M621 — 20 Watt Monitor Amplifier

The M621 20 watt audio power amplifier is an ac operated, plug-in module designed for professional applications in the broadcast_ motion picture and sound recording industries The unit represents the continuing development and expansion of the well proven WBS 600 series of 3-1/2 inch modular components and offers a wider scope of selection for monitor amplifiers from this design category.

The circuit utilizes differential operational amplifiers to produce an ultra-reliable transformerless design capable of developing a minimum of 20 watts rms to drive an 8 ohm loudspeaker directly. Other load impedances (4, 16 ohms, etc ) may be accommodated with appro- priate power output interpolation. A unique protection circuit incorporated within the M621 activates instantaneously during adverse amplifier load conditions or at a pre- determined power output level.

The amplifier does not sustain damage even when deliberately shorted at full power output. combination of conditional frame strapping and a variable front panel level control permits the M621 to operate over an input signal range of 20dBm to 18dBm The M621 presents a permanent 20k ohm impedance at the input and is capable of operating from a balanced or unbalanced source.

The unit exhibits exceedingly uniform frequency response with Iow noise and distortion over the frequency range 3OHz to 20kHz. An internal muting relay is included to provide amplifier cut-off when an external (closure to ground) command is initiated via muting logic control circuitry, etc. The modest size of 5.1W x 3.4H x 13.70 inches allows three M621 monitor amplifiers t0 be accommodated in one standard rack mount- ing (19W x 3.5H) MF6 equipment frame.

FEATURES 2Ow rms direct output into 8 ohms Compact design mounts in standard WBS 3-1/2 inch MF6 rack frame. Self contained power supply Integral muting relay Operational amplifier transformerless 1C design with unique short-circuit protection 20k bridging input balanced/unbalanced Active elements contained on plug-in subsidiary PC card WBS M621

The M621 20 watt audio power amplifier is an ac operated, plug-in module designed for professional applications in the broadcast, motion picture and sound recording industries: The unit represents the continuing development ad expansion of the well proven WBS 600 series of 3-1/2 inch modular components and offers a wider scope of selection for monitor amplifiers from this design category.

The circuit utilizes differential operational amplifiers to produce a ultra-reliable transformerless design capable of developing a minimum of 20 watts rms to drive a 8 ohm loudspeaker directly. Other load impedances (4, 16 ohms, etc ) may be accommodated with appro- priate power output interpolation. A unique protection circuit incorporated within the M621 activates instantaneously during adverse amplifier load conditions or at a pre- determined power output level.

The amplifier does not sustain damage even when deliberately shorted at full power output. A combination of conditional frame strapping ad a variable front panel level control permits the M621 t0 operate over an input signal range of ~20dBm to 18dBm: The M621 presents a permanent 20k ohm impedance at the input ad is capable of operating from a balanced or unbalanced source.

The unit exhibits exceedingly uniform frequency response with low noise ad distortion over the frequency range 30Hz to Z0kHZ An internal muting relay is included to provide amplifier cut-off when a external (closure to ground) command is initiated via muting logic control circuitry, etc. The modest size of 5.1W x 3.4H x 13.70 inches allows three M621 monitor amplifiers to be accommodated in one standard rack mount- ing (19W x 3.5H) MF6 equipment frame: FEATURES 2Ow rms direct output into 8 ohms Compact design mounts in standard WBS 3-1/2 inch MF6 rack frame.

Self contained power supply Integral muting relay Operational amplifier transformerless 1C design with unique short-circuit protection 20k bridging input balanced /unbalanced Active elements contained on plug-in subsidiary PC card 22488

4 3 or 63 dB matched gain (condi tional frame strap) . Front pane l variable co ntrol.

FREQUENCY RESPONSE : ±.0 .25 dB from 20 Hz to 20 kHZ

80 dB below 20 W

'l'QTAL HARMONI C DIS'l'QRTION: l e s s than 0 .25% from 20 Hz to 20 kHZ mea s u r e d at 20 W output l ev e l .

- 20 dBtn nomina l, 0 dam maximum (6 3 d B gll.in ) o dam nom i na l , +18 dBll'l maximum ( 4 3 dB ga in) LONGITtlOINA L BAlANCE: greater than 60 dB

SOURCE IMPEDANCE: 600 Ohms or less , balanced or u nba lanced

INPUT IMPEDANCE: 20 kOhms

LOAD IMPEDANCE: 8 Ohms nominal . 4 or 16 Oh1ll$ wi th appropriate power output correction .

OUTPUT IMPEDANCE: leas than 0 . 5 Ohms

the low termina l number of the i nput pair is i n phase with the di rect output t e rmi n a l.

