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BLOG #15. A Relatively Affordable Way To Stop Staying Totally “Passive”

Both in home and in portable audio, the ultimate audio performance can happen only while using the best “active” systems.
A system is “active” when not only each transducer drivers section, or its audio band, is driven with its own dedicated power amplifier, but also when an arsenal of each section’s system parameter adjustments is available for an application (via an electronic crossover which, possibly, can be augmented with some additional measurements and tuning hardware).

In this context, again be it either home or portable environment, there is not a chance for any of the “best of the best” single amp “passive” systems, especially if we are talking about systems with a single driver, to be on a par sonically, and to compete in terms of their total capabilities, with well adjusted multi-way/multi-amps fully “active” “absolute” systems.

Even the best multi-way “passive” audio systems, that is, the ones which use a single amplifier with a set of s pass-band “passive” frequency filters, can’t compete in absolute terms with the level of sonic performance typically demonstrated by the best fully “active” multi-amps installations.

Especially, when, in the latter case, a sophisticated set of contemporary tools is available to allow both basic adjustments, and more sophisticated fine tuning in real time to set the optimal system parameters, which depend on a concrete acoustic environment and a concrete set of goals the audio system should achieve.

Because here at StereoPravda we’ve been fully aware of the above hierarchy since the hey-days of our home High End Audio past, our portable two-way “active” DACCA unit was specifically designed, with all the necessary capabilities and features, to fully support our portable systems’ absolute sonic pretensions.
It’s got two independent sections of DACs/adjustable crossover/tone controls/differential amplifier: one is for our ear monitors’ “high” frequency section, and other is for their “low” one.

Most of the Balanced Armature-based earphones’ stigmas are due to the fact that almost all of them are currently used with a single amplifier and some “passive” on-board filters. Due to the intended portable operation and its size restrictions, the filter designs are very limited in their scope and execution, and as the result of it, in the sound quality they deliver.

At the same time, “active” sound band sectioning with several separate amplifiers and “active” filters inside the external electronic crossovers, where components’ size is not as limited, allows some additional opportunities for BA-driver designs to sound much better.

Besides an obvious advantage of using several amplifiers instead of one, in portable audio, when used with separate batteries for each section in the “active” mode, you can get a complete separation of the “grounds” between them.

But, as already stated above, the most important “active” mode advantage to elevate BA-driver assemblies’ audio performance to a much higher level lies in this mode’s capability to do all sorts of real time in-band and overall adjustments and fine-tuning.

That’s why our “upper-tier” two BA-driver arrays’ in StereoPravda SPearphone-series of ear monitors are built ready for such two-way “active” configuration, so they can be used with two different amplifiers, and can benefit from some additional adjustments provided by our DACCA unit to achieve their full potential.

A few years ago, Jerry Harvey flirted with the same right idea commercially by releasing a portable three DACs/three-way adjustable/three separate amps “active” custom ear mold system, but they quickly abandoned it.
As I see it (and I heard the demo at a CES), the form factor of a cigarette pack would not cut it in terms of acceptable sound quality, but to blow up its physical and weight proportions to some “sonically acceptable level”, JH, in their turn, probably, have found too commercially unacceptable.

No doubt, our DACCA is an expensive and bulky unit, so recently I run into some much less expensive way to elevate our StereoPravda SPearphones’ performance from a conventional single amplifier “passive” playback to a two-way “active” configuration.

This relatively affordable way is… (roll of the drums)…


…To add another player to the portable system! (pic. 1 and 2)

A few weeks ago we demonstrated this "solution" with our StereoPravda SPearphone SB-7 ear monitors at the last Moscow "HiFi & High End Show-2016".

As a rule, this upgrade requires two separate modifications for the appropriate hardware: digital output addition mod for “the master” transport+DAC player and digital input addition mod for “the slave” DAC-only one (pic.2 and 3).
Both of these mods can be relatively easily done.

It goes without saying that, preferably, the players should be identical, and their circuitry should allow for such a modification (older player circuitry design, as a rule, allows it, and even the newer ones, like, for instance, Lotoo PAW Gold, do also allow for such an upgrade).

Being in love with the sound of HiFiMan “HM-801”, in was an obvious choice to test this idea.
Especially, considering that I just got a second sample of the player for about $500 (original player I bought in 2009 for $800).
The balanced I2S-out/I2S-in mod which was done by our stuff engineer set me back for another $200.

