A Full Preamplifier

 

This project was born as a conceptual challenge: reach the finished object by following just the Pspice suggestions without any benchmarking, in order to estimate the impact...... and the risks, on the final result , of a full  Computer Aided Design, Fig. 38. The SRPP line stage uses  E182CC (7119) vacuum tubes, Table 5.

                                                             The E182CC-SQ Pinout

 

E182CC-SQ QUICK REFERENCE DATA
Life Test 10,000 hours
Base Noval
Heating Indirect
Heater Voltage 6.3 or 12.6
Heater Current 640 or 320 mA
S (nominal) 15mA/V
m 24
Max Anode Dissipation 4.5W
Max Anode Voltage 300V
Max Cathode Current 60mA
   

This “computer grade” vacuum tube is used rarely but I think it perfect in an “iron fist in a velvet glove” line stage; Table 6 summarizes the electric performances of this line stage.

E182CC-SQ Line Stage Characteristics
Vp 150V
Gain 22dB
Bandwidth (0.5dB) 1MHz
THD (Vout=24Vpp) 0.1%

The used approach for the phono stage follows the guidelines shown in a previous article appeared on GA [2]. The input stage resorts to the services of a 6CW4 nuvistor. I find it perfect in this context. 

Full Schematic (Click on it to enlarge)

 

  The chosen Split RIIA approach permits very accurate results, Table 7.

Tab. 7 MM Phono RIIA Response
Frequency (Hz) Simulated Values (dB) Measured Values (dB)
10 49.903 49.890
100 42.861 42.189
1k 29.941 30.078
10k 16.070 15.834
100k -3.768 -3.830

 

Table 8 shows its Spice models based on  little change of Koren’s model [ 3].

Modified Koren’s Model for 6CW4 Nuvistor

.subckt 6cw4 1 2 3 ; placca griglia catodo NUVISTOR R.C.A.

+ params: mu=68.75 ex=1.35 kg1=160 kp=250 kvb=300 rgi=200

+ ccg=4.1p cgp=.92p ccp=.18p

+ a=2.133e-7 b=-9.40e-5 c=.0139666 d=.64

e1 7 0 value=

+{v(1,3)/kp*log(1+exp(kp*(1/mu+v(2,3)/sqrt(kvb+v(1,3)*v(1,3)))))}

re1 7 0 1g

e2 8 0 value=

+{a*v(1,3)*v(1,3)*v(1,3)+b*v(1,3)*v(1,3)+c*v(1,3)+d}

re2 8 0 1g

g1 1 3 value= {(pwr(v(7),v(8))+pwrs(v(7),v(8)))/kg1}

rcp 1 3 1g

c1 2 3 {ccg}

c2 1 2 {cgp}

c3 1 3 {ccp}

r1 2 5 {rgi}

d3 5 3 dx

.model dx d(is=1n rs=1 cjo=10pf tt=1n)

.ends 6cw4 

 

 

Bill of Materials

Part  Used   PartType                    Designators

 

     1      8    RCA Fem                     LINE 1 LINE 2 LINE 3 LINE 4 LINE 5 OUT1 OUT2 PHONO IN 

     2      3    .47u                              C1 C7 C9 [250Vcc Polyestere Philips]

     3      1    1M                               R14

     4      2    1n4007                         D1 D2

     5      1    1n4736                         DZ1                               

     6      1    1n5401                         D3

     7      1    1u                                 C17

                                                        [63Vcc Electrolitic Nippon Chemi/con]

     8      1      3H                              L1 Custom

     9      1    6cw4                            V1 RCA

    10     1    10.000u                        C16 [25Vcc Elecrolitic Panasonic]

    11     1    11k                               R15 [1W 1%]

    12     1    6.8+8.2n                       C6 [63Vcc Polystirene Philips]

    13     1    18k                               R16 [1W 1%]

    14     1    20k                               R13 [1W 1%]

    15     1    47k                               R3

    16     1    47k//43k                       R11

    17     5    47u                               C10 C11 C12 C13 C14

                                                        [250Vcc Electrolitic Rubycon]

    18     7    100                               R1 R2 R4 R8 R10 R19 R22 [1/2W 1%]

    19     1    100n                             C19[63Vcc Polyestere Philips]

    20     1    160                               R20

    21     1    180                               R21

    22     1    180k                             R23 [1/2W 1%]

    23     2    200k                             R6 R12 [1/2W 1%]

    24     1    250                               R17 

    25     1    430                               R5

    26     1    2x220p                         C4

                                                        [63Vcc Polystirene Philips]

    27     3    470u                             C3 C18

                                                        [16Vcc ARD Series ELMA]

                                                        C15 [250Vcc Electrolitic Rubycon]

    28     1    510                               R9

    29     1    800                               R18

    30     1    820k                             R7

    31     1    BDX53                         Q1 SGS

    32     1    BlueLED                       D4 Kingbright

    33     2    E182CC                       V3a V3b Philips

    34     1    EZ81                             V4 Sylvania

 

    35     1    RS 210-263

                                                        Line_Filter

                                                       with IEC plug       FLT1

    36     1    RS 223-7816

                                                       Nuvotem-Talema      T1

    37     1    Volume1                     100k Log

    38     2    e188cc                       V2a V2b

    39     1    RS 223-7759

                                                      Nuvotem-Talema      T2

    40     1    RS 223-7945

                                                     Nuvotem-Talema           T3

    41     1    2Way 6Pos Sel.         Elna

    42     1    100k Log Stepped     Elna   

    43     2    6CW4                       V1a V2b                 RCA                      

 

 

Photo 1 - Front View

 

Photo 2 - Rear View

 

Photo 3 - Inside the Power supply

 

Photo 4 - Inside the Preamp Unit

 

 

Photo 5 - Wiring Details

 

 

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