REVIEWS: “Brand X” Portable Tube Headphone Amplifier Prototype
Mar 16, 2002 at 6:45 AM Thread Starter Post #1 of 54
I'm starting this thread to encourage those who've evaluated the "Brand X" portable tube amp to post their opinions of it.

I'll post my review of this amp just as soon as I can find the time, and as soon as I complete my other scheduled reviews (which are behind schedule).

For a little background on the "Brand X" name:

I'm not trying to be mysterious. The person who sent us this amp did not tell us the amp's name, the name of the company, or really much else. We were given some specifications, and instructions on its use. It was sent in a prototype case that is riveted shut (to keep out curious testers I'm guessing
wink.gif
). This case is, as I understand it, nothing like the production case that this amp will come to market with. Though there will be some technical adjustments made to the amp, I believe the circuit of the amp we evaluated will be very similar -- if not identical -- to the production model.

To this day, I do not know the name of the company that will produce this amp, the name of the amp, its price, or its release date. I just know how it sounded to my ears, and I'll comment on that later.
 
Mar 17, 2002 at 5:30 AM Post #2 of 54

Tuberoller

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review with pics coming monday........really!!!
 
Mar 18, 2002 at 9:54 PM Post #4 of 54

KurtW

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This is a review of a prototype AC/DC tube headphone amp identified only as Brand-X. I haven’t included any physical description, as this is clearly a prototype as far as its case is concerned. It has four different 1/8" output jacks (different taps of an output transformer?) which do affect the sound and can be chosen based on the headphones used and the user’s preference. There is a battery indicator, which is nice.

CDs used for comparisons:
Dave Holland, Extensions, tracks 1-3
Brahms Trio Op 114 for Clarinet, cello and piano, BMG 9026-63504-2, tracks 1-3
John Hait, The Tiki Bar is Open, track 4
Bob Dylan, Love and Theft, track 2

My first impression of the Brand-X amp could be summed up by my roommate’s comment the first time he heard it: "hey, this sounds nice!" I was driving it with the Sony D-25S CD player with DIY Kimber cables and using Sennheiser HD 580 headphones. It has the classic tube sound, very relaxed, warm and open with rich full bass and slightly soft at the very top. This amp doesn’t bombard you with detail, but rather baths you in beauty.

I compared it to a couple other portable amps with this same set-up. The Porta-Corda sounded crisper, maybe a little too much so. It also sounded a little more compressed than the Brand-X. The Brand-X also seemed a bit cleaner overall and more relaxed. Next up was the HeadRoom Supreme. This is the older version of this amp. The Supreme is generally a step up from the Porta-Corda in sound, but again the Brand-X was smoother and more spacious sounding, with beefier bass.

At this point the Brand-X was ready to take on one of my favorite amps, the David Berning Micro-ZOTL. This amp can run from a high current 12V source such as a car battery. Without a battery it’s fairly light, but its four tubes require some decent ventilation. The Brand-X actually runs very cool. My comparison was with the ZOTL plugged in and the Brand-X running from its battery. This time the CD player was the Linn Ikemi, taking advantage of its two sets of outputs. The cables for both amps were DIY Beldon 89259, which I find fairly neutral. Most of the listening was with Sennheiser HD 600 with the blue Clu cable. I experimented with the various output jacks on the Brand-X but usually preferred either the 100-250 or the 20-40 ohm jack with these phones, depending on the music chosen.

The ZOTL is a tube amp, but actually sounds very neutral to me. The bass was flatter and tighter, i.e. more solid state like than the Brand-X. Both amps had a nice open airy sound, but the ZOTL sounded much faster throughout the range, making the Brand-X sound a little sluggish and rolled off at the top in comparison. After I was done listening I repeated the test with my roommate, switching back and forth between the Brand-X and the ZOTL without exposing which was which. His comments were very close to mine. The Brand-X is a very romantic sounding amp, where the ZOTL is more neutral and transparent while still not sounding too analytical.

