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The Pioneer Super Linear Circuit
The Pioneer Super Linear Circuit
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Old 18th March 2018, 04:41 PM   #151
Algar_emi is offline Algar_emi  Canada
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The Pioneer Super Linear Circuit
Hi Patrick. A little precision here, look at both inputs JFET and BJT. The instruction says to ommit R1,R2 if using the JFET, but the JFET input schematic still shows R1, R2, and on the PCB there are pads for 0603 (input) and 0805 (to gnd) size resistor, but without name.

Are we still using these two input resistors with the JFET input, and if yes what are the values? Thanks
SB
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File Type: jpg JFET Input.JPG (16.8 KB, 460 views)
File Type: jpg BJT Input.JPG (16.9 KB, 452 views)
File Type: jpg JFET Input resistors.jpg (5.2 KB, 451 views)

Last edited by Algar_emi; 18th March 2018 at 04:45 PM.
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Old 18th March 2018, 06:03 PM   #152
EUVL is offline EUVL  Europe
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> but the JFET input schematic still shows R1, R2,

Those represents the source resistance and the input grounding resistor.
Forgot to chnage the resistor numbers from Spice model.
Sorry for that.

> and on the PCB there are pads for 0603 (input) and 0805 (to gnd) size resistor,

0603 (2x) are gate stoppers for J1 & J2. Use 220R.
The 0803 that you showed in the photo (on the top side) should be left open.
(Use 0805 0R there ONLY when NOT using J1,2.)

There is another resistor to Gnd at the bottom side of the input pin.
This is the input grounding resistor. Use 100k at that position.
They should be on the Bill of Materials.

> but without name.

PCB too small ......


Patrick
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Old 18th March 2018, 06:15 PM   #153
EUVL is offline EUVL  Europe
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See also both photos in post #1 showing the component placements with J1,2 being used.


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Old 18th March 2018, 06:43 PM   #154
Algar_emi is offline Algar_emi  Canada
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The Pioneer Super Linear Circuit
Great. Thanks
SB
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Old 19th March 2018, 06:25 PM   #155
Algar_emi is offline Algar_emi  Canada
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The Pioneer Super Linear Circuit
First amp prototype working like a charm, with CCS, and without Servo, 24mv dc offset before trimming the CCS. Bias at 150ma and testing for a few hours...
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Old 19th March 2018, 07:40 PM   #156
Morde is offline Morde  Finland
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Nice progress Algar_emi! Itís going to be a superb build Iím sure.

You got me inspired to finally update my front plate and the vol knob. I think the new knob is a bit too big and heavy - so still to do another update on that behalf.
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Old 19th March 2018, 08:25 PM   #157
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Old 19th March 2018, 09:50 PM   #158
Algar_emi is offline Algar_emi  Canada
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The Pioneer Super Linear Circuit
Wow, mine won't be so gourgeous , but I have a lot of amps, have to save somewhere

Both channels are now tested, working very nicely. Second channel DC offset is so low at less than 4mv (2.5mv under 33R load), that probably I won't bother trying to tune it to zero. Anyway without servo it will always fluctuate around 0mv anyway... Now time to assemble the protection PCB

Also check how the circuit is sensitive to +-15V exact value variation. Probably thanks to the CCS, not that much. Set one supply from +14.90 to +14.40, while keeping the other at -15.0V, and the DC offset didn't move. Excellent!

Here my first measurements, with lab power supply, and without enclosure...
All measurements done using a 33R resistor.

Gain: (Vin: 100mV, Vout: 10V) = 10X or 20dB
Vout max: 20Vp-p or 7.3Vac, that gives 1.6W
Vin max: 0.723V
BW (Ref 1Khz, Vout 1V): 3.1Mhz...
Noise (gnd input): < 1mv (THD graph showing noise floor close to -115dB
THD (Vout 1V): < 0.005% (limit of my equipment), see graph
Output DC offset: 2.5mv
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Last edited by Algar_emi; 19th March 2018 at 10:04 PM.
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Old 19th March 2018, 10:01 PM   #159
EUVL is offline EUVL  Europe
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Noise floor will go down with proper PSU and case.
Even as it is now, with the limit of your measuring equipment, you should be very pleased.
It will not shy from any commercial amps of any price.
And all that without global NFB.

Time to finish off and have a listen with a less expensive headphone.
(Should use SHPP with your reference phone.)


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Old 20th March 2018, 10:08 PM   #160
Algar_emi is offline Algar_emi  Canada
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The Pioneer Super Linear Circuit
Hi Patrick. I have problem with the SHPP leds, 0805 format. None of the Red, Green or Yellow turns on. I test all the leds with my DVM, diode mode, and they are working, but inside the circuit, they don't turn on when activated. I have

D1 (Red): channel fault
D3 (Grn): Power On
D6 (Yel): Delay

What led part number did you used, mine seem to be not of the correct voltage?

Thanks
SB
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