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JDS Atom Amp+ Review (Headphone Amplifier)

Suppa92

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@jseaber is there any effect on what type(coax/twisted pair) of RCA cables used to connect atom amp+ with atom dac+?

I'm asking this based on a youtube video which describes it is better to use coax rca if the amp is single ended & if the amp is "differential" using a twisted pair RCA is better. video linked below

 

Labjr

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@jseaber is there any effect on what type(coax/twisted pair) of RCA cables used to connect atom amp+ with atom dac+?

I'm asking this based on a youtube video which describes it is better to use coax rca if the amp is single ended & if the amp is "differential" using a twisted pair RCA is better. video linked below


I never heard of this before today. It appears some car audio products use balanced over RCA. Seems rather confusing. Why not use XLR or TRS connectors? Far as I know Adam DAC+ is single-ended.
 

Suppa92

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I never heard of this before today. It appears some car audio products use balanced over RCA. Seems rather confusing. Why not use XLR or TRS connectors? Far as I know Adam DAC+ is single-ended.
I also didn't know this until today. But I think he doesn't say that is "Balanced" he calls it as "Differential".
AFAIK THX 789 amp is a "Differential" amplifier not a "Balanced" one.

If Atom amp+ is a single ended and not differential, then according to this video it's better to get a coax rca cable.
 

Labjr

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I also didn't know this until today. But I think he doesn't say that is "Balanced" he calls it as "Differential".

From what I've read, balanced signals have equal impedance to ground. And also doesn't have to be differential. But I've never seen one without the other.
 

JohnYang1997

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From what I've read, balanced signals have equal impedance to ground. And also doesn't have to be differential. But I've never seen one without the other.
For example condenser microphones with single ended amplifier built in can use two resistors one at signal one at ground then connect to the XLR cable. This is preferable because single ended topology is inherently less noisy.
Recommended RCA output connection of hypex and other balanced input only amplifiers is also similar to that. Only that the impedance is not identical but the idea is the same and can work wonders. The key for this type of connection is adding an extra wire connecting the grounds of the two devices.
 

Labjr

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For example condenser microphones with single ended amplifier built in can use two resistors one at signal one at ground then connect to the XLR cable. This is preferable because single ended topology is inherently less noisy.
Recommended RCA output connection of hypex and other balanced input only amplifiers is also similar to that. Only that the impedance is not identical but the idea is the same and can work wonders. The key for this type of connection is adding an extra wire connecting the grounds of the two devices.
I think I'd have to see the circuit to follow?
 

jseaber

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@Suppa92 I found the video you shared to cover the differences between balanced amplifiers and unbalanced amplifiers, the necessity of which was not discussed. The simplified schematics are a bit misleading. The inverting terminal of an unbalanced amp is not directly connected to ground, and RF noise is still injected into the + and - pins no matter what RCA cables one uses. RF rejection is strongly related to symmetry of the circuitry, especially at the IC level. Noise enters in the power supply cables and headphone cables also, not just the amplifier inputs!

But this is overthinking.

In most unbalanced setups for headphone equipment, no, there is no difference between coax and twisted RCA interconnects. Noise mitigation is possible in setups with large amounts of RF noise, however, induced RF noise is rarely correlated to the RCA input cables in headphone amp/DACs due to the use of low gain and short cable runs. Balanced XLR / TRS inputs are preferred in amplifier systems with long cable runs and/or high gain (speakers). Again, there are numerous entry points for RF noise in an amplifier: Headphone cable, power supply cable, interconnects, traces on the PCB, non-symmetry of circuitry and IC feedback.

Despite all of these considerations, the video has a spark of truth. A twisted RCA cable may achieve greater RF symmetry for a balanced input.

We use coax style RCA cables.
 

Suppa92

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@Suppa92 I found the video you shared to cover the differences between balanced amplifiers and unbalanced amplifiers, the necessity of which was not discussed. The simplified schematics are a bit misleading. The inverting terminal of an unbalanced amp is not directly connected to ground, and RF noise is still injected into the + and - pins no matter what RCA cables one uses. RF rejection is strongly related to symmetry of the circuitry, especially at the IC level. Noise enters in the power supply cables and headphone cables also, not just the amplifier inputs!