By the way, as, through the years, I’ve been watching endless audio forum battles unraveling over which portable music player has got the best sound, I saw the effort as the waste of time, as the answer has been always seemed to be lying on the surface: as always in audio, the best one should be the biggest and the heaviest one.
In that department “801” has got no competition. Passing that nomination, it would be almost impossible for the player to not to become the total winner in all the other sonic departments.
And the time proved this “rule of he thumb”: through the years I’ve been also comparing “801”’s sonic performance with that of some of the most well known “desktop” DACs costing up to, say, $3000 (Benchmark, Lavry, etc), and, as a separate DAC, this player has always been winning hands down.

The heft of any player is in the weight of its battery and its chassis, in that respect the rest of the player’s components add unsubstantially.
The “HM-801” uses two Burr-Brown 1704 multi-bit DAC chips which require two power supplies with the opposite polarity, so the battery in “801” is, actually, two (big) batteries in one.
Contrary to the vast majority of the current DMPs this player was built literally from ground up: its creator, Dr. Fang, started working on this project with a survey on the head-fi.org community regarding the sonic quality and the functionality wishing lists for the product. That’s why it’s multi-bit DAC chip set, that’s why the two batteries in one, and that’s why the heft of the player.
And the size of that battery is the biggest one I’ve ever seen in a portable music player. Because it’s got so much of a “juice” running in its system, it sounds so “liquid”.
Two players would mean twice of the “juice” available.

So, what you see in the attached pictures is a two player stack with four Burr-Brown 1704s multi-bit DACs, two decent analog stereo volume controls on each of the two players, and four independent large capacity battery power supplies.

One of the truly ingenious qualities of “801” is its capability to swap its amp cards in the slot behind the door on the back of the player (pic.4).

The latter allows you in the two-player stacked mode to use different, for each of the two sections, optional cards in each player (the opportunity I would rather skip with, but anyway), but what this player also allows you to do is even more important: it allows you to relatively easily fit each section’s output amplifiers with your own custom filtering circuits (which I am in the process of experimenting with).

I don’t think it’s possible to save a lot of weight and/or expense designing and building a similar custom unit.

As I already mentioned, most of the digital music player’s weight is in its batteries’ and its chassis’ weight. By stacking the produced-in-quantity commercially available players, which you can still buy used starting at $500, there is no way you can get a better deal building your own custom unit.

By the way, if anybody needs some help to do the digital in/out mods for some applicable hardware, they can ask us, and we will gladly help them to get those mods done.

Sonically, via our StereoPravda SPearphone SB-7 ear monitors, the “active” stacked “HM-801” two-amps’ sound is much more dynamic, seamless and three-dimensional.
It’s less bright and shrilling than with a single player, but all the original resolution is kept intact, with the song lyrics becoming much more intelligible.

Having switched to the two players’ stack, you’ve got not only the additional volume adjustment capability between “high” and “low” earphones’ sections to work on the overall sound presentation, but you also have got two stereo amps, instead of one in the original player, and two independent ground levels.

When used with the SB-7s, despite all the (insignificant) hassle of the necessary player modifications, both the absolute sonic gains of the “active”/two players system, and its much better relative “price/performance ratio” over the “passive”/single player one, not simply supported all the sonic expectations about the advantages of “active” systems over “passive” ones, but, in quantitative terms, happened to be more, than worth the trouble.

I know, it all looks a little crazy: pic.5 shows the whole assembly with two players stuck to each other back-to-back with a strip of some “Velcro” tape and the SB-7s connected to the stack, in ready-to-go mode.

Never mind the clutter, the whole thing can be conveniently carried around in a common belt sack, and if you want to go from the stacked players back to conventional “normal” mode of one player operation, to disassemble the stack would take you no more than a minute.

If you want to get back again, it’d take you as quick, so you can swiftly go back and forth between the two configuration as many times as you’d like to hear the difference.


At the very least, for the total cost of the StereoPravda SPearphone SB-7/2xHifiMan “HM-801” complete audio system rig in the approximate amount of $3500, it’s, currently, the most convenient and cheapest way to hear the main advantages of a fairly decent fully “active” two-amps audio system vs almost exactly the same one, but set up in a conventional “passive” one-amp operation.

With no proper crossover/tone control to speak of, this portable audio system is just a teaser for what can be expected from a full blown “active” two-way assault on the sound quality (using StereoPravda DACCA, as an example).

But even from such a basic comparison many music lovers can draw some very productive conclusions about what they could have been possibly missing sonically, either at home, or while “on the go”, when they’ve been stuck with that “passive” system configuration approach for all these years.

That is during the time when they’ve been taking for granted an idea that “passive” is the only proper way to deal with the audio matters.


18.05.2016 // Author:  (Bigmisha) // Number of views:  604

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