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Bijou All Tube Futterman Headphone Amplifier - Page 109

post #1621 of 3981
10/18/08 at 5:53pm
Quote:
Originally Posted by steel View Post
I want to buy some tubes for my Mijou.

6n6p & 6n6p-i which is right?

Thanks..
Both would work fine. 6N6P-i is the the military spec version of the 6N6P.
However the 6N6P-i requires more heater current than the 6N6P (~900mA instead of ~750mA).
I have 6N6P-i in mine, work like a charm.
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post #1622 of 3981
10/18/08 at 7:37pm
Source of low price 4uf/450V Kimber caps -- for output by pass

K&K is having some "upgrade pull out" 4uf Kimber caps avaialbe, the ad is here.

They will be good for output by-passing. For $5 a pop they are great bargins (normally sells for $16 each new).

I have not contact K&K to see how many is left. But the original post was from the end of last month so I supposed they should still have some left.


-- update: they have 4 pieces left.
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post #1623 of 3981
10/19/08 at 12:36am
Quote:
Originally Posted by steel View Post
I want to buy some tubes for my Mijou.

6n6p & 6n6p-i which is right?

Thanks..
IIRC, 6n6p is the preferred device.
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post #1624 of 3981
10/19/08 at 12:39am
Quote:
Originally Posted by huskydawg9 View Post
Would I benefit with better lower end response by increasing the value of C5 (I'm using 30ohm phones)? Such as 1800uF.
At some point increasing the size of the O/P cap doesn't really buy you much more. The 1db point with 470u is about 6Hz. That's pretty low. Larger caps will make it lower.

However, there are three other caps in the circuit that also matter to LF response: C1, C3, C4. Increasing C1 to even just 22u should help a little. Increasing C3 and C4 to 220n will also lower the bass cutoff.
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post #1625 of 3981
10/19/08 at 1:12am
Srserl, I will definitely be taking Pabbi's amp, but won't know if it will be finished until it is time to go. It is that tight of a deadline.

Quote:
Originally Posted by srserl View Post
That might entice me to head over to Burning Amp! I'm looking for a headphone amp project for the new year (that's when I will hopefully finish up everything I have committed
to building now). Please post here if you are definitely going to take it to Burning Amp.

Scott
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post #1626 of 3981
10/19/08 at 1:28am
Ferrari, runeight, thanks...

I just want began to built Mijou
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post #1627 of 3981
10/19/08 at 3:37am
If it’s safe to use C3/C4 (amp) capacitors with 300v voltage rating instead of 400v (I have some vitamin Q 0.68mf/300v)?
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post #1628 of 3981
10/19/08 at 6:40am
Quote:
Originally Posted by miky View Post
If it’s safe to use C3/C4 (amp) capacitors with 300v voltage rating instead of 400v (I have some vitamin Q 0.68mf/300v)?
This amp is feed by 250V DC, so caps rated at 300V should be fine.
BTW, the actual voltage at C3/C4 is much lower than the PS 250V.
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post #1629 of 3981
10/19/08 at 7:15am
Thank you Ferrari.
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post #1630 of 3981
10/19/08 at 2:41pm
Quote:
Originally Posted by steel View Post
...

I just want began to built my Bijou


I see a second transformer-alike thing on the pic, is that a choke or a transformer for the 6.3V heater separately?
Knowing your Dynahi and M³, I’m sure there is a very nice Bijou in the making.
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post #1631 of 3981
10/19/08 at 3:33pm
It's a choke.


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post #1632 of 3981
10/19/08 at 6:00pm
Quote:
Originally Posted by runeight View Post
At some point increasing the size of the O/P cap doesn't really buy you much more. The 1db point with 470u is about 6Hz. That's pretty low. Larger caps will make it lower.

However, there are three other caps in the circuit that also matter to LF response: C1, C3, C4. Increasing C1 to even just 22u should help a little. Increasing C3 and C4 to 220n will also lower the bass cutoff.
Increased C1 to 33u. Replaced C3 and C4 with .22uF Clarity caps. It did improve the lower end response (In my case using Grado 325i) , but is probably insignificant for most setups. I imagine this might improve somewhat as the Clarity's break in.

I'd like to hear comments about a comparison between the Bijou and the SOHA2. dBEL84 obviously you've heard both...do you have a comparison somewhere I can reference?
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post #1633 of 3981
10/19/08 at 6:11pm
This sounds about right. Dropping the LF corner freq from 8Hz to 5Hz really shouldn't be audible.

I actually have a Bijou and SOHA II. I have yet to compare them because I'm not sure that I can do an unbiased comparison and. But, maybe I'll give it a try.
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post #1634 of 3981
10/19/08 at 6:11pm
comparing my bijou to the soha + jisbos (not soha II)...

Bijou, beautiful valvey mids, stunnign highs, very organic. Play something rocky and i want it to have a bit more bite. Its a rolls royce, smooth, elegant, and you can drive it all day.

Soha+ jisbos
Strong bass, very good detail. I listen to it for about 45 minutes before i fire up the bijou, which then stays on for the remainer of the night. more like a mustang, strong and fast. justa it....lifeless compared to the bijou.

IT would be interesting to see measurements, my scientific side thinks the jisbos would have better specs than the bijou. my musical side picks the bijou everytime.
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post #1635 of 3981
10/19/08 at 6:54pm
Your scientific sense is probably right but . . .

This depends on the exact configuration of your jisbos. If you are using any of the gain reduction schemes that have been suggested for the buffer, then you are almost certainly supplying a load for the tube that is too small.

If the jisbos is running stock with a 1M resistor at its input it will still show a rapid decrease in Zi with frequency. You are probably hearing this too.
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