Skylab
Reviewerus Prolificus
Another Head-fier asked me if I would be interested in reviewing the Bijou, a DIY amp design from Alex Cavalli. Of course, I said yes
. Extensive information on the design can be found here: The Bijou Stereo Headphone Amplifier and as such, I am not going to describe the design in any detail. For those who can’t be bothered, the Cliff Notes is that the Bijou is derivative of the Futterman output transformerless tube amp design. In the version here, the amp uses 6DJ8/6922 for the driver tube, Russian 6N6P’s for the output tubes, and a EZ80 rectifier tube. I auditioned the amp with Amperex EZ80’s and 6DJ8’s.
Pics:
This is the first amp I have ever heard with a variable negative feedback control. This will allow the greatest flexibility in use with headphones of widely varying impedance. My preference was to use as little feedback as possible, and since the lowest impedance can I tried with the Bijou was the 80 ohm Darth Beyers, this was not a problem. With the 600 ohm DT990s I used the minimum amount of feedback possible, with good result. And the sonic signature of the Bijou made it a better choice for the DT990’s (see below).
The amp was totally free of any sort of hum or noise, which is always nice from a tube amp, and certainly not always the case in my experience. This gives the amp a very black background, which helped contribute to the excellent dynamic swing the amp has. And it sounds terrific overall. Some of what I will say below will sound like I am picking on the Bijou. I am really just trying to describe its sound, which it does have, but it was, throughout my audition, incredibly fun to listen to, and it’s an amp I would recommend to anyone who has a desire (and the skills) to tackle a DIY project like this, or can find someone to talk into building one for them. It is also important to note that I’m sure the sound can be altered even further by using different 6DJ8s. All my 6DJ8s were Amperex made (I have some branded RCA but they also were made in Holland by Amperex – RCA never actually manufactured 6DJ8s), but there are clearly lots of other options that might change the sound further.
I initially used the Bijou with 6N6Ps as both driver and output tubes (meaning 4 total). This produced a meaty and dynamic sound, but it lacked a little detail and nuance. This has often been my experience with Russian tubes. Using Amperex 6DJ8’s as the driver tube improved this significantly. Used with the latter tubes, the Bijou sounded truly excellent. Still plenty of dynamics and a robust sound, but also good detail. It isn’t the world’s airiest tube amp, and it has a more “tubey” sound than my Singlepower Extreme (which is of course a very different amp). Using more negative feedback makes the sound a little leaner, but doesn’t make it any more extended in the treble. Still, this really isn’t a complaint – the Bijou sounds lovely, and is a very, very musical sounding amp. It was very easy to enjoy a very wide variety of music using the Bijou – the mids were so lush and pretty that it was addicting to listen to it.
Bass is quite good with the Bijou – there is a healthy amount of it, and it’s reasonably deep and tight, especially for a tube amp. The bass was not overly ripe or fat, and had good punch. No one will mistake it for a solid state amp in any aspect of its performance, and this is true for the bass as well – my Blue Circle SBH has noticeably tighter and deeper bass. Of course, the SBH is a $1200 SS headphone amp, so it’s a different breed. The SBH also has a more extended treble. But while the SBH has a very nice midrange for a SS amp, the Bijou’s midrange is purer and prettier than the SBH’s.
That is really true about the SP Extreme, too. The Extreme sounds much more like the Blue Circle amp than the Bijou does. The Bijou sounds more like my Ming-Da EL84-based tube amp – its got that more classic tube sound, which of course I think is incredibly fun to listen to, depending on the headphone. The Bijou is TERRIFIC with the Beyer DT990/600. It brings out the mids, and the 990’s supreme treble extension mates well with the slight roll-off of the Bijou’s treble.
So what we have here is a terrific DIY OTL tube headphone amp that gives full measure of what tube amps are about. I confess that occasionally I wish the Singlepower Extreme sounded a little "tubier" than it does, and the same with the Darkvoice 337. As such, it’s really nice to have amps like the Bijou available that sound like we all think a tube amp sounds, and has that breathtakingly beautiful, lush midrange which is what keeps us lovers of the thermionic valve so deeply in love
So all you skilled DIY’ers, have at it!
Pics:
This is the first amp I have ever heard with a variable negative feedback control. This will allow the greatest flexibility in use with headphones of widely varying impedance. My preference was to use as little feedback as possible, and since the lowest impedance can I tried with the Bijou was the 80 ohm Darth Beyers, this was not a problem. With the 600 ohm DT990s I used the minimum amount of feedback possible, with good result. And the sonic signature of the Bijou made it a better choice for the DT990’s (see below).
The amp was totally free of any sort of hum or noise, which is always nice from a tube amp, and certainly not always the case in my experience. This gives the amp a very black background, which helped contribute to the excellent dynamic swing the amp has. And it sounds terrific overall. Some of what I will say below will sound like I am picking on the Bijou. I am really just trying to describe its sound, which it does have, but it was, throughout my audition, incredibly fun to listen to, and it’s an amp I would recommend to anyone who has a desire (and the skills) to tackle a DIY project like this, or can find someone to talk into building one for them. It is also important to note that I’m sure the sound can be altered even further by using different 6DJ8s. All my 6DJ8s were Amperex made (I have some branded RCA but they also were made in Holland by Amperex – RCA never actually manufactured 6DJ8s), but there are clearly lots of other options that might change the sound further.
I initially used the Bijou with 6N6Ps as both driver and output tubes (meaning 4 total). This produced a meaty and dynamic sound, but it lacked a little detail and nuance. This has often been my experience with Russian tubes. Using Amperex 6DJ8’s as the driver tube improved this significantly. Used with the latter tubes, the Bijou sounded truly excellent. Still plenty of dynamics and a robust sound, but also good detail. It isn’t the world’s airiest tube amp, and it has a more “tubey” sound than my Singlepower Extreme (which is of course a very different amp). Using more negative feedback makes the sound a little leaner, but doesn’t make it any more extended in the treble. Still, this really isn’t a complaint – the Bijou sounds lovely, and is a very, very musical sounding amp. It was very easy to enjoy a very wide variety of music using the Bijou – the mids were so lush and pretty that it was addicting to listen to it.
Bass is quite good with the Bijou – there is a healthy amount of it, and it’s reasonably deep and tight, especially for a tube amp. The bass was not overly ripe or fat, and had good punch. No one will mistake it for a solid state amp in any aspect of its performance, and this is true for the bass as well – my Blue Circle SBH has noticeably tighter and deeper bass. Of course, the SBH is a $1200 SS headphone amp, so it’s a different breed. The SBH also has a more extended treble. But while the SBH has a very nice midrange for a SS amp, the Bijou’s midrange is purer and prettier than the SBH’s.
That is really true about the SP Extreme, too. The Extreme sounds much more like the Blue Circle amp than the Bijou does. The Bijou sounds more like my Ming-Da EL84-based tube amp – its got that more classic tube sound, which of course I think is incredibly fun to listen to, depending on the headphone. The Bijou is TERRIFIC with the Beyer DT990/600. It brings out the mids, and the 990’s supreme treble extension mates well with the slight roll-off of the Bijou’s treble.
So what we have here is a terrific DIY OTL tube headphone amp that gives full measure of what tube amps are about. I confess that occasionally I wish the Singlepower Extreme sounded a little "tubier" than it does, and the same with the Darkvoice 337. As such, it’s really nice to have amps like the Bijou available that sound like we all think a tube amp sounds, and has that breathtakingly beautiful, lush midrange which is what keeps us lovers of the thermionic valve so deeply in love
So all you skilled DIY’ers, have at it!