POWER REQUIREMENTS : 11 5 VAC, 60 HZ, 60 VA

AMBI ENT TEMPERATURE:

DIMENSI ONS: 5 . 1w x 3 . 4H x 13 .7D i nches

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Model H6Z1·T ZOW Monit or AlIl p l if ie r

TECHNICAL OATA:

GAIN: 42 Dr 62 lIa t c he d ga in (c on diti on al ) ga tn st ra p ). Fr ont pan e l va r h bh! c ontro l. FREQUENCY RESPONSE: Wit h ln I dB 30 Hz to 15kHz . NOISE: 80 dB b elow ZOW. TOTAL HARMONIC DISTORTION: Less tha n O.ZSI fr oll 50Hz t o 20Hz lIe n ur e d a t 20W ou tpu t t evet . INPUT LEVEL: - 20 dBIl no. i na 1 0 dh lIax. (6ZcIl gain) OdS. nOll t nal +18 dBIl Mn. ( 4ZdBgain) LONGITUDINA L BALANCE: Gr ute r t han 60dB. SOURCE I MPEOENe E: 60 0 oh lls Dr le ss . ba la nce d or unb a la n c ed. INPUT IMPEDENC E: 20 1: 0tll1S.

LOAD I MPEDENCE: 4 ,8,1 6 , I SO, or 600 01111$ ( co nd it lo na l tran s for ller s t ra ppi ng) OUTPUT (JIIIPEDENCE: Le ss th an 1/5 lo a d IIl pedence. PHASI NG: The l ow t e ,.,l1na 1 n Ullber o f t ile i npu t pai r is in ph ase with the l ow te r llina1 nUMber o f tile output tran sfo r ller strappi ng con fi gurati on . POWER REQUIREMENT S: llSV ac 60VA. AMBIENT TEMPERATURE: 00 to 60°C. DIMENSIONS : S . l W x 3 .4H x 13 .70 in c he s . a .c

WE IGHT: 6 1bs . ne t . ps BS W :// tp ht

Model M621/M62 1T 2 0W Monitor Amplifie r

AMPLIFIER AOOUS1'MEm'S

1. Longi t uC!i na l Ba lance AC!1u e t men t

Suap t he aillpl itier t o r low gain a nd. a pp ly a signal. Ad j ust the input a i qnal level f or a c on venie nt ou t pu t le vel. Th is ou t pu t l e v e l wi ll be the r eference le~l f or the fol l o.rinq adju.ebDen t a .

Tie pins 8 . nC! 16 on the flIOdule c onnector P2 t ogether a nd apply the same s ignal volta ge between t his junction and g round . Th e i n pu t s igna l is nOW' longitud i n ally applie d.

Adj us t R18 • 2 00 Hz f o r mi n im.ua output . Th e output s hou l d be better than 6 0 dB down .

i- Strap the alllpHf i er t or high 9ain a nd r e Cluce the input l ev el by 2 0 dB. Ad jus t R13 for mn imum ou t pu t a t 200 Hz .

Repeat both s te pe a t least tw ice, s i nce there is some interaction between the contro ls .

With the amplifie r strapped for high 9ain , change t h e input frequency t o 1 0 :kHz and adj us t e ll for mi n illlU18 output .

The adjustments ahou ld res u lt in an ov er-a ll common moile re j e ction of 60 dB or greater from 6 0 Hz to 6 ltHJl: .

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Mod el M621 /M62lT 20 W Mo ni tor Amplifi er

DC VOLT1>.GE CHART

The fol lowing DC vo ltages a re typic a l and may va ry +l ~ . The idle cur r en t should be between 35 and 4 5 IlIA. At 20 wat ts output the c ur rent drain should be I A. This can be convenient ly measu red by r ectOVi ng fuses Fl and F2. The vo ltmeter us e d f or the mlllllsurementl . should have III stnuitivity of 20 .000 Ohma pe r vol t .

I ntegrated circuits .

Pi ns

Z1

GAIN: 43 or 63dB matched gain (conditional frame strap) Front panel variable control. FREQUENCY RESPONSE: +0.25dB from 2OHz to 2OkHz NOISE: 8OdB below 2OW TOTAL HARMONIC DISTORTION: Less than 0.25% from 2OHz to 20kHz (measured at 2OW output level)_ INPUT IMPEDANCE: 20k ohms LOAD IMPEDANCE: 8 ohms nominal, 4 or 16 ohms with appropriate power out- put correction. OUTPUT IMPEDANCE: Less than 0.5 ohms PHASING: The low terminal number of the input pair is in phase with the direct output terminal.

