Roll Call: Who's building, built, or thinking of building a beta22? - Page 189

I thought you could buy the TO-220 thermal and electrical isolation package from Mouser and that was what I did for each and every heatsink in my Beta22. 

Quote:

Originally Posted by K3cT 

I thought you could buy the TO-220 thermal and electrical isolation package from Mouser and that was what I did for each and every heatsink in my Beta22. 

You can (and I did as well).  What I was stressing earlier is that they are definitely not required, though some were giving Chrono the idea that they were.  Either way, that wasn't his problem so we can move on.

It appears I put in the trim pots in backwards, as Anonanimal guessed. I had assumed that the marking on the board should have matched up with the arrow symbol on the trim pot, but it seems that marking was referring to the position of the control screw. I verified my mistake by checking the trim pot data sheet and Beta 22 schematic.

I guess the question now is what parts are likely to have blown as a result.

Quote:

Originally Posted by chronomitch 

It appears I put in the trim pots in backwards, as Anonanimal guessed. I had assumed that the marking on the board should have matched up with the arrow symbol on the trim pot, but it seems that marking was referring to the position of the control screw. I verified my mistake by checking the trim pot data sheet and Beta 22 schematic.

 

I guess the question now is what parts are likely to have blown as a result.

Check output MOSFETs for shorts and R34/R35 for correct resistance.

Hi,  I just wanted to ask those that purchased a Glass Jar Audio kit whether or not some of the important components are matched as recommended by AMB?

Also a general question regarding the B22.  I have this desire to have a remote control input and source selection, the easiest implementation I thought would be to bypass all attenuation on the B22 and use it as a headphone "power amplifier" and using a high quality (possibly Audio GD Phoenix) pre-amp as the control center and using its remote source switching and volume knob.  Is this feasible or would it be self defeating in the pursuit for "perfection"?  The absolute best speaker setups seem to always have an active preamp ahead of the power amplifier.

Quote:

Originally Posted by SP Wild 

Also a general question regarding the B22.  I have this desire to have a remote control input and source selection, the easiest implementation I thought would be to bypass all attenuation on the B22 and use it as a headphone "power amplifier" and using a high quality (possibly Audio GD Phoenix) pre-amp as the control center and using its remote source switching and volume knob.  Is this feasible or would it be self defeating in the pursuit for "perfection"?  The absolute best speaker setups seem to always have an active preamp ahead of the power amplifier.

Sounds like you're looking for the upcoming LCDuino-1 + δ1 + δ2, if you're willing to wait a little time for their release.

An example implementation is my new α10 buffer preamp, except you'd be using β22s instead of JISBOS.  Discussions about the α10 are found here.

^ wow. Awesome.

From my comm & b22 kit buying from Jeff, he matched the "important" devices to match & did not match the "less important" devices to match. 

Don't remember specifics from amb's "Which devices to match", but you can communicate/confirm/request things to be sure.

May take Jeff a couple days to reply but I've always been happy w/my dealings w/him.
 

Quote:

Originally Posted by SP Wild 

Hi,  I just wanted to ask those that purchased a Glass Jar Audio kit whether or not some of the important components are matched as recommended by AMB?

Ti... you are an evil man!  I now absolutely have to build that!

haha X2 on that....
 

Quote:

Originally Posted by FallenAngel 

Ti... you are an evil man!  I now absolutely have to build that!

Guess what? I de-soldered the trim pots for all of the boards and put them in the right way, and everything works now! Everything checked out during the initial setup.

Now I cannot stop listening to it. The music just flows effortlessly.

I want to give a big shout out and thank you to AMB for designing such an awesome piece of equipment. Also, thanks to everybody who helped me out in this thread, especially Anonanimal for suggesting I check the orientation of the trim pots.

Here are a few pictures:

I decided to go ahead and use the two stepped attenuator volume control I discussed a few pages back. It turns out it works really well. I use the one on the right as pre-attenuator to allow the left attenuator to get in the 12 o'clock range. I can then use the left attenuator to adjust the volume in two decibel steps. If I had just used one attenuator, even the current gain of 5x would have made it very difficult to control the volume (i.e. normal volume would be reached at 7 or 8 o'clock.

what a strange fix. it shouldnt matter which way the trimpots are installed... it only alters the direction of adjustment, not the total adjustment as pin two is the wiper. Something else must have happened, maybe a bad joint or something?>

Quote:

Originally Posted by adamus 

what a strange fix. it shouldnt matter which way the trimpots are installed... it only alters the direction of adjustment, not the total adjustment as pin two is the wiper. Something else must have happened, maybe a bad joint or something?>

When VR1 and VR2 are mounted backwards, their direction of adjustment is indeed also reversed.  If you then follow the β22 website initial setup procedure and pre-set those trimpots fully-counterclockwise before powering up, you've just set them up for maximum bias.  On a β22 this means a lot of current is going to flow through the stages, and the output MOSFETs are going to get really hot in no time.

Great to hear that it's up and running!  Enjoy your new amp- over a year after building mine I rarely go a day without listening to it...

Quote:

Originally Posted by amb 

When VR1 and VR2 are mounted backwards, their direction of adjustment is indeed also reversed.  If you then follow the β22 website initial setup procedure and pre-set those trimpots fully-counterclockwise before powering up, you've just set them up for maximum bias.  On a β22 this means a lot of current is going to flow through the stages, and the output MOSFETs are going to get really hot in no time.

I've got a better one for trimpot screwups. I put the wrong trimpot in the VR1 spot, and after I noticed it and got it desoldered so I could put the right one in instead, I went and put the same one right back in. I felt pretty dumb that day.