Just Finished 10 x Gain Block One pre-amplifiers for one of our German OEM customers. Check out the SNR of these preamp modules measured at a gain of two over a 20hz - 20khz bandwidth. The noise even at higher gain settings only shifts less than 0.5dB. Signal to Noise Ratio of the Gain Block One is typically over -124dB Un-Weighted @ a THD+N of 0.00052%. Not a bad result!
See Link below. www.stereo.net.au/forums/topic/285144-a-holton-experience/