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Bijou All Tube Futterman Headphone Amplifier - Page 259

post #3871 of 4164

This one was about $600, with all the tubes, IIRC.

post #3872 of 4164
Quote:
Originally Posted by pabbi1 View Post

This one was about $600, with all the tubes, IIRC.


Thanks pabbi1. So indeed I am selling this amp at way below part cost.
post #3873 of 4164

What are limitations of B+ supply? I think of rolling-up the currents...

My trafo is rated for 200ma, and i use just ~66ma.

 

The issue i try to deal with:

There is some threshold in the amplifier. It sounds like "noise gate" - i hear the large-signal music and it's low-signal counterparts (echoes e.t.c.). But when i try on a record which have some silence, with music rolling off the silence (volume growing) i hear some "step":

Instead of smooth ____.......---------'''''''''''' i get __________----------''''''''''''. where "_____" is silence.

 

I have tried the same records on other amp (chip based) and haven't heard this issue.

By the way, it seems my Bijou lack some details against my other amp...

 

Maybe that's what 6N1P tubes do :) (i have 6N23P ordered).

Should i address the issue to output capacitors first?

 

 

UPD:

Seems i can get 100ma from the PS. The heatsink, as said, has 10C/W rating. With minimum input/output voltage difference of 10v on the regulator FET i get 1w power lost - 10c degrees temperature rise is on the heatsink.

My 250v windings are a bit lower than on recommended 370/270 transformers, therefore i should use lower (240v) B+ voltage.

Ok, regal mods to follow cool.gif after i fix the heatsink cooling (large hole in the case underneath the PS).

 

 

UPD2:

Ok, regal mod is up and running, B+ at 238v, C4 at 249v. 73ma current draw.

Now it's time to upgrade the convection.


Edited by S3TUP - 4/19/11 at 8:18am
post #3874 of 4164

I found a bouch of theese filters:

http://img25.imageshack.us/f/20110418188.jpg/

 

They have been used för 5-10 years, would they do any good in my bijou?

 

 

 

 

 

 

 

 

 

post #3875 of 4164

If u plan to add both ur psu and ur amp in the same case, by adding one of those filters before the transformer, it would remove all emf caused buy the power grid :) So simply yes it would help:)

post #3876 of 4164

Hi!

 

   I have some questions on the Bijou Amp. I have read thru the thread but my technical knowledge is very limited.

 

A. I am very happy with the bijou amp. I have all the 0.1uf and 1uf cap replaced with Mundorf Silver Gold. This is by far the best amp I have listened too. I wonder if it is possible to increase its performance further like, replacing the huge electrolytic cap with a cap similar to the Mundorf???

 

B. The transformer runs especially hot (370DAZ, input 230V), Should I be running a seperate filament transformer?? I have JJ EZ81, JJ ECC99 Gold Pin and Siemens E88CCA installed.

 

C. Will building it as a monoblock include the performance of the amp?

 

   Thank in advance!

 


Edited by IloveHP - 4/25/11 at 3:35am
post #3877 of 4164

A Yes, replaceing electrolytics in the signal path with film improves SQ. If you have senns you can get away with roughly 120uf cap for output coupling.

 

B Those hammonds get pretty hot, even within specs. Your setup skouldn´t be a problem.

 

C Ivé built mine as dual mono. It improved SQ for me, since I couldn´t do regals mod with one PS other than that I dont know. The extra power is hans when rolling tubes too.

 

I recomend you to try this too:

Regals mod

Remove cathode bypas caps

 

I dont think Ivé heard anyone who dont like regals mod, the bypass cap is moore a matter of taste. In theory its better without it.

 

 

post #3878 of 4164
Quote:
Originally Posted by vlb View Post

A Yes, replaceing electrolytics in the signal path with film improves SQ. If you have senns you can get away with roughly 120uf cap for output coupling.

 

B Those hammonds get pretty hot, even within specs. Your setup skouldn´t be a problem.

 

C Ivé built mine as dual mono. It improved SQ for me, since I couldn´t do regals mod with one PS other than that I dont know. The extra power is hans when rolling tubes too.

 

I recomend you to try this too:

Regals mod

Remove cathode bypas caps

 

I dont think Ivé heard anyone who dont like regals mod, the bypass cap is moore a matter of taste. In theory its better without it.

