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Extreme Hi-End Hybrid
started on January 1 st , 2015
whereso we need to keep this value very low to eliminate strange peak on frequency band.
|Tube model||Pd max (W)||Ri (ohm)||Va (V)||Ia (mA)||Rk (ohm)||Voltage gain (dB)||THD 30Vrms load 30K||THD 40Vrms load 30K||THD 30Vrms load 15K||THD 40Vrms load 15K|
1/4W 1% or better use only R1
27K MK132 Caddock
R2,R14 10ohm 1/2W 1%
R3,R36 280ohm 1/4W 1%
R26,R27 2700ohm 2W
R34,R35 15ohm 2W
R23,R33 270ohm 1W
R24,R28 5600ohm 2W
R5,R6,R7,R8,R17,R18,R19,R20 0.47ohm 5W
R15,R16 220K 1/4W 1%
R55,R56 2200ohm 1/4W 1% or better use only R55 1K MK132 Caddock
R51,R52,R53,R54 470ohm 1/4W 1% or better use only R51 and R53 220 MK132 Caddock
R4,R13 6800ohm 2W
R49,R50,R21,R22 10Kohm 1/4W 1%
R11,R10,R12 0ohm (jump)
C6,C8,C9,C14 0,47uF 63V Wima
C1,C2,C10,C11 100uF 25V
C5 0.1uF 100V Vishay MKP1837
C7,C17,C4,C24,C18,C20,C25,C19 4700uF 63V Nichicon KG type 25x50mm
C15,C16 1000uF 63V Panasonic or Nichicon 100°
D1,D2 Zener 15V 1W
D3,D4 UF4007 or 1N4007
D9,D13 0ohm (jump)
F1,F2 FUSE 5A FAST (with fuse holder)
U1 2N5550 o 2N5551
Q1,Q3,Q16,Q18 MJE15033 (PNP)
Q2,Q4,Q14,Q17 MJE15032 (NPN)
Q9,Q5,Q6,Q7,Q13 NJW0281G (NPN)
Q12,Q11,Q8,Q10,Q15 NJW0302G (PNP)
IC1 OPA134 (you can use many others single op-amp)
mention in the characteristic list at the begin of this page in this
project the passive components are without compromise on any section.
On vacuum tube cathode there is an Sanyo OS-CON capacitor, my choice is .... available in the Parts Connexion web store.
The SANYO OS-CON is an aluminum solid capacitor
with high conductive polymer or organic semiconductor electrolyte
The LL1668AM/25mA with an inductance of 100H, an air gap to support a current of 25mA and a static resistance of 680ohm give a sure result.
All the resistors in the current amplifier has been duplicated to use for any resistor a parallel of two components mounted with opposite direction to reduce parasitic inductance and electromagnetic flux.
I learned this method many years ago by the owner and designer of a famous American factory of amplifiers and it use the same also with Solen interstage capacitors.The alternative to this method is to use Caddock MK132 with advantages.
About the power supply capacitors near the output transistors there are no alternatives to the NIchicon KG capacitors because the my last experience made the Amplifier End has demonstrated that these components without bypass have unsurpassed musical performance.
I have used 8 x 4700uF 63V NIchicon KG capacitors for each channel so we have a great reserve of power available in a very short time.
The 0.47ohm output resistances present on the emitter of final stage transistors are necessary to compensate some differences on output transistors, stabilize operating point and to merge all the outputs.
In order to have no bad effects on the sound the my choice has been the MILLS MRA-5 non-Inductive wirewound resistors with 5 watt and with 1% tolerance.
Using the transistors specified I have on any 0.47ohm a voltage about 0.180V so the bias current is 0.38A so 4 x 0.38A = 1.5A.
Here all the files to simulate this circuit with LTSpice software.
