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iBasso PB-2 Pelican fully balanced portable, DB-2 Dac . . HiFlight recommended op amps page 16. . - Page 50

post #736 of 1401

Hi Grev,

 

Regarding the Stepdance vs. PB2...

 

I still use the original Meier Stepdance (not the 2Stepdance or the newer offerings) and I drive it with external 15V battery packs (to maximize its output power to the headphones).  I use the Stepdance in my "walkabout rig" - where I want to keep the weight and size of everything to a minimum with this chain:   Sony PCM-M10 -> 15V Stepdance -> headphones 

 

I love the sound of the 15V Stepdance so much, that I bought another Stepdance, just to keep on hand as a spare, in case the first one dies or gets damaged / stolen / whatever.  I really like the Meier Stepdance and consider it to be far more sophisticated a design than the iBasso PB2.

 

Where the Stepdance is sophisticated and sounds great, the iBasso is somewhat crude, but can be upgraded to sound even BETTER than the Stepdance WHEN you are using power hungry headphones like the Sennheiser HD650, the Audeze LCD-2 or LCD-3, or especially the HiFiMan HE-6.  

 

With a 16-Volt external battery pack (not the internal, 12.6-Volt battery) and the use of balanced output to your headphones, the iBasso PB2 is far more powerful than the 15-Volt Stepdance (up to 2500 mW vs. perhaps 900 mW).  

 

After upgrading the PB2 with the "right" op-amps (which, in my opinion, are the LME49990's and HA5002 buffers), and buying balanced headphone cables (which, in my case, are the Silver Poison by Toxic Cables), the iBasso PB2 definitely SOUNDS BETTER than the 15V Stepdance, into the LCD-2.

 

It's a matter of MORE POWER plus BALANCED OUTPUT winning the day, with the LCD-2 really coming to life when given sufficient power.  

 

When using IEMs or far more efficient headphones than the LCD-2 (like my Shure SE530, Sennheiser HD280 Pro, or Philips CitiScape Downtown), the 15V Stepdance has no problem competing with the iBasso PB2.  In fact, I would give the Stepdance the edge in terms of sheer transparency, neutrality, and resolution.  

 

But overall, I'm willing to suffer a slight reduction in resolution and transparency, as well as suffer the PB2's noisy, archaic, analog volume control, to get the awesome dynamic range, bass extension, and bass control (detail), that comes with running the iBasso PB2 with a 16-Volt regulated external battery pack, LME49990 op-amps, HA5002 buffers, and balanced output to the LCD-2, via Toxic Cable Silver Poisons.

 

Replace the LCD-2 with efficient headphones, and I'm back to using the Stepdance instead of the PB2.

 

My interest in USB DACs is strictly for desktop use, where I would always be using the LCD-2, and thus, the 16V iBasso PB2.

 

Regarding your forthcoming comparisons of the Triad L3 and ALO RX Mk-3...  

 

Will you be using balanced output with either of them?  I suspect that singled-ended into power-hungry headphones, they wouldn't be able to compete with the balanced-output,16V-powered iBasso PB2 - but I'm just guessing.  

 

I'm really looking forward to your impressions.  Will you please send me a PM when you've posted your findings?

 

Thanks!

 

Mike

post #737 of 1401

On the subject of my upcoming comparisons of the Centrance LX vs. iBasso DB2 vs. JDS Labs ODAC...

 

Back in May of this year, I had posted the following to the CLAS impressions thread, but no one ventured a response:

 

    Quoting my May 2012 post to the CLAS thread:

I was just reading a Six Moons review of the ALO Audio Rx-MK3-B, and asking myself, "When will ALO start working on a balanced version of the Solo?"  My conjecture: Maybe never.