 

 


How do you know what amount of uf to put in the output? i pair bijou with a DT990/600 ohm and was planning to upgrade the output caps. Everything in my bijou is stock

 

post #3879 of 4164

i guess experimenting but am not sure, if u replace the huge electrolytic with a plastic one u'll no need a bypass cap then so just remove it :)

Also i havent done regals mod as i am obsessed with resistor accuracy and cnt find that high W with 1% offset, if anyone can show me a shop it i would appreciate :)

post #3880 of 4164

SBoy:

I only know the calculation the other way around, how to calc -3db freq with a given resistance and capacitance.

fc  = 1 / (2*pi*R*C)

Just remeber to enter the capacitance in F and not uF.

 

If you have a texas ti 82 or similar you can enter this to get a graph on the cutoff.

319/sqr(319^2+(1/2pi*X*120e-6))^2  319 is the headphones impedance and 120 is the capacitor size in uf.

 

I tried some values, signal level @ 20hz into 600ohm

60uf - 97,6%

40uf - 94,9%

30uf - 91,5%

20uf - 83,3%

 

yiancar:

Regals mod will improve sq much more than perfectly matched resistors.You can buy a couple extra resistors and measure them yourself. If your really picky you can heat them in the oven first so the resistance settles.

 

I have a question too:

Will the choke mod improve the sound of the amp?


Edited by vlb - 4/28/11 at 1:26pm
post #3881 of 4164
Quote:
Originally Posted by vlb View Post

SBoy:

I only know the calculation the other way around, how to calc -3db freq with a given resistance and capacitance.

fc  = 1 / 2*pi*R*C

Just remeber to enter the capacitance in F and not uF.

 

If you have a texas ti 82 or similar you can enter this to get a graph on the cutoff.

319/sqr(319^2+(1/2pi*X*120e-6))^2  319 is the headphones impedance and 120 is the capacitor size in uf.

 

I tried some values, signal level @ 20hz into 600ohm

60uf - 97,6%

40uf - 94,9%

30uf - 91,5%

20uf - 83,3%

 

yiancar:

Regals mod will improve sq much more than perfectly matched resistors.You can buy a couple extra resistors and measure them yourself. If your really picky you can heat them in the oven first so the resistance settles.

 

I have a question too:

Will the choke mod improve the sound of the amp?


well, i do know how to calculate the value of the cap from the given db freq, but how much is of a drop is sufficient? is it totally up to our preference and we just play around with the value? 

 

Heat them up in the oven? wow, i didn't know that! lol. let us know how it goes yiancar. 

 

post #3882 of 4164

WRT 6n1p, I found that they take 50-100 hours to get rid of the static.

post #3883 of 4164


 

Quote:
Originally Posted by SBoy View Post




well, i do know how to calculate the value of the cap from the given db freq, but how much is of a drop is sufficient? is it totally up to our preference and we just play around with the value? 

 

Heat them up in the oven? wow, i didn't know that! lol. let us know how it goes yiancar. 

 

 

I want the amp to be "totaly" linear 20hz-20khz so I use a 120uf cap with 330ohm senns. It gives me -3db @ 4hz and 97.9% at 20hz. But of course its a matter of taste. I recommend a little NFB if you go big with this cap, the lowest bass feels slow and slobby without it, at least in my setup..
 

 

 

Edit:

Found this page: http://my.hrw.com/math06_07/nsmedia/tools/Graph_Calculator/graphCalc.html

Just enter 319/√(319^2+(1/(2π*x*0.000120))^2)

Replace 319 with you phones impedance at both positions, and replace 120 with you capacitor size in uf. This gives you a graph on the lower limit of the bandwidht.


Edited by vlb - 4/27/11 at 7:24am
post #3884 of 4164

Quote:
Originally Posted by vlb View Post


 

 

I want the amp to be "totaly" linear 20hz-20khz so I use a 120uf cap with 330ohm senns. It gives me -3db @ 4hz and 97.9% at 20hz. But of course its a matter of taste. I recommend a little NFB if you go big with this cap, the lowest bass feels slow and slobby without it, at least in my setup..
 

 

 

Edit:

Found this page: http://my.hrw.com/math06_07/nsmedia/tools/Graph_Calculator/graphCalc.html

Just enter 319/√(319^2+(1/(2π*x*0.000120))^2)

Replace 319 with you phones impedance at both positions, and replace 120 with you capacitor size in uf. This gives you a graph on the lower limit of the bandwidht.



Thanks vlb, i will still have my NFB as im driving a wide range of headphones.

 

post #3885 of 4164
Quote:
Originally Posted by yiancar View Post

If u plan to add both ur psu and ur amp in the same case, by adding one of those filters before the transformer, it would remove all emf caused buy the power grid :) So simply yes it would help:)



So it won´t do any good as long as the ps is in a separate box?

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