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New Leckerton UHA760 Coming Soon!!

post #1 of 97
Thread Starter 

"

The UHA760 USB DAC and amplifier combo features digital upsampling to 192 kHz, digital volume control, crossfeed, and a three-position gain selector. The UHA760 can be powered by USB or by its internal rechargeable battery.

The UHA760 uses an asynchronous sample rate converter (ASRC) to upsample the USB audio stream to 192 kHz.* The output side of the ASRC is clocked by a stable, low-jitter crystal oscillator. This has the effect of decoupling the jitter which exists on the streaming USB audio signal, resulting in a cleaner and more stable digital signal to the DAC. The ASRC also has the effect of pushing the high-frequency image signals (inherent to all DACs) away from the audio band. This allows the DAC chip to use a gentler low-pass filter which, in turn, avoids the pre-ringing (or pre-echo) resulting from the steep low-pass filters commonly used at lower sample rates such as 44.1 kHz or 48 kHz.

The digital volume control provides a stable and centered stereo image across the entire volume adjustment range, even at the lowest settings. Adjustment steps are 1 dB.

The crossfeed function feeds a delayed and filtered version of the sound in each channel to the opposite ear, mimicking the way we hear sounds in a natural acoustic environment. This helps to reduce the fatigue and unnaturalness produced by some headphones, especially on recordings with wide stereo separation. The crossfeed feature allows three settings: high, low, and bypassed.

Like the UHA-6S MKII, the UHA760 includes a charge enable switch. When disabled, the UHA760 operates entirely from its internal battery, enabling use with tablets and other devices which limit USB output power."

 

I was looking to buy my 3rd Uha-6.MKII , yes the 3rd one just keep coming back to this great amp, and i saw this in the product list, This company indeed got one of the best amplifiers if not the best for its price, got to like the fact that there is 3 gains options, maybe it is due a lot of us CIEMs owners asking neck to lower the gain for UM Miracle etc, seems like neck decided to add this new gain option to avoid making people lose money and time wasted to adjust their MK II, nice idea indeed. 


Edited by Shini44 - 9/4/13 at 7:12am
post #2 of 97
That is cool news. Is there any more information on the internals?
post #3 of 97
Thread Starter 

non so far :P i thought that people knew about that product, but there were no posts about it so i made one, i want to get one :< was about to buy the Uha again but i think i will wait for few weeks to hear more about this one. 

post #4 of 97
Quote:
Originally Posted by Shini44 View Post

non so far :P i thought that people knew about that product, but there were no posts about it so i made one, i want to get one :< was about to buy the Uha again but i think i will wait for few weeks to hear more about this one. 

I will wait for a review and for the price. Last time with UHA6, I was pretty much hyped up, till the price gave me a cold shower.

I think the main feature, that makes this one interesting is its crossfeed.
post #5 of 97
Thread Starter 
Quote:
Originally Posted by RAFA View Post


I will wait for a review and for the price. Last time with UHA6, I was pretty much hyped up, till the price gave me a cold shower.

I think the main feature, that makes this one interesting is its crossfeed.

will for me the Uha 6 MKII is really really good, the Uha 6 was kind of a fail so you were more like a victim :P yet feel free to check  project86's review on the MKII, he is one of the best reviewers on the site. 

post #6 of 97

I'm very interested in this. I just recently picked up a 6S.MKII and I'm very happy with it.  But if the new 760 is even better, I might just have to pick up one of them, as well.

post #7 of 97
An e-mail that went out today regarding the 760:

The new UHA760 Upsampling USB DAC and Amplifier will be shipping this fall
I'm excited to share some new information about the upcoming UHA760 Upsampling USB DAC and Amplifier combo. I'm currently working on a few final design tweaks of the pre-production model. As soon as I have everything to my liking, I'll be starting up production, with the first units expected to ship later this fall.

