PS Audio BHK preamp bruker en modifisert variant av dette kretsdesignet for tapsfri volumkontroll:
https://en.m.wikipedia.org/wiki/Gilbert_cell
Prinsippet, kortfattet:
´The idea behind the Variable gain cell is simple. Instead of adding additional circuitry to the signal path to vary loudness, the preamplifier’s actual amplifier stage varies its gain in response to the user’s front panel volume control. This method requires zero additional circuitry in the signal path, offers more than 80dB of attenuation, and if designed properly performs to the equal of most high-end preamplifiers.´
I Audio-gd sine amper kan man velge mellom linær og eksponensielt fungerende volumkontroll:
´The volume control is also different from conventional technology. Conventional volume control technology is the volume control implement in the analog amp input stage through a volume pot to reduce the signal. The volume pots quality effect the sound quality direct , the low quality volume pot cause lost the detail and channels imbalance cause the soundstage distortion. Even the high performance volume pot still cause the detail lose. Whatever quality volume pots, must cause the S/N worst.
But in the Master-1, we applied the I/V conversion volume control, the volume control just a variable passive I/V conversion place at the ACSS amp output, where the output is the current signal, not the voltage signal. The volume control is I/V conversion, and the volume depends on the current (I) conversion to the voltage (V). (Like R-2R D/A chips output passive I/V conversion) It can keep the signal frequency band flat and not lost any detail. It can't degrade on sound quality in every volume level. After the volume, there are four groups dual FET non-feedback buffer output stages offer the very low output impedance.
The volume control quality is much important in the real balance gear. It must guarantee the four channels signal control exact to achieve the performance of the real balance gear. If the cool and hot of the balance signal can't guarantee exact, the balance output will has large distortion cause the sound quality and performance even much worst than a single end gear waste the balance gear design and the cost.
In Master-1 is applied a four channels digital control relays based volume control. Master-1 has total four channels through changing the DALE resistors to control the volume for avoid channels imbalanced, achieve the best performance and sound quality of the gear.
Master-1 allow users select between 99 steps exponential characteristic volume control and 70 steps linear characteristic volume control, whatever volume control allow users smooth to control the volume level. While change the volume, the different relays break or close, it may had slightly switch sound on output and disappear while stop change the volume.´