I was trying to see how the Melbourne could be made into an Opamp. A 5 active opamp with nice sonic performance is kind of cool.
10Vpp into 600ohms:
Here is 4Vpp into 600ohms:
10Vpp into 600ohms:
Code:
10Vpp into 600ohms
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 5.148e+00 1.000e+00 0.07° 0.00°
2 2.000e+03 2.004e-04 3.892e-05 92.48° 92.41°
3 3.000e+03 2.127e-05 4.132e-06 1.90° 1.83°
4 4.000e+03 2.736e-06 5.314e-07 -144.17° -144.24°
5 5.000e+03 1.918e-06 3.727e-07 -179.82° -179.89°
6 6.000e+03 1.488e-06 2.891e-07 179.56° 179.49°
7 7.000e+03 1.272e-06 2.471e-07 -179.98° -180.05°
8 8.000e+03 1.115e-06 2.165e-07 -179.96° -180.02°
9 9.000e+03 9.893e-07 1.922e-07 -179.99° -180.05°
10 1.000e+04 8.904e-07 1.730e-07 -179.96° -180.03°
11 1.100e+04 8.084e-07 1.570e-07 -179.99° -180.06°
12 1.200e+04 7.405e-07 1.438e-07 -179.99° -180.06°
13 1.300e+04 6.825e-07 1.326e-07 -179.99° -180.06°
14 1.400e+04 6.332e-07 1.230e-07 179.98° 179.92°
15 1.500e+04 5.898e-07 1.146e-07 -179.99° -180.06°
Total Harmonic Distortion: 0.003915%(0.004216%)Here is 4Vpp into 600ohms:
Code:
4Vpp into 600ohms
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 2.059e+00 1.000e+00 0.07° 0.00°
2 2.000e+03 3.126e-05 1.518e-05 94.45° 94.38°
3 3.000e+03 3.442e-07 1.672e-07 7.31° 7.24°
4 4.000e+03 8.807e-07 4.277e-07 -177.41° -177.47°
5 5.000e+03 7.051e-07 3.424e-07 -179.98° -180.04°
6 6.000e+03 5.862e-07 2.847e-07 -179.99° -180.06°
7 7.000e+03 5.022e-07 2.439e-07 -179.99° -180.05°
8 8.000e+03 4.391e-07 2.132e-07 -179.99° -180.06°
9 9.000e+03 3.900e-07 1.894e-07 -179.99° -180.06°
10 1.000e+04 3.507e-07 1.703e-07 -179.99° -180.06°
11 1.100e+04 3.185e-07 1.547e-07 -179.99° -180.06°
12 1.200e+04 2.916e-07 1.416e-07 -179.99° -180.06°
13 1.300e+04 2.688e-07 1.306e-07 -179.99° -180.06°
14 1.400e+04 2.493e-07 1.211e-07 -179.99° -180.06°
15 1.500e+04 2.324e-07 1.128e-07 -180.00° -180.06°
Total Harmonic Distortion: 0.001520%(0.002151%)Attachments
Last edited:
Sorry, not much progress over past several weeks as JPS64 has been unavailable to make the layout. He should be returning soon.
x- sorry for the noob question. After having finished the Karlsonator, I will go into the Melbourne - have got prints from you - Does the extra numbers in the parts list in post 7 refer to something - such as numbers at a supplier?
Hi HenryLarsen,
Cool that you are going to make this preamp! The 3rd column is normally the "package type" as auto-generated by Eagle. I think 0207 are SMT resistor size 0207 for example, and the CMF55 are the axial 1/4-watt 1% metal film resistors by Vishay-Dale. But things like TO92 EBC is generic and you need to make sure it is the variant with EBC pinouts vs BCE, etc. The caps with E3, 5-7 refer to the E3 series of 3 values per decade and the 5-7 probably is the pitch and diameter? JPS64 would probably be best person to answer. Hope that helps.
Cheers,
X
Cool that you are going to make this preamp! The 3rd column is normally the "package type" as auto-generated by Eagle. I think 0207 are SMT resistor size 0207 for example, and the CMF55 are the axial 1/4-watt 1% metal film resistors by Vishay-Dale. But things like TO92 EBC is generic and you need to make sure it is the variant with EBC pinouts vs BCE, etc. The caps with E3, 5-7 refer to the E3 series of 3 values per decade and the 5-7 probably is the pitch and diameter? JPS64 would probably be best person to answer. Hope that helps.
