[LeMat]

Thanks to oneplustwo who sent me a spare BJ550, I've been able to finish and listen to my B22 ! While still not encased, it's working perfectly. The sound is really different from by WA2... much more dynamic and with a huge soundstage. It's on the bright side, making my HF2 quite sibilent but it's maybe because of my silver interconnect.
Still, I have an issue with my ALPS blue velvet... Basically it's not working, or only on the first 10%, then after it has no effect on the volume. Any idea what could cause that ?

Don't tempt me with a DACT....

 

[linuxworks]

I suspect you don't have it grounded at the end of the pot. a series R might act like that with a 'floating' shunt part of it

 

[LeMat]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif I suspect you don't have it grounded at the end of the pot. a series R might act like that with a 'floating' shunt part of it

indeed the end of the pot is not grounded (the amp is "breadboard style" for now).... but I don't really understand why it affects its behavior like this. I'll try and let you know ! Thanks

 

[amb]

dude_500, maybe posting some clear pics of the guts of your amp would help.

 

[dude_500]

Quote:

Originally Posted by Anonanimal /img/forum/go_quote.gif Which ground did you tie to earth? How many boards did you use in your Beta? If it's an active ground (3ch+) and you tied the output to earth ground I can see that causing problems. Either that or I'm not 100% understanding what you tested.

It's 2-board non-active ground. I just earthed one of the ground terminals on the sigma-22, which previously earth was nowhere at all in the amp wiring as someone suggested to me a while back.

It's quiet today, although I think I just heard one little pop.

Here are a few picts. It is not in a case, I rarely get around to enclosing my projects in a reasonable time frame. It's been just like this since I built it last July though and I've not had this problem until a few weeks ago.

 

[amb]

dude_500, an uncased amp might pick up all kinds of junk in the airwaves. Earthing the power supply ground on an uncased amp is also not a useful exercise. You should really put everything into a metal case and follow the "wiring & ground" instructions. You may find that's all is necessary to fix the problem. I don't know why this noise only seems to have occurred recently, maybe there is a strong interference from outside your own house.

Oh btw, those green mylar caps you have on the σ22 are sub-optimal. These are used for high frequency compensation in the design, and should have good high-frequency performance. Unfortunately, those green mylar caps are inductive and do not work well in this application. I don't think this is the source of your noise problem, but who knows, I would recommend replacing them with non-inductive film or multilayer ceramic caps.

 

[dude_500]

Quote:

Originally Posted by amb /img/forum/go_quote.gif dude_500, an uncased amp might pick up all kinds of junk in the airwaves. Earthing the power supply ground on an uncased amp is also not a useful exercise. You should really put everything into a metal case and follow the "wiring & ground" instructions. You may find that's all is necessary to fix the problem. I don't know why this noise only seems to have occurred recently, maybe there is a strong interference from outside your own house. Oh btw, those green mylar caps you have on the σ22 are sub-optimal. These are used for high frequency compensation in the design, and should have good high-frequency performance. Unfortunately, those green mylar caps are inductive and do not work well in this application. I don't think this is the source of your noise problem, but who knows, I would recommend replacing them with non-inductive film or multilayer ceramic caps.

I'll case it up soon and replace those caps and see if the problem persists. I'd need to case it before heading off to college next year anyways, so may as well get it done now.

 

[digger945]

Do you listen to the amp with the tower it's sitting on powered up?
I don't see a PS in the computer where one should be so I'm guessing it's just a table atm(been there done that

)

 

[dude_500]

Quote:

Originally Posted by digger945 /img/forum/go_quote.gif Do you listen to the amp with the tower it's sitting on powered up? I don't see a PS in the computer where one should be so I'm guessing it's just a table atm(been there done that )

No, it hasn't been on for many years, I have more scrap computer cases than tables in my room

 

[UKToecutter]

hmmm....

I got the exact same mylar caps on my s22.

They were listed on a bom that someone posted.

Oh well. I'd better change mine too.

 

[Fitz]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Oh btw, those green mylar caps you have on the σ22 are sub-optimal. These are used for high frequency compensation in the design, and should have good high-frequency performance. Unfortunately, those green mylar caps are inductive and do not work well in this application. I don't think this is the source of your noise problem, but who knows, I would recommend replacing them with non-inductive film or multilayer ceramic caps.

It would probably be a good idea to take them (Xicon PF) off the parts list on the σ22 page then, otherwise people are likely to keep using them.

 

[amb]

I didn't realize the Xicon PF was those green mylars, I don't remember why I added them to the parts list. Anyway, they are obsolete anyway, and now removed from the BOM.

 

[Fitz]

Mouser still has some of the higher tolerance versions of the Xicon PF, plus the Xicon PEI which seems to be the current equivalent. I only know what they are because I ordered some a while back trying to avoid making a separate order at Digikey just for those caps.

 

[nattonrice]

AMB, I found that everything was obsolete (for c14/15) except for the one from digikey.

 

[pompon]

For a B22 balanced (4 board) with dual sigma 22 ... We want cable inside with silver wire.
(that include, volume control and 1 input)
What would be the required length of cable about? 5 foot, 10 foot, 25 foots?

Silver cable is pretty expansive ... it's why I ask!