I also tried the AKG 501 phones, but the Brand-X had to be turned all the way up to get a decent volume from them. I understand that this is being corrected on the production version of the amp. On the Sennheisers, I usually had the gain controls set to between 7 and 8. By the way, I didn’t mind the separate controls for L and R channels (there is no master volume control knob), particularly since the knobs had numbers on them. I’ll admit though I have a passive preamp that has dual switched attenuators so I’m sort of used to this.

I don’t know how much of the cost of the amp is related to the battery operation, but the manufacturer might consider also providing a non-battery version. I found the size and weight to limit the portable use. It was nice to take it into another room and not have to bother finding an available outlet, or to take it out on the patio without having an extension cord. On the other hand, the Supreme, even with it’s heavy 4 D cell pack, is much smaller and somewhat lighter and would probably get more true portable use from me even though it doesn’t sound quite as good.

After I completed all of my listening tests I took some measurements. I was a little surprised to see a gradual rolloff in the low frequencies, as the bass sounded quite rich. It was down 1.5 dB at 100 Hz, 3.7 dB at 50 Hz and 7.4 dB at 25 Hz. It was within 0.5 dB between 200 Hz and 12.5 kHz, and only down 1.3 dB at 20 KHz. The ZOTL, in comparison, is only down 0.2 dB at 20 Hz and 20 KHz. Total Harmonic distortion also rose at lower frequencies but was very low at most frequencies and was mostly second harmonic in nature. I sent all of the measurement details to the manufacturer, and he was quite surpised by them and thought that the output transformer may not have been within spec. Therefore, these measurements may not be representative of the production model.

I don’t know how the final version of this amp will look or how much it will sell for, but it is a nice sounding amp.

 
Mar 19, 2002 at 1:55 AM Post #5 of 54

Driftwood

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hmm, sounds like a nice amp!

why do I get the impression though that this amp is going to be made by someone who we really wouldn't expect to be making a nice tube amp? It seems to me that they are trying to hide their name so that people don't write off the amp due to biases that they might already have with the name.

I can't think of any reason why and big maker of tube amps would want to hide that this is their product for the purposes of getting initial impressions and trying to get some free promotion on their product. If it were a big name product, it seems like they would use their name as a selling point.

Anyway, I think I am going to be prepared to be surprised by who makes this amp. But all the same, I think if it is not too expensive, I might buy one. A portable tube amp! Fantastic!

Driftwood
 
Mar 19, 2002 at 2:36 AM Post #6 of 54

Dusty Chalk

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Well, since this is a prototype, I would think that they could just leave the name off of it...unless there is some sort of "signature look", such as the 1920's sci-fi of the Moths...but I really like what it adds to the mystique...dam, I'm already saving up for this thing...portable tube goodness...mewants...
 
Mar 19, 2002 at 3:32 AM Post #7 of 54

Tuberoller

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This is my review/comparison of the "Brand X" portable tube amp and six other head amps and a tube receiver.Why so many?the designer of the amp insisited and actually wanted me to try to procure a Cary integrated amp as well.The Cary never got here in time for a comparison but I will offer a review when I get it.The designer is very confident that his amp will stack up well against the best.


I first must say that there is a lot I don't know about this amp.The wishes of the designer to keep the name of the amp,the circuit design,the projected price and release date secrets did not do much to aid my impressions of the amp.This amp would have to sound damn good for me to forgive all the secrecy surrounding it.In conversations with designer I was able to get some details:The amp uses ECC88 tubes in the output stage.the production version will be in a smaller case and have a very similar circuit to the prototype.The production version may have switchable impedances instead of seperate jacks for each impedance range(I like the individual jacks).

In the pics(pictures removed at the request of designer)you can see the Brand X and the other amps used for this test.I also took a pic of the tubes that are supposedly installed in this amp.I have no way of verifiying this as the case was riveted shut.please note that this is the prototype case and the production version is likely to look much different.the designer asked that the amp not be judged by it's looks.this made the absolute need for this amp to sound great even more important.This amp has four 1/8" headphone jacks of varying impedances which would allow it's use with many different headphones.this unit was not light by any means and I was very concerned about possible microphony( audible noise in the tube stage caused by outside vibrations) with this amp.I did not weigh it but the shipping weight with the wallwart and extra tubes was 12 pounds.

