[subtec]

From the Indiegogo comments section, there's this explanation:

Q: What is the maximum power output from the 3.5mm jack in milli-watts into 32 ohms headphones? I do not understand what 2x current means.

A: The 2x current mode is a kind of parallel bridged amplifier mode. EarStudio has two stereo DAC and integrated HP AMP, which means it has 4 output ports available. In the 1x current mode to 3.5mm jack, EarStudio activates only two of them, having the other two remained at idle. In the 2x current mode to 3.5mm jack, all four output ports are activated, being coupled two ports for L-ch, two ports for R-ch.

Each output port drive voltage up to 3.2 Vpp. Thus, for a 32-ohm unit, we can have 40mW/ch with EarStudio. In the 2x current mode, two output ports are bridged/combined to a single channel, we can get the output impedance lowered by half, and as a result, get the better damping factor and slew rate. Especially for a 16-ohm unit, current saturation degrades the linearity, and the 2x current mode gives us the better performance.

 

[jeffhawke]

From radsone: “For 3.5mm single-ended output, the DualDrive technology reduces the output impedance by half and gives twice much current than one single AK4375a can deliver. For 2.5mm full- differential output, the voltage is increased by twice“

From akm: “Output Power: 25mW @ 32ohm, 40mW @ 16ohm”

Would be nice to know what the output impedance is though. And besides, 25mW into 32ohm is still 25mW into 32ohm, so even if you double that (50mW) it's not nearly enough to drive 250ohm cans like the DT1770.

 

[notyourtree]

WS[/QUOTE]

Quote (notyourtree): I also saw the warning about disconnecting the cable while media is playing potentially damaging the equipment

What? are they serious?

Wow that's pretty shocking. Of all the things you can expect are almost certain to happen at some point, pulling the cable out while it's playing is pretty high up there.

@notyourtree:

Hello, I'm WS, Technical Director of Radsone.
At first, sorry for the inconvenience.

As you pointed out, the warning message is popped up, when you plug/unplug 3.5mm jack while listening any music.

Every 2.5/3.5 dual output device has switching IC between Amplifier out and 2.5/3.5 connector.
But, Semiconductor switching IC is not ideal and degrades signal quality.

But, ES100 has NO switching IC between Amplifier out and 2.5/3.5 connector. Amplifier output signal goes to the connector directly without any loss.
Furthermore, +/- differential output is bridged together by inverting polarity +/+ to 3.5mm output.
In that way, ES100 can provide better sound quality than XB10, as you agreed.

For your information, XB10 use those switching IC for routing to 2.5/3.5 output connector.
And For 3.5mm output, XB10 uses only the half of the amplifier resource, while ES100 uses full of them.

For more information, please refer the technical documentation on our Dual Drive Technology:
http://radsone.com/radsone-home/whitepapers/EarStudio_DualDrive.pdf

Anyway, this is the reason why we add the warning message just in case.

Also when you go to Audio Output Mode and lock the audio output, then it's 100% safe, and you can plug/unplug at any time.

It's tricky but is the design choice for the better audio quality.

Hope this helps you.

Regards
WS

@notyourtree:

BTW,
you mentioned only the right channel of 2.5mm output is dead, but it's quite strange I think.

ES100 has two DAC, one for the left, one for the right. If the DAC/AMP for the R-ch is dead
and no signal out from 2.5mm R-ch, then
3.5mm R-ch should also be gone. But you mentioned 3.5mm output still works fine.
I'd like to help you figure out the issue.
Please feel free to contact us.
support@radsone.com

Thanks a lot.
WS

Thank you for your quick and informative response, WS! Apologies that I haven't jumped back on here sooner to follow up with my experiences, BUT the good news is that my 2.5mm balanced connection is working again. I used the 3.5mm port for a while after the incident, and I then tried locking the connection as WS suggested before trying the 2.5mm connection again. I didn't think to perform a test before that, so I can't confirm it was the lock or perhaps the unit just needed to "recover."
Overall I'm very happy with the device and the sound quality. The voice quality has been excellent too; nobody's complained when I've been on a call. Battery life seems better than initial experience too. I still haven't been able to install the firmware update, but I just received a new laptop and will try again soon. The equalizer has been a nice option when using my JH16s, and it actually works to reduce the bass without impacting the other frequencies across the spectrum. I do wish that there was an easier way to control the ambient mode as others have requested, perhaps a widget in the next app release or a button configuration via the firmware? I do wish the play button was positioned elsewhere given that I'm using the 2.5mm connection, but I wouldn't be surprised if design decisions had to be made to account for the unit holistically. It would be nice to mute the firmware update message too -- it pops up every time I open the app.
I do receive many questions about the ES100, so hopefully you will have a bunch of new orders from Seattle when they're available for sale!

