[fishski13]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Ah. I did this calculation quite a while ago and I don't remember how to do it again, but the output impedance is given by: Zo = rp / (2 * (1 + mu)) The ECC99 has an rp of 2300R and a mu of 22 so ... Zo = 2300 / (2 * 23) = 50R The 6N6P has an rp of 1800R and also a mu of 22 so ... Zo = 1800 / (2 * 23) = 39R In this configuration, with the crossed outputs from the phase splitter, both O/P triodes operate as cathode followers. So the Zo is essentially the paralleled Zo of two cathode followers.

thanks!

 

[rolotube]

Anyone tried the Reflektor 6H23P-EB? Appears to be a Russian low-noise military spec variant of the 6922.

 

[Forte]

Have tried the regular 6h23p tube, got one in a batch of 6n1p by mistake. Prefered it to the 6n1p IIRC (haven't listened to it in a long while)

Edit - This was in a CTH(getting threads mixed up)

 

[rolotube]

Thanks. All reports I've seen where these have been used in other amps have been positive. Got some coming this week so I'll find out soon enough.

 

[Proutch]

Hey guys,

Just sharing my recent experience with the Bijou: I replaced the ECC8 with vintage Orange Globe Amperex tubes made in Holland.
And I must say the improvement is drastic! Sound is much cleaner, more transparent, slightly tighter, still sweet and full.

In case you're still running the stock tubes, this is clearly worth the investment!

I must say I had a hard time to chosse between Orange globes and Bugle boy. The latter get so much positive comments, including in this thread. At the same time, they look slightly overpriced because of their reputation and Orange Globes were made in the same factory, and should sound very similar.

This being said I'd be very curious to compare my Orange Globes with Bugle boys...
Has anyone had a chance to do so?

 

[regal]

I also found the orange globes to be a better match to the Bijou than the bugle boys. I don't know if its because most average bugle boys on ebay are spent or if there is some technical reason. Lets hope these two posts dontt drive the orange amperex price up.

 

[rolotube]

I've had a set of Bugle Boys in for a few weeks now & have been extremely happy, especially as I got them for a very reasonable price. The Orange Globes were also available but were very little cheaper, so I went for the BB's largely on reputation. But I remain curious as to the differences between the "classical" old 6JD8 variants. Given their relatively high cost & increasing scarcity, it may take some time & quite a few $$'s to work through them all.

I'm currently enjoying something different; Reflektor 6N23P-EB, dated 1986. Just put them in tonight & initial impressions are extremely favourable. Not as full & rounded as the Bugle Boy, more "in your face" & analytical perhaps, but very musical. Bass is more solid, mid & upper mid not quite so forward. Maybe not quite the same expansive soundstage & 3D imaging the Euro tubes are famous for. And absolutely dead black quiet. They may possibly be a slightly better match for my rig than the Bugles. I'm running all film caps (no electros) including Silver/Oils & Jupiters so the sound may be bit "softer" compared to stock. Early days yet but I'm very impressed, especially as they were less than $50 for a matched pair.

As Proutch highlights, the stock tubes are OK but there's much to be gained in trying the many different types that the Bijou design permits.

 

[kansei]

I set my mind on building a Bijou in December. My initial plan was to resell some tubes on eBay to make $ for the kit. I ended up getting distracted buying and selling on eBay for about 6 months until I finally decided to order the kit.

Last year I had no tubes and no tube equipment. I now own 4 tube testers (3 Hickok and 1 Eico), a bunch of tube amps, bunch of testing equipment and a few thousand tubes. I'm not sure what happened.

First Bijou impressions:
- sounds incredible, it squeezes every bit out of the music you play
- Diana Krall, Dido, The Cardigans, wow
- this amp really drives my HD600s, bass response is terrific
- it really worked, even the first time, yay!
- needs burning in

I first used the "cheapo" GE 6dj8 tubes, then switched to the Bugle Boy tubes. I have other 6922 tubes, will have to try a few different sets.

Building impressions:
- it was easy to solder together, took no time at all
- my brain went into a spasm when the time came to wire it together, had to power through wiring it together
- I mounted it on a shabby 12x8 chassis that used to belong to an old Lafayette PA amplifier (that was left in someone's basement for too long).
- I'm afraid to post pictures because it looks awful
- it's time to buy a nice Hammond chassis
- now I need another project, rats

 

[runeight]

That's great Kansei. I'm glad you like the sound. Still one of my favorite amps.

Since I'm a real old-time, I kind like the chassis. Reminds of long, long ago. But, you'll probably be happier when it's in something that you like better.

As for another project, far be it for me to suggest, but you could try either the SOHA II or the EHHA. Both a fun amps and are each quite different from Bijou. There are threads here on headfi dedicated to both amps.

 

[kansei]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif That's great Kansei. I'm glad you like the sound. Still one of my favorite amps. Since I'm a real old-time, I kind like the chassis. Reminds of long, long ago. But, you'll probably be happier when it's in something that you like better. As for another project, far be it for me to suggest, but you could try either the SOHA II or the EHHA. Both a fun amps and are each quite different from Bijou. There are threads here on headfi dedicated to both amps.

I had a good amount of anxiety finishing this project. I wanted to get the amp up and running and kept hitting roadblocks with wiring it together. Finally, I decided to just hack it as best as I could and fix it later.

Don't get me wrong, I like the chassis, it is very "old school" (that's why I decided to use it). What I need to do is to take it all apart, then polish the chassis and neaten the wiring.

This is the first time in months I've had a working headphone rig, the clean-up will wait until I get something else up and running.

SOHA II is on my list, one of these days.

 

[rolotube]

kansei, good to learn of another Bijou up & running with a satisfied owner/builder. I'm still knocked over with sound every time I fire mine up.

As for other projects, I can heartily recommend the SOHA II. I've just finished mine (first iteration, anyway) & am very satisfied with the results.

 

[kansei]

I ran my Bijou overnight after I first built it. The second time I wanted to use it it would not work. It turns out that R5 in the power supply flamed out. I had to hack up a replacement since I don't have an exact value (ran four 80k resistors in parallel). Still, the replacements are running super hot.

I have 2 questions:
- when adjusting the power supply, is it absolutely essential to put the 100k resistor over over the 250v output and GND? I adjusted mine without it and it appeared to be OK
- is it possible that my power supply is incorrectly adjusted and that's why it blew out the R5?

Thanks.

 

[runeight]

Kansei, it is very possible that your PS is not working right. Measure the B+ with the amp boards connected. My guess is that you will not read 250V. Usually this is caused by a short to the PS (even briefly). This, in turn, causes the mosfets to die and when the do lots of current is passed through R5. However, R5 is spec'd at 1W to handle this condition so that even if the fets go out R5 will survive. But if R5 is toasted too, the PS is surely gone.

Sorry to for this news, but I think this is correct. However, please measure the B+ and tell us what is says.

Thanks.

 

[kansei]

I assume that B+ is the output voltage of the power supply, marked 250v and star ground. If my assumption is correct, I get 103v on B+ with both of the amp boards connected and 250v with the boards disconnected.

 

[runeight]

Correct. I'm sorry to say that 103V indicates that both of your mosfets have died and have to be replaced. When you do that it would be good to check other components in the PS and replace R5 with the right size if you have it.

It is very difficult to protect a high voltage supply against shorts without going to a lot of expense. The Bijou HV supply is simple (and cheap), but it can be blown.

However, my supply is more than 3 years old now and it still regulates. So, normal power-up and power-down do not cause the PS to die. Only short circuits or massive overloads.