For the purposes of consistency and the desire to eliminate any degradation of the audio signal to the various amps, all sources were connected directly to the amps and no other equipment changes were made during this test.

Equipment:

Sources:

Marantz SA-14 SACD player.This is a two channel player and the analog outputs were used(of course)

Sony D-25s portable.The Brand X is touted as being portable so I tried it with two portables.

Sony D-FJ61 This is the only other portable I have at the time

MusicHall MMF-5 Turntable.This table is all stock and equipped with the standard Goldring 1012GX cartridge.I aslo used a Creek OBH-8 phono stage with the OBH-2 power supply.

Cables:

Modern Audio Design Silver Pro I like these cables a lot and they seem to sound pretty good with tube and solid state gear.I used a Nutrik dual female RCA to single male mini stereo adapter for use with the portables.

Conditioner:

Monster DTS-3500-I was using this in my main systems but I switched to a BPT recently.

Other amps:

Creek OBH-11 w/OBH-2 power supply

Wheatfield HA-2

Rega Ear

MG Head DT this the original non OTL version with the attached cord and no cage.

Grado RA-1

XCANV2

HeadPhones:

Senn HD600-stock cable

Grado RS-1

Grado SR325

Grado SR80

Music:

Miles Davis "Kind of Blue" SACD-My reference disc

India Arie "Acoustic Soul" CD

Particia Barber "Modern Cool" JVC XRCD

"Gladiator" original soundtrack CD-an excellent test disc

"She's gotta Have It"original soundtrack LP-What a fantastic find of great music.All music performed by Spike Lee's father Bill Lee.

"Siesta" Original soundtrack LP-Marcus Miller and Miles Davis.Another incredible find with outstanding music.

All tube amps were used with stock tubes.


for the sake of sanity here I will not break down the individual sonics of each amp used in this test.First I'll say that the "brand X" amp had a lot to live up to.I hate that I know next to nothing about this amp.I guess for the purpose of pure objectivity I know all I need to about it.I gotta say I liked it,a lot.Compared to it's closest tube competition,the Wheatfield,it offers a nice open soundstage.I think that a SACD like "Kind of Blue" sounds best on solid state gear(that was hard to swallow and repeat).It is a rare tube amp that maintains the stunning detail of this recording and allows the music to shine in that "tubey' kind of way.the Brand X is that rare tube amp.Sweet, with the depth of soundstage of SACD,Impressive.Compared to it's closest solid state amp competition,the Grado,it does not offer that last bit of minute detail or frequency extension but it is just as quiet.I don't think that it is possible to design an AC powered amp that is this quiet.The brand X has very good bass extension but I think it losses some control(the bass notes seem to overlap)on some of the passages on the India Arie disc.No other digital recording I tried was able to trip up the brand X and I doubt anything other than a heavy bass laden track could do so.I never thought I would use the terms"dead silent" and "laid back" when describing the same piece of equipment,especially an amp,but here goes.The Brand x has both these qualities which I think in combination make for a unique product.Whenever I listen to a tube amp I expect a certain amount of backround noice and have learned to accept the presence of that noise.I was pleasantly surprised to find such backround noise absent from the brand x amp.I also expected this amp to exhibit some type of micophonic problems when used in a portable environment.I shook this amp while it was in use and was not able to discern any noise caused by the vibration of the tubes.I must say this is amazing and lead me to doubt that this amp is actually tube staged.I love this amp's vocal performances.The Brand x seemed to really like Ms. Barber's voice and really opened up on this disc, played on all players.I fully expected the brand x to run out steam on some of the complicated passages on the "Gladiator" soundtrack.this would not have been a great embarrassement as few amps,loudspeaker or headphone,can do this disc justice.I am happy to report that the brand x takes this disc on and does so in the same relaxed manner it does any other music.

