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Bijou All Tube Futterman Headphone Amplifier - Page 279

post #4171 of 4182
Quote:
 have u rolled any tubes?

Yes

I use Tungsram E88CC (red label, mil/industrial, 1965, 1968 years) and USSR 6N6P (1978 year)

Regal mod (for 6922/6DJ8) applied.

 

Also I modify heater wiring (like "star" topology) with each tube heater wires shielded. All heater shields connected with main star ground bolt.

post #4172 of 4182
Quote:
Originally Posted by LV26 View Post
 

Yes

I use Tungsram E88CC (red label, mil/industrial, 1965, 1968 years) and USSR 6N6P (1978 year)

Regal mod (for 6922/6DJ8) applied.

 

Also I modify heater wiring (like "star" topology) with each tube heater wires shielded. All heater shields connected with main star ground bolt.

I use 6H30 which i find to be more dominant(powerful) than the 6DJ8.

Can we have a picture of or heater shielding?:)

post #4173 of 4182

Yes

Lot of photos

http://postimg.org/gallery/4b4au5w6/

 

especcially

http://postimg.org/image/cwjob0ggl/

huge white DIY cables (twisted wires + shield + fiber tube):)

post #4174 of 4182

(I know it is probably somewhere in this giant thread, but somehow I can not find it.......)

 

which  electrolytic caps are good for using as output caps? Is there a particular brand/model that is noticeably better than the others?

post #4175 of 4182

I used standard audio nichicon snap in caps (~$4 each). Or, if you have a large budget, you could use Black Gate 150uf 350V ones (they have them on sale at Parts Connexion for 60 each, down from 180 each) which are good if you don't intend to use anything lower than 250 ohm impedance (lower than that, and you might experience a bit of bass cut off, I think). I personally use 100 uf Obbligato Film and Oil caps, whitch are good for my 600 ohm Beyers.

Quote:
Originally Posted by AudioCats View Post
 

(I know it is probably somewhere in this giant thread, but somehow I can not find it.......)

 

which  electrolytic caps are good for using as output caps? Is there a particular brand/model that is noticeably better than the others?

post #4176 of 4182

Hey AudioCats!  Been a long time!

 

To find the discussions in this thread for the output caps, just search for C5.  Certainly lots of options.

The stock one, for reference, is the 470u with a 1u bypass (C6).  


Edited by bhjazz - 11/20/14 at 8:36pm
post #4177 of 4182
Quote:
Originally Posted by AudioCats View Post
 

(I know it is probably somewhere in this giant thread, but somehow I can not find it.......)

 

which  electrolytic caps are good for using as output caps? Is there a particular brand/model that is noticeably better than the others?

 

There was a big deal about photo-flash caps but IMHO some of that was based on the idea that they are somehow magical pixie dust because they were revolutionary 40 years ago. but today they are just slightly more robust than good switching power supply caps. 

 

I am using CDE LX380 470uf bypassed by a 1uf wima. I like it, but I'm weird. 

post #4178 of 4182
Quote:
Originally Posted by ady1989 View Post
 

Maybe someone here can help me. I've been searching around online and I have been unable to find out the power output of the Bijou. Does anyone know what it measures? I think it's unable to drive the HE500's to very high volume due to bad bass distortion when the volume pot is at around 60% and no negative feedback. It could also be the headphones and their limitation. Anyone have experience with HE500's and their Bijou amp?

 

huh, that was months ago, but, the maximum power output of both halves of a 6n6p is about 8 watts. 

 

the bijou is probably not pushing that much since it is an OTL design for headphones but you'd have to ask Alex. 

post #4179 of 4182

The output stage iddles at 20ma. That means the max current (peak) is 40ma at best. Into a 38r load, peak power is thus 38*0.04*0.04= 60mW peak, about 30mWrms.

 

Into the HE500, with its 89db/mW rating, it means you can at best get up to roughly 104dB before distortion gets crazy. But without feedback, distortion will already be quite high at that point. With feedback, it could be a bit better.


Edited by 00940 - 11/24/14 at 2:16am
post #4180 of 4182
Quote:
Originally Posted by bhjazz View Post
 

Hey AudioCats!  Been a long time!

 

To find the discussions in this thread for the output caps, just search for C5.  Certainly lots of options.

The stock one, for reference, is the 470u with a 1u bypass (C6).  

 

Thanks!

 

I will search C5 see what has been said and done.

post #4181 of 4182

I just completed the power supply and on of the channels.

The output tube, V2,  on my board are idles at 30ma, and V1 at 10ma (I changed the resistors to run each side of V1 at 5ma).

The 6n6p with a bios voltage at 2.3v @125v plate voltage = 30 ma.

 

R3 = 30k

R3 = 487

R5-7 = 10.2k (Regal's mod shows 10k. but if you do the math, it should be 10.2k).

post #4182 of 4182

Since you did the Regal's mod, you might want to change R7 & R8 in the power supply.

The Mod increases the idle current from 32ma to 40ma per channel ( @250V ).

 

Depending on which power transformer, you want to decrease them to keep at least 30V across Q2.

I used the R80-36 R-core, so I changed R7 & R8 to two 75R 3W in series (150R).

-Putting 2-75R together fits very nicely into the PBC-

 

Also note that if you us the Hammond 270DAX, its plate resistance is too low (177R Plate to Plate, 88R5 from center tap) for the EZ81,

You should add a plate resistor to match the specs of the EZ81.

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