Integrated Amplifiers

Arguably the 5510’s most significant update over the older 3510 amplifier [HFN Nov ’21] is the new stepped-resistor volume control, replacing Exposure’s traditional ALPS potentiometer. A total of seven relays are used to switch a bank of precision resistors offering a full 99 steps (plus mute), each step representing a ~1dB increment in level. The network is positioned under the main PCB [see pic, p72] although the driver IC can be seen above. This new volume circuit is also the reason why Exposure has equipped the 5510 with an OLED display – the same facility will also be debuted on the forthcoming 5510 preamplifier.

Stepped attenuators offer the promise of very accurate level adjustment and precise channel matching, unlike traditional pots that typically drift below –60dB where L/R errors of 1-3dB are not uncommon. Exposure’s attenuator proves its mettle – over the top 10dB (‘99’ to ‘89’ on the display) the increments are –1.1dB; –2.3dB; –3.3dB; –4.1dB; –5.1dB; –6.25dB; –7.25dB; –8.1dB; –9.1dB and –10.1dB. Stepping down 10 increments at a time yields an attenuation of –20.5dB (79); –30.6dB (69); –40.7dB (59); –50.2dB (49); –60.2dB (39); –70.1dB (29) and –80.1dB (19), all with a channel matching within ±0.1dB. Below ‘9’ on the display the steps lie between 0.8dB and 1.0dB reaching a final attenuation of –96.7dB at ‘1’. This is an excellent result, and correctly buffered too, so the 5510’s freq. resp. does not change with volume setting [see Lab Report]. PM