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

[oneplustwo]

It's doable. The B22 is not an easy build, but there's lots of help on the board (which I've taken full advantage of myself). One thought is to go ahead and buy the parts for your 2 channel + sigma and then build the sigma first. The sigma is a bit more straight forward and will give you a sense for whether or not you feel comfortable continuing on with the beta boards or if you would prefer to stop, tackle another project or two first, and then continue on.

I would also recommend taking your time, reading the pages on Amb's site multiple times, and focusing especially on the wiring/ground sections. I've already blown up one set of boards by missing one important detail (not isolating speaker posts... strangely, it was my third beta build... first two went flawlessly.)

One thing to consider in your plan... if you do go balanced using the existing 2 channel you had already built, keep in mind your effective gain will double unless you redo the existing boards for a lesser gain.

 

[johnwmclean]

DemonicAngelz, sounds like a good plan, you’d be fine. But do the research, read AMB’s website carefully, a process of elimination is the key, ie ensure all components are installed correctly and you lower the chances of ever having to do any troubleshooting.
The Headwize threads are a valuable source of information, read them, I found following the problems other people had with their builds helped. Good Luck.

 

[DemonicAngelz]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif It's doable. The B22 is not an easy build, but there's lots of help on the board (which I've taken full advantage of myself). One thought is to go ahead and buy the parts for your 2 channel + sigma and then build the sigma first. The sigma is a bit more straight forward and will give you a sense for whether or not you feel comfortable continuing on with the beta boards or if you would prefer to stop, tackle another project or two first, and then continue on. I would also recommend taking your time, reading the pages on Amb's site multiple times, and focusing especially on the wiring/ground sections. I've already blown up one set of boards by missing one important detail (not isolating speaker posts... strangely, it was my third beta build... first two went flawlessly.) One thing to consider in your plan... if you do go balanced using the existing 2 channel you had already built, keep in mind your effective gain will double unless you redo the existing boards for a lesser gain.

I intend on printing the whole b22 amb site out and study it carefully, highlighting important parts.

As for the gain, i'm ordering two boards with gain of 5. If I upgrade i'll just get two more with gain of 5, totalling at 10. I figure this is not too bad considering I have 600ohm dt880 to drive too.

The main thing i'm not comfortable with is the s22. Its the first time i'm working live voltage. Scared that I may electrocute myself!

 

[UKToecutter]

Quote:

Originally Posted by DemonicAngelz /img/forum/go_quote.gif I intend on printing the whole b22 amb site out and study it carefully, highlighting important parts. As for the gain, i'm ordering two boards with gain of 5. If I upgrade i'll just get two more with gain of 5, totalling at 10. I figure this is not too bad considering I have 600ohm dt880 to drive too. The main thing i'm not comfortable with is the s22. Its the first time i'm working live voltage. Scared that I may electrocute myself!

You might try soldering the components without the mains plug in....

 

[oneplustwo]

I was nervous about live voltages as well which is probably healthy actually. But it's not so bad as long as you use normal safety measures. But like I said, a healthy respect for it is good for you.

Gain plan sounds reasonable.

 

[UKToecutter]

After a number of 'healthy belts', I too have a healthy respect for mains voltage.
Especially the 240V we have in the UK.

 

[LeMat]

It was my first build and I've been trough the whole process without too much pain. My s22 and 2 b22 boards are working perfectly... but while I wanted to avoid trouble shooting, I'll have to do it since my ground channel board is not working properly. The Q25 even blew up big time !
I'll update this post with the picture which worth a look

DemonicAngelz, you can do it... just do your homework

 

[tintin47]

Quote:

Originally Posted by DemonicAngelz /img/forum/go_quote.gif The main thing i'm not comfortable with is the s22. Its the first time i'm working live voltage. Scared that I may electrocute myself!

Working with mains voltage is really just about respect. As long as you respect that you can be electrocuted you'll be fine. There isn't a ton of risk as long as you are careful with wiring. If wired correctly, testing the thing takes 30 seconds. In my whole build, I had the case of the sigma open with the power on for about 5 minutes.

Just know when the power is on and don't go near the mains.

 

[UKToecutter]

Quote:

Originally Posted by tintin47 /img/forum/go_quote.gif Working with mains voltage is really just about respect. As long as you respect that you can be electrocuted you'll be fine. There isn't a ton of risk as long as you are careful with wiring. If wired correctly, testing the thing takes 30 seconds. In my whole build, I had the case of the sigma open with the power on for about 5 minutes. Just know when the power is on and don't go near the mains.