 

I read that they have a couple of other projects already underway, and then I read this:

 

 

Quoting Ken Ball, of ALO:

 

"To obtain a balanced working signal, a non-inverting amplifier buffers the input signal. The output of that amplifier is inverted with a unity-gain amp. The balanced signal is then taken from the outputs of both amps which are contained within the same IC. The worst-case mismatch between inverting and non-inverting outputs is 0.02dB. Going in single-ended [as input to the balanced Rx-Mk-3-B] is thus no worse than balanced. The real advantage of the RxMk3-b is its fully balanced amplification circuit and ability to drive all headphones in balanced mode."

 

Ken Ball is saying that nothing is accomplished feeding his balanced amp with a balanced input vs. a single-ended input.  Thus, what incentive, other than market expectations (which should not be ignored, of course), would ALO have to pursue a version of the CLAS that offers balanced output?  

 

And thus, what benefit is there in putting an iBasso DB2 between a CLAS and an SR71-B, for example - other than to acquire changes to overall sound quality that have nothing to do with providing the amp with a balanced input?

 

And thus, what need is there to purchase a fully balanced USB DAC, like the HRT Music Streamer Pro, for use with a balanced amp, vs. a less-expensive single-ended DAC?

 

Mike

 

Has anyone here tried feeding either the RSA SR-71B  or  ALO Rx MK3-B  or  iBasso PB2, using the iBasso DB2 with first, single-ended output to the amp, then with balanced output to the amp?  How about in a blind study?

 

A friend of mine (the owner of the Centrance DACport LX that I've borrowed on several occaisions), will be helping me to perform comparisons of all four of these possibilities:

 

96/24 WAV -> USB -> DB2 single-ended -> PB2 balanced -> LCD-2

96/24 WAV -> USB -> DB2 balanced      -> PB2 balanced -> LCD-2

96/24 WAV -> USB -> DACPort LX (single-ended) -> PB2 balanced -> LCD-2

96/24 WAV -> USB -> Objective DAC (single-ended) -> PB2 balanced -> LCD-2

 

Given what Ken Ball says, I'm especially curious about comparing the first two chains, above! 

 

Mike

post #738 of 1401

The Triad L3 is only a single-ended output as far as I know, maybe others that know more about the technical side of the amp can chime in.  So I have the Norse Audio cables coming in, with balanced and single-ended connections, I will try and do single-ended comparisons first and then go on with balanced.

 

I am quite interested in the PB-2 though, the voltage and amperage is making me very curious.

post #739 of 1401
Quote:
Originally Posted by Grev View Post

The Triad L3 is only a single-ended output as far as I know, maybe others that know more about the technical side of the amp can chime in.  So I have the Norse Audio cables coming in, with balanced and single-ended connections, I will try and do single-ended comparisons first and then go on with balanced.

I am quite interested in the PB-2 though, the voltage and amperage is making me very curious.

i have the PB2 and right now I only have a pair of T50RP "Mad Dogs" made by MrSpeakers hooked up single-ended to it and while it can drive them to pretty loud listening levels I feel that there isn't any headroom. I know the "swing" comes when balanced but I have nothing to test it with yet. Was thinking about doing a hardwire split on them to iBasso just to see.
post #740 of 1401

Hi kskweri,

 

I realize that you're currently operating the PB2 with single-ended output, but keep in mind that all of these op-amp based headphone amplifiers (single-ended or balanced) offer their highest possible power output (and thus, their best performance) when the supply voltage is at the maximum permitted by the amp's manufacturer.  Not only do they put out higher Watts RMS per channel, a quick look at their datasheets reveals that they all have lower THD and Noise measurements when operated at higher supply voltages.  

 

For example, the datasheet for OPA1611s documents that they can handle an absolute maximum supply voltage of +- 20V (40V swing), but when used in the Stepdance, Jan Meier mandates that the maximum permissible supply voltage is 15V, not 20V.  When the same OPA1611s (or OPA1612s) are used in the PB2, iBasso says that you can use supply voltages as high as 16V.  The datasheet indicates that THD+N is lowest with a +- 15V supply voltage to the OPA1611.  (That's why I advise people to forget about using the Stepdance' internal 9V battery.)  This is pretty much the case with all op-amps for which I've studied datasheets - you get more Watts with less distortion and noise when operated at or near their absolute maximum supply voltage.

