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Bijou All Tube Futterman Headphone Amplifier - Page 122

post #1816 of 3977
11/8/08 at 8:23am
shall i regal mod it? are there any problems with regal modding and using the 6n1p's with 6n6p's?
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post #1817 of 3977
11/8/08 at 12:45pm
Quote:
Originally Posted by fishski13 View Post
ooh, ooh... this may work: Wakefield 634 series

Digi-Key - 345-1027-ND (Wakefield - 634-20ABP)

and scroll down to pg. 15 on the data sheets:
http://www.wakefield.com/PDF/board_level_heat_sink.pdf
That looks perfect. I assume you'll use the 637-25ABP - the curves say a heatsink temp rise above ambient of 30C at 4W. This will be good.
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post #1818 of 3977
11/8/08 at 12:48pm
Quote:
Originally Posted by adamus View Post
shall i regal mod it? are there any problems with regal modding and using the 6n1p's with 6n6p's?
The current draw of this combination may pull the voltage down in the PS before the regulator to the point where it drops below 250V. We have seen this before.

However, if this happens we posted a PS mod a few pages back that fixes this. fishski13 has pioneered testing this mod and we do know that it works.
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post #1819 of 3977
11/8/08 at 1:53pm
great, i think i will do it next week. Should have done the whole lot whilst i had the amps out.

by the way, the 6n1p's make the amp sound more lively, slightly less polite.
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post #1820 of 3977
11/8/08 at 2:05pm
Quote:
Originally Posted by adamus View Post
by the way, the 6n1p's make the amp sound more lively, slightly less polite.
glad to hear some impressions on tubes. I also found the white amperex 6dj8's to be more punchy and aggressive than the standard jj/sylvania 6922's. I'm looking forward to trying some 6n1p's myself if I ever get around to it.

on a different note, I will have regal's mod in by the end of the night and I'll try it out with both the jj's and the 6n6p's. My PS seems to have about 15v worth of headroom atm with 6n6p/6dj8/EZ81 combo, so we'll see what happens.
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post #1821 of 3977
11/8/08 at 3:34pm
Quote:
Originally Posted by fishski13 View Post
ooh, ooh... this may work: Wakefield 634 series

Digi-Key - 345-1027-ND (Wakefield - 634-20ABP)

and scroll down to pg. 15 on the data sheets:
http://www.wakefield.com/PDF/board_level_heat_sink.pdf
Digi-Key - HS386-ND (Aavid Thermalloy - 531302B02500G)
531302B02500G

I use those on my SOHA II. They fit the board outline just fine on the Bijou as well. I will use them on my Bijou as well.

They "seem" a little better than the Wakefields. I've used both in the past, and I can't say I really notice a difference, but the datasheet shows some.

Digikey and Mouser only stock the 2.0" Wakefields, but they have the 2.5" Aavids.

Edit: BTW, the 634s you linked to won't fit the board, but I suppose you can let it dangle and rest on the board. You need the space underneath for convection. The bigger sinks are better (637 or the Aavid).
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post #1822 of 3977
11/8/08 at 7:00pm
sigh...well scratch that. Just as it is too late to run to parts express for a replacement, my ez81 is blowing fuses left and right and arcing internally so I'm back to ez80 for now. No mods till monday. I'm a sad panda
edit: I need to shoot that black cat outside of my house or something. My JJ 6922 just lost one of its pins while swapping tubes
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post #1823 of 3977
11/9/08 at 12:57am
Quote:
Originally Posted by amphead View Post
Chobint, here's the schematic you were looking for.......



Pabbi, let me know if there is anything I can do to help. I hope that damn intermittent ON/OFF is found. The amp was working so well, I just don't get it.
Check out message #121.
HeadWize: DIY Workshop > β22: A discrete, cascoded, fully complementary, pure class A amplifier (part 3)
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post #1824 of 3977
11/9/08 at 1:29am
runeright and holland,
thanks guys! i've removed the internal divider between the transfos and PS boards to free up some air movement. with the divider in place, the PS boards are effectively in a partitioned "chamber". i'm going to keep the BJT multipliers - i sacrificed a $12 EZ81 to get it operational damn it .

chobint,
i feel your pain - losing a tube is a real bummer. the arching noise is a bit unsettling as well.
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post #1825 of 3977
11/9/08 at 6:19am
Thanks Funch, yeah that's a good way to listen to a balanced amplifier in unbalanced/SE mode.

Chobint, sorry to hear about those tubes.

Well, I had to do some roadie work for my nephew Saturday. I Put some ear protection in for the show.

My nephew on the right......



The drummer.......

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post #1826 of 3977
11/9/08 at 7:42am
drummer looks like he could do some damage!

I have been pulling tubes in out out to get a good picture of the differences.

The is no contest, the 6n1p wins on detail, bass (tuneful..its tightened up no end since intitial testing), soundstage. to my ears its all round a better experience. Quiet strange really, looking at the datasheet the point we are operating at is more linear with the 6922s.
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post #1827 of 3977
11/10/08 at 6:58pm
How would i use a meter such as this

100mA mA meter for BIAS 300B 2A3 6L6 EL34 6550 Tube Amp - eBay (item 250321873157 end time Nov-14-08 19:40:38 PST)

With the bijou to measure bias?

Looks an intresting idea.
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post #1828 of 3977
11/10/08 at 8:15pm
Parts inbound, so I'll start the procedure tomorrow evening - where I have Phoenix connectors, do I just screw in the NFB resistor? Guess I need to fill out where I only had some 2 position connectors to cover the 3 holes, since I was never going to need NFB...
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post #1829 of 3977
11/10/08 at 8:47pm
rhys h, there is an alternative to using that meter. You would solder a 1ohm 1w resistor in series with the tube cathode you want to measure to ground and put a 100mv scale meter across the 1 ohm resistor. Then 1mv=1ma of bias current(V/R=I and 1mv/1ohm = 1ma). Remember that you will be measuring the bias of an individual tube, and there are 5 tubes, in a single ended Bijou all fixed biased with their individual resistors.

Pabbi, once you have installed the 3 position phoenix, it is a simple procedure of just cutting the resistor leads and bending them to fit and tightening down with the connections. This allows you to experiment with different values to find what sounds right to you.
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post #1830 of 3977
11/11/08 at 12:23am
blah...so my brand spanking new ECC99's are drawing more current than my 6n6p's, which is the opposite of what's supposed to happen right?

Readings taken with the PSU pot in the same position (somewhere in the middle):

EZ81/6n6p -
R8 - 315.5v
R7 - 278v
B+ - 256v

EZ81/ECC99
R8 - 306v
R7 - 263v
B+ - 250.8

EZ80/ECC99 combo also proves unable to give 250V @ B+. The reading seem to indicate that the ECC99's are actually drawing the EZ81 PSU below the intended operating points?? Any reasonable explanations for such behavior, or should I be sending these back for a new pair?
edit: this is the the boards setup in stock config
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