 

[waynes world]

I do receive many questions about the ES100, so hopefully you will have a bunch of new orders from Seattle and Canada when they're available for sale!

Fixed that for ya!

 

[wslee]

Unless the product is released to the general public, there isn't too much to talk about I guess. I have a question though: what is the output power? I read on one early review that it's 25mW into 32ohm, which appears to be very low indeed. Then, in a later review on Majorhifi http://majorhifi.com/radsone-earstudio-24-bit-hi-res-bluetooth-receiver-review/ the reviewer claims to have tested it with Beyer's DT1770 (250ohm) and the results were, in his words, quite good. If the Earstudio puts out 25mw into 32ohm, how can it drive 250ohm cans and still sound "quite good"? So, I'm confused as to the actual output of this product. The web page does not indicate the power output in the specs.

You're right.
ES100 3.5mm single-ended output may not able to give you enough loudness with 250-ohm or 300-ohm unit.
For high impedance unit, we highly recommend using 2.5mm balanced output since it provides 2x voltage output up to 6.4Vpp.

The reviewer from MajorHifi just tested ES100 during AES conference in New York last year and asked me a sample for the review.
(No reward or payment has been made for the review.) He wrote it with his own will.

I didn't try DT1770 by myself.
But as I checked the DT1770 pro specification,

https://europe.beyerdynamic.com/amfile/file/download/file_id/3864/product_id/3871/

It provides nominal SPL(Sound Pressure Level) 102dB, with 1mWatt amplifier output.
ES100 can deliver up to 4mWatt output power to 250 ~300 Ohm unit.
That means:
ES100 with DS1770 can give you the loudness level up to 107 dB SPL.

According to the Figure #2 on web page below,

http://www.shure.com/americas/support/find-an-answer/understanding-earphone-headphone-specifications

I guess 107 dB SPL might be OK; It's not too loud and not too small, but just OK.

Furthermore, as I measure the performance using Audio Precision,
ES100 achieves 91dB THD+N at 300-Ohm 4mWatt, while Astell & Kern AK70 delivers 85dB THD+N in the same condition.

Assuming you listen to 16-bit CD quality source audio and 107 dB SPL is enough,
I guess ES100 would provide the better sound quality than AK70 or mobile phone.

Hope this helps you.

Thanks and Regards,
WS

 

[zolom]

Any news about orders launch date?

 

[Raketen]

"0.5dB step with EarStudio mobile application and 2dB step with EarStudio HW buttons"

Is this in the final product? If so, a little disappointing- for me the most appealing feature is the discrete volume control (which a surprising number of BT receivers lack), because most android phones have terrible volume control with large increments. IMO it would be much better for the HW buttons to have the 0.5 increment with a bigger step from long press (or button hold with accelerated increase like a lot of DAP use).

Other than that this looks pretty close to my ideal for a bluetooth reciever which I have avoided to date- particularly appreciate the Sansa Clip-esque design.

 

[jeffhawke]

You're right.
ES100 3.5mm single-ended output may not able to give you enough loudness with 250-ohm or 300-ohm unit.
For high impedance unit, we highly recommend using 2.5mm balanced output since it provides 2x voltage output up to 6.4Vpp.

The reviewer from MajorHifi just tested ES100 during AES conference in New York last year and asked me a sample for the review.
(No reward or payment has been made for the review.) He wrote it with his own will.

I didn't try DT1770 by myself.
But as I checked the DT1770 pro specification,

https://europe.beyerdynamic.com/amfile/file/download/file_id/3864/product_id/3871/

It provides nominal SPL(Sound Pressure Level) 102dB, with 1mWatt amplifier output.
ES100 can deliver up to 4mWatt output power to 250 ~300 Ohm unit.
That means:
ES100 with DS1770 can give you the loudness level up to 107 dB SPL.

According to the Figure #2 on web page below,

http://www.shure.com/americas/support/find-an-answer/understanding-earphone-headphone-specifications

I guess 107 dB SPL might be OK; It's not too loud and not too small, but just OK.

