[Comfortable]

I want a gain of 8 or better for a particular pair of headphones while less gain for others, is it possible to use a volume knob for gain (for example, 1-8)?

 

[cfcubed]

Guess I might as well tell you... Although you install an input volume pot, the configured gain is a matter of some components installed on each board, see Parts -> "gain" here: http://www.amb.org/audio/beta22/

 

[nattonrice]

No it is not possible.
A gain of 5 would be a nice middle ground.

 

[digger945]

What I did was to socket the gain resistors (2 resistors per channel) so that they could be changed quickly and easily with a small pair of needle nose pliers. I also did this to the S22 power supplies to make changing voltages easy. There are instances where you would want a gain setting that is much higher than normal. One would be some hard-to-drive planars. Another would be some Stax transformer boxes, or for ultra low level listening without using a transformer box(just driving the stators with the amp output). Low gain is good for other dynamics. It's nice to have the capability so you can listen and experiment for yourself.
 
You should also consider socketing the feedback caps as well, if you decide to do the resistors.

 

[FallenAngel]

Did you also socket the compensation caps C2-C5 for stability vs bandwidth?

 

[nikongod]

If the volume knob is not resting comfortably against its minimum attenuation position (maximum volume) you have more gain than you need. 
 
This dosnt account for the fact that different sources put out different nominal signal levels, and some recordings are quieter than others, and that some headphones are truly inefficient. Throw in a comfy 20db of headroom to account for that - if your volume knob is not pointing to 2 or 3 o'clock at your average listening level you have too much gain.
 
If you have VERY different source outputs, and headphones, and have never spun the volume knob past noon on a clock face your wasting ooh so very much.
 
Try voltage gain of 4 (which is still too much for most headphones, but mneh) . Its the same as having gain of 8 (only better) if you just spin the knob a few degrees/clicks on a stepper higher. 
 
IIRC, attempts to switch feedback resistors on the B22 have caused instability. The hardest thing about selecting gain for a headphone amp is admitting that you only need a very little bit, and often not even that much.

 

[jcx]

the B22 should have extremely low input noise - so a low impedance volume pot should not give noise probelms even at 20 dB attenuation - source distortion driving the pot impedance and with analog pots the poor matching at higher attenuation may be problems
 
if your source does good digital attenuation - 24 bit or properly dithered 16 bit you should use digital attenuation - "bit loss" need not be a probelm in good digital source
 
another wonderfully wasteful approach is a power output resistive divider "Hiss Buster" style - with the B22's high power you could have a 1 Ohm output Z divider

 

[qusp]

Quote:

the B22 should have extremely low input noise - so a low impedance volume pot should not give noise probelms even at 20 dB attenuation - source distortion driving the pot impedance and with analog pots the poor matching at higher attenuation may be problems
 
if your source does good digital attenuation - 24 bit or properly dithered 16 bit you should use digital attenuation - "bit loss" need not be a probelm in good digital source
 
another wonderfully wasteful approach is a power output resistive divider "Hiss Buster" style - with the B22's high power you could have a 1 Ohm output Z divider

agree 100%, I changed to digital last year (32bit and over 1mhz) and theres no turning back now, all of my sources use it and none of my amps have a pot. its not terribly audiophile approved though, I'm not sure why, as I cant imagine a more transparent solution for digital source than a well designed digital attenuator; preferably one that uses the dac registers like the sabre

 

[daltonlanny]

Sorry to revive an old thread, but I just bought a Beta 22 here on Headfi, but the gain is 2, which is alittle too low for me, and my headphones. I need a higher gain.
So how exactly would I change the gain on my single-ended two channel Beta 22 from 2 to 5, step by step, and without any side effects?
If no one here knows, do you know anyone I could contact for help?
Thanks for your help.

 

[daltonlanny]

Anyone?

 

[muskyhuntr]

Hi,
 
Hope this helps.
From AMB's websie:   http://www.amb.org/audio/beta22/ 
The values are as follows.
R3...392R
R4...1.5K
C2 - C5...47pF
 
Me

 

[daltonlanny]

Is there anyone out there who would be willing to modify my Beta 22 to the default of 8?
It is currently set at 2.
It was already set at 2 when I bought it used.
If anyone would be interested in modifying it for me, please shoot me a PM .
Thanks for your help!

 

[daltonlanny]

If not, could someone tell me where good places to buy the parts are?
Thanks.

 

[jcx]

if your profile location is correct http://www.chattlab.org/blog/about/  looks from the web like they're still alive, should have people with tools, skilz
 
you may have missed closing RadioShack parts being sold off by the pound - Digikey is convenient, stocks real parts

 

[daltonlanny]

If anyone out there is willing to build me two brand new working Beta 22 circuit boards using top quality parts, including the caps and resistors for the default 8x gain, or if you happen to maybe have a pair of them with the default 8x (or higher) gain laying around somewhere that you would consider selling, drop me a PM.
After researching all this, I feel this might be my best and safest bet.
I am not really very skilled at all building new circuit boards, but I have removed and reinstalled them before.
If I could get someone to do this for me, I could just remove my old boards from my Beta 22, and install the new ones myself.
Much less complicated.
Again, if anyone would be willing to build me two boards, let me know.
Thanks.