POWER REQUIREMENTS: 115V ac, 6OHz, 6OVA AMBIENT TEMPERATURE: 00 to 6OOC DIMENSIONS: 5.1W x 3.4H x 13.7D0 inches WEIGHT: 6 Ibs net_ INPUT LEVEL: ~2OdBm nominal , OdBm maximum (63dB gain) OdBm nominal , +1 8dBm maximum (43dB gain) LONGITUDINAL BALANCE: Greater than 6OdB SOURCE IMPEDANCE: 600 ohms or less balanced or unbalanced ACCESSORIES: MF6-600 Series Mounting Frame 19W 3.5H x 14.5D (less rear cable tray and cover) Standard EIA rack mounting: Accom- modates three M621 modulesor any combination of single, double or quadruple units not exceeding ten single width modules MFR6-6O0 Series Frame Receptacle.

Two required per M621 _ WARD-BECK SYSTEMS LTD_ WARD-BECK SYSTEMS INC_ 841 Progress Ave,Scarborough Ont; M1H 2x4 290 Larkin St;, Buffalo; New York 14210 Telephone: (416) 438-6550 Telex: 06-23469 WBS

GAIN: 43 or 63dB matched gain (conditional frame strap) Front panel variable control. FREQUENCY RESPONSE: +0.25dB from 2OHz to 20kHz NOISE: 8OdB below 2OW TOTAL HARMONIC DISTORTION: Less than 0.25% from 2OHz to 20kHz (measured at 2OW output level)_ INPUT IMPEDANCE: 20k ohms LOAD IMPEDANCE: 8 ohms nominal, 4 or 16 ohms with appropriate power out- put correction. OUTPUT IMPEDANCE: Less than 0.5 ohms PHASING: The low terminal number of the input pair is in phase with the direct output terminal.

POWER REQUIREMENTS: 115v ac, 6OHz , 6OVA AMBIENT TEMPERATURE: 00 to 6OOC DIMENSIONS: 5.1W 3.4H x 13.7D inches WEIGHT: 6 Ibs net. INPUT LEVEL: ~2OdBm nominal , OdBm maximum (63dB gain) OdBm nominal , +18dBm maximum (43dB gain) LONGITUDINAL BALANCE: Greater than 6OdB SOURCE IMPEDANCE: 600 ohms or less balanced or unbalanced ACCESSORIES: MF6-600 Series Mounting Frame 19W 3.5H x 14.5D (less rear cable tray and cover) Standard EIA rack mounting: Accom- modates three M621 modulesor any combination of single , double or quadruple units not exceeding ten single width modules MFR6-600 Series Frame Receptacle.

Two required per M621_ WARD-BECK SYSTEMS LTD_ WARD-BECK SYSTEMS INC_ 841 Progress Ave,Scarborough, Ont; M1H 2x4 290 Larkin St;, Buffalo, New York 14210 Telephone: (416) 438-6550 Telex: 06-23469 WBS

1 Longitudinal Ba lance Adjustment Strap the amplifier for low gain and apply signal. Adjust the input signal level for convenient output level_ This output level will be the reference level for the following adjustments Tie pins 8 and 16 on the module connector P2 together and apply the same signal voltage between this junction and ground. The input signal is now longitudinally applied_ Adjust Rl8 200 Hz for minimum output_ should be better than 60 dB down .

The output Strap the amplifier for high gain and reduce the input level by 2 0 aB _ Adjust R13 for minimum output at 200 Hz _ Repeat both steps at least twice since there is 5 ome interaction between the controls With the amplifier strapped for high gain, change the input frequency to 10 kHz and adjust Cll for minimum output _ The adjustments should result in an over-all common mode rejection of 60 aB or greater from 60 Hz to kHz

Longitudinal Balance Ad justment Strap the amplifier for 10w gain and apply signal Adjust the input signal level for convenient output level This output level will be the reference level for the following adjustments Tie pins and 16 on the module connector P2 together and apply the same signal voltage between this junction and ground. The input signal 15 now longitudinally applied.

Adjust Rl8 @ 200 Hz for minimum output. should be better than 60 aB down. The output Strap the amplifier for high gain and reduce the input level bY 20 dB . Adjust R13 for minimum output at 200 Hz Repeat both steps at least twice interaction between the controls since there 18 some With the amplifier strapped for high gain change the input frequency to 10 kHz and adjust Cll for minimum output.

The adjustments shoula result in an over-all common mode re jection of 60 aB or greater from 60 Hz to kHz