Goodie or Gimmick? The BSG Technologies Reveel Signal Completion Stage for Headphones Page 2

BSG_reveel_Photo_Jackside Operation
The reveel is contained in an all plastic, relatively ordinary looking enclosure. The top of the unit has a power switch and accompanying blue LED to indicate power on. The end panel has two 3.5mm jacks for input and output, and includes a bypass switch. Turning the switch to bypass allows only the normal stereo signal to arrive at the headphone jack, and the reveel has unity gain in bypass mode. Turning the bypass off allows you to hear the device in action, but measured gain increases to 3.24dB@1kHz. Actual, gain when on may vary somewhat depending on the program material and how much difference signal is present...I would assume.


The other end of the reveel has a USB micro-B jack for charging the battery and an LED to indicate charge state—LED lit when charging, off when fully charged.

Included with purchase is a three foot long 3.5mm plug male-to-male cable for use as input cable; a USB Charging cable; and a couple small squares of DualLock material to attach the reveel to another device.

First of all, the effect is not subtle...nor is it terribly easy to describe. Generally speaking, I hear a substantial widening of the stereo image and hear significantly more ambient information. This is completely in keeping with the nature of these devices; for the most part what's going on is an enhanced response for the difference information in the mix. Because ambient information (hall reverberance, noise) is largely uncorrelated between channels it is strongly enhanced by the process.

I also hear the center image sound sources moving closer to me as the stereo image gets wider, this may be a bit of an illusion however as going into bypass mode collapses the stereo width and lowers the apparent volume making it seem like the central vocalist moved backwards. Additionally, when the effect is turned on more ambient information is apparent behind the singer creating an additional layer behind and seemingly pushes the vocalist forward as well.

The problem I had was that the effect of the reveel would change depending upon the nature of the music. For example with large orchestral and choral works where the normal headphone image was slightly forward and up in my head and stereo image wasn't terribly wide, turning the reveel on would broaden the image and present significantly more ambience, but it would often be a preferable listening experience. But with Rickie Lee Jone's "Dat Dere" from her "Pop Pop" album—a close mic studio mix—the bass to the left and guitar to the right are nicely positioned in the standard mix, but with the reveel the instruments move wider by a disconcerting amount. Bottom line, I found the reveel a bit hit and miss with many recordings. I'll also mention that to my ears the reveel is not a particularly good headphone amplifier, meaning in bypass mode it doesn't perform up to the level headphone enthusiasts would desire for an amplifier product. While not having great refinement the output impedance measure at 1.4 Ohms so the damping factor is good and there should be little EQ changes due to interactions between the reveel and you headphones. I'd say it's mid-fi...good mid-fi, but mid-fi none-the-less.

One thing mentioned in the BSG marketing information is "an audio experience with fullness and richness beyond comparison." Numerous people have mentioned this sense of richness and fullness to the sound of this gear. One of the things this type of effect can accomplish is widening of a mono image. I believe the part of the circuit that sums the left and right channel into mono and then passes it through filters to isolate bass and treble and then adjust the phase before recombining it with left and right channels gives this impression. A lot of old recordings are in mono and are well served by the reveel. I have a mono recording of Django Reinhardt playing "Honeysuckle Rose", in bypass the audio is congested and uninvolving coming from directly in the middle of my head. With the reveel on the image widens some and becomes richer with texture. Similarly old Beatles recordings like "It Won't Be Long" from the With the Beatles album are stark with vocals that are hard panned to left, right, or center. In bypass mode the recording is a hard blob on the left, blob on the right, and blob in the middle with nothing between leaving it sounding thin and spare. With the reveel on the image doesn't change much in overall width, but the blobs seem to spread out some leaving less empty space between and giving a richer, more involving listen.


Another area in which the reveel seems to excel is for movie and TV listening. Audio for video can be fairly center channel heavy, and the reveel does a very nice job of broadening and sweetening that center image. Additionally—and I don't know if this has anything to do with the surround channel matrixing but it would make sense—it seems the reveel does a great job of improving the sense of ambiance on soundtracks. I will almost certainly be using the reveel for my iPad movie watching on an ongoing basis. I like it very much in this application.

The BSG Technologies reveel fits into a category of audio devices that could be called "stereo wideners" or "ambiance processors", which manipulate stereo signals using mid-side (or sum-difference) matrixing operations. Generally, these devices are used in the music production process and are adjustable in their effect. BSG Technologies claims their approach of using the Golden Ratio remixing the various signals present is central to the performance of the product. I feel a one-size-fits-all approach is misguided, and would prefer a product with some degree of adjustability.

I found results were somewhat hit-and-miss. It seemed large ensemble performances recorded with simple mic techniques would benefit quite a bit from stereo widening, while close-mic studio recordings would be overwidened at times. Old mono and ping-pong stereo recordings were often aided by the reveel's ability to broaden and make sound richer sound sources in the mix. Movie watching was particularly helped by the reveel and I don't think I'll be watching flicks on my iPad without it in the future.

