The A1 is our first ana­log in­put/out­put only prod­uct. A state-of-the-art mi­cro­phone/line pre-am­pli­fier with a de-esser in the pop­u­lar API 500 Se­ries for­mat. The side-chain of the de-esser uses a DSP – unique but ad­van­ta­geous for the pre­ci­sion of the side-chain and en­abling the use of a very low noise gain el­e­ment. Two mod­ules can be side-chain linked for stereo operation.

It has a trans­former bal­anced wide level range in­put with a pad for line level sen­si­tiv­ity. The in­put gain is set with a six­teen po­si­tion switch. A low cut fil­ter is use­ful for mi­cro­phone work. Phan­tom power can be switched on or off.

The out­put is also trans­former bal­anced and has an ad­di­tional po­ten­tiome­ter to set the out­put level in­de­pen­dently from the lev­els the de-esser is run­ning at. A po­lar its switch al­lows to change the ab­solute po­lar­ity of the out­put signal.

The de-esser sec­tion uses a band­pass fil­ter to split the au­dio band. The band­pass fil­ter pa­ra­me­ters are the cen­ter fre­quency and the Q. The Thresh­old pa­ra­me­ter de­fines the sen­si­tiv­ity of the de-esser side-chain. A few at­tack and re­lease times and ra­tios can be se­lected via DIP switches at the bot­tom of the unit. A LED in­di­cates whether there is any gain-re­duc­tion hap­pen­ing and a “lis­ten” switch al­lows to lis­ten to the sig­nal fil­tered by the band-pass. Use­ful to zoom in on e.g. spe­cific sibi­lances. The de-esser can be by­passed with a switch. Sev­eral LEDs al­low to mon­i­tor the in­put and out­put levels.

In­put, pre-amplifier

The A1 mi­cro­phone pre-am­pli­fier stage uses a trans­former-bal­anced, dis­crete, class A de­sign with a cur­rent-feed­back am­pli­fier ar­chi­tec­ture for low dis­tor­tion and wide band­width across the full gain range. The pre-am­pli­fier sports very low noise for a wide range of source im­ped­ances, across the full gain range. The gain is vari­able in 3 dB steps be­tween 15 and 60 dB. A 24 dB pads al­lows to feed line lev­els as well. A high pass fil­ter can be switched in. The cor­ner fre­quency can be se­lected to be 40 or 80 Hz.

De-esser

The de-esser sec­tion uses an ad­vanced mixed sig­nal de­sign: The di­rect sig­nal path is fully ana­log while the side-chain works in the dig­i­tal do­main. This en­ables the use of a low dis­tor­tion pre­ci­sion MDAC (Mul­ti­ply­ing D/A Con­verter) as the vari­able gain el­e­ment. The side-chain is built for very low la­tency, us­ing a 500 kHz sam­pling frequency.

Front panel controls

The front panel con­trols for the de-esser sec­tion are knobs for fre­quency, band­width and thresh­old. Fur­ther pa­ra­me­ters (ra­tio, at­tack and re­lease time) can be set via DIP switches.

Out­put

The out­put also uses a trans­former bal­anced de­sign with a high max­i­mum out­put level of +27 dBu. An ad­di­tional out­put gain po­ten­tiome­ter al­lows to set the out­put level in a wide range.

Power

• Com­pat­i­ble with API Se­ries 500 power racks

• Cur­rent con­sump­tion ±16 V sup­ply: ≤ 150 mA

• Cur­rent con­sump­tion +48 V sup­ply: ≤ 15 mA

Size

• Depth: 15 cm

• Width: 3,8 cm (1 slot)

• Height: 13,3 cm

In­put

• In­put gain range, pad off: +15 dB to +60 dB, 3 dB steps

• Pad at­ten­u­a­tion: 24 dB

• Max­i­mum in­put level at min­i­mum in­put gain, pad on: +29.7 dBu (for THD+N ≤ −80 dB)

• In­put im­ped­ance at 1 kHz, pad off: 8.4 kΩ

• In­put im­ped­ance at 1 kHz, pad on: 2.8 kΩ

Out­put

• Out­put gain range: −∞ dB to +12 dB, continuous

• Max­i­mum out­put level, 100 kΩ load: +27.0 dBu (for THD+N ≤ −80 dB)

• Out­put im­ped­ance at 1 kHz: 290 Ω