I do a lot of my listening over USB using source material sampled at 44.1 kHz (like my CD collection, Spotify streaming, etc). With the UHA760, my goal is to provide a high-end amp geared for that type of use. I've included an asynchronous upsampler because this enables some improvements to the digital-to-analog conversion process. I've incorporated digital volume control and a three-position gain adjustment because it allows precise control of the volume setting and guarantees channel matching even at the lowest volume setting (great for sensitive IEMs!). I've included a two-position crossfeed control with bypass, handy for reducing listener fatigue on recordings with hard panning or excessive stereo separation.

For more information on the features mentioned here and some additional enhancements you can expect to see on the UHA760, take a look at my recent blog post:
http://www.leckertonaudio.com/blog/2013/10/a-look-at-the-new-uha760-upsampling-usb-dac-and-amp

The UHA760 will be regularly priced at $439, and I will be offering a special, limited-time introductory price of $379. Details of that sale will be made available on the website and on this email list.

Nick
Leckerton Audio, Inc.
www.leckertonaudio.com
post #8 of 97
Quote:
Originally Posted by Shini44 View Post

non so far :P i thought that people knew about that product, but there were no posts about it so i made one, i want to get one :< was about to buy the Uha again but i think i will wait for few weeks to hear more about this one. 

As theGrobe mentioned above, news is out. Can you please add Nick's blog description which is quite detailed and informative about the amp, here is the info:

A look at the upcoming UHA760 USB DAC and Amp

Here's a look at my latest design, the UHA760. My goal with this model is to provide a high-end USB DAC and amplifier combo geared for those who, like me, listen mostly to source material recorded at 44.1-kHz (ripped CDs, Spotify, etc). The UHA760 can handle USB audio rates up to 16-bit/48-kHz. It includes an asynchronous sample rate converter (ASRC) which upsamples the digital audio to 192-kHz. The upsampling process, while not intended to create or replace audio signal content, does have some nifty benefits: because it is an asynchronous process, it isolates the DAC chip from jitter on the USB interface; it also shifts the digital filter in the DAC away from the audio band, allowing for a higher performance external filter. In addition to the ASRC, the UHA760 includes digital volume control and adjustable crossfeed with bypass.

Asynchronous Upsampling

There are numerous DAC designs on the market with upsampling capability, but it's not always clear what upsampling is or why it might be desirable. The upsampling process creates interpolated digital audio samples which sort of "fill in" the space between the original samples. Suppose the original sample rate is 48 kHz. The output of the SRC, running at 192 kHz, would have four samples for every one sample in the input signal.

Although it may seem counterintuitive, the ASRC is not actually creating signal content or replacing anything lost along the way. A digital audio signal at 44.1 kHz can only contain frequencies up to about 22 kHz. After upsampling this signal to 192 kHz, it still only contains frequencies up to 22 kHz. Nothing is added. So why bother? The benefits, it turns out, are a bit more indirect.

USB Jitter Isolation

The first benefit is isolation from USB interface jitter. The USB data stream can be jittery, meaning the digital bits don't arrive at an exact, fixed rate. The edge of a data bit can arrive slightly early or slightly late, depending on when the host (i.e., the computer) sends it. Normally this wouldn't affect the actual audio signal content - as long as the USB interface chip can determine whether the bit is a 1 or a 0, there's nothing lost. And there's usually plenty of margin to accomplish this with practically no errors. The trouble occurs when the jittery USB data stream is used to generate the clock signals that are needed by the DAC. This is how the jitter can get translated into something potentially audible, such as increased distortion. Using an asynchronous SRC means the clock signals for the DAC don't need to be derived from the USB data stream. Instead, the clock signals are generated by an on-board crystal oscillator which has very low jitter and is very stable. This prevents any jitter on the USB interface from having an effect on the digital-to-analog conversion.