 

With either amp, the Stepdance or the PB2 (or for that matter, just about any portable headphone amp), you'll not get nearly as much power to your headphones when using their respective internal batteries (9V for the Stepdance or 12.6V for the PB2).  One of the unsung features of the RSA SR-71B is that it has a 4-cell, 16.8V internal lithium-ion battery pack instead of a 3-cell, 12.6V internal battery pack (as with the iBasso PB2).  But even the SR71-B offers its best performance when supplied with a higher voltage from an external supply.    

 

The hot tip, therefore, is to use an external power supply that provides the maximum permissible supply voltage.  See my photo albums, below, for more info on how to do that and stay portable with the Energizer XP8000 5-cell, external lithium-ion pack, used in combination with the appropriate inline voltage regulator cable.  

 

One of the not so obvious features of using the XP8000 with a voltage regulator cable is that as the XP8000 discharges from 21.0 Volts when fully charged, down to 16 Volts, the iBasso PB2 will ALWAYS see16 Volts throughout the external battery's discharge cycle.  Compare that to using the internal lithium ion battery, where you start at 12.6 Volts, fully charged, but immediately start slipping to lower voltages until 9.0 Volts is reached and the PB2 shuts off.  Thus, your performance will constantly decay (both in terms of decreased Watts RMS and increased THD+N, when using an internal battery pack, as the battery discharges to lower and lower voltages.  

 

That does not happen with the XP8000 + inline voltage regulator, where the PB2 always sees the regulated 16 Volts until the battery pack's voltage drops from 21 Volts to 16 Volts through use, at which point, it's time to recharge the XP8000.  

 

It seems most people who buy portable amps want them to tiny and have batteries that magically last several days. I say forget about convenience!  Give me PERFORMANCE!  Give me a portable amp that has a 5-cell lithium ion battery in it with its own, internal voltage regulator that pushes the op-amps with their highest permissible supply voltage that does not degrade THD+N - all the time - while the battery is fully charged, all the way down to the point where it has to be recharged - giving the op-amps a constant, regulated supply at the ideal voltage.  (Distortion and noise are usually lowest at some voltage just below absolute maximum supply voltage, depending on the op-amp.)  

 

That way, I wouldn't have to carry an XP8000 and an inline regulator cable with me everywhere I go, with every portable amp I own, just to gain access to everything the amps have to offer.  If an amp's case was large enough to hold a 5-cell lithium-ion battery that delivers four hours of play on a single charge, I'd be content. I don't need even 10 hours of play time, if it can only be had at the expense of a lower than ideal supply voltage!

 

Enough of building tiny amps with tiny batteries and tiny performance!   frown.gif

 

Mike

post #741 of 1401

Hi Grev,

 

Quote:
Originally Posted by Grev View Post

The Triad L3 is only a single-ended output as far as I know, maybe others that know more about the technical side of the amp can chime in.  So I have the Norse Audio cables coming in, with balanced and single-ended connections, I will try and do single-ended comparisons first and then go on with balanced.

 

I am quite interested in the PB-2 though, the voltage and amperage is making me very curious.

 

I wasn't sure, but I thought the L3 was single-ended only.  

 

Can you tell me what the specs are for the L3's internal battery pack?  Volts?  Amp-Hours? 

 

How about the voltage rating on the external power supply that came with the L3?

 

The L3 case is so large, I'm now wondering if it's got a big, high-voltage battery pack in it, instead of the wimpy, lower-than-ideal-voltage battery packs every other amp manufacturer is using.  To my knowledge, only Ray Samuels is using even a 4-cell battery pack (16.8V), but I doubt that it's regulated to some lower, constant voltage, and thus, the performance just decays as the battery pack's voltage drops throughout the discharge cycle.  