while I was impressed with the Brand x amp's performance with digital mediums,I was most eager to see how it performed with my preffered vinyl medium.in this arena it gets beat up by the Wheatfield.The brand x seems unable to convey the intimacy of the "siesta" soundtrack or the genuine compassion of the "She's gotta Have It" LP.On several passages of the "Gotta have it" lp several horns are playing at once(tenor and alto sax and flugel horn)the Wheatfield seems to pick the cord changes and overlapping harmonies right out of the air,The brand x does not get this right, the same passage that sounds wonderful and flawlessly performed with the Wheatfield seems somehow "compressed" when played over the brand x.This was the case with all the phones and through all the jacks.I wasn't completly disappointed with the brand x, but as I said before it just seems to lack that last bit of "warmth' and tube type resolution.Miles' horn on the Siesta lp sounded "faded" like he had taken a big step back from the mike,whereas with the wheatfield he seems to be playing right next to you.Marcus Miller's heavy handed bass attack on the Siesta lp is so brutal I really thought I might damage my speakers when I first played it and It conveys the same power and brutality when played on the Wheatfield and Grado amps.The Brand X makes this track sound like a long drawn out "thud"or a humming.None of these traits endears me to the brand x and I would never use it when listening to by beloved vinyl in it's present circuit configuration. When I audition a headamp I place great emphasis on that amp's low level resolution and warmth or detail depending on what type of amp it is(tube or solid state).I wish to preserve my hearing so I don't blast the music that I play throuh headphones,this desire makes an amp's low volume level performance crucial to me.I can say that the brand x offers no great loss of detail at lower volume levels.the low level bass performance is especially good and is perhaps the best I have heard.



I think that the Brand x offers some very good performances and is simply the most silent tube amp I have ever heard.My dad and brother also came by to listen to it and my dad is convinced that it is not tube staged at all.my brother thinks it is a hybrid and the tubes are not in the signal path.this was all a mystery to me and remained to be determined.the fact that this amp has no microphonic characteristics and the fact that the battery power lasted almost nine hours did not help quell this concern.Factor in that this same amp has been shipped all over the country to many different people without any damage or degredation of sound quality and the likelihood that this amp actually had tubes in the signal path was getting smaller.When I tried the two Tungsram ECC88 tubes provided by the designer to roll into my own components, I found the tubes to be very microphonic .A small thud on the side of the XCAN caused an audible buzz for a quick second.I was having serious doubts about this amp and the claims it's designer made and I felt I knew enough about tube gear to know what tubes sound like.I was wrong.When I took the amp to the UPS terminal at Midway(I was working in the area)they chose to x-ray the package.Right there plain as day was a tube.I only saw one but it was inside the amp and wired up.This is truly incredible.I have had UPS damage a a four inch thick 20"by 24" Hard rock Maple butcher block,the fact that this amp has been all over the country without suffering any damage is unreal.My hat is off to the designer of this amp.

In conclusion I would offer that this amp is a real solid piece of engineering and I hope that a slightly improved version of this circuit sees production.The designer asked what I think the cost should be and I'll answer ,that if this amp had that last bit of "tubeiness" and warmth I would pay big bucks for it($1000-$1500)in a nice case.In it's present form(circuit design only)I would pay $500-$750 for it solely because it would be the only tube amp around that could claim to be portable.It does indeed stack up well against the best amps I had on hand for this review and is only bested by the Grado and Wheatfield in the areas that they are strongest in.It is a strong contender for most versatile headphone amp.

side note:
I found it strange that Grado headphones(low impedance) sounded best when plugged into the higher impedance jacks and vice - versa with the Senns.???????????

Update 3/20/2002:
I recieved several emails from the designer asking that the pics be removed immediately.I have done so at his request.I apologize for this misunderstanding.
 