Furthermore, as I measure the performance using Audio Precision,
ES100 achieves 91dB THD+N at 300-Ohm 4mWatt, while Astell & Kern AK70 delivers 85dB THD+N in the same condition.

Assuming you listen to 16-bit CD quality source audio and 107 dB SPL is enough,
I guess ES100 would provide the better sound quality than AK70 or mobile phone.

Hope this helps you.

Thanks and Regards,
WS

Thank you for your exhaustive reply. What's the output impedance of the ES100? I will have to give it a try myself. Where and when could I buy one? Thanks again.

 

[wslee]

"0.5dB step with EarStudio mobile application and 2dB step with EarStudio HW buttons"

Is this in the final product? If so, a little disappointing- for me the most appealing feature is the discrete volume control (which a surprising number of BT receivers lack), because most android phones have terrible volume control with large increments. IMO it would be much better for the HW buttons to have the 0.5 increment with a bigger step from long press (or button hold with accelerated increase like a lot of DAP use).

Other than that this looks pretty close to my ideal for a bluetooth reciever which I have avoided to date- particularly appreciate the Sansa Clip-esque design.

Thanks for the input and I agree with you.
We're preparing the next F/W update and will update the feature as you requested.

BTW, please keep that always in your mind that Android phone volume control with any Bluetooth device is always performed before BT audio encoder.
Thus, you will get considerable loss in audio quality when adjusting the volume on the phone.
Setting the volume on the phone at the maximum (0 dBFS) and adjusting ES100 analog volume would give you the best audio quality.

Thanks and Regards,
WS

 

[wslee]

Thank you for your exhaustive reply. What's the output impedance of the ES100? I will have to give it a try myself. Where and when could I buy one? Thanks again.

ES100 archives output impedance around 1-Ohm.

As you may know,
the voltage at the load unit is as below:

V-load = V-out x Z-load / (Z-load + Z-out)

where, the V-out = output voltage with no load.

For the 16-ohm unit,
you will get 16/(16+Z-out) of the V-out.
The lower Z-out is absolutely better.

However, for the 250-ohm unit,
you will get 250/(250+Z-out) of the V-out.
In this case, the output impedance is not that much critical.

And the output impedance itself does not have any meaning without V-out.

Below two examples would give you the same sonic performance.

V-out (3.2) x 16/(16+ Z-out 1) = 3.2 x 16/17 = 3.01 V
V-out (4.0) x 16/(16+ Z-out 5) = 3.2 x 16/21 = 3.04 V

No difference other than the later consumes more battery power.

Anyway, hope this helps you when you choose an amplifier for your preferred headphone unit.

Thanks and Regards,
WS

 

[jeffhawke]

ES100 archives output impedance around 1-Ohm.

As you may know,
the voltage at the load unit is as below:

V-load = V-out x Z-load / (Z-load + Z-out)

where, the V-out = output voltage with no load.

For the 16-ohm unit,
you will get 16/(16+Z-out) of the V-out.
The lower Z-out is absolutely better.

However, for the 250-ohm unit,
you will get 250/(250+Z-out) of the V-out.
In this case, the output impedance is not that much critical.

And the output impedance itself does not have any meaning without V-out.

Below two examples would give you the same sonic performance.

V-out (3.2) x 16/(16+ Z-out 1) = 3.2 x 16/17 = 3.01 V
V-out (4.0) x 16/(16+ Z-out 5) = 3.2 x 16/21 = 3.04 V

No difference other than the later consumes more battery power.

Anyway, hope this helps you when you choose an amplifier for your preferred headphone unit.

Thanks and Regards,
WS

Again, a very comprehensive and comprehensible reply: you should start a thread on output impedance, it's a hot topic these days .
You did not reply to my other question though : where and when could I buy one?
Cheers

 

[meinname123]

Thanks for the input and I agree with you.
BTW, please keep that always in your mind that Android phone volume control with any Bluetooth device is always performed before BT audio encoder.
Thus, you will get considerable loss in audio quality when adjusting the volume on the phone.
Setting the volume on the phone at the maximum (0 dBFS) and adjusting ES100 analog volume would give you the best audio quality.

