[wolf18t]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Just try to develop the habit of turning the volume down before you plug or unplug the headphones. It becomes second nature after a while. This is not just for the β22, but is a good thing to do in general.

Or maybe adding fast blow fuses to PS rails or output L/R jacks? Better to blow a fuse than an output stage.

Just an idea, and probably a very dumb one...

 

[amb]

Fuses are a mixed bag of problems. They're either too slow or too fast, too low in rating or too high. Fuses work by heating (and eventually melting) its element, and under normal conditions the heating and cooling actually cause the element to expand and contract (and changing its resistance at the same time) as the amount of current flowing through changes. It has undesirable sonic consequences, and thus I would not put them in the supply rails because they hurt the PSUregulator performancel, and certainly not in the signal path.

 

[johnwmclean]

Quote:

Originally Posted by rockcod /img/forum/go_quote.gif Additionally, inspect the boards carefully before building to reduce the chances of having shorted traces.

Is this a common occurrence?

 

[Ech0]

Not to imply it's common, but, it happened to me on one of the boards in my beta22. IMO, it's worth the time for any board.

 

[amb]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif Is this a common occurrence?

It is very rare as far as the percentage of boards distributed goes, but it does happen, and you read about every one of those instances in the forums...

Nevertheless, it is a good idea to examine the board(s) carefully before beginning work, and do some sanity checks with your DMM (making sure that there are no shorts between any of the major "nodes", such as V+, G, V-, Output, etc.

 

[JB197]

Thread resurection!
 
Guys, regarding your Beta 22 builds I would like to know about oscillation...
 
Who has experienced oscillation?
How did you detect it?
What caused it?
What did you do to fix it?
 
 
Thank you,
J.

 

[johnwmclean]

Quote:

Thread resurection!
 
Guys, regarding your Beta 22 builds I would like to know about oscillation...
 
Who has experienced oscillation?
How did you detect it?
What caused it?
What did you do to fix it?
 
 
Thank you,

​

[size=medium][size=13.0px]These are the watch outs I know

1) Do not socket the compensation capacitors (C1-C5), solder as close to the board as possible.
2) Adding a zobel network to the output as described at the β22 website.
3) If using off-board heatsink’s always try and attach the legs of your mosFET’s to the boards, avoid extending them with cable or wire etc.[/size][/size] 

 

[FallenAngel]

1) Can't imagine why you would, set a little higher if needed for hacked-up "adjustable gain" if necessary.
2) Only for speakers or VERY low impedance headphones like some vintage models and IEMs.
3) Generally not advised to air-wire MOSFETs so definitely good advice.
 
As for adding to the thread of mistakes, I burned a board, still haven't figured out why, probably installed something backwards.

 

[johnwmclean]

FallenAngel, this was is response to JB197’s post regarding oscillation, FWIW. 
 
Quote:

1) Can't imagine why you would, set a little higher if needed for hacked-up "adjustable gain" if necessary.
2) Only for speakers or VERY low impedance headphones like some vintage models and IEMs.
3) Generally not advised to air-wire MOSFETs so definitely good advice.
 
As for adding to the thread of mistakes, I burned a board, still haven't figured out why, probably installed something backwards.

 

[AudioCats]

haven't gotten a chance to build a Beta yet, but the Sigma-22 kit from GlassJar was a super easy build, took 2 hours and nothing got fried, yet. It was a long wait for GlassJar to ship the kit though (over a month).
 
Will probably do a 11x gain balanced amp sometime soon, for speakers.

 

[rarebear]

Coming Here asking Questions

 

[JB197]

Thanks for your comments guys (even your dark humour Mr. rearbear!). I am just about to dive into the "thread of threads" kindly posted by johnwmclean. So far the only real issues that I can see with Beta 22 builds is oscillation and potential blown output stages at disconnection of 3 pole jacks. Once I find difinitive answers to these then I will feel more comfortable.
 
Thanks again,
J.

 

[ShinyFalcon]

Both can be relieved by using a zobel network and using 1-2.2ohm resistors for R34-R35.

 

[cfcubed]

Quote:

Both can be relieved by using a zobel network and using 1-2.2ohm resistors for R34-R35.

Yep & amb provided the math for VR2 adjustment, with specifics for 1 ohm, here:
 
http://www.head-fi.org/forum/thread/375627/let-s-fix-swt61-s-beta22/60#post_6238950
 
Believe there is no downside to adding the zobel, some cans maybe even require it IIRC.
I'd do both of these as a matter of course now. 
Haven't done the 1 ohm bit yet on by budget b22 as its harder to do so when your build is complete.

 

[JB197]

Thanks guys, I think I have enough to work on now.