Mar 21, 2002 at 1:18 AM Post #10 of 54

Tuberoller

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Anyone else who has auditioned this amp is strongly encouraged to post reviews/impressions.I have heard from the designer today several times.He was not pleased that I posted the pics but I understand his concerns fully.He has stated that he will reply to the reviews once they are posted.As I said I liked it a lot and I do believe there is a market for this amp and hope to see it in production.No,I have no idea when it will see production or how much it will costsor anything else.Those questions will most likely be answered by the designer when the other reviews are posted.
 
Mar 25, 2002 at 5:31 AM Post #11 of 54

Mike Walker

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When I first agreed to review the Brand X headphone amplifier, I was very eager to receive it, and anxious to get started…believing that I would be able to give a fair, unbiased review of it’s strengths and weaknesses. Now I’m not so sure (about the job I’m able to do). The reason? I had assumed that, being a tube amplifier, the sound of the “Brand X” would be distinct, with some of the syrupy sweet “tube warmth” that we who love tubes (and yes, I AM one of “them”) appreciate. Well, TO IT’S CREDIT the Brand X amplifier has none of that tube “personality”. From purely a sonic point of view, it seems to have no personality at all. And perhaps that’s the kindest thing that can be said of a component whose job is simply to amplify, WITHOUT CHANGING the sound that passes through it. This Brand X does magnificently.

The Brand X is one of the least “colored”, most “neutral” pieces of audio gear, tube or solid state, which I’ve ever encountered. This delights the purist in me. But I must admit that the tube lover in me was a bit disappointed, as I can point to absolutely nothing as being “tube-like” in the sound of the Brand X. It is supremely NEUTRAL. More so in fact than most solid state headphone amplifiers. Take the models from Headroom, for instance. Headroom products have a family “sound”…warm, “glowing”, with slightly rolled-off extreme highs. Compared to my “Total Airhead”, the only portable headphone amp which I own, it is the “Total Airhead” which to these ears sounds more “tubey”. It also is the “Total Airhead” which is the most “colored”, the Brand X simply passing the signal through (with gain…more comments about which later) without adding any editorial commentary on how the music being reproduced should sound!

When I first unpacked the “Brand X”, I plugged in my Philips Expanium 203 portable cd/mp3 player (with Radio Shack gold plated cables) into the Brand X, and fired up “Don’t Worry Baby” by the Beach Boys, a long-time favorite. Admittedly neither the recording, nor the source materials are “audiophile approved”, (although I think the Philips portable is a completely reasonable companion to a supposedly “portable” amplifier) through my Sennheiser HD-580 headphones, plugged into the 250-400 ohm jack, the sound was wonderful…. Sounding JUST AS this same recording does through the headphone amplifier of my Yamaha MD-8 digital workstation, and the (excellent headphone section of the) Mackie 1604vlz, a console noted for it’s superb headphone amplification.

Interestingly I got far better results (in terms of dynamic “punch”), and noticeably more gain when using high impedance ‘phones such as the HD-580, HD-600, and Beyerdynamic DT-990 Pro than when used with lower impedance, generally more "sensitive” ‘phones such as the Sony MDR-7506/MDR-V6 and Grado SR-80. Interesting, and quite unusual!

Criticisms? I have a few. First of all gain. I’ve been assured that the production model will have “twice as much gain” as the unit supplied for review. A good thing! For several days after first using the prototype Brand X with my MDR-7506 ‘phones, I referred to it as the “straight wire WITHOUT gain”. Honestly, gain was very nearly unity (NO gain) when feeding the 7506 from the output of portable CD players, mp3 players, and portable MD and DAT units. GIMME SOME GAIN, PLEASE! (Again, I have been assured that gain will be a non-issue in the production model. But I leave this observation in because it was of concern to me with this prototype!)

Just three more “nits to pick”. First of all, I’m not a fan of dual (separate left and right) volume controls. I understand the purist ideal of keeping channels as separate as possible. Blah, blah, blah. I still say…”Give me a single STEREO volume pot, and if you really feel generous, a balance control, too.”