 

Mike

(Getting off my soap box....)

post #742 of 1401

The Triad L3 uses two 9v rechargeable batteries, which I remember even the Tenergy 9v batteries go up to 10v when fully charged, which I also have a set of the Imedion 9.6v (might even get higher voltage) that i might consider changing.  I was also informed that li-ion 9v batteries can be swapped into it too.

 

The power supplies which is safe for charging and operating is at 24v, which is also the default, but the LLP (L3's official power supply) can go up to 32v output as I was talking to Brad at Triad Audio, and in order to operate at that voltage, you need to take the batteries out.

post #743 of 1401

Sweet!  

 

So, going portable, the L3 can at least start out at around 18 Volts (higher than either the PB2's 12.6-volt internal pack or the SR-71B's 16.8-volt internal pack).  But hearing that the designer permits use of a 32-volt external PSU is intriguing!   That tells me that you could theoretically rig up a 32-Volt, regulated external battery pack!   

 

MO' POW-WUH !

 

tongue_smile.gif

post #744 of 1401

Also as a note for 9v rechargeables, I use the Maha Imedion 9.6v ones, and they're 11.3v when fully charged!

 

http://metaldetectingforum.com/showthread.php?t=118012

post #745 of 1401

That's 22.6 Volts as you head out the door!  Excellent!  All the more Watts RMS per channel.

 

Maybe, just maybe, this has a little something to do with why the L3 sounds good with power hungry phones...  wink.gif

 

Mike

(voltage evangelist)

post #746 of 1401

.


Edited by seeteeyou - 11/5/14 at 12:29am
post #747 of 1401

Yes!  Lithium-Ion batteries made for RC hobbyists are the least expensive way to go, but they are not nearly as convenient to use as an XP8000 (for voltages up to 21 Volts).   Above 21 Volts, you would have to use something other than the XP8000.

 

Lithium-Ion battery packs are made of multiple cells.  Each cell has a maximum voltage of 4.2V when fully charged, and 3.0V when fully discharged.  

 

You do NOT want to discharge a lithium-ion cell below 3.0V, because they can do bad things - like spontaneous combustion - not explosions, just fires that emit toxic smoke and burn whatever's within reach.  rolleyes.gif

 

So, if you decide to use a mutli-cell Lithium-ion battery pack with your portable amp, you'll need some way to monitor the voltage of the pack while using it to make sure that you don't discharge it below 3.0V per cell!  

 

That's a pain, let me tell you, if all you've got is a standard multimeter to carry around with your portable rig.  It can be made easier, however, through the use of one of these:

 

 

 

                                        Hyperion EOS Sentry

 

This sells for about $30 and makes battery monitoring in the field very easy.  It works with five different chemistries, and allows individual measurement of each cell in battery packs having up to 7 cells.  It also calculates disparity between cells - revealing whether one cell is discharging more rapidly than another - which can happen if you don't use a balancing charger, like this $40 Thunder AC 6 (pictured in the following PDF file):

 

http://home.globalcrossing.net/~zilch0/images/Zilch0MD-Stepdance-on-LiPo.pdf

 

 

For my "Walkabout Rig," where I keep the size and weight down by using 4-cell Lithium-Ion packs with the Stepdance, I fully charge them to 16.8V, then use a feature of my charger to discharge the packs down to the 15.0-Volt maximum allowed by the Stepdance.  In other words, I am pre-discharging the 4-cell battery packs from 16.8 down to 15.0 before I begin using them with my amp. 

 
Yes, it's a lot of work, but I enjoy the results!
 
biggrin.gif
 
Mike
post #748 of 1401

.


Edited by seeteeyou - 11/5/14 at 12:28am
post #749 of 1401

I'd be worried about the inverter making noise, but I love the idea!

 

Mike

post #750 of 1401

But need PB-2 impressions!

 

And portability, whatever YOU want to carry!

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