But this is overthinking.

In most unbalanced setups for headphone equipment, no, there is no difference between coax and twisted RCA interconnects. Noise mitigation is possible in setups with large amounts of RF noise, however, induced RF noise is rarely correlated to the RCA input cables in headphone amp/DACs due to the use of low gain and short cable runs. Balanced XLR / TRS inputs are preferred in amplifier systems with long cable runs and/or high gain (speakers). Again, there are numerous entry points for RF noise in an amplifier: Headphone cable, power supply cable, interconnects, traces on the PCB, non-symmetry of circuitry and IC feedback.

Despite all of these considerations, the video has a spark of truth. A twisted RCA cable may achieve greater RF symmetry for a balanced input.

We use coax style RCA cables.
:)Thank you so much for your valuable time. I'll also get a short coax RCA cable. ;)
 

catman

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This is a review and detailed measurements of the JDS Labs Atom Amp+ headphone amplifier. It was sent to me by the company and costs US $99. It was announced today.

An excellent review, and squares well with my own listening experience. I have the Atom Amp and DAC for a while and have always be struck by how much they hold ground against units that cost significantly more. Recently, I realized that I could deploy them for travel as well, as they are lightweight and compact (both fit together in a small travel pouch), and are small enough to be placed in my laptop bag or carryon. I can not imagine a better combination for listening to music whilst in a hotel room. Simply fantastic intrinsically, not just with reference to their price point, and they play with a range of headphones. I just invested in 220v bricks that the company sells, which makes this combination good to go around the world.

A big shout also to their customer service. They always respond to emails promptly and give the sense that even at a $ 99 level, they care for the customer.
 

MRC01

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Can it drive power-hungry planar magnetic headphones like Hifiman HE-560?
The short answer is yes.
The longer answer is you can figure this out from the HE-560 specs. It is rated at 45 ohms and 90 dB SPL for 1 mW. From Amir's measurements, the Atom+ can deliver about 6 V output cleanly into 45 ohms, which is about 800 mW. 10*log(.8/.001) = 29, so that's about 29 dB louder than 1 mW. That would drive the HE-560 to about 119 dB SPL, enough to rattle your ears off of your head.
 

Harvey

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The short answer is yes.
The longer answer is you can figure this out from the HE-560 specs. It is rated at 45 ohms and 90 dB SPL for 1 mW. From Amir's measurements, the Atom+ can deliver about 6 V output cleanly into 45 ohms, which is about 800 mW. 10*log(.8/.001) = 29, so that's about 29 dB louder than 1 mW. That would drive the HE-560 to about 119 dB SPL, enough to rattle your ears off of your head.
Thank you for your reply!
 

Jimbob54

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The short answer is yes.
The longer answer is you can figure this out from the HE-560 specs. It is rated at 45 ohms and 90 dB SPL for 1 mW. From Amir's measurements, the Atom+ can deliver about 6 V output cleanly into 45 ohms, which is about 800 mW. 10*log(.8/.001) = 29, so that's about 29 dB louder than 1 mW. That would drive the HE-560 to about 119 dB SPL, enough to rattle your ears off of your head.
On the assumption there isn't hefty eq in play.
 

MRC01

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On the assumption there isn't hefty eq in play.
True, yet an SPL ceiling of 119 dB leaves plenty of room for EQ. Of course, "hefty EQ" is a higher bar than regular old EQ; does 15-20 dB of excess headroom (conservatively rated, assuming someone wants to listen super loud) qualify as "hefty"?
 

Jimbob54

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True, yet an SPL ceiling of 119 dB leaves plenty of room for EQ. Of course, "hefty EQ" is a higher bar than regular old EQ; does 15-20 dB of excess headroom (conservatively rated, assuming someone wants to listen super loud) qualify as "hefty"?
Super hefty! Aka ludicrous.
 
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I've got the previous Atom, it's better than my headphones and my hearing. If that ever dies I'll gladly get this.
Same. Still works after well over a year or maybe even 2 now, so its built well. Channels are a bit uneven at low volume but its not a problem really. Listening to classical pieces is bliss.
 
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