My digital pre-amp

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Ive attached a schematic of a pre-amp design i've been working on and i was hoping that you smart people could take a look at it and tell me if anything looks wrong.

The amp is controlled by 2 rotary encoders, one for crossove control (MAX260) which will have an adjustable cutoff frequency from 60Hz to 120Hz in 5Hz steps. The other encoder is for the volume control (PGA2311) My code is set up so so that the first 10 steps are 3db, the next 10 are 2db and the last are 1db.
 

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Hi, looks like a nice project!

The gain stage should not be required as the PGA2311 can provide 31.5dB of gain. I am not sure about the amplification stage either. The inverter isn't required if you just reverse the connections at the output of the amp. Are you trying to wire in bridge mode? In that case, remove the inverter, and wire the speaker from + of one side of the amp to the - of the other side of tha amp. I don't quite understand what the wire from out1- to out2- is doing. It looks to me like in the current configuration it will create a short circuit, though I don't have much experience with the exotic amplifier configurations.
 
I am bridging the input of the amplifier and out1- and out2- are power ground so technically i didnt need to "wire" them together, or even show them for that matter. Ive been advised by numerous people that hte PGA2311 should really only be used for attenuation. I also added that gain stage at the beggining casue im having a serious noise issuse which i turn up the gain on the pga2311 so i decided to gain the input signal first. Works a lot better gaining first, however this severely limits the size of my input signal. The inverter i got from the data sheet of the amplifier. The TK2350 is a 2 channel amplifier. So i needed to send one channel the inverse of the signal, so that the output voltage will be effectively doubled.
 
Deltat said:
I also added that gain stage at the beggining casue im having a serious noise issuse which i turn up the gain on the pga2311 so i decided to gain the input signal first.
Well from my understanding, adding an external gain stage can only increase the noise level, but if it works for you then go for it.

Deltat said:
The inverter i got from the data sheet of the amplifier.
I just had a look at the datasheet for the TK2350, and no inverter is required. For bridge mode see figure 8.
 
Sorry I have misunderstood you. You are using the RB-TK2350 which is a completed amplifier board, not just an amplifier of your own design using the TK2350 IC. In this case, yes just adding the inverter will do the job just fine. It is explained in the datasheet that by processing one channel out of phase it removes problems associated with switching supplies. Using this configuration, you could add a switch to select between bridge and non-bridge modes.

In your datasheet (RB-TK2350), the paragraph above figure 10 is explaining what figure 8 in the TK2350 datasheet is doing. This is optimal if non-bridge mode is never required as it removes the need for another op-amp in the signal path.
 
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