Improved Digital Filter Response

The second benefit has to do with something called an interpolation filter. This is a digital filter which comes into play whenever a digital signal is upsampled. Upsampling creates unwanted, high-frequency signals, and the job of the interpolation filter is to remove these signals. This filter is present not only in the sample rate converter chip, but also in the DAC chip itself. Most modern DAC chips use a technique called sigma-delta modulation, and this involves upsampling the digital signal to a very high sample rate, usually somewhere between 1 and 6 MHz. The interpolation filter in the DAC chip removes anything higher than about half of the sample rate, while ideally leaving everything in the audio band untouched. So if we start with a digital signal at 44.1 kHz, the interpolation filter must let through audio at 20 kHz while removing everything above about 22 kHz. This requires a steep filter, and the more processing power given to this filter, the better job it can do. The approach taken by some high-end DAC manufacturers these days is to run the DAC chip at a high sample rate and let some other, more powerful processor handle the steep filtering. Running the DAC chip at 192 kHz means its interpolation filter can be configured to have a high cut-off frequency and a very gentle (i.e., non-steep) roll-off. This essentially pushes the effects of the filter away from the audio band.

The UHA760 uses the CS8422 ASRC chip from Cirrus Logic. The interpolation filter in this chip has some advantages over the filter in the CS4398 DAC chip. The CS8422 filter has almost no pre-ringing in the impulse response, for example. The debate over this is ongoing, but DAC designers suspect that pre-ringing can have negative audible effects because it produces a sort of "time smear". Pre-ringing generally does not occur in nature, so it sounds especially strange to our ears. In addition to minimal pre-ringing, the CS8422 also provides near-constant group delay across the audio band, meaning that all frequencies are delayed almost equally through the filter.

Digital Volume Control

The advantage of the digital volume control is that it provides excellent channel-to-channel level matching, better than almost any analog potentiometer. Even a high-quality analog pot can exhibit some channel level mismatch at the ends of the adjustment range (near minimum volume, for example). The digital volume chip in the UHA760 guarantees channel-to-channel matching within +/-0.5 dB at all settings, even minimum and maximum volume settings. My lab measurements show the performance is typically even much better than that. What this all means is that the stereo image in your phones remains stable and centered as you adjust the volume, even if you are using high-sensitivity IEMs which require relatively low levels to drive.

An analog potentiometer is used as the control mechanism on the UHA760, but instead of connecting directly to the amplifier circuitry, the potentiometer provides a signal to the microcontroller which is then converted into the control signal for the digital volume chip.

Some users of the UHA-6S.MKII have commented that the volume knob is a bit too easy to turn, sometimes resulting in unintentional adjustments when the amp is in a pocket or bag. The UHA760 uses a smaller knob and a potentiometer with higher physical resistance, and this should help reduce the chance of an accidental adjustment.

Crossfeed

The crossfeed in the UHA760 is an analog type, very similar in design and performance to the crossfeed in the UHA-4. The UHA760 offers two levels of crossfeed along with a true bypass.

Improvements to Power Supply and Turn-On Pop

The UHA760 has some additional circuitry improvements over the UHA-6S.MKII. The UHA760 includes an improved power supply design with better regulation and lower noise. Along with an increase in total power supply capacitance, this new design provides supply voltages to the audio amplifier circuitry which are more stable and less susceptible to ripple caused by high-amplitude transients in the audio signal.

Just prior to the headphone jack of the UHA760 is a mechanical relay. This relay opens automatically during turn-on and turn-off, preventing pops or clicks at the headphones when flipping the power switch.

Available This Fall

I'm currently working on performance characterization of the pre-production version of the UHA760. At this point, all the kinks have been worked out, and the amp is just about ready to begin production. The amp will be available to purchase later this fall. The regular price will be $439. I will be offering a limited-time introductory price of $379.

