To get more information contact me at: firstname.lastname@example.org
Extreme Hi-End Hybrid
started on January 1 st , 2014
This project collects all the experiences made in these years then it born with all these characteristics:
This project is based on the
version of the my 100W hybrid amplifier but here some aspects has been
changed to increase the sound quality.
Now the throne of the Amplifier End could collapse because this amplifier should have the same details of the Amplifier End but a better control with complex signals.
All the pcb can be produced at low cost by Quanghao or you can download the Eagle files to produce these in your local area.
Update 17 April 2014
This evening there was the first listening session of this
amp and was attended by a friend of mine with a great experience in audio
recording and playback.
This friend of mine is also the owner of the Sony VFET I recently updated with new power CLC and pre-ampl bypass.
The impression is listening a pure class A amplifier very refined but without the limitations in the dynamics of these type of amplifiers.
The level of detail and the transients speed are comparable to the Amplifier End but you immediately notice the superiority to control the speakers and and every kind of music is played without problems.
The sound is not soft but it is also not cold, this effect was probably obtain by using MKP on voltage amplifier stage and electrolytics capacitors on current amplifier.
The channels separation is perfect like a pure dual mono operation.
Obviously this amp to achieve its full potential requires a source without compromise like the new ES9018 DAC born with the collaboration with Quanghao.
Update 21 April 2014
At the switch-on there is no noise and no bump on loudspeakers because this amplifier has been design to have a very soft start.
During the switch-off phase there is a little bump but if you switch-off the amp during the music play you will have no noise because the output stage will go down quickly.
Although this amp. is self protected with 2 ways you can add an extra protection that shuts down the amplifier in case of problems.
At this time I still have not done the output short circuit tests but in the diamond buffer design the output current is limited by the driver bias.
VOLTAGE AMPLIFIER + CURRENT AMPLIFIER
use a single ended vacuum tube stage with anode choke to have
a very low distortion and best frequency band as seen in the
Also in this project I used the unsurpassed D3a connected to triode, just look at the following measures to realize the incredible potential of this tube.
We will use less output voltage because 40Vrms mean
40*40/8ohm = 200W and the target is about 100W.
I am using Lundahl LL1668/50mA anode chokes, these are not the standard, you could use the normal LL1668/25mA but probably it is necessary adjust the cathode capacitor.
If we use an anode choke or an inter stage transformer is necessary consider the effects of the inductance because you create a RLC circuit with a specific resonance.
This is the formula to calculate the resonance frequency
so we need to keep this value very low to eliminate
strange peak on frequency band.
Using the Ck=1000uF and L=50H (LL1668/50mA) we get a resonance frequency of only 0.7Hz.
The value of the internal resistance of the tube can modify the peak width generated in the resonance.
The current amplifier is a perfect Diamond Buffer used in some chip like the LH0002 and the BUF634.
This configuration has been analyzed very well in the article Bulding better buffer on Electronics World november 1992.
The same design as been used in many Audio Research amplifiers like the Audio Research D100 and the Audio Research D-400.
Also the Pioneer A-09 and the Pioneer M-6 use a Diamond Buffer on output stage but these implement dynamic current generators with some stability problems.
This current amplifier have an input impedance near to 20Kohm and it absorbs a max peak current of 2mA also when it drive 2 ohm load.
I have add a power supply regulator to eliminate any ripple coming from main capacitors after the diode bridge and it allow a soft start with these advantages:
This regulator integrate a DC loudspeaker protection
copied from an old
Bartolomeo Aloia design to shunt the regulator capacitors so switch-off the
output stage if there are fault on output transistor.
The op-amp in the circuit is a DC servo to eliminate DC offset and it work in very low frequency band.
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%
R51,R52,R53,R54 470ohm 1/4W 1%
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
D1,D2 Zener 15V 1W
D9,D13 0ohm (jump)
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 2 x 560uF 4V available in the Parts Connexion web store.
The SANYO OS-CON is an aluminum solid capacitor
with high conductive polymer or organic semiconductor electrolyte
As tested in the first version the anode choke give the most low distortion and the best frequency band, also the interstage transformer it more invasive so it should be used only if it is essential in the circuit as a phase shifter, see the Amplifier End.
The LL1668/50mA with an inductance of 50H, an air gap to support a current of 50mA 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.
I have some output stage pcbs and I could sell
these at 40$ for a pair + shipping.
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
Here the output of the power supply simulation, dual 33VAC, load 4ohm, 20Hz sine
30Vp => 113W and only 10000uF after diode bridge.
Here the output of the power supply simulation, dual 33VAC, load 4ohm, 20Hz sine wave output 30Vp => 113W and 22000uF after diode bridge.
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 Amplifier
but you can start to assemble this project also with a common diode bridge like the IRF 36MB60.
About the capacitors I don't leave many choices because only with these types you can be sure to get the best result and no bypass will be necessary.
In this project I have used 8 x 4700uF 63V KG
(size 25x50mm) on any channel and these are very near to the output
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 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 by DiyClub.Biz with primaries 2 x 115v and the secondaries 0-165v(0.2A) and 2 x 0-9v (1.1A).
R6,R8 1ohm 2W
R74 47Kohm 1/4W
R7 1Kohm 1/4W
R9 220ohm 1/4W
R12 100ohm multi-turn trimmer
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
B1 diode bridge 3A 100V
The cabinet is a Hi-Fi 2000 model 04-400B Silver 10 (1NPD04400B) buy on the Audiokit webshop.
Formato: 4 Units
1x Frontal Panel in aluminium 10mm oxidised silver 450 mm
1x Back in metal painted black anti-scratch
4 Lateral Heatsinks 200mm oxidised black (each with Rt °C/W = 0,48)
2x Covers in metal painted black anti-scratch
width: 450mm internal 360mm
depth: 400mm Internal
height: 165 mm
weight:: 11,5 KG
To add a 1BASEPD400 Inner pierced Base for Pesante Dissipante 400mm.
To create a base to fix the transistors on heatsink I have used a pair of 3PDA0302 Rear Panel of Dissipante 3U aluminium cut on both sides at 28cm to have a pair of 3mm panels 12 x 28 cm.
PCB ERROR !!!
|description||unit price||quantity||total (euro)|
|Solen 56uF 250V||20||2||40|
|4700uF 63V KG||6||16||96|