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Bijou All Tube Futterman Headphone Amplifier - Page 265

post #3961 of 4123

Unless you have a very good reason* to do it any other way the left and right channels should always be in phase.

 

*There is a technique of wiring single ended amps and speakers with one channel "double out of phase" as an effort to improve the performance of the amp. The end result is that the sound is in phase, but the electronics are out of phase. Nobody does it because they can sell monoblocks for what a stereo amp costs and its tricky to explain. This technique has basically no effect on amplifiers with balanced power stages, so dont worry about the Bijou, just posting because maybe someone will use it to their advantage someday. 

post #3962 of 4123

Hey Ari!  how are you doing?  Is there a way with a DMM to test the phase on each amp channel so it's notw ired wrong?

post #3963 of 4123

If your using the RCA inputs Im pretty sure that the 2 outputs will both be in phase on your amp. You run into trouble with balanced amps and amps with transformers: OTL's are usually pretty tame for phase. The bijou does invert phase, but since it does the same to both channels its not important. You run into real trouble when one channel is in phase, and one is out. 

 

Since both channels are probably in phase by default when using the single ended inputs, Just check that the right XLRs are hooked up to the right boards. plug in only one XLR, if sound comes out of only one channel your good. 

 

If you realllllly want to check it out there is a way, but its probably easier to just listen. 

 

I would start by just tracing the signal from the jacks through the amp boards and out with the amp off, and after discharging the caps... Use a DMM set to ohms for this - nice and quick. 

 

After that, or with an amp with transformers:

Connect 2 100 ohm resistors together. Love the alligator jumpers. 

Connect the ends of the resistors to the SE outputs of the amp. 

Play a mono sine wave into the RCA jacks. Best way is to just use one output from your source and use a y-spliter to both inputs. I have 440hz saved on a CD just for this.

Turn up the volume until you have about 0.5vac from either (both!) end of the resistors to ground. 

Measure ac volts from the CENTER of the resistors to ground. If its about 0.5vac, your good. if its ~0vac your out of phase. 

post #3964 of 4123

wow nikon very clever technique :)

 

as for my tube balancing quest, it seems more "correct" for the tubes to be balanced but as u guys explained lots of trouble with minimal gain

post #3965 of 4123

Hi

I've been using my heavily modded  Bijou with LCD-2 which are  50 ohm  and love the combination, bass is superb,

my output caps are 3 x 150uf of solen film bypass by 1uf mundorf silver oil, I've been wondering, would the amp get damaged if I connected it to

8 ohm speakers?

Fostex 207e driver 95db/w that I use with 2a3 set.

Any answer other than "try it and let us know what happens" would be helpful.deadhorse.gif

post #3966 of 4123

So i just bought qty3 Voskhod 6n23p on ebay. 

 

I searched the thread and saw some favorable impressions of them, but does anyone have a fully formed, over-the-novelty opinion on them? I bought the trio because i need a 6dj8 type for a completely different project (a chip amp with a tube buffer) but since I got three of 'em . . . . 

 

I am of course currently running 6n1p-ev and 6n6p-i and find the sound signature to be warm, syrupy smooth, engaging, etc. relaxing as all getout, which is why the bijou is next to my bed. 

 

So, anyone who listened to the 6n23p in this amp long enough to get tired of it - what do you think? 

 

Especially interested if you have compared them to 6n1p. 


Edited by ericj - 9/24/11 at 8:20pm
post #3967 of 4123
Quote:
Originally Posted by MrClean View Post

Hi

I've been using my heavily modded  Bijou with LCD-2 which are  50 ohm  and love the combination, bass is superb,

my output caps are 3 x 150uf of solen film bypass by 1uf mundorf silver oil, I've been wondering, would the amp get damaged if I connected it to

8 ohm speakers?

Fostex 207e driver 95db/w that I use with 2a3 set.

Any answer other than "try it and let us know what happens" would be helpful.deadhorse.gif


This amp doesn't have that kind of power. 

 

At best there will be almost no bass. 

 

Try the bijou as a preamp hooked up to your favorite solid state power amp instead. 

 

post #3968 of 4123



 

Quote:
Originally Posted by ericj View Post

This amp doesn't have that kind of power. 

 

At best there will be almost no bass. 

 

Balanced it does...    :-)



Quote:

Originally Posted by ericj View Post

So i just bought qty3 Voskhod 6n23p on ebay. 

 

I searched the thread and saw some favorable impressions of them, but does anyone have a fully formed, over-the-novelty opinion on them? I bought the trio because i need a 6dj8 type for a completely different project (a chip amp with a tube buffer) but since I got three of 'em . . . . I am of course currently running 6n1p-ev and 6n6p-i and find the sound signature to be warm, syrupy smooth, engaging, etc. relaxing as all getout, which is why the bijou is next to my bed. 

 

So, anyone who listened to the 6n23p in this amp long enough to get tired of it - what do you think? 

 

Especially interested if you have compared them to 6n1p. 


I am a big fan of the 6n23p, and think they are a serious upgrade over the 6n1p, especially the -ev. I also liked them in my source far better than the stock EH 6922 (iirc), but not as well as the CCa (the eventual winner), which is teamed with some 1980 date code 6H30-DR, which might well be masking everything else. Sadly, the amp I targeted the 6n23 for (Raven) is now in other, more capable, hands. I was also wanting to hear some feedback on the 6n23 in the LF, and dedicated my remaining tubes for someone to roll these in, but haven't heard yet... but, didn't find the 6n23 until after I'd sold the Bijou.
 

 

post #3969 of 4123
How do I use it as a Preamp? Any special modification needed?
post #3970 of 4123

When I built my Bijou I added phono L/R outputs in the rear to use the Bijou as a preamp.  Basically you just wire the outputs in parallel (I think, its been a while) to the headphone output.  

post #3971 of 4123
Quote:
Originally Posted by wdahm519 View Post

When I built my Bijou I added phono L/R outputs in the rear to use the Bijou as a preamp.  Basically you just wire the outputs in parallel (I think, its been a while) to the headphone output.  



Yes, just wire them in parallel or use a switched jack such as the neutrik jacks. 

 

 

post #3972 of 4123
Quote:
Originally Posted by ericj View Post

Yes, just wire them in parallel or use a switched jack such as the neutrik jacks. 

 

 



What he said..  tongue_smile.gif

post #3973 of 4123


 

Quote:
Originally Posted by ericj View Post

Yes, just wire them in parallel or use a switched jack such as the neutrik jacks. 


Good information.  I'll do that once I get back to building this.  

Picked up a Goldpoint 50K miniV for my Bijou build just last week.  All I really need now is a case design I can work towards, and TIME!  Geez.  

post #3974 of 4123

If I look at the output stage we have the 6n6p biased with 3 diodes =2.3V,  am I correct the the max output of this amp is 2.3Vx2=4.6V ?

post #3975 of 4123

Hi guys,

 

I'm purchasing a Bijou from a fellow member and would like to know what needs to be done to be able to switch from ECC99's to 12BH7 power tubes.

 

There's more of a variety of 12BH7's (as well as other models) to go through some tube rolling. I know some rewiring needs to be done on the heater elements.

 

Any info would be appreciated.

 

Thanks

Thomas

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