Yes, I am going to recommend the reveel. While I don't find it to be a magic bullet for broadly improved headphone listening, I do feel it brings some good things to particular aspects of the listening experience. Its low price, real value in some applications, and most of all its ability to give the listener an unusual and playful listening experience, for better or worse, has me quite willing to give it a solid recommendation. It's an audio's fun...go play! Nothing wrong with that.


BSG Technologies home page and reveel mini-site.
BSG patents here and here.
Reviews of q0l Signal Completion Stage by John Atkinson and Robert Harley.
Article on Blumlein Shuffler.
Similar products: Algorithmix K-Stereo Ambience Processor; Voxengo MSED; Rupert Neve Stereo Field Editor.
Threads on Head-Fi here and here; DIY Audio; What's Best; Argh!, double Argh!
ST Microelectronics V914i datasheet.pdf.

BSG Technologies
3007 washington boulevard
suite 225

Byrnie's picture

I'm not trying to nitpick but help out.  I noticed you used "though" when you meant "thought" a few times in the second paragraph.  Great article!  I can't wait for your 1540 review!  I hope all is well!

Tyll Hertsens's picture

Fxt, thanks.

Got quite a few things in for review, the 1540 is maybe 4 or 5 away.

markus's picture

On a portable player with a custom rockbox firmware, you can adjust the stereo width in percent. Values above 100% will progressively remove components in one channel that is also present in the other. This has the effect of widening the stereo field. A value of 100% will leave the stereo field unaltered.

What do you think of that, Tyll? Isn't this the same effect?

bogdanb's picture

maybe I am wrong. maybe i did not get it, but if I did, I might be right with the suggestion I am about to make:

Could you record the from the headphone output of the device to a computer an then post a sample of the effect on and off for us to understand the device. 10-20 seconds would be enough (something free of copyright)

Since it is not a headphone or a sound producer (speaker, amp, dac), but a sound mixer in a way, I think you could let us listen to what it does and explain even more if you think it is necessary.

MacedonianHero's picture

Hi Tyll:

Are you going to measure this amp's performance?

DrForBin's picture


i remember long, long ago when Klipsch was touting the ultimate 2 channel speaker set-up to be a pair of Klipschorns for the left and right channels with a Cornwall in the middle playing a mono signal. at least now it fits into your pocket instead of taking up a 16' wall!


GNagus's picture

Is there a type of headphone (closed, open, brand, impedance, etc) that this device works best with?

RPGWiZaRD's picture

So would you say this is like a hardware stereo image tweak with only one fixed setting?

It's a shame they don't offer an ampless/gainless mode and just let it run through the filter that does the stuff it does, it probably increases the noise floor quite a bit and I reckon it could become a problem from noisy sources or if you'd want to use your own amp with this, especially with portable setups/IEMs.

I agree with you on the "one-size fits all" argument, I'd also greatly prefer some configurability to increase its usefulness. One size fits all only works in the Apple-world, which is why I'm not part of it. 


dAd's picture

I did get to hear it briefly at a friends house.  I heard the gain difference and the additional ambient info pushed up front on the two tracks when I did a bypass comparison.  The effect was iinteresting yet I felt like I was hearing less of a black background and more noise along with the additional info.

I did notice a widening of soundstage on both cuts and a ever so slight loss of focus or imaging on some instruments.  They got bigger and less defined in space.

Would love to spend more time with it to fully develop an opinion, but for now more important things to listen to for me.

AGB's picture

This was Tyll's most important observation:

"... a recording is and will never be like "the real sonic event."

It is true for too many reasons to list here, Tyll's is a great observation.

Electro-mechanical devices do not hear or speak the way organic devices will; their "understanding" and conversion of the dimensonal aspects of sound does not resemble how organic devices, live instruments propagate sound or how the human ear hears.

I am not saying the problem cannot be overcome, I am saying it is not likely to be entirely overcome, and if ever, not soon.

This device seems to be some sort of crossfeed manipulator, no big deal, DSP technology already does the same function in the digital domain far better, and it's only time before the better technology will be incorporated into DACs or other discrete chips.

Some music players already have a similar technology, DSP-based, albeit the effects will not be exactly the same.

Fidelia - resampler and music player - has FHX, a headphone module that does more or less a similar trick...but it is natural entirely, and will not make one uncomfortable.

I never need to turn FHX off, it works.

Reticuli's picture

I would love to buy a good, inexpensive stereo to mid-side box. I tend to think M-S is the best format for stereo listening, particularly in live PA setups of pre-recorded music or DJing.

TechAdventurer's picture

I love listening music every time I travel - but every time I need to take with me the charger of the phone, also of the amp - is there a model that is without battery - to use the power of the phone for example?