[MoodySteve]

Thanks for the review! I'm eagerly awaiting my kit from Jeff Rossel, and it sounds like the Bijou is exactly what I wanted ;if I'm going to build an all-tube amp, it may as well sound like one!

 

[dizzyorange]

I've had a chance to audition Mazuki's Bijou (the same unit Skylab reviewed) for a few weeks now. Some thoughts:

The Bijou is unequivocally the best headphone amplifier out of the list below (amps which I have owned):

Bijou
"Pink Floyd-modded" Musical Fidelity X-Can V3
Heed Canamp
Meier HeadFive
High-end Millet Hybrid
Doge 6210
Eddie Current EC-01
Zero Audiocraft Portable Amp

My source is a passively bypassed DAC-AH, headphones are HD650, cables are copper DIY. I listen to lots of vocals, classical, jazz.

The most immediately noticeable quality of the Bijou is its silent background, nearly totally devoid of hiss. With the volume turned to reasonable listening levels and no music playing, there is dead silence even at a quiet time like 1 in the morning. It's what the night sky looks like in upstate New York, away from light pollution: a twinkling lattice of white on black madness. Or as Shakespeare would say: "This majestical roof fretted with golden fire!"

With 6N6P driver tubes, the amp puts out a rock n' roll flavor, with that midrange/lower-treble hardness that makes rock enjoyable. The impact of percussive instruments is forceful, and it feels like air is being moved on deeper bass notes. The bass extends quite deep (but not the deepest I've ever heard the HD650), and is somewhat emphasized in a slightly round way. It's PRATTY.

(Btw, I know what PRAT means, but what does it stand for??)

I had a pair of Amperex 6922 tubes that I swapped in for the driver positions. This made quite a difference. The sound was more balanced, closer to neutral. The bass seemed quicker. Basslines felt more staccato, with a bit less of that fart-like (where air is moved) bass that the HD650s occasionally put out. The mids were wonderfully transparent. Nicely recorded vocals like Alison Krauss or Vienna Teng hung in midair clearly separated from the bass guitar, which was nicely separated from the guitar accompaniment.

Highs are buttery smooth. There is never a feeling of harshness, fuzz, or artificial detail up top. That is not to say the Bijou isn't detailed. It captures as much detail as any amp I've heard. It just presents it in a way that is very non-etched. Another way to describe this is that the detail never stands and out announces "THIS IS DETAIL!". Rather, the detail works to make a vocal or instrument seem more "present" in the room, and more "focused". Thinking of the presence knob on a guitar amp, at 0 it sounds a bit far away, at 3 - 5 it sounds like it's right there next to you, at 10 it sounds like like an Etch-a-Sketch. The Bijou is right at a 4.

I will point out the highs are probably affected a bit by the NOS DAC I am using. However, the passive bypassing of the opamps in the DAC results in a sound that sounds extended up all the way to my ears. That is, there doesn't sound like there is any treble cutoff. Without worrying too much about freq curves, the DAC-AH and Bijou sound damn good together.

Best word to describe the Bijou is ORGANIC. I don't think the tube bloom is as noticeable as Skylab did. It may be because we are using different tubes. It's got a touch of liquid mids compared to, say, a Meier Headfive, but the bass isn't fat and loose and the mids aren't bloated at all. The sense of dead black space surrounding a solo vocal is the best I've heard.

There is a negative feedback control next to the volume control. To me, the amp sounded best with a small amount of negative feedback. Increasing the negative feedback seemed to dial up the "presence knob" at the cost of overemphasizing detail. With no negative feedback, the sound was very relaxed, perhaps slightly too relaxed for the Senn HD650s. 3D depth was best with less negative feedback. As NFB was increased, the imaging flattened out. One thing of note is that the volume range is more restricted with no NFB. Even turning the volume all the way up on zero NFB did not result in a satisfying listening level. Adding just a small amount of NFB appeared to increase the gain of the amp by quite a bit.

If you are using low impedance headphones, you will probably want to use some NFB for more current output (not 100% about the technical accuracy of that).

Finally, the amp has the coolest POWER ON indicator ever. Reminds me of the Harmon Kardon volume control on their receivers, except miniaturized.

 

[edisonwu]

Oh man! You did a great job. Thanks~!

 

[Skylab]

Nice review, DizzyOrange! Thanks.

BTW, PRAT = Pace, Rhythm, and Timing.

 

[antonyfirst]

Wow! How much will it cost, more or less?

 

[huskydawg9]

I've had a chance to audition Mazuki's Bijou (the same unit Skylab reviewed) for a few weeks now. Some thoughts:

The Bijou is unequivocally the best headphone amplifier out of the list below (amps which I have owned):

Dude...(or dudette), perform the mod and replace the 6922's with 6H30's and then redo this evaluation. It will take something very special and turn into a whole another amp...it will blow you away...I guarantee it. Check out Alex's website for info (or headwize).