Would it be possible to add a option to the app like "lock phone volume at max" ?
It should set and maybe lock (periodically recheck and set) the Phone/Source Volume to the max. Level if Earstudio is connected or if it is playing music

 

[Cane]

@shrisha:

For your information,
SBC codec (mandate) is free to use for any Bluetooth device. (No license fee)

aptX, aptX-HD belong to Qualcomm CSR.
Qualcomm, formerly CSR, has been releasing the aptX encoder for FREE. NO license fee.
That means every mobile phone as a Bluetooth source device needs to pay nothing for aptX encoder.
(In my opinion, that's the primary reason why every Android device supports aptX.)

In the meantime, Qualcomm CSR makes the revenue in Bluetooth sink device.
Every Bluetooth sink device, receiver, headphone, speaker, need to use Qualcomm CSR chipset solution, to support aptX or aptX-HD decoder.
Broadcom, Texas Instruments, and other Bluetooth chipset makers can't support aptX because it belongs to CSR.
Plus, we need to pay the license fee for aptX decoder per every unit.

Per every ES100 unit, we need to pay CSR8675 chipset + aptX/aptX-HD license fee to Qualcomm CSR.
(+AAC license fee to MPEG)

It seems that Sony has the same policy.
LDAC encoder is free for any source device, but LDAC decoder isn't free.
Technically, we're ready to support LDAC by F/W update based on current ES100 H/W.
But, we need to pay the additional license fee to SONY.

At the beginning of ES100 development, we've seriously considered supporting LDAC,
but we've ended up the decision that we hardly can afford the license fee assuming the current retail price of ES100.

Your kind understanding would be appreciated.

Hope this answers you.

Regard,
WS

How about adding a option for the end user to pay for the function, if they need/want it?
Pay, and unlock the extra feature via F/W update.

 

[xatnys]

Has anyone done any AB testing between aptX HD and LDAC? LDAC has a higher overall bitrate, but what if aptX HD has a codec that's efficient enough to retain quality at moderate (~300-600kbps) bitrate? Might be enough perhaps.

 

[wslee]

Would it be possible to add a option to the app like "lock phone volume at max" ?
It should set and maybe lock (periodically recheck and set) the Phone/Source Volume to the max. Level if Earstudio is connected or if it is playing music

Basically, Bluetooth AVRCP(A/V Remote Control Profile) provides an option to synchronize volume between mobile phone and receiver via Absolute Volume control.
That is:
The source device(i.e., Mobile phone) can set the sink device(i.e., receiver) HW volume
and the sink device can notify any volume change on it to the source device back and forth.
In that way, the volumes of the source and the sink can be synchronized.

However, it's a design choice for the mobile phone and the receiver to support the volume synchronization.
If both the mobile phone and the receiver support volume synchronization,
then the mobile phone remotely controls the receiver's HW volume while transmitting source audio at 0 dBFS(Full Scale) always.

iOS and OS X support the volume synchronization.
So it depends on the receiver.
If the receiver supports the volume synchronization, Apple device always transmits the audio at 0 dBFS over Bluetooth.
iPhone just remotely controls the receiver's HW volume.
And any volume changes by the receiver's vol+/- button are notified to iPhone and eventually displayed in iPhone volume popup.
In that way, iOS always keeps the maximum quality as best as AAC encoder can perform across any volume levels.
It's the easiest and safe way to keep the sound quality over Bluetooth as best as possible.
Apple Bluetooth Accessory Design Guideline recommends Bluetooth receiver supports the volume synchronization for Apple device.
(There are some other design considerations like this which make iOS Bluetooth better than Android.)

However, there's one drawback.
Since iPhone volume step is limited, the fine control of the volume is not possible.
That's the primary reason why ES100 does not support the volume synchronization with iOS.
(As I mentioned, the volume synchronization with iOS depends on the receiver.)

In the meanwhile, Android OS does NOT support the volume synchronization.
No receiver can support the volume synchronization with Android.
Android always scales the PCM down before the Bluetooth encoder, when adjusting Bluetooth volume.
Android Users need to keep that in their mind all the way.

The rule of thumb:

For Android, set the mobile phone volume to the maximum with any Bluetooth receiver.

For iOS, if Bluetooth receiver vol +/- button actions result on iPhone volume popup consequently,
then the receivers supports the volume synchronization.
You don't need to care anything about that.
If not, the receiver doesn't support the volume synchronization,
and you need to set the iPhone volume to the maximum.

Hope this helps you.

Thanks and Regards,
WS