As for the internal rechargeable battery, frankly I don’t give a damn. There’s no way I’m going to carry something this large (about the size of a typical “1 rack space” piece of rack-mount studio gear) as a portable, so I simply don’t care about the battery power. Didn’t use it (except to confirm that it works), and wouldn’t.

And the final “nit”: if absolute transparency (with no audible coloration) was the design goal, as it obviously was with this unit, why use a vacuum tube at all? Yes, I realize that any level of sonic accuracy that’s achievable with solid state devices can also be achieved in “hollow state” designs. It just seems (to me) that achieving these results is more difficult with tubes, and can result in products which are less stable, and less reliable. Wait, didn’t I say I was a tube-lover? Yes, I certainly am! But I admit that my favorite tube designs are the ones that actually sound like there’s a light show going on “under the hood”. For many years I used an early 60s vintage Fisher tube amp to drive headphones simply because of the “warm, silky smooth sound” of tubes, with the expected “liquid midrange”, “sweet highs”, etc. Colorations? You betcha! Which is why I would NEVER use a tube amp for monitoring in my studio. Except, perhaps, for the Brand X. because it DOES NOT color the sound, as do other tube amplifiers. Whether this neutrality (in a tube design) makes you more or less likely to buy the Brand X (when available), only you can decide. I DO like this amp very much, and anxiously await the finished product, which I WILL evaluate for possible inclusion in my studio (as opposed to my home or portable systems). It’s that good! Enough said!

I shall end with a technical description of the unit, “lifted” from the literature supplied to me with the amplifier:
First a description of the unit. For that, I defer to the literature provided to me with the amp:

Headphone Jacks: The four headphones jacks have the following impedance ranges: 20-40, 100-250, 250-400 and 500-700. You may find that certain music will sound better when using a jack other than the one for which your headphones are rated. Experiment, you may be surprised.


Technical Stuff

· Input impedance: 25K ohms
·Input volts for maximum power output: 1V RMS
·Maximum power, from any output jack into a matched load: 25 milliwatts
· Triode design
· Incorporates components by Allen-Bradley, Electra-Print, Westcap, and Spectrol
· One NOS Tungsram ECC88 tube – Made in Hungary in the 1970’s, this tube provides the warm tone, wide stage, and coherence we like. During production, alternate tubes can be installed upon request.


Mike Walker Owner/Operator “The Production Room”
Host/Webmaster “The Production Room Dot Net”
Air Personality “Ninety Five Point Seven, ‘XRC” in Charlotte, NC
 
Mar 25, 2002 at 5:41 AM Post #12 of 54

Mike Walker

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While admittedly I didn't measure the Brand X (sorry, didn't have time), I DID listen to a variety of test tones on it that I generated on my computer using Cool Edit 2000. And I heard none of the rolloff in the deep bass that Kurt W. measured (I consider the treble rolloff to be much less of a sin, since I accept the fact (which other audiophiles refuse to) that most adults hear little if anyting beyond 15-17khz. Sorry if that shatters illusions or preconceived notions, but it happens to be true!). I wonder how the measurements were made, and if they were duplicated under different conditions (there are simply so damn many ways to hookup and listen to this unit!).

While I believe that MOST of what we hear can be quantified (not all, but most), when confronted with a product which sounds one way, yet measures another, I trust my ears!
 
Mar 25, 2002 at 6:13 AM Post #13 of 54

Serow

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Wow, seems like one heck of an amp! It should be interesting to see who actually made it.

Mike, haven't heard from you in a while
cool.gif
. Just wanted to let you know that Sennheiser is again producing the HD40 that you liked so much. It's now 32 Ohms like the later HD-40s were, and is now called the m@h40 - see here . I remember you saying you'd kill for an unused pair
evil_smiley.gif
.
 
Mar 25, 2002 at 7:31 PM Post #15 of 54

Serow

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Sorry for another off-topic post, but it more than just looks like it - they are the same. I spoke to a Sennheiser service tech when I needed mine repaired, and he mentioned that there was still such a demand for the HD40 parts that they decided to start producing them again.
 

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