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

Dec 30, 2009 at 11:39 AM Post #2,086 of 3,218
Alrighty, did the resistance to ground comparison with one of my other boards.
Found the problem in the Q11, Q12, Q15, Q16 cluster.

Pulled them all out and looked at the traces and the from R11 and R12 to the base of Q11 and Q12 were mis-etched under the components themselves. See attached pics.

I dug out some old very very thing wire from back in the day when I had to do similar fixes. (though back then it was more my fault not picking up the error in protel before sending to fab)
Soldered on the wire and fired it up.
Works just fine.

Thanks to everyone who gave suggestions and ofcourse linuxworks for giving me the idea for that test.

 
Dec 30, 2009 at 12:15 PM Post #2,088 of 3,218
Well in this case it was over-etched.
Attachment 24153

Just finished biasing and zeroing DC offset.
Still a fair bit of casework/assembly/wiring left to do.

Can't wait to get it up and running
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But I've had enough for today. Closing in on midnight here down under.
 
Dec 30, 2009 at 12:46 PM Post #2,089 of 3,218
Ah, ok. Instead of the long wires you could have just scraped a little bit of the soldermask away and tack-soldered a little resistor lead cutoff to bridge it. But anyway...
 
Dec 30, 2009 at 3:54 PM Post #2,091 of 3,218
Well done on that fix, I've been in that boat before and you start to lose the will to live but making it working is an amazing feeling!
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Can somebody clarify how to connect a SE source please?

If I understand the diagram correctly, I must short the input of two of the boards (the -) ones to ground but this must take place between the boards and the pot, not between the pot and the jacks?
Can I just bridge the input and gnd pads on the two boards?

I guess I lose half the gain by doing this also?

Thanks
 
Dec 30, 2009 at 4:58 PM Post #2,092 of 3,218
Quote:

Originally Posted by Magsy /img/forum/go_quote.gif
Can somebody clarify how to connect a SE source please?


Just like how you saw it in the diagram at the β22 website "Other options" section.

Quote:

If I understand the diagram correctly, I must short the input of two of the boards (the -) ones to ground but this must take place between the boards and the pot, not between the pot and the jacks?


Correct, because you don't need a volume control on the "cold" amps when switched to unbalanced inputs. You only need those board to become referenced directly to ground.

Quote:

Can I just bridge the input and gnd pads on the two boards?


Isn't that basically what the diagram does with the switch?

Quote:

I guess I lose half the gain by doing this also?


Yes, but only if your unbalanced source outputs half the total output voltage swing compared to your balanced source.
 
Jan 3, 2010 at 12:15 PM Post #2,093 of 3,218
Where can we find ß22 and sigma22 complete kits? (w/out chassis of course)

I want to buy all kit and pcb's, and only solder them, then start to use...
 
Jan 3, 2010 at 1:28 PM Post #2,094 of 3,218
Blind stuffing comes highly unrecommended.
Casing that is not well thought out (or non-existent) is asking for hum and other problems.

I believe Glass Jar Audio stocks pcb+component kits.

Before diving into this you will want to read the threads here and especially the 3 threads at headwize FROM START TO FINISH.
Most epic failures can be prevented that way.
 
Jan 3, 2010 at 5:11 PM Post #2,095 of 3,218
Thanks nottonrice... I will look at Glass Jar Audio..

I know it's like diving but i am not unfamiliar to pcbs and all these stuff. (Electronics Eng.) But i will listen your advice and read the threads...
 
Jan 3, 2010 at 5:18 PM Post #2,096 of 3,218
do not build a b22 unless you are prepared to DEBUG it.

this is not a heathkit and this is not just 'solder parts and it goes'. sometimes there are bad parts. sometimes there are bad boards. sometimes there are other things.

do not be fooled that its just assembly work.

don't let your ego assume that you can build this.

that's all I have to say. I see a lot of bravado about 'I want to build the best!' but people FORGET that debugging is often a part of the build and most builders, sorry to say, are just not up to the task (being really honest, here).

work your way up. start sensible. that's my suggestion.

b22 is a final build not a FIRST BUILD.
 
Jan 3, 2010 at 7:13 PM Post #2,097 of 3,218
My desire to get all parts in one time is because where I live. Its hard to find audiophile parts here. Only a missing capacitor loses me at least 10 days...

This is why I am so on to finding all parts as kits..
 
Jan 3, 2010 at 7:50 PM Post #2,098 of 3,218
I would suggest ordering extra parts, then. I've had to re-order and even getting the parts the same week for me is too much wait
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order extras of the things that need matching and also the final transistors AND .47 resistors. order lots of those
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just in case.

no need for extra crd's but do order extra fets and transistors of all kinds.

maybe extra caps (electros) in case you reverse some. I did (just 1 but it blew out a WHOLE SUB CHAIN of parts due to that!)

again, can't say this enough: order extra parts since you are making 1 big shipment.
 
Jan 3, 2010 at 8:48 PM Post #2,099 of 3,218
Even before soldering any components a continuity check with the pcb matching back to the schematic would be advisable.
 
Jan 3, 2010 at 9:32 PM Post #2,100 of 3,218
Thanks for advices, i am noting down them all...
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