Oh, and make sure that the electrolytics are discharged as well.
It might not kill you but, boy it hurts!!!

 

[DemonicAngelz]

I would like to ask one more thing.

What are the advantages and disadvantages of using one 100VA s22 to power 4x B22 boards versus two 50VA s22 to power two sets of 2x B22 boards.

I'm kinda on budget and using one s22 saves me quite a bit if it does not compromise on sound.

 

[johnwmclean]

DemonicAngelz, using 2 σ22 is better for heat dissipation. One σ22 is good for headphones, alternatively use larger sinks on the one σ22.

Further reading:
http://gilmore2.chem.northwestern.ed...num=3&tid=6525

 

[linuxworks]

I'm reboxing my b22 (happens every springtime, this being the first) and I'm now wondering, should the speakers use the 3rd channel as a common ground or should they use the input-ground as their ground?

I have the 3ch backplane board and that has a molex connector on the edge (4 cond) marked for speakers. their ground is the 3rd channel out (the unity gain amp's out).

the last 2 b22's I did had speakers *not* burdening that 3rd channel. and my speaker/phones A/B switch was easy since I only had to switch 2 wires (DPDT). the phones ground was always tied to the 3rd channel-out and the speaker grounds were tied directly (very directly) to spare PSU ground screw terminals.

this build, I want to use relays instead of a mechanical DPDT switch; but I wonder if its really worth having the speakers on the ground-channel or not. what do you experts say? should speaker-mode be a 2ch mode when *in* speaker mode and then go to 3ch mode when its a *phones* mode amp? in fact, power to the 3rd channel can be dropped (a heavy DPDT relay) in speaker mode and that 'donates' more of the psu over to the remaining 2 boards.

comments on that kind of config?

 

[amb]

You could go either way.

If you skip the ground channel for speakers, then the speakers' "-" binding posts should be wired directly to the σ22 PSU "G" terminals. Do not wire them to the β22 board's signal ground. The small-signal ground reference should not "ride" on the same wire as the high current return from the speakers.

On the ε22 backplane board, the speaker "-" pads are wired to the ground channel output. The reason for this is because I do not assume that it would be feasible to run wires to the PSU (the builder may have an external σ22, and only has 3P connectors for V+, V- and signal ground). Using the ground channel avoids having to run those separate ground wires, but does put additional load on the ground channel amp. Since ε22 has no provisions for offboard heatsinking, it should only be used as a light-duty speaker amp anyway.

Oh and btw, you should not turn off the ground amp's power by switching it on the DC rails. The σ22 does not take kindly to this sort of thing -- there are warnings on the σ22 website.

 

[linuxworks]

Quote:

Originally Posted by amb /img/forum/go_quote.gif If you skip the ground channel for speakers, then the speakers' "-" binding posts should be wired directly to the σ22 PSU "G" terminals. Do not wire them to the β22 board's signal ground. The small-signal ground reference should not "ride" on the same wire as the high current return from the speakers.

check. I forgot to mention that I have the luxury of having the s22 inside the same chassis and so it was an obvious choice to pick a pair of ground terminals from there and leave the backplane's ground alone.

Quote:

Oh and btw, you should not turn off the ground amp's power by switching it on the DC rails. The σ22 does not take kindly to this sort of thing -- there are warnings on the σ22 website.

that would not be live, of course! what I had in mind was a controlled power down style change-over. it would be the equivalent of turning off the amp, waiting about 10 seconds for things to bleed (the stones actually wrote a song about that, I think) then plugging or unplugging that last cable on the backplane board; the one that connects the b22 gnd channel to, well, everything. I've done that almost daily, in fact. I power the whole amp down, wait a bit (for all the leds to go off and then a bit more), then either yank that last cable or insert it (if I'm going with phones). been doing that for a few months, now

I just simply want to automate the whole thing.

but it was more about: since speakers tend not to be as high a resolution device as headphones, would they truly benefit from '3rd channel isolation' or would the energy available in a single s22 be better used to keep 2 b22 modules warm instead of 3? that was my whole reason for this complicated change-over.

if there's a compelling case to continue to drive speakers from a 3rd channel config then I guess I'll try that; but it seems a lot harder to drive speakers and adding a 3rd channel may not work for this. works great for phones but I just wonder if its optimal for spkr use?

 

[amb]

A powered-on and idling ground amp will add less than 200mA of load to the PSU, depending on how heavily you biased it. That's not too much in the grand scheme of things, I'm not sure it's worth the hassle to shut it off, especially with the complicated scheme you describe. I also would not plug/unplug the Molex connectors too much. They are good connectors, but are not designed for that kind of use.