Add these lines in the file C:\Program Files\LTC\lib\cmp\standard.bjt to have the transistors models:
.MODEL Qnjw0302g pnp IS=5.16751e-16 BF=114.657
NF=0.895716 VAF=50.2189 IKF=6.409 ISE=3.9641e-15 NE=4 BR=1.47167 NR=0.923324
VAR=255.567 IKR=6.34299 ISC=3.96408e-15 NC=2.82194 RB=2.66347 IRB=0.1 RBM=2.0828
RE=0.0001 RC=0.0652395 XTB=1.45322 XTI=1.08126 EG=1.05 CJE=2.14504e-09 VJE=0.4
MJE=0.376227 TF=2.16864e-09 XTF=1000 VTF=843.737 ITF=501.348 CJC=5e-10 VJC=0.95
MJC=0.251547 XCJC=1 FC=0.8 CJS=0 VJS=0.75 MJS=0.5 TR=1e-07 PTF=0 KF=0 AF=1
.MODEL Qnjw0281g npn IS=4.36849e-12 BF=98.1488 NF=1.01332 VAF=37.9046 IKF=9.71849 ISE=1e-16 NE=1.8326 BR=0.79921 NR=1.09994 VAR=339.743 IKR=5.77305 ISC=1e-16 NC=2.71592 RB=2.74892 IRB=0.33289 RBM=2.74892 RE=0.000344671 RC=0.03203 XTB=1.7742 XTI=1.12262 EG=1.20598 CJE=3.66793e-09 VJE=0.74806 MJE=0.85 TF=2.27115e-09 XTF=1000 VTF=912.955 ITF=296.602 CJC=5e-10 VJC=0.95 MJC=0.270858 XCJC=0.98254 FC=0.8 CJS=0 VJS=0.75 MJS=0.5 TR=1e-07 PTF=0 KF=0 AF=1
.MODEL Qmje15032 npn IS=3.7344e-10 BF=86.8313 NF=1.23974 VAF=31.5491 IKF=9.1678 ISE=9.2499e-12 NE=3.28127 BR=5.59346 NR=1.33161 VAR=2.1791 IKR=5.15023 ISC=4e-13 NC=4 RB=9.54492 IRB=0.1 RBM=0.1 RE=0.000568481 RC=0.0931741 XTB=0.737036 XTI=1.04983 EG=1.206 CJE=3.05969e-09 VJE=0.648491 MJE=0.352663 TF=4.94819e-09 XTF=1.50001 VTF=1.0001 ITF=0.999982 CJC=3.00108e-10 VJC=0.600021 MJC=0.40991 XCJC=0.8 FC=0.534651 CJS=0 VJS=0.75 MJS=0.5 TR=1e-07 PTF=0 KF=0 AF=1
.MODEL Qmje15033 pnp IS=7.51228e-10 BF=134.35 NF=1.25737 VAF=12.5778 IKF=1.88497 ISE=7.74267e-12 NE=3.34528 BR=5.14173 NR=1.47488 VAR=1.4505 IKR=7.47186 ISC=3.25e-13 NC=4 RB=4.37743 IRB=0.1 RBM=0.1 RE=0.000332989 RC=0.381218 XTB=0.223027 XTI=1 EG=1.05 CJE=3.06005e-09 VJE=0.64838 MJE=0.352991 TF=4.78203e-09 XTF=1.50001 VTF=1.00006 ITF=0.999988 CJC=3.00101e-10 VJC=0.600019 MJC=0.409916 XCJC=0.8 FC=0.534975 CJS=0 VJS=0.75 MJS=0.5 TR=1e-07 PTF=0 KF=0 AF=1
POWER SUPPLY FOR THE CURRENT AMPLIFIER
The power supply for the current amplifier use two
500VA toroidal transformers.
The good power supply transformers for audio should have an electromagnetic flux 20% lower than normal (14000 gauss instead of 17000).
I have used a rectifier module based on four ON Semi MBR40250 Schottky diode to create a full wave bridge rectifier.
Here a good description of the benefits derived from the use of Schottky diodes in audio amplifier.
The same diodes as been used in my
but you can start to assemble this project also with a common diode bridge like the IRF 36MB60.
About the capacitors near the output transistors (on pcb) use only Nichicon KG as specified in the list 8 x 4700uF 63V KG (size 25x50mm) per each channel.
POWER SUPPLY FOR THE VOLTAGE AMPLIFIER
To get the max sonic performances the my choice is a slow turn on power supply for the filaments using a common LM317 or LM350 and a virtual battery operation power supply for the anodic with a power mosfet.
For this power supply I have used the R-CORE model R26-90 got on Ebay shop with primaries 2 x 115v and the secondaries 0-165v(0.2A) and 2 x 0-9v (1.1A).
R74 47Kohm 1/4W
R7 1Kohm 1/4W
R9 220ohm 1/4W
R12 100ohm multi-turn
R4,R5 10Kohm 1/4W 1%
R3 470Kohm 1/4W 1%
R1 39K 2W
R2 100K 3W
CY1,CY2,CY3,CY4 10nF 400V
C2 150uF 400V
C1 33uF 400V
US10,US11 56uF 400V Solen MKP
C3,C7 2200uF 25V
C4,C5,C6 220uF 16V
D5,D9 zener 10V 1W
B1 diode bridge 4A 100V
IC1 LM350 or LM317
Follows the distortion analysis of the complete amplifier on 8ohm load, obviously until 30V this is the distortion of vacuum tube voltage stage because the current amplifier have a distortion value 10 or 20 times less and only after 27 volts rms it goes into clipping zone for the supply voltage limitated by project. On 4 ohm load the plot is very similar.
If you will use a 2 x 36VAC transformers the power to dissipate is near to 150W for each channel.
PHOTOS & CONSTRUCTION DETAILS
1) set the variac to about + 2v and -2V dc to check that the heatsink is not
connected to these tensions
2) control the voltage after the regulators these should rise slowly in a few seconds
3) set the variac to + 15V and -15V to verify that the output voltage goes to zero volts dc
4) set the variac and -20V to + 20c to verify that the voltagee across the resistance from 0.47ohm is almost equal among all the transistors (0.05V - 0,06V)
5) set the variac at the final voltage