[nkd]

Bit of a noobish question, i'm sure! I'm working on a three channel beta22 at the moment, using all the standard component values from the site (gain 8). If I want to use it as a preamp too, is it as simple as having a switch to choose between the headphone output and output phono sockets?

 

[MoodySteve]

You don't even need a switch.

You can use a switch to either disable headphone output, disable preamp output, or to toggle between them, but that's up to you.

I do not have any switched on mine and I use it as a full-time preamp as well as headphone amp.

 

[ivant]

I've built a 3 channel B22 as a preamp connected to a gainclone. I started out with 8X gain but found that it was too high. Normal listening volume is only at 7-8 o'clock on the knob. Unless you plan to use very inefficient headphones, i suggest 5X gain instead.

As for switching between headphone and preamp, I used a switched 1/4" headphone jack. Just unplug the headphone and it will be in preamp mode.

There is a diagram on wiring the B22 as a preamp under "other options" at the amb website.

 

[Iniamyen]

And remember, the ground channel is connected only to the headphone out. The ground connection on the pre-out should be connected to signal input ground to prevent grounding issues. I have yet to correct this mistake that I made on my B22

 

[qkizz]

nkd: if you use input selector use shorting one or otherwise do not switch grounds. Like ivant said 8x gain is to much for most instances as a preamp.

I also have a question regarding preamp/headamp combination. I plan to use 5 board configuration: 4 boards for balanced + 1 boards for active ground for SE headphone output. The question is: what to do with gain differences between balanced and unbalanced? As I understand in balanced gain gets doubled. 2x gain for each board will get me 4x in balanced and 2x in SE. Would directing signal from SE input to two boards for output (SE L in > board L1(2x) + board L2(2x) > SE L (4x) output) solve the problem?

 

[linuxworks]

my b22 is also set to 5x.

I started higher. then I lowered it. then lowered it ONCE MORE to 5. wow. so many unsolderings

stick with 5, I think

 

[nkd]

Phew, I read this about a gain of 5 just before I put in the order for the final parts too! Thanks for the tip!

 

[ivant]

Quote:

Originally Posted by qkizz /img/forum/go_quote.gif nkd: if you use input selector use shorting one or otherwise do not switch grounds. Like ivant said 8x gain is to much for most instances as a preamp. I also have a question regarding preamp/headamp combination. I plan to use 5 board configuration: 4 boards for balanced + 1 boards for active ground for SE headphone output. The question is: what to do with gain differences between balanced and unbalanced? As I understand in balanced gain gets doubled. 2x gain for each board will get me 4x in balanced and 2x in SE. Would directing signal from SE input to two boards for output (SE L in > board L1(2x) + board L2(2x) > SE L (4x) output) solve the problem?

Arranging the board in parallel configuration don't increase gain. Also, shorting the B22 outputs is not a good idea.

 

[amb]

Before you worry about gain difference between balanced and unbalanced, you need to know what the output levels are for each of these types of sources you will use. Some sources let you change the default balanced gain, either via a switch or jumpers (because there is really no "standard" for this for consumer grade audio).