# How to match gain between DSP and Amp

#### diegoAlm

I have a miniDSP with an output level of 0.9V and a tpa3255 amplifier with an input sensitivity of 2V, I have bought a preamp that says to multiply the signal by 5, how should I adjust the gain inside the dsp to get 2V at the output of the preamplifier? can it be calculated? Is it better to measure at the output of pre amp with a multimeter directly while playing a 400Hz signal and adjusting the DSP gain?

#### diegoAlm

Can anyone help me?

#### DonVK

It would be helpful to post links (model part numbers) of the preamp and amp you are using. I'm assuming the signal chain is [pre-amp]->[DSP]->[amp].

The miniDSP (non HD models) max output is always 0.9 and the amp max input is 2V so the output of the amp will be limited to Pmax*0.9/2 assuming the amp output maxes at 2v input. This may be OK, how much power do you need?

The DSP max input can be either 0.9v or 2v depending on a jumper setting.

The preamp is ??? . Link needed.

#### diegoAlm

The signal chain is [BT receiver]->[DSP]-> [pre-amp]->[amp] because BT receiver and DSP has 0.9V of output and the amplifier has a input sensitivity of 2V so i need to amplify the signal agter the DSP.
DSP max input is set at 0,9V to match Bt receiver.
The pre amp is this https://amzn.eu/d/0kAHOrk

#### DonVK

Actually, you might not need the pre-amp. I depends on how much amp power you need? An example, if the amp is Pmax=100W, then using 0.9v input, the output will be 100w*0.9v/2v = 45W without a pre-amp.

If you want max power from the amp, then the max pre-amp gain should be = 2/0.9 = 2.2. However, with your selected pre-amp gain =5, the amplifier will clip (saturate), because 0.9*5=4.5V. The miniDSP output will have to be limited to 2v/5=0.4v ( or 20*log(0.4/0.9)=-7dB ) to prevent clipping.

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