Roll Call: Who's building, built, or thinking of building a beta22?
Sep 25, 2009 at 7:30 PM Post #1,831 of 3,218

fishski13

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Quote:

Originally Posted by DoYouRight /img/forum/go_quote.gif
its a difficult thing the gain settings. you can get extra stuff and try a few settings and settle on one. but thats a huge PITA. I went with what John uses its loud alright. If I get the new beyer flagships I might double what I have.


i have the dt990/600 and went with the default gain of 8. i'm hoping this will be adequate.
 
Sep 25, 2009 at 8:08 PM Post #1,832 of 3,218

DoYouRight

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are you making a balanced beta22?
 
Sep 25, 2009 at 8:29 PM Post #1,833 of 3,218

fishski13

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no.
 
Sep 25, 2009 at 9:28 PM Post #1,834 of 3,218

wolf18t

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Quote:

Originally Posted by fishski13 /img/forum/go_quote.gif
i have the dt990/600 and went with the default gain of 8. i'm hoping this will be adequate.


Should be just fine but, I suggest you order the parts for 5x gain for a buck or two extra. If you change your mind you'll save on shipping later...
smily_headphones1.gif
 
Sep 26, 2009 at 3:35 AM Post #1,835 of 3,218

fishski13

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Quote:

Originally Posted by wolf18t /img/forum/go_quote.gif
Should be just fine but, I suggest you order the parts for 5x gain for a buck or two extra. If you change your mind you'll save on shipping later...
smily_headphones1.gif



my M3 has the default gain 11x and 12 o'clock is pretty loud for most recordings. i'll hopefully have the B22 cranking tunes by late tomorrow. i just need to finish the chassis wiring.
 
Sep 26, 2009 at 4:51 AM Post #1,836 of 3,218

fishski13

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i have a friend that runs a CNC machine all day long for a mill-work shop. among other "drop cuts", he gave me some perf steel. for the top-plate, is steel a problem in this application with regards to EMI creating noise? should i ground it, or leave it floating?

http://i23.photobucket.com/albums/b3...ki13/010-4.jpg
 
Sep 26, 2009 at 12:50 PM Post #1,837 of 3,218

Karu

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If I have a six board β22 setup and want to use it in different skenarios what is the correct way to connect the ground?

For unbalanced headphone ground I gather this is the way to do it
  1. Passive
    1. Ground connected to PSU ground
  2. Active
    1. Ground connected to ground amplifier
  3. Balanced
    1. Ground connected to ground amplifier

How to connect preamp ground (RCA/XLR) when in balanced mode?
  1. Passive
    1. Ground connected to PSU ground
  2. Active
    1. Ground connected to signal ground
  3. Balanced
    1. Ground connected to signal ground

EDIT: I think I got the preamp ground in balanced mode right.
 
Sep 26, 2009 at 6:13 PM Post #1,838 of 3,218

Fitz

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Quote:

Originally Posted by Beefy /img/forum/go_quote.gif
I don't know whether most non-DIY people appreciate how much volume you could get from an balanced B22 with an effective gain of 16. A standard 2VRMS source is 5.65V P-P. At max volume, you would be trying to push 90.5V P-P, clipping even with a ±30V power supply, and 100% certainly deaf.


This is only true if the balanced output from the source is twice as strong at 4Vrms, which is where the so-called doubling of gain actually comes from. The amplifier when considered by itself still has the same amount of gain... a 2Vrms unbalanced signal into a single board with a gain of 8 yields the same amplitude output as a 2Vrms balanced signal into a pair of boards each with a gain of 8, because each board only "sees" half the signal.

But regardless, it's not so much that one chooses that much gain to try to get that much volume out of the amp, but that the higher gain will allow one to reach the desired listening volume even if the recording or source is relatively soft.
 
Sep 26, 2009 at 7:04 PM Post #1,839 of 3,218

askforwhy

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Today I've just fix most noise problems, but unfortunately one of my boards may blow some mosfets.
I turn up the amp, then I found two output resistors on my R+ channel start glowing like a bulb, I turn off the amp ASAP. After some inspection I found the output pad shorted to V-. So I think I will have to replace Q22/Q24, anywhere else I should check with care too?
Arrrrrh~ PAIN.
 
Sep 26, 2009 at 9:10 PM Post #1,840 of 3,218

Beefy

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Quote:

Originally Posted by Fitz /img/forum/go_quote.gif
This is only true if the balanced output from the source is twice as strong at 4Vrms, which is where the so-called doubling of gain actually comes from. The amplifier when considered by itself still has the same amount of gain... a 2Vrms unbalanced signal into a single board with a gain of 8 yields the same amplitude output as a 2Vrms balanced signal into a pair of boards each with a gain of 8, because each board only "sees" half the signal.


True. I must admit I don't know much about a lot of sources, but many DIY sources I have looked at do indeed have double the output from their balanced outputs.

Quote:

But regardless, it's not so much that one chooses that much gain to try to get that much volume out of the amp, but that the higher gain will allow one to reach the desired listening volume even if the recording or source is relatively soft.


True. But I would imagine that even for the most quiet recordings a gain of higher than 8x is very rarely going to use the whole range of the volume pot.
 
Sep 26, 2009 at 11:51 PM Post #1,841 of 3,218

amb

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Quote:

Originally Posted by fishski13 /img/forum/go_quote.gif
i have a friend that runs a CNC machine all day long for a mill-work shop. among other "drop cuts", he gave me some perf steel. for the top-plate, is steel a problem in this application with regards to EMI creating noise? should i ground it, or leave it floating?


You'll get better shielding if it's grounded, but depending on whether RFI is a problem in your area, it may or may not make a difference.
 
Sep 26, 2009 at 11:56 PM Post #1,842 of 3,218

amb

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Quote:

Originally Posted by Karu /img/forum/go_quote.gif
If I have a six board β22 setup and want to use it in different skenarios what is the correct way to connect the ground?

For unbalanced headphone ground I gather this is the way to do it
  1. Passive
    1. Ground connected to PSU ground
  2. Active
    1. Ground connected to ground amplifier
  3. Balanced
    1. Ground connected to ground amplifier



Not sure what the third bullet refers to. How does an unbalanced headphone get "balanced"?

Quote:

How to connect preamp ground (RCA/XLR) when in balanced mode?
  1. Passive
    1. Ground connected to PSU ground
  2. Active
    1. Ground connected to signal ground
  3. Balanced
    1. Ground connected to signal ground


The first bullet is incorrect, and the second bullet is meaningless. Preamp outputs should always have passive ground, and always wired to signal ground.
 
Sep 26, 2009 at 11:57 PM Post #1,843 of 3,218

amb

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Quote:

Originally Posted by askforwhy /img/forum/go_quote.gif
Today I've just fix most noise problems, but unfortunately one of my boards may blow some mosfets.
I turn up the amp, then I found two output resistors on my R+ channel start glowing like a bulb, I turn off the amp ASAP. After some inspection I found the output pad shorted to V-. So I think I will have to replace Q22/Q24, anywhere else I should check with care too?
Arrrrrh~ PAIN.



Start measuring the MOSFETs for shorts.
 
Sep 28, 2009 at 3:24 PM Post #1,845 of 3,218

askforwhy

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Quote:

Originally Posted by amb /img/forum/go_quote.gif
Start measuring the MOSFETs for shorts.


Thanks, Ti.
I've just replaced 4 MOSFETs on the board and now my Beta22 sings again.
Still some hiss/hum noise with my earbuds but as long as I can't hear them with my K701, I will leave it as it is.
smily_headphones1.gif

Will post pics next few days, my room is a mess.
 

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