Fall 2007 Prototype builds
12/18/07 Bijou thread started for new amp design
12/19/07 Group buy is available here: Bijou Group Buy
12/21/07 Production boards ordered

Initial Post

Hello everyone. Your wait is finally over.

The Bijou amplifier boards and kits are now ready for production. JeffR will be setting up a marketplace thread for group buys in the next day or two and boards and kits will be available from:

Glass Jar Audio

The Bijou has been redesigned to fit on two small boards: a one channel amp board and the power supply board. A full stereo amp will need two amplifier boards and a single ps board. The purpose of the redesign is to make building a high voltage, all tube amplifier as easy and as safe as is reasonably possible. If you've avoided building a tube amp because of the HV, the new Bijou might just make it possible for you to try this.

A handful of intrepid prototypers have been generous with their time and effort to build the first board-based prototypes and provide feedback. I want to thank dBel84, Mazuki, vixr, and Ferrari for the time and effort. And JeffR for making prototype boards available to the team.

As a result of the prototype work the original boards have been modified to improve their design and to give the builders more flexibility. We also changed the standard PS from 220V to 250V, improving the amp and making it possible to use a wider variety of transformers.

A full explanation of the Bijou amplifier can be found at:

Cavalli Audio

The website also has schematics and instructions for building the boards and amp, along with initial setup and troubleshooting.

The Bijou is a fully balanced Futterman topology that uses only two tubes per channel: 6922 and ECC99 (or 6N6Pi). The power supply uses a tube rectifier (EZ80/6V4) with a mosfet 250V regulator. The power supply requirements have been simplified to require only one HV winding and one heater winding on the transformer, keeping down cost and complexity.

I built my own Bijou about two years ago and was delighted with the sound. To me it's a very charming amplifier with a rich tone and lots of detail and sound stage. Hopefully other builders will post their comments on this thread.

This will also be the primary support thread for the production builds and for those of you who do P2P builds on your own. The prototype process, however, has indicated that the build process is simple and the amp is fairly immune to mistakes (except for shorting out the regulator as described on my website).

Another thread on the Bijou was started by Tai West who built the second Bijou after mine. There is good information here along with helpful discussions and a Tai's review of the amp.

Cavalli Lovell Futterman

The Bijou thread on the "other" forum is:

HeadFi Bijou Thread

I'll post more information at the top of this post as it is available.

[Edited by runeight on 12-24-2007 at 06:15 PM.]

I'll be building one for myself in the near future as well and promise you you won't be disappointed if you build this amp .

p.s. Runeight, don't forget to post a pic of YOUR Bijou too!

[Edited by batman on 12-18-2007 at 07:44 PM.]

and here is what I did with it...

this is a very sweet sounding amp. I have hours and hours on it now and it still surprises me.

[Edited by vixr on 12-19-2007 at 08:44 AM.]

Now I'm stuck between SOHA+JISBOS or this little sweetheart.
Does somebody know if Jeff will offer the transformer, too?

best regards,
bearmann

The SOHA+jisbos and the Bijou are very different amps. Since I only have a Bijou I can't offer a comparison. However, instead of building the SOHA with strapped on buffers, you could wait until we release the SOHA II.

Thanks

This question may not be suitable here but here goes:

1) How good is a Bijou as a preamp for a speaker system? (I don't need source switching)
2) What are the design parameters for a preamp / headphone amp?

Asking as I'm now looking towards building a preamp - I don't do enough listening on my headphones (at home) to build 2 more nonportable headphone amps.

I presume the transformer can be wired for 240v inputs, right?

her shann

There are lots of good headphone amps available right now in different categories. These range from the CK2III to the beta22 to the MMax to the SOHA and others. They are really all different in their designs and in the ideas behind the designs.

The Bijou is an all tube amplifier and it should hit the mark as good or, probably, better than the BCJ amps. I know from comparing it to the CL MK I that it bests these amps easily. I think that batman confirms this too.

hershann - The Bijou can make a nice preamp. A headphone amp needs to have some power gain to be able to supply many mA of current to the headphones. It is designed to see loads as low as 32R.

A preamp generally doesn't see loads less than 10k (usually higher) so it only needs voltage gain. Its output stage doesn't need to supply much current to the load although it has to be strong enough to deal with cables, etc.

The large electrolytic on the output of the Bijou gives it good low frequency response into low impedance headphones. If you really want to use it as a preamp, I would simply suggest replacing the output cap with a 1u film cap. On the new, production Bijou boards, there is a spot for this type of cap. So all you would do is to not install the electrolytic cap. Then if you ever wanted to use it as a headphone amp, you could just insert the electrolytic cap and you're ready to go.

The amp can be wired using a 240-0-240 transformer. There is an explanation of how to do this on the cavalliaudio website.

---

[Quoting bearmann]

Now I'm stuck between SOHA+JISBOS or this little sweetheart.
Does somebody know if Jeff will offer the transformer, too?

---

Having heard both the SOHA and the Bijou, I can tell you that they are in totally different categories. The SOHA was our attempt to squeeze as much performance as possible out of 50 bucks worth of parts. IMHO we succeeded far beyond our expectations.

The BIJOU costs significantly more to build and offers levels of performance commensurate with its cost and complexity. It is the best headphone amp I have heard but YMMV, there are some other high performance designs in the Headwize library and elsewhere. Nevertheless I will be building one of these too because I have never forgotten the sound of Runeight's unit.

p.s. Runeight you really should post a pic of your unit as well so folks can see the chassis.

[Edited by batman on 12-20-2007 at 09:43 AM.]

BUT! Till now I thought, that the Bijou will squeeze around $250 out of my wallet - true? false? (without the case)

Hummm... I think I'll just wait till Jeff offers some kits.

Ouh... but I have one technical question:
On most designs you see the transformer far away from the audio circuits. Mostly the power supply is in a different enclosure. But it seems to me that there is no need for this when it comes to tubes. There you see transformers next to the tubes (which are in the audio-circuit path) ... probably a stupid question but why are there no problems with transformers when it comes to tubes?!

best regards!
bearmann

JeffR will have to comment on how much his kits will cost.

Tube amps are the same as transistor amps regarding the transformer and PS. Bijou builds should keep the tranformer and PS board as far away as possible from the audio boards if they are in the same enclosure. However, many builders, like vixr, will get good results with a just some decent spacing between the parts.

My original Bijou actually had buzz problems at the beginning because I put the rectifier tube too close the audio circuitry. I fixed that in my prototype and the production Bijou, with its separate boards, allows you to use as much distance between boards as you have available.