Level 3 – Remove pre-pre amp

I call it pre-pre amp (tubes B2, B102) with intension as this amplifier works from 6-30mV, which is totally unnecessary as the majority of devices has a line level of 1-2V, which is far-far stronger, no need for pre-preamplification before the real preamp ECC83 (B3, B103) which drives the EL86 tubes. So the aim is to bypass everything between R51 (R151) and C21 (C121). This is an very easy solution, but has the dissadvantage that we have no longer phono input as then we have nothing which amplifies to proper level the output of the EF86 tubes (impedance! and some gain is needed) . If you just have network player, CD or other line level of device, then this is not an issue. But if you wish to keep the phono input operating, then you need a solution:

-Create a new RIAA, see level 4.

-Modify place pre-preamp before the phone input selector, see below

Step1: Remove R43, R45 circuits (R143, R145) with the SK8 switch, they add unwanted capacitance and noise to the phono input. (Components are close to the phono input with the Magnetic/Ceramic switch, in newer models the components were moved close to the tube and the switch was connected with a grey shielded cabling) (skip this point if you plan to use ceramic cartridge – why would you???) You may replace phono cable as it adds 100pF of input capacitance, while this should be kept as low as possible.

Step2: Disconnect C11 from the input selector (SK12) . This output of the EF86 (C11, C111) requires a new on the other side grounded resistor (1M) to avoid overcharge of the capacitor. This output will be connected to the input of the old pre-preamplifier.

Step3: Disconnect pre-pre amplifier input B2 (B102) ECC83 tube pin 7 at the volume knob and connect it to C11 (C111).

Step4: The negative feedback path resistors/capacitors of the pre/preamp need to be thrown out (R16, C33, C42 and R116, C133, C142) and replace with one/channel 20K resistor in series (use carbon composite!).

Step5: Also the SK13 switch 8-9, 11-12 wire should be removed. There are no more negative feedback resistors where you switch the amplifying.

Step6: Connect the end of C15 (C115) to SK12 (so the old wires of the phono input) to select with the phono button the old pre-pre amplifier as input.

The rest are changes from level 1, and level 2 + I also recommend to separate power supply to left and right while adding double sized power supply capacitors (resistors double size as well to have the same voltage drop on it). Schematic below + pictures about the procedure (will follow). Fuse left-right is random, if mixed, resolder it to make life easier once you have an issue.

NOTE: Using factory high capcaity cables from the 1M driver (volume control) is building an low pass filter with 10kHz (volume control dependent. Set volume to max it is not limiting… ) Recommend to swithc to 100K-500K potentiometer and swap the canbles to low capacity types.