Roll Call: Who's building, built, or thinking of building a beta22?
Apr 9, 2010 at 10:45 PM Post #2,656 of 3,218

Beefy

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Yep, spot on. No worries at all
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Apr 10, 2010 at 6:44 AM Post #2,657 of 3,218

jh4db536

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So i am finally listening to my 4 board b22; it put a big smile on my face and i am not easily impressed. Source is a balanced/Dual mono Opus DAC (no output stage). The only time i ever heard a B22 (active ground) was at CJ2009 when i went to TK's table for a very brief time. That's when i became set on building my own.

I love it. It is dead quiet even with my hack job mock up since i havent cut my faceplate or backpanels, all the AC wires are unshielded because i havent installed my umbilical yet. No hiss no transformer hum.

Every note hits with Massive weight and control especially bass, yet it still has a balanced tone and a little laid back. I would say the bass is right up there compared to my Apache, which i think is the best i've heard so far. Sound signature is definitely different, the RSA being VERY Airy, expansive, yet powerful at the same time. The Beta22 sounds heavy, fast at the same time and quite intimate, not exactly extremely neutral compared to my experience with Dynalo/Gilmore/Headamp amps.

This is reflective of the Opus Dac which has a very rich and heavy sound signature compared to my DAC1. The B22 just amplifies and refines/tightens up that characteristic.

Another thing i don't regret is using the TPA JT attenuator. 128 steps is superior to 24 steps. I cant stand the DACT unit, as nice as it is, in my apache. It doesnt have enough settings.
 
Apr 12, 2010 at 5:26 AM Post #2,658 of 3,218

m11a1

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Quick question: I'm planning to building a 6-channel B22, what's available as for the attenuator?
 
Apr 12, 2010 at 7:09 AM Post #2,659 of 3,218

johnwmclean

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Quote:

Originally Posted by m11a1 /img/forum/go_quote.gif
Quick question: I'm planning to building a 6-channel B22, what's available as for the attenuator?


m11a1, a 4 channel attenuator should do the trick
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Apr 12, 2010 at 7:24 AM Post #2,660 of 3,218

m11a1

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Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif
m11a1, a 4 channel attenuator should do the trick
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Much Obliged, John
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One more question though, my intended custom volume knob is roughly 2 inches in diameter and of 2 inches in depth, which potentiometer is suitable for this kind of knob?
 
Apr 12, 2010 at 8:18 AM Post #2,662 of 3,218

m11a1

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Quote:

Originally Posted by nattonrice /img/forum/go_quote.gif
You should start by measuring the shaft size of the knob otherwise we can't help you.


It's custom like I just said. The diameter of the shaft is customizable. I just need to find the right potentiometer that can handle that big of a knob.
 
Apr 12, 2010 at 8:57 AM Post #2,663 of 3,218

MrMajestic2

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Quote:

Originally Posted by m11a1 /img/forum/go_quote.gif
It's custom like I just said. The diameter of the shaft is customizable. I just need to find the right potentiometer that can handle that big of a knob.


Most attenuators have a 6mm shaft and most will have no problem accommodating your large knob. Man, that last part sounded so wrong
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Apr 12, 2010 at 10:51 AM Post #2,664 of 3,218

nattonrice

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Oh right. The way you said it I thought you already had it made.

Anything would be fine and (as above) most have a 6mm shaft.
Only thing to keep in mind is that on stepped attenuators (like the dact) the steps will feel softer/looser with larger knobs.
 
Apr 19, 2010 at 2:45 PM Post #2,665 of 3,218

LeMat

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I've spent sometime this week end listening to my bare B22... still an incredible sound, especially with the HF2.
But one thing I noticed is its ability to play the radio antenna... Many told me to be careful with EMI while I was building it but it's freakin true.
I can create hum noise only by approaching my hand to the input wire (from pot to board)... is it normal to be that sensible ??
Even without playing with the input cable, I always have a slight background noise. (FYI the PSU is shielded)
RCA inputs to pot is wired with a shielded cable so I don't have this problem.
I really hope the problem will be solved once I'll use an enclosure.
Do you guys use shielded wires throughout your build ?
 
Apr 19, 2010 at 2:49 PM Post #2,666 of 3,218

amb

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Yes, a proper enclosure should fix this problem. You should make sure your pot's body is making contact with the case metal. This is all shown in the β22 website "Wiring & ground" section.
 
Apr 19, 2010 at 4:37 PM Post #2,667 of 3,218

Anonanimal

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LeMat- I did use shielded wire on the input side on my build, but not the output. Though I did not do much listening before I cased it up, I have not had an issue with this type of noise. As amb mentioned, the enclosure should help you out quite a bit.
 
Apr 19, 2010 at 5:14 PM Post #2,668 of 3,218

LeMat

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Thanks for your answers
My pot's body is already connected to the signal ground but I have some remaining noise.
We'll see how when everything will be cased up. Worse case, I'll swap to shielded cable and add mu-metal sheet. Nothing too tricky here.
I should order cases this week. Can't wait because I know what to expect...pure sound !
 
Apr 20, 2010 at 1:58 AM Post #2,669 of 3,218

fishski13

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Quote:

Originally Posted by LeMat /img/forum/go_quote.gif
Thanks for your answers
My pot's body is already connected to the signal ground but I have some remaining noise.
We'll see how when everything will be cased up. Worse case, I'll swap to shielded cable and add mu-metal sheet. Nothing too tricky here.
I should order cases this week. Can't wait because I know what to expect...pure sound !



if it's any reassurance, i used mostly wood for my 2 chassis, and other than the TX, didn't shield any wiring. it's dead quiet. please post pics when finished!
 
Apr 20, 2010 at 8:54 AM Post #2,670 of 3,218

MrMajestic2

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Quote:

Originally Posted by MrMajestic2
Ok guys, I need some pointers in the right direction. I have a B22 board that measures 4.5V on R9, but around 3.5V on R10, R11 and R12. Any ideas where I should start looking? Everything looks like its soldered into the right place.


Quote:

Originally Posted by amb /img/forum/go_quote.gif
A bad JFET in the Q1-Q4 quad? This should not have anything to do with the CRDs.


Ok, I swapped out the quads, but the problem is still the same. R9 = 4.5V and R10, R11 and R12 are ~3.5V. R34 is still ~100mV at VR2s minimum position. Should I try changing the Mosfets?
 

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