Following the UHA760

The UHA760 lacks S/PDIF optical and coax inputs, and this is mostly due to a lack of room on the circuit board for the connectors. I know these types of inputs are useful for a lot of folks, so I'm planning a model based on the UHA760 which will be a bit larger in size but will also include S/PDIF inputs, a DAC line output, and socketed op-amps. Support for 24-bit/192-kHz USB streaming is another feature you can expect to see soon.
Edited by musicheaven - 10/6/13 at 4:07am
post #9 of 97

Get hyped! Nick might consider trade in program as well!

post #10 of 97

So expensive...a big jump in cost from their current amps.  We'll have to see if the improvements are worth it...

post #11 of 97

The crossfeed is very interesting combined with the digital volume control. I would like to see a version without the DAC.

 

Worth monitoring...

post #12 of 97
Quote:
Originally Posted by cooperpwc View Post

The crossfeed is very interesting combined with the digital volume control. I would like to see a version without the DAC.

Worth monitoring...

I was thinking the same, it might be even smaller and perfect.
post #13 of 97

Three position gain switch, digital volume control, crossfeed. I think these address many of the usability issues us UHS-6S.MKII users have with the amp/dac. I emailed Nick with a few questions about the UHA760 and I thought I'd share his responses here, hope he doesn't mind.

 

Quote:
1) That is correct, the UHA760 does not include socketed op-amps due

to space limitations on the circuit board. The next model I mentioned
will be slightly larger in order to accommodate socketed op-amps and
the additional input/output. The UHA760 has an amplifier circuit which
is very similar in design to the UHA-6S.MKII. There are some
improvements to the power supply circuitry which I believe improve the
performance of the amplifier.

 

2) For some of my customers using sensitive IEMs, I have been offering
a gain reduction of 12 dB, and that seems to work great for the
UHA-6S.MKII. The challenge there is reducing the gain enough so that
the user can turn the volume high enough to get past the point where
there might be channel imbalance. The UHA760 is well balanced across
the entire pot because it is digitally controlled. Having the -12 dB
gain setting also maximizes the usable volume adjustment range because
it prevents the output from getting too loud too quickly.

 

3) I have been considering a trade-in program, but I don't have any
details to give yet.

 

4) I'll release whatever details I can about future products, but keep
in mind those details might change as I develop the design.


Edited by yaluen - 11/7/13 at 10:46pm
post #14 of 97
Quote:
Originally Posted by yaluen View Post

Three position gain switch, digital volume control, crossfeed. I think these address many of the usability issues us UHS-6S.MKII users have with the amp/dac. I emailed Nick with a few questions about the UHA760 and I thought I'd share his responses here, hope he doesn't mind.

Thanks truly appreciate your convo with Nick.

I am waiting for the full blown UHA 760 with coax in. As far as DAC connectivity with the USB world, I am not that anxious for an implementation of it. I got other amps I can use for that specific purpose, no need to add to the otherwise crowded collection.

Now crossfeed is definitively interesting but what steals the show is digital volume control, I can't go in bed without a good amp with digital control because you want to listen to a very low music level without channel imbalance else your left brain will ask what are you listening to while the right brain is sleeping biggrin.gif
Edited by musicheaven - 11/6/13 at 9:22am
post #15 of 97

Yeah, the new gain switch plus digital volume control is a great boon for low level listening, very nice indeed.

 

Looking at the UHA760 product page, it seems it has been updated by Nick, I've copypasted the additions here.

 

Of note:

  • Default gain values of -12dB/0dB/+12dB (0.25x/1x/4x)
  • AD8610 output opamps
  • +/-7 VDC voltage rails (vs +/-6 VDC on the UHA-6S.MKII)
  • Battery life of 12 hours, analog input; 6 hours, USB input (vs >30 hours typical, analog input; >10 hours typical, S/PDIF input on the UHA-6S.MKII. I guess battery size was sacrificed in favour of more room on the board for features)

 

Features:

Asynchronous upsampling to 192 kHz. Upsampling provides isolation from jitter on the USB interface; it also shifts the digital filter in the DAC away from the audio band, allowing for a higher performance external filter.

High-performance Cirrus Logic DAC. The CS4398, Cirrus Logic’s flagship digital-to-analog converter, is a long-time favorite of audio enthusiasts due to its exceptional performance and audio quality.

