Quad 34 Preamplifier (1982-1996)
The Tilt. Certainly the most intelligent and least widespread corrector! Around a central point (800 Hz), the Tilt switches the response curve between +2, +1.0, -1, - 2dB. If we put it in position -2dB in the bass, the curve rocks very slowly to reach +2dB in the treble. The converse and all positions between 1dB between these two limits, passing through total linearity, its obviously possible. On the curve, this correction seems very minimal. Try it, you will immediately understand its qualities, in general opinion much more interesting than those of a traditional stamp corrector, even and above all more Powerful.
Approx Serial Number 2000
ISS 2 p.c.b. introduced incorporating the following changes: 1. Wire links replaced by printed copper links on the top side of the p.c.b. 2. Two holes added in the power supply area of the p.c.b. These are to house two electrically redundant tags added to the transformer to ensure that the transformer is mechanically secured.
Approx Ser Nº 3700 FEB 1983
R55 and R60 changed from 680K to 2M2, stock number R2M20J1. This gives improved bass response.
Approx Ser Nº 4000 MARCH 1983
C83 added to decouple the HT rails to earth. C83 is soldered to the rear side of the p.c.b. and on some 34's is 47nf, stock number C47 NOZL soldered between negative rail and earth whilst on other units C83 is 680nf, stock number C680NKT soldered between positive rail and earth.
Ser Nº 4130 MARCH 1983
Red filter 1, filter 2 and slope buttons replaced by similar brown buttons, stock numbers MBOOF1B, MBOOF2B and MBOOSLB respectively.
Ser Nº 6001 JUNE 1983
ISS 4 p.c.b. introduced incorporating the following changes; 1. Radio analogue switch control is now derived directly from pin 10 of IC11. This reduces selection clicks. 2. C81 and C82, 47n stock number C47NOZL added to minimise the effects of external RF clicks. 3. R125, 220 ohms stock number R220RG1 added to protect zener diode D32. 4. C44 moved from the input selector board to the main p.c.b. whilst keeping the same electrical location.
Ser Nº 8001 NOV 1983
ISS 5 p.c.b. introduced incorporating the following changes; 1. C83 removed. C84, 22uf stock number C22UOZE fitted to the top side of the board between negative rail and earth. C58 is moved to be connected between positive rail and earth. 2. Tape and Auxiliary input circuits completely changed. Auxiliary input sensitivity is now 300mV or 100mV according to the plug in flag selection. With 300mV sensitivity auxiliary is suitable for use with compact disc.
Ser Nº 8305 DEC 1983
34's are now fitted with CD select buttons stock number MBOOCDY, and chassis print is changed accordingly.
Approx. Ser Nº 15000, Feb 1986
R95, R96 and R97 changed to 2k2 ohms (R2K20J4). R109 and R116 changed to 5k6 ohm (R5K60J4). To reduce brilliance of LEDs.
Approx. Ser Nº 16000, May 1986
Iss. 6 PCB introduced with following changes: 1. Phono sockets fitted for ail inputs and outputs 2. Combined mains/fuse inlet socket fitted. 3. Voltage selector dropped. Voltage change now by soldered links on PCB.
Approx. Ser Nº 16900, Aug 1986
C68 and C79 increased fram 4n7F to 47nf (C47 NOMA). To prevent 34 coming on with F1 or F2 selected.
Approx. Ser Nº 19000, Feb 1987
C93 and C94 6p8F (C6P80KJ) fitted to rear of PCB in parallel with R66 and R76. To reduce downward turn at higher frequency limit.