You can quote me on this...


Huskydawg9

 

[huskydawg9]

Let me clarify...after modding and either using 6N1P's or 6H30's you will NEVER go back to 6922's!

 

[Clutz]

Hey huskydawg, welcome to Head-Fi and sorry about your walllet. Anyway, would you mind expanding upon your preference for the 6h30's or the 6N1P's over the 6922s, either here or at headwize?

Thanks,
Brad

 

[Mazuki]

Quote:

Let me clarify...after modding and either using 6N1P's or 6H30's you will NEVER go back to 6922's!

One problem with using those two tubes is your tube rolling options suddenly shrink to, well, almost nothing. While I don't doubt the outstanding performance of Russian tubes, part of the tube lure is to change flavours depending on your current listening preference...

 

[huskydawg9]

Quote:

Originally Posted by Mazuki /img/forum/go_quote.gif One problem with using those two tubes is your tube rolling options suddenly shrink to, well, almost nothing. While I don't doubt the outstanding performance of Russian tubes, part of the tube lure is to change flavours depending on your current listening preference...

I rolled all sorts of 6922's and posted my comments over on headwize. I was particually fond of the Sovtek 6922's. That caused a commotion over there, including the following quote:

Quoting dsavitsk
"6dj8 family are a pretty high distortion valve in general, so it seems an odd choice if the tube's sonics are really important here. But, that said, those sovteks are just horrible. I am surprised at the good reviews, though mine were made in the early 90's, so maybe they have changed since then? Why not a 6n1p, or a 6h30, or 6n6p? They should all be able to be made to work, and all are lower distortion than the 6dj8 family"

The question was posted to Alex, and he replied with the needed modifications. First thing I did was put a 1uF Clarity cap in parallel with the electrolytics (which by itself...was a nice improvement). Then, I purchased a small 6.3V transformer to provide the additional heater current needed. Also socketed the bias resistors so I could roll back to 6922's if desired. First tried 6H30's. And you are right...there are very few choices here. I'm using new Sovtek's. The sound was much improved. I'm not very good at describing the improvement...but it really opened it up and made it more transparent. Really could notice fine details that I didn't notice before. Next I obtained several different NOS Russian 6N1P's. These are very close to the 6H30's as far as sound quality, but have a much different gain (higher). Because of the gain, my Grado's tended to like the 6N1P's better. That was before I got my DDDAC up and running (last couple of days). Now gain is not as much of an issue and have swapped back to the 6H30's. Also since switching my Bijou source from my Ipod to lossless audio and the DAC...we are talking a whole 'nother ball game (and I still have another dac tower to build)...

 

[Skylab]

I don't know about the 6H30, but Amperex 6DJ8's sounded much better than 6N1P's, IMHO.

 

[huskydawg9]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif I don't know about the 6H30, but Amperex 6DJ8's sounded much better than 6N1P's, IMHO.

That may be true... but I wasn't going to spend $240 to find out...

 

[Mazuki]

Quote:

I don't know about the 6H30, but Amperex 6DJ8's sounded much better than 6N1P's, IMHO.

It's hard to compare those tubes directly without taking into consideration circuit topology. Often people use 6N1Ps in circuits designed for 6DJ8s and that's not going to work correctly.

Then there's the cost consideration.

For this amp, the best thing to do is probably what Huskydawg did and socket the cathode resistor so that different tubes can be used. The more tube options, the better. There's no arguing against that.

 

[Ferrari]

The sound impressions described by Skylab and dizzyorange are very familiar to my ears.
I'm using Siemens E88CC (gold pins) for the driver stage, Russian 6N6Pi for the output stage and MKP//K75 PIO capacitors at the output. The NFB circuit is not implemented in my amp since I use 250Ω/300Ω headphones only (however the NFB circuit was implemented in the prototyping phase). Nothing fancy in the chain: my old favourite CD player (Rotel RCD990) as source => Bijou => Sennheiser HD650

Time after time, I really enjoy the music this amp produces... pure music and nothing else.
I feel a bit guilty that I can't find the time (as a busy guy that I am sometimes) to do the case work for it.
This little baby deserves a neat enclosure

.

 

[runeight]

Hello everyone. Just a comment about swapping input tubes.

As Mazuki points out, you can swap 6n1p and 6h30 in the input stage but you really need to change the cathode resistor for this to work properly. When you do change this resistor the amp will be at the correct operating point for the new tube and you'll get the best audio results.

You can find information on the value for this resistor at: Cavalli Audio

Many thanks to the reviewers and those of you who are making Bijou builds.

Now Ferrari, when are you going to case up your amp???