Digitally-controlled volume. Volume adjustment is controlled digitally in 1-dB steps, with excellent channel-to-channel level matching across the entire volume adjustment range.

Three-position gain control. Optimize the volume range for your headphones or earphones by choosing from three gain settings.

Adjustable crossfeed with bypass. The crossfeed circuit sends a delayed and filtered version of the sound to the opposite ear, mimicking the way we hear in a real acoustic environment. This reduces the unnatural sound which can occur with heavily-panned recordings.

True ground audio reference. With bipolar voltage rails at +/-7 VDC, there is no need for an output ground buffer which can cause additional output distortion and other audio artifacts. This also allows the UHA760 to be used as a low-noise DAC/preamp into a line input such as an A/V receiver. Additionally, there are no DC-blocking capacitors in the signal path, which can cause harmonic distortion.

Advanced battery management. Use any high-power USB port or USB charger accessory to charge the UHA760. When charging is disabled via the rear-panel switch, the UHA760 operates entirely from its internal battery. The front-panel power LED indicates low-battery status. The UHA760 is compatible with most standard 5V USB wall chargers.

Plug and Play USB operation. The UHA760 uses the standard USB audio drivers which are included in Windows and Mac operating systems.

 

Specifications:
  • Max output power (1% THD, 1 kHz):
    •     30 mW into 16 ohms
    •     55 mW into 32 ohms
    •     100 mW into 62 ohms
    •     125 mW into 100 ohms
    •     55 mW into 300 ohms
  • THD+N (1 kHz, USB input, 20 Hz to 22 kHz bandwidth, no weighting):
    •     16 ohms
      •         1 mW: 0.0040%
      •         10 mW: 0.0033%
    •     32 ohms
      •         1 mW: 0.0027%
      •         10 mW: 0.0042%
      •         30 mW: 0.0078%
    •     62 ohms
      •         1 mW: 0.0029%
      •         10 mW: 0.0027%
      •         50 mW: 0.0059%
    •     100 ohms
      •         1 mW: 0.0033%
      •         10 mW: 0.0024%
      •         50 mW: 0.0046%
    •     300 ohms
      •         1 mW: 0.0047%
      •         10 mW: 0.0037%
      •         40 mW: 0.0028%
  • Frequency response, USB input (48 kHz sample rate)
    •     <3 Hz to 23 kHz, ±1.0 dB
    •     5 Hz to 22 kHz, ±0.1 dB
  • Frequency respose, analog input
    •     <3 Hz to >55 kHz, ±1.0 dB
    •     5 Hz to 22 kHz, ±0.1 dB
  • Output impedance (1 kHz): <0.2 ohm
  • Battery life:
    •     12 hours, analog input
    •     6 hours, USB input
  • Dimensions: 70 x 84 x 20 mm (2.8 x 3.3 x 0.8 inches)
  • Weight: 6.0 oz (170 g)

 

Summary:
  • 16-bit/48kHz USB digital audio
  • Asynchronous upsampling to 192 kHz
  • 1/8″ analog input
  • Automatic input selection
  • Digitally-controlled volume, 1-dB steps
  • Three-position gain select (-12dB/0dB/+12dB)
  • Two-level crossfeed with bypass
  • DAC: Cirrus Logic CS4398
  • DAC filter op-amps: OPA1641
  • Output stage op-amps: AD8610
  • Bipolar voltage rails (+/-7 VDC) with true ground reference
  • Uses standard USB audio drivers
  • Compatible with Mac OS X and Microsoft Windows XP, Vista, and Windows 7
  • Rechargeable battery, charged through USB or standard 5V wall charger
  • Charge disable switch
  • Power/low-battery and charge indicator LEDs
  • Available in silver or black
  • Includes Micro-USB cable and self-adhesive rubber feet

Edited by yaluen - 11/7/13 at 1:05am
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