will try that one once I get back.

And thanks again for all the support Keith, you never disappoint .

 

[garbulky]

Thanks a lot for the detailed response. I tried disconnecting the source gear today and my headphone still hums when I touch its shell, albeit not as loud. I'll take your advice and ground A100's chassis, as well as the DAC's chassis to earth ground.

I think both the A100 and the source gear are at fault here. Right now I'm using an ifi portable DAC and its clearly not grounded: Tried plugging my ABYSS in and it hums as well. I guess the designer doesn't have low-efficiency planars in mind when he designed this DAC, cuz IEMs with plastic shell have no such problem.

Right now I'm on a family trip outside the US, and the only cable I brought is the stock one. I've got a 14AWG 2-prong cable with floating ground back home. Will try that one once I get back.

And thanks again for all the support Keith, you never disappoint .

First if you have your A-100 with the resistors bypassed (jumpers engaged) then this is the wrong setting for high efficiency IEM.
As for the ground, have you tried the RCA ground loop isolator? They are between 7 and 10 bucks and are designed to get rid of of a ground loop buzz.
Search Amazon for ground loop isolator and youll find quite a bit
They look like this