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Bijou All Tube Futterman Headphone Amplifier - Page 89

post #1321 of 3981
9/20/08 at 1:24pm
well its the only amp i have that lets me hear the noise on the usb line (e.g scrolling on a web page causes noise).

plug my soha + jisbos in and its perfect.

Must be a grounding issue. Should the signal ground be star grounded?
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post #1322 of 3981
9/20/08 at 1:31pm
Almost certainly a grounding issue.

Are the input jacks grounded to each board at the In G connection?
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post #1323 of 3981
9/20/08 at 1:33pm
yes, signal ground goes to ground on the pot, and then to signal ground on boards.
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post #1324 of 3981
9/20/08 at 1:37pm
Is the amp in a case? Is the amp star g connected to the case? And is the case connected to the line (mains) ground?

Just doing some detective work on you.
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post #1325 of 3981
9/20/08 at 1:43pm
star g connected to IEC earth, IEC earth connected to chassis. Star G bolt on exposed chassis.

By the way, this thing sounds superb, the space it gives is unreal.



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post #1326 of 3981
9/20/08 at 1:52pm
Hmmm. I don't have a good next step. I don't use dacs and don't have enough experience with the problems that they cause. Can anyone else offer a thought about what this problem might be?

Quote:
Originally Posted by adamus View Post
By the way, this thing sounds superb, the space it gives is unreal.
That was my reaction when I first heard my proto version. It was what convinced me that I had to find a way to create a simple Bijou build to make available. It really is a gem. Wait until you get some hours.
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post #1327 of 3981
9/20/08 at 2:26pm
is it normal to have very little travel in the volume pot? the gain seems very high with no NFB.
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post #1328 of 3981
9/20/08 at 2:37pm
Yes, it's normal. The gain with no NFB is about 25X. With a source that is putting out 1V or more, there is little that can be done.

The is one of the reasons for the NFB. With the NFB pot, even when the NFB is turned to minimum, there is still enough NFB to reduce the gain considerably.
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post #1329 of 3981
9/20/08 at 3:05pm
BTW, you can cut the gain in half by removing the cathode bypass cap on the first stage. Don't know what will happen to the audio.
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post #1330 of 3981
9/20/08 at 3:22pm
The noise i hear has probably always been there, my soha is really low gain (attenuated jisbos). Maybe its juts the high gain thats making it apparant. I will try my other dac and report back.
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post #1331 of 3981
9/20/08 at 6:02pm
Quote:
Originally Posted by amphead View Post
While on the one hand, it may be possible to build a quiet balanced Bijou in the NABU chassis, I think that with ample room it would be like shooting fish in a barrel to do one successfully. This hinges of coarse on whether or not the 270HX is up to the task of powering 2 PS boards and 4 amp boards quietly, which it should be. I don't think there would be a problem, having your amp wired like mine. While the hum is small, there is just enough of it to be unacceptable to your ears, my ears and most members of the forum.
Well, the drilling and layout work seems a lot to offload, not to mention remounting IEC, pots, and jacks. Then, the ventilation, and whether to top mount the tranny... <sigh>. At least I have plenty of wire for all the required rewiring. IFF it seems like a prudent way to go, I can have a new case there by Wednesday, but feel like that is a mess I should be cleaning up.

With your investment in this to date, I am all for you seeing this to completion. Besides, I have another box to send you, anyway, but this one is for keeping... :-)
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post #1332 of 3981
9/20/08 at 8:38pm

Bijou hum

Quote:
Originally Posted by amphead View Post
Pabbi, I just finished the listening test after the ground mod and the hum is still there. I notice that the hum slowly fades when the amp is turned off. On my amplifier before the ground mod the buzz/hum immediately stopped when the amplifier was shut off. This leads me to believe that more shielding might help with your amplifier.

I am by no means an expert. But I built my Bijou with a steel Hammond case. Boards mounted on top, star ground dead center underneath the chassis. I have a thick sheet of plastic on top of the chassis to shield the transformer. There is absolutely no noise or hum. I have to believe that a balanced version built in this manner would yield similar results. Just a thought. I'm seriously thinking of pursuing a balanced version further, as I have two more sets of pc boards...
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post #1333 of 3981
9/20/08 at 8:45pm

cap upgrades

Quote:
Originally Posted by chobint View Post
Hey guys, I'm looking to make a few inexpensive upgrades to my bijou in hopes to improve overall SQ, especially bass response. I am considering upgrading the cathode bypass(amp:C2) and psu:C3 to nichicon kz or panasonic FM, and the psu:C2 and psu:C6 to better plastic caps. I am unfamiliar with amp architechture and don't know how these will affect the sound. Any comments on how any of these proposed upgrades will affect SQ especially with regard to bass response? Thanks

I used Clarity caps 1.0uF for the cathode bypass, and am very pleased with their results. Reasonably priced also.
I might add...if you haven't done it already... mod it to use 6N1P tubes (see Cavalliaudio website, bijou tweeks section) Unless you want to spend big bucks for premium 6922's, this is a very cheap upgrade and you will love it. The 6H30's are an improvement also, but the 6H1N-BN RUSSIAN VALVE's (6N1P) that I am using blow them away.
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post #1334 of 3981
9/21/08 at 2:16am
just finished soldering the tube sockets and C6 (Sonicap 0.47 uF). i used SIP sockets for the RLED and R2 - i will be experimenting with some trick LED lighting, and will no doubt want to try rolling more tubes. i also soldered R3,5,6,7 on the bottom in case i want to try Regal's Mod.

hopefully my enclosure will arrive this week. i'll probably place an order for a PEC pot on Mon. from Digikey. going balanced will have to wait a month - i just bought a pair of HD650 that sound absolutely stonking via my M3.

i may get the guts to "fire" this sucka up sans enclosure. i'm going to try playing with FPE tonight.





PACE
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post #1335 of 3981
9/21/08 at 4:45am
fishski13, looking very good!

Pabbi, let's pull the trigger on doing the 17x17. I only have your budget in mind with any of this. And the mounting of parts into the new chassis, with new wiring is going to proceed fairly quickly. The only thing that could slow it down with new chassis would be if there was a borderline/bad component installed right now. And I don't believe that is the problem. Thanks for peaking my interest in the "mystery" box. ;-)
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