[amb]

ting.mike, the quiescent current will drift up and down based on heatsink and ambient temperatures. Your readings are not out of line.

 

[johnwmclean]

Quote:

Originally Posted by ting.mike /img/forum/go_quote.gif I'm trying to adjust the VR2, while getting the measurements on the R34, supposedly in the range of 55mV to 75mV. I can't seem to pin down an exact reading on the multimeter. The number jumps around from roughly 68mV to 74mV. Is the variation supposed to be that great? This is at amp operating temperature, and following all the guidelines from the amb website. I've measured the AC line, and AC voltage is pretty stable at 224-223 volts. DC power from the S22 is also pretty stable at 29.8 to 29.9 volts.

Looks good to me, leave it on for 15-20mins then take your reading over R34, it should stabilise a little.

 

[n_maher]

Anyone working on a beta22 should have at least one pair of mini grabbers. Hook the pair to R34, leave the DMM on, take readings for the first hour every 10 minutes or so and see how it goes. Repeatedly sticking probes in there while being blinded by blue LEDs gets old fast.

 

[cfcubed]

Yes, like the pic in amb's initial setup, lots of good info up there... Mounting parts w/a bit of clearance, resistor markings/value up, etc.
Clip leads w/those mini grabbers come in very handy too.

 

[ting.mike]

Thanks, all.. yes, I'm using the mini grabbers like in the one told by AMB.

The Balanced Beta22 actually has been running flawlessly, and gosh, the sound is out of this world. I've never heard a headphone sounding so three dimensional. I'm just trying to adjust the VR2 to be more precise, but apparently that's quite a challenge due to the voltage always drifting up and down.

I'll take pictures and post them soon!

Thanks, Ti Kan, for this awesome amp!

 

[fishski13]

Quote:

Originally Posted by ting.mike /img/forum/go_quote.gif Thanks, all.. yes, I'm using the mini grabbers like in the one told by AMB. The Balanced Beta22 actually has been running flawlessly, and gosh, the sound is out of this world. I've never heard a headphone sounding so three dimensional. I'm just trying to adjust the VR2 to be more precise, but apparently that's quite a challenge due to the voltage always drifting up and down. I'll take pictures and post them soon! Thanks, Ti Kan, for this awesome amp!

the B22 is an awesome amp.

 

[cfcubed]

Just a little update to my 1st frugal 2-ch b22 post. BTW updated the pic in that post.

Some quick-n-dirty wire up this morning & she's sounding very sweet. All the good things (absolutely black background, amazing range, Vs & temps on the money).

"Just" have casework to go (offset protection, $50 fleabay case) and should make it for the NYC Fall meet. BTW, getting two DA-20-24 24VAC 830mA adapters for $15 shipped makes this look to be coming in a bit below $350 USD.

 

[Anonanimal]

Hey all- I'm currently building a 3-channel β22 and I'm wondering if anyone has any input with respect to the use of the ε12 Muting/Protection Circuit. i.e. has anyone found significant turn-on/off noise with their β22s without this circuit? I do understand the usefulness of the circuit as protection from high DC offsets but I'm trying to decide if it's absolutely necessary. Thanks for any and all input!

 

[ShinyFalcon]

Without an ε12, there is no turn on noise (music fades in after power is applied), and maybe a turn off squeak when power is cut off.

 

[amb]

β22 is very well-behaved at turn-on and turn-off. There should be no thump or transients.

 

[Anonanimal]

Excellent. Thank both of you very much for the quick responses.

 

[Possede]

Thanks again for your reply amb.

As I do not trust myself with power tools, I am having all my panels sent away to be professionally machined (even the base of my case).

amb, I would be most grateful if you could provide the board measurements (the distances between the holes for spacers) for the ε22 backplane and the ε24 power switch driver circuit, like you have for the σ22:

 

[amb]

The ε22 backplane board dimensions and mounting hole locations are found here:
HeadWize: View Post [DIY Workshop » β22: A discrete, cascoded, fully complementary, pure class A amplifier (part 2)]

The ε24 board dimensions is 2.0" x 1.2". Its four mounting hole centers are at:

0.2", 0.2"
1.8", 0.2"
1.8", 1.0"
0.2", 1.0"

 

[Possede]

Many thanks for the quick reply. Now I will be able to get this
project on the way to completion. I'll post an image of my
panels once I've finalised them to gather some feedback.

 

[Possede]

Delete.