Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Bijou All Tube Futterman Headphone Amplifier
New Posts  All Forums:Forum Nav:

Bijou All Tube Futterman Headphone Amplifier - Page 76

post #1126 of 3981
8/22/08 at 5:52pm
Quote:
Originally Posted by n_maher View Post
I fail to see how it's possible without using entirely surplus parts and I have no idea what for an enclosure. The Hammond trafo alone is going run $60 w/ shipping.
Dang it - true I always underestimate since some of this I have laying around.
OK, more like $300 bare minimum.

The Nabu is actually tall enough except for the tranny (assuming Hammond) - just needs vent holes.
Reply
post #1127 of 3981
8/22/08 at 10:33pm
Quote:
Originally Posted by amphead View Post
Holland, I tried the top view of the Gem and it was too plain looking to me.

How about this........
Is this a vector image, and can you post it? The only thing better might be to fill the socket square full black. The vector will make a far better engraving... :-)
Reply
post #1128 of 3981
8/22/08 at 11:26pm
Quote:
Originally Posted by amphead View Post
This is the way that I will be looking to wire the amp for balanced mode............
Yes, that looks right except that the pinouts on the cannon connector on the output are not correct. At least I don't think so. Pin 1 is usually grounded.

Any progress??
Reply
post #1129 of 3981
8/23/08 at 4:30am
Runeight, I have just ohmed out a few things with my meter, but have not started in earnest yet. Not until we have Amb's scope Saturday. Yeah, I wondered about the wiring on the output xlr in my diagram.
Reply
post #1130 of 3981
8/23/08 at 8:35am
Today a replaced the eletrolytic coupling caps with 80 uF Sprague oil filled can capacitors. It is amazings how much clarity comes thru now.

What are the opinions of the Bijou with no NFB powering a pair of 300 ohm Sennheisers? My current headphones are 600 ohm and they definetaly sound better without the NFB.
Would the ouput impedance be too high sans NFB to work with 300 ohm phones?
Reply
post #1131 of 3981
8/23/08 at 8:12pm
No, I don't think the Zo will be too high. Headphones are mostly resistive loads and high damping factors are not usually necessary.

IIRC the Zo of the no NFB amp will be around 30R.

amphead, let us know what you find at the inputs to each board as measured with respect to ground. Thanks for working on this.
Reply
post #1132 of 3981
8/24/08 at 2:37am
Quote:
Originally Posted by regal View Post
Today a replaced the eletrolytic coupling caps with 80 uF Sprague oil filled can capacitors. It is amazings how much clarity comes thru now.

What are the opinions of the Bijou with no NFB powering a pair of 300 ohm Sennheisers? My current headphones are 600 ohm and they definetaly sound better without the NFB.
Would the ouput impedance be too high sans NFB to work with 300 ohm phones?
Regal, I'm a bit confused by that difference between electrolytical cap and non-electrolytical one. Especially on 300-600R load.

I checked the specs for the electrolytical cap that came with Jeff's kit (Panasonic TS-ED 470u/250V 105d Al Electrolytic). ESR of this cap is 0.37R on 120 Hz and less at high frequencies (i.e. 20kHz). Impedance (capacitive) of this cap at 120Hz is ~3 Ohm. I just don't see how ESR can make any difference especially when output Z is 30R and the load is 300-600R. ESI (equivalent serial inductance) is another thing. But at low frequencies it should be very low anyway and at high frequencies a small parallel cap with reduce it (that's the reason we have it there). Do you still have a 1uF cap in parallel to 80uf? My guess here is that 1 uF is kind of low for mid-high frequencies (doesn't lower total ESI enough) and we need a third cap in parallel (mid value - 80uF). But I just don't see here how the ESR can make any effect here unless the electrolytical cap is really a cheap one. Am I missing something else here?

Runeight, could you comment on that?
Reply
post #1133 of 3981
8/24/08 at 7:19pm

Wire Gauge

Hi Guys, just bought the Bijou kit from glass jar audio and waiting for delivery, so looking forward to the build

I'm based in the UK and am struggling with AWG (American Wire Gauge). The Cavalli site recommends 20awg wire for all internal connections and 22awg for connections from the transformer.

None of the suppliers here in the UK seem to deal in (or know about awg) and I’m getting conflicting advice about how to convert to UK gauges. Can anyone give me the specs for the wire they are using in this build? Are you using solid or stranded core?
Reply
post #1134 of 3981
8/25/08 at 2:41am
Pabbi, Runeight, the problem was narrowed down to wiring on the input connectors/stepped attenuators with the Bijou's troubleshooting following the testing of the Krmathis Beta22 group build. More info to come, after recovering from driving, testing Beta22, testing Bijou, and more driving. ;-)
Reply
post #1135 of 3981
8/25/08 at 4:56am
I bit the bullet and ordered boards and parts, so another bijou will hopefully live within a couple of months.
This is going in 330 x 230 mm hifi2000 case. all tall parts on the underside of the boards. I will use obbligato caps in place of the mkp's.

just deciding on a transformer. I can either go with the dax370, which is $66 + $30 shipping. Or go with the Rcore from vt4c. My issue with that is it doesnt have the 240v primaries, so i suspect all my voltages will be on the hot side. it would save me $40, and i am sure could tweak some values to bring down the heater voltage etc.

what are your views? anyone used the Rcore?
Reply
post #1136 of 3981
8/25/08 at 6:42am
hey jamsandwich, try using this online wire gauge converter. Comes in handy from time to time.

PS>Replaced most of the electrolytics with film caps and she's kicking like a whole new beast. Makes me wonder what Ferari's souped up bijou sounds like. Now if those mosfets would just get here...
Reply
post #1137 of 3981
8/25/08 at 8:53am
Quote:
Originally Posted by rfsam View Post
Regal, I'm a bit confused by that difference between electrolytical cap and non-electrolytical one. Especially on 300-600R load.
Read about caps here, ESR has little correlation with sonics.

ecp.cc
Reply
post #1138 of 3981
8/25/08 at 2:44pm
Quote:
Originally Posted by regal View Post
Read about caps here, ESR has little correlation with sonics.

ecp.cc
Regal, thank you. I mentioned ESR because people (and in this thread too) are talking about ESR when they compare the audio quality of different caps. I don't think (as I mentioned before) ESR matters that much (agree with you here). But what parameter "drives" the cap's sound quality? Unfortunately the link you gave me doesn't have an explanation (it does have some basics and practical comparison of different brands - a very good source on choosing a cap!) on why there is hearable difference. I think it's self inductance (ESI).
Reply
post #1139 of 3981
8/25/08 at 2:50pm
The only measuring device for ranking capacitors are the ears.
Reply
post #1140 of 3981
8/25/08 at 5:16pm
for my build i am quite tempted to use the 70uf obbligato oil film caps. 125mm tall they will have to be mounted through the case with a cap mounting kit.

the only phones i really listen to are hd650's. so corner frequency will be fine (7 hz, pushing 70 for 32 ohms).

or i could just stick a $2 electrolytic in there.
Reply
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Bijou All Tube Futterman Headphone Amplifier