The Beta 22 Thread
Dec 6, 2016 at 4:08 AM Post #92 of 100

milosz

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The two chassis are from eBay, but I machined the front panels to my design, and cut ventilation slots in the top and bottom panels
 

 
Here's a chassis before machining.  Very good quality for the money.
 
Here's an ebay item for one of these chassis (note, this ebay link will eventually die...)  http://www.ebay.com/itm/Aluminum-chassis-Power-amplifier-Enclosure-DAC-case-preamp-PSU-Box-DIY-AUDIO-/130953831714
 
Jul 28, 2017 at 7:43 PM Post #97 of 100

milosz

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AHHH! IEMs!

Well, it depends on the gain that the Beta 22 was built with. Generally, it's a fairly powerful (5 watts or so) amplifier and that sort of thing isn't usually suitable for IEMs.

My Beta 22's are built with a gain of 5. I think this is to much gain for IEMs. A gain of 2 would be better.

Some Beta 22s are built with a gain of 8, and even higher gains like for those people who have AKG 1000's.

There are a few parts in each channel that have to be changed to change the gain

From: http://www.amb.org/audio/beta22/parts.shtml

The following table shows the left and right channel part values when building the β22 with a non-default voltage gain (gain of 8x is the default):

L & R Part Gain 11x Gain 8x Gain 5x Gain 2x
R3 100Ω 182Ω 392Ω 2.49KΩ
R4 1KΩ 1.21KΩ 1.5KΩ 2.49KΩ
C2-C5 22pF 33pF 47pF 100pF​
 
Jul 29, 2017 at 3:00 AM Post #100 of 100

milosz

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So x2 gain is as low as I can go effectively? I want the quitest amp possible with PSU outside of chassis.

You could post to the AMB Beta 22 Forum, they can better advise you as to what would be best with IEMs. I never use IEMs, they hurt my ears, I can't wear them, so I have not explored using any of my headphone amps with IEMs.

http://www.amb.org/forum/beta22-amplifier-f12.html
 

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