GB1040574A - Improvements relating to electrical reverberation circuits - Google Patents

Abstract

1,040,574. Reverberation systems; stereophonic systems. ELECTRIC & MUSICAL INDUSTRIES Ltd. March 27, 1963 [March 28, 1962], No. 11796/62. Heading H4R. An electrical reverberation circuit includes a direct signal path and a plurality of individual reverberation circuits each of which produces a delayed component and an undelayed component, the circuits being connected to form a reverberation signal path, and means for combining a direct signal from the direct signal path with a reverberation signal from the reverberation signal path in desired proportions, means being provided for substantially cancelling the undelayed components from the reverberation signal path. Signals from input terminal 1 (Fig. 1) are applied to adjustable attenuators A 1 , A 2 , and to reverberators R 1 ... R N providing delayed and undelayed output signals. A differencing network 3, conveniently a pair of inductive ratio arms, is such that when attenuator A1 is suitably adjusted the undelayed signals applied to it from both paths cancel while the delayed signals pass to a variable attenuator A3. The outputs of attenuators A2, A3 are added in combining network 4 to provide a direct signal with an added artificial reverberation signal at output terminal 2. Attenuators A 2 , A 3 and network 4 may be omitted, an output being taken from network 3 directly. Attenuator A 1 is then varied to vary the proportions of the direct and reverberated signals. In this arrangement attenuator A 1 is preferably divided into two attenuators, one of which is adjustable to cancel out the signal from chain R 1 ... R N while the other controls the magnitude of the direct output signal. A two-channel stereophonic system may have a circuit arrangement as shown in Fig. 1 in each channel. Preferably, however, a single chain of reverberators R 21 ... R 2N (Fig. 2, not shown) is used for both channels. Stereophonically related input signals traverse separate direct signal paths each including a variable attenuator. Combined stereophonically related input signals are applied to reverberators R 21 ... R 2N and to a variable attenuator A 21 in parallel with the reverberators. The output signals from the reverberator chain and attenuator A 21 are applied to a differencing network 6. Only the reverberation signal appears at the output of network 6 and this is applied through a variable attenuator A 22 to reverberators R 2L and R 2R which have equal delays but feedback of opposite sign to provide quasi-stereophonic quality to the reverberated signals. The output of reverberator R 2L is added to the L channel and the output of reverberator R 2L is added to the R channel. In a further stereophonic arrangement (Fig. 3) two subtracting networks 10, 11 are provided, together with individual attenuators A 31 , A 35 for one channel and individual attenuators A 32 , A 36 for the other channel. Reference has been directed by the Comptroller to Specification 1,001,518.