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Roll Call: Who's building, built, or thinking of building a beta22? - Page 198

post #2956 of 3166

Why not add the second PSU?

post #2957 of 3166
Quote:
Originally Posted by alota View Post

correct,  but is possible one sigma22 for 4 boards, right?

yes - just make sure that the heat sinks are sized correctly based on the voltage supply and quiescent bias current of the amp boards since the total current load/power dissipation is spread across less devices/heat sinks. 

post #2958 of 3166
Hey everyone, my Beta22 is build is chugging along, but I'm not sure how the grounding should work out for the layout I've chosen.

It's a 1 Chassis build with the transformer isolated into a smaller aluminum enclosure inside the main body. The box for the transformer is isolated from the main body with rubber feet. I think that places it similar to wiring scheme #2 on the AMB site.



The IEC Inlet will be in contact with the main chassis. The Input and Headphone Output XLRs will be in contact with main chassis as well. Could someone confirm if this setup causes any grounding issues?

Reference image in case anyone wanted to draw suggestions.

post #2959 of 3166

I don't think there is any reason to isolate the transformer in an isolated aluminum chasis inside of the main enclosure.  Aluminum won't provide any EMI sheilding at all.  I think it would be a better idea to just build this as a one case solution using the single case wiring scheme.  The IEC inlet will not have any electrical contact with the main case and can be grounded to the internal chasis if you really want to.  The problem is that even if you ground the IEC ground to the internal aluminum chasis, there is still a chance that a wire leading to that case could come loose and come into contact with the main chasis causing a dangerous situation because it won't be properly grounded.

 

I hope this makes sense and I could be wrong since I am not an expert, hopefully someone else will weigh in.  I did build a 2 channel B22 with a seperate Sigma22 PSU.


Edited by haejuk - 7/16/13 at 4:45pm
post #2960 of 3166
Quote:
Originally Posted by haejuk View Post

I don't think there is any reason to isolate the transformer in an isolated aluminum chasis inside of the main enclosure.  Aluminum won't provide any EMI sheilding at all.  I think it would be a better idea to just build this as a one case solution using the single case wiring scheme.  The IEC inlet will not have any electrical contact with the main case and can be grounded to the internal chasis if you really want to.  The problem is that even if you ground the IEC ground to the internal aluminum chasis, there is still a chance that a wire leading to that case could come loose and come into contact with the main chasis causing a dangerous situation because it won't be properly grounded.

I hope this makes sense and I could be wrong since I am not an expert, hopefully someone else will weigh in.  I did build a 2 channel B22 with a seperate Sigma22 PSU.

I was under the idea aluminum is a very popular material for shielding though? The aluminum box should be preventing EMI leak from the transformer is what I was led to believe.

The issue is that the IEC inlet contacting the outer main body of the amp is not my choice. The flange mount forces the metal body of the IEC inlet to make contact. I'll double check once it's actually mounted to make sure that's the case. However, that means grounding it to the inner transformer box isn't an option.

I do have the components for the ground loop breaker on hand, but I don't quite understand why I need to use it with my set up.

Sorry, I'm not trying to be difficult. I'm just trying to clarify things before rushing ahead.
post #2961 of 3166

Generally it's a good practice to keep the trafo's separate from the PCB's in separate enclosures. But you can eliminate interference issues or crosstalk between the components if you have it well isolated/insulated in it's own cover in a single box enclosure.

 

I prefer the simplicity of wiring and less effort involved with having a single unit enclosure but prefer the look of a dual enclosure one for the amp itself and 1 for the psu. Do post pictures of the build too. I'm in the process of converting my 2 board to possibly a balanced setup (if enough space) so I can steal some ideas off you. hehe biggrin.gif

post #2962 of 3166
Quote:
Originally Posted by Senpai3330 View Post


I was under the idea aluminum is a very popular material for shielding though? The aluminum box should be preventing EMI leak from the transformer is what I was led to believe.

The issue is that the IEC inlet contacting the outer main body of the amp is not my choice. The flange mount forces the metal body of the IEC inlet to make contact. I'll double check once it's actually mounted to make sure that's the case. However, that means grounding it to the inner transformer box isn't an option.

I do have the components for the ground loop breaker on hand, but I don't quite understand why I need to use it with my set up.

Sorry, I'm not trying to be difficult. I'm just trying to clarify things before rushing ahead.

 

After thinking about this some more I think that you are basically making a single box enclosure.  The box with the transformer is basically just for sheilding if I understand correctly.  This would neccesitate using the use of wiring as shown in the single enclosure wiring diagram and I am not sure it would matter if the transformer box was isolated or not.  In my own B22 build I used aluminum case for the amp and the PSU and I still got transformer noise until I replaced the transformer with a sheilded one.  It is pretty hard to block out transformer noise without using one that is build sheilded, or at least that is what I was told by Amb.

 

Once again, I am not 100% sure.  If no one else has any suggestions, you could always ask on the amb labs B22 forum.  I got help from amb himself when I posted my questions there for my build.

post #2963 of 3166
Thanks, I did make a post there as well, but the board seems to move quite a bit slower. I think I will just install the ground loop breaker under the assumption that I'll essentially be building Option 3.

Also, how exactly does one isolate XLR's from the main chassis? It shares a ground with the 4 amp boards and the output XLR as well as the volume pot which is listed as "connected" to the main chassis in option 3, so is there any point?
post #2964 of 3166

That board does move quite a bit slower, but usually you will have some responses within 24 hours or so.  I am not familiar with the balanced wiring scheme, but I can see your question is valid.  The diagrams on amb's site don't seem to address this.  Looking at the B22 gallery on his site I am starting to have a bad feeling about this build as I don't see any balanced B22s that are in a single enclosure.  I don't think I can be of any further help, but I hope someone will address this.  If you get any help on the amb labs forum let us know here.

post #2965 of 3166
Will do, thanks for the replies.
post #2966 of 3166
I also have a cookie tin and no shame if it really comes down to using 2 chassis.
post #2967 of 3166
I figured out a way to still do a pseudo option 2 grounding scheme. The IEC inlet will be insulated from the outer chassis using U-trim (C-trim, edge trim, a lot of names for it but it's the rubber trim PC case modders often use when they make a cut to their chassis) and the ground will be run to inner transformer box still. The flange mount should work fine even with a slightly elastic material around the edge of the cutout. I don't really worry about the grounding wire coming loose and shorting anything because there's literally nothing between the inlet and the inner box. Solid gauge wire over a short distance, should be fine.

Gonna go dote over aesthetic things like electroetching the front panel design and whatnot while I wait for my last 2 boards to come in the mail.
post #2968 of 3166
Quote:
Originally Posted by Senpai3330 View Post

I also have a cookie tin and no shame if it really comes down to using 2 chassis.

hahaha.

 

Why not just do a 6 channel? xD

 

http://www.head-fi.org/t/669613/fs-rockhopper-6-channel-beta22-amplifier-price-drop


Edited by DefQon - 7/16/13 at 9:45pm
post #2969 of 3166
Quote:
Originally Posted by DefQon View Post

hahaha.

Why not just do a 6 channel? xD

http://www.head-fi.org/t/669613/fs-rockhopper-6-channel-beta22-amplifier-price-drop

Christ just populating 2 amp boards was boring enough to make me antsy. The builder's patience must be incredible.
post #2970 of 3166

Shame the original builder wasted there money on 2 extras boards which have no improvement over a 4 board balanced configuration.

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