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Bijou All Tube Futterman Headphone Amplifier
Oct 25, 2009 at 4:50 AM Post #2,911 of 4,278
viction - The case I'm using is a Hammond Aluminum case that measures 8x12x3 in. It's a pretty good fit. I got all my jacks and switches from mouser.com, I'm sure other people will have other suggestions.


Everyone - I finished putting everything together and noticed that my two 6h6n tubes don't light up. The three other tubes do. I measured heater voltage and it reads: 6.5VAC across the tube pins. That's a little high, could that be causing a problem?

It seems to work, but volume seems a bit low. I need to get up to around 11 o'clock for a decent volume (I don't listen very loud) with the HD650s. Is this normal? NFB is at it's lowest (for highest impedance phones).

Thanks for the help!
 
Oct 25, 2009 at 6:23 AM Post #2,912 of 4,278
Quote:

Originally Posted by xxbaker /img/forum/go_quote.gif
Everyone - I finished putting everything together and noticed that my two 6h6n tubes don't light up. The three other tubes do. I measured heater voltage and it reads: 6.5VAC across the tube pins. That's a little high, could that be causing a problem?


The 6.5VAC heater voltage is within tolerance. There are different heater wiring configurations for V2 depending upon the tube (see this link Bijou Wiring). Did you use pins 4-5 for the heater?
 
Oct 25, 2009 at 7:31 AM Post #2,913 of 4,278
Quote:

Originally Posted by balderon /img/forum/go_quote.gif
The 6.5VAC heater voltage is within tolerance. There are different heater wiring configurations for V2 depending upon the tube (see this link Bijou Wiring). Did you use pins 4-5 for the heater?


You were totally right! I wired the other way (4, 5 and 9). Now I feel a bit silly for not even thinking about what tubes I was using. Just finished listening to the first 20 minutes of bliss.
L3000.gif
I'll probably post some pics in a few days (or less).
 
Oct 28, 2009 at 6:34 AM Post #2,915 of 4,278
So recently my bijou has developed a channel imbalance. The imbalance doesn't follow the tubes when I switched them. I bypassed the pot with no difference. I also redid most of the wiring since it was messy and the heater wire was probably a little too thin. I think that the lower frequencies are more imbalanced than the higher frequencies but I could be wrong. Any ideas for where to start? The only active parts are the tubes and it seems odd that a resistor or cap would change value significantly. This problem did start after I brought the amp back from a meet so it maybe something shifted inside?
 
Oct 28, 2009 at 8:10 AM Post #2,916 of 4,278
check the star grounding point (as its mechanical). Check the input circuit first (with the amp off, remembering the otuput caps can still pack a shock (I always discharge them. check the resistance of the pot for each channel. IF that shows nothing...

Check the voltages, B+, then the anode voltages of the valves. should point to what is going on?

Also, have you ruled out the source + phones?
 
Oct 28, 2009 at 8:11 AM Post #2,917 of 4,278
check the star grounding point (as its mechanical). Check the input circuit first (with the amp off, remembering the otuput caps can still pack a shock (I always discharge them. check the resistance of the pot for each channel. IF that shows nothing...

Check the voltages, B+, then the anode voltages of the valves. should point to what is going on?

Also, have you ruled out the source + phones?
 
Oct 28, 2009 at 6:05 PM Post #2,918 of 4,278
Hey guys

I'm enjoying so much the superb sound of my Bijou, that I thought of using it as a preamp to drive a DYI tripath power amp

What do you think? Does it make sense?
Do I need to tweak the Bijou to use it as a preamp?

Thanks in advance for your help
atsmile.gif
 
Oct 28, 2009 at 6:23 PM Post #2,919 of 4,278
Quote:

Originally Posted by Proutch /img/forum/go_quote.gif
Hey guys

I'm enjoying so much the superb sound of my Bijou, that I thought of using it as a preamp to drive a DYI tripath power amp

What do you think? Does it make sense?
Do I need to tweak the Bijou to use it as a preamp?

Thanks in advance for your help
atsmile.gif



Some have raised concerns about it having too much gain for preamp use, but I think it works just fine. You just need to make sure that the output impedance of the bijou isn't too high for whatever power amp you're using (see runeight's post for specs). I forget what the desirable ratio is off hand. I think those are the main concerns.

edit: actually, I think most amplifiers have really high input impedance. I'm sure someone will correct me if I'm wrong.

Quote:

Originally Posted by runeight /img/forum/go_quote.gif
Yep, I have a bunch of those too. And I use them for some holes.

The Zo of the Bijou is 60R with no NFB (no nfb pot connected).

With the normal NFB arrangement the Zo is about 20R when the pot is set to its halfway position (125k).


 
Oct 29, 2009 at 10:27 PM Post #2,920 of 4,278
Alright so here we go... This is my first time posting pictures on here so let me know if they don't work.

First one is of me drilling, second is with the boards in and the wiring half done. Last two are of it in operation
beyersmile.png


Of course there's still some more work to do (mount feet, grind down volume knob, track down some stray buzzing, etc.) but it works!



 
Oct 30, 2009 at 2:15 AM Post #2,922 of 4,278
Looking good xxbaker! I *really* hope that that the workpiece in the first picture is securely clamped at the bottom - safety first!
 
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