Cheers,
X
Code:
Part Value Attributes Package Description
C101 220p C5B4.5 CAPACITOR
C102 1µ0 C5B3.5 CAPACITOR
C103 10µ E3,5-8 POLARIZED CAPACITOR, European symbol
C106 47µ0 E2,5-7 POLARIZED CAPACITOR, European symbol
C111 47µ0 E2,5-7 POLARIZED CAPACITOR, European symbol
C116 33p C1206 10µ, 16V, X7R, 1206
C118 100µ E2-5 POLARIZED CAPACITOR, European symbol
C121 47µ0 E5-10,5 POLARIZED CAPACITOR, European symbol
C122 1µ0 C5B3.5 CAPACITOR
C131 470µ E3,5-8 POLARIZED CAPACITOR, European symbol
C132 470µ E3,5-8 POLARIZED CAPACITOR, European symbol
C133 470µ E3,5-8 POLARIZED CAPACITOR, European symbol
C134 470µ E3,5-8 POLARIZED CAPACITOR, European symbol
C135 470µ E3,5-8 POLARIZED CAPACITOR, European symbol
C136 470µ E3,5-8 POLARIZED CAPACITOR, European symbol
C137 1µ0 C2.5-6 CAPACITOR
C138 1µ0 C2.5-6 CAPACITOR
R101 2k2 CMF-55
R102 100k CMF-55
R103 61R9 CMF55-ON-LUG
R104 14k9 CMF55-2V
R105 33k0 CMF-55
R106 15k0 CMF55-2V
R111 1k8 CMF-55
R112 6k8 CMF55-2V
R113 47R0 CMF55-2V
R114 47R0 CMF55-2V
R115 220R CMF55-2V
R116 100R CMF55-2V
R117 68k0 CMF55-2V
R118 5k6 CMF-55
R119 33k0 CMF55-ON-LUG
R121 270R CMF55-2V
R122 470R CMF55-2V
R123 12R0 CMF-55
R124 27R0 CMF55-2V
R125 8R2 CMF-55+9MM
R126 47k0 CMF55-2V
R131 10R0 0207/2V RESISTOR, European symbol
R132 10R0 0207/2V RESISTOR, European symbol
R133 10R0 0207/2V RESISTOR, European symbol
R134 10R0 0207/2V RESISTOR, European symbol
V113 BC557B TO92-EBC PNP Transistror
V114 BC557B TO92-EBC PNP Transistror
V115 1N4148 DO35-2V
V116 KSC1845 TO92-ECB
V121 DN2540N5 TO220S N-Channel Depletion Mode Vertical DMOS FET
V122 KSA1381 TO126V
X101 M3 M3_VIAS
X121 M3 M3_VIAS
X131 M3 M3_VIAS
X132 22-27-2021-02 6410-02 CONNECTOR
X133 M3 M3_VIAS
X1021 SK95-25-STS SK95-25-STS
X1022 SK95-25-STS SK95-25-STS
X1023 2MM8 ST2,8 RIBBON CABLE CONNECTOR
X1024 2MM8 ST2,8 RIBBON CABLE CONNECTOR
No, it works great as such. It can drive 50ohm headphones no problem when DC coupled. 600ohm loads pose no challenge for even maximum output of 40Vpp when running +/-25v rails. 10kohm or higher load of typical high impedance is of course, no problem.
JPS64 is back and I should have new Gerbers tomorrow. Here are the new improved layouts for the TH board. With correct pin outs for M2X of course.
GB thread for the Melbourne is here:
https://www.diyaudio.com/forums/group-buys/333653-melbourne-daughterboard-m2x.html#post5690033
https://www.diyaudio.com/forums/group-buys/333653-melbourne-daughterboard-m2x.html#post5690033
JPS64 is working on an integrated motherboard that will hold the Melbourne daughterboards and provide 4 selectable inputs, volume pot, linear power supply with dual rail cap multiplier. It should be a pretty nice stand-alone preamp or
headphone amplifier. Will be offered as a GB later.
headphone amplifier. Will be offered as a GB later.
Hi X, I have 100s of KSA992, can I use it in place of BC557B? if so any changes to the circuit?
Regards
The other M2x daughter cards use a 220uF output coupling capacitor instead of C121=47uF here. The lower C will produce a measurable difference of a few degrees of phase shift at low bass frequencies. (Phase response at a roll off corner begins sooner, and slopes more gradually, than amplitude response; try it in a spreadsheet or a circuit simulator).
220uF x 600-800 ohm load, gives a longer timeconstant than 47uF, but it will have no effect upon M2 power-up "thumps". Why? Thanks to the even slower operation of M2's optical bias NFB loop. Connect a Kill-A-Watt (inexpensive mains wattmeter) between M2 and the mains, and take a video of its readings when you turn on the M2. Watts versus time. Surprise!
220uF x 600-800 ohm load, gives a longer timeconstant than 47uF, but it will have no effect upon M2 power-up "thumps". Why? Thanks to the even slower operation of M2's optical bias NFB loop. Connect a Kill-A-Watt (inexpensive mains wattmeter) between M2 and the mains, and take a video of its readings when you turn on the M2. Watts versus time. Surprise!
Thanks for reminding us that a 600ohm load needs a bigger coupling cap. I will make a note to update the BOM to 220uF although this Preamp can be optionally driven with DC coupling and cap would be bypassed.
I know that the M2 has a slow soft start ramp up - one of the best features. I have indeed measured the voltage as function of time and recall it takes about 45 seconds and if you play music it starts off at distorted Class B then slowly goes to Class A.
I know that the M2 has a slow soft start ramp up - one of the best features. I have indeed measured the voltage as function of time and recall it takes about 45 seconds and if you play music it starts off at distorted Class B then slowly goes to Class A.
We just checked and a 220uF/35V UFG, UKW, UFW cap fits the existing location (diameter 10.5 x 5mm pitch). This should cover it for those who decide not to go with DC coupled outputs.
It's a straightforward calculation which you and your engineering team could have performed back in November 2018 when this was written:
Or you could have simply copied that portion of the (well liked for good sonics) Tucson daughterboard, to name one example. The 220uF output coupling capacitor is plainly visible there on the schematic.
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