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Old 18th August 2003, 10:11 AM   #361
Nexus is offline Nexus  Netherlands
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power supply:
2x15V 120VA C-L-C topology.

After building it without C4a, I noticed some oscillations around 14KHz,
cause of this was the inductive component of C4,
100nF was placed in parallel with it, and the oscillations were gone.

further the higher spectrum was checked, and some oscillations were found in the higher regions.
after placing a capacitor of 33pF in parallel with R8, this was solved also.
The spectrum is from 8Hz to 94KHz now (-3dB),
with a good looking sine wave (no distortion meter present to check).

When Q3 is replaced with a BD139, the the extra cap over R8 can be removed and
the spectrum gets much larger, so I will test the sonics of both configurations.
And I will do some test with WIMA input capacitor and elna silmic for C4.

Greetings.
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Old 18th August 2003, 11:47 AM   #362
Nexus is offline Nexus  Netherlands
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For one or the other reason, the schematic failed to display, so another attempt:
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Old 6th September 2003, 08:59 PM   #363
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Default 1 J-amp 2003 working..

Hi all,

I've got one JLH 2003 Esl version working (one minor mechanical bug to fix)
It'll take some days to complete the second amp
and it'll not leave my shack until all bugs are fixed. so no serious impressions for now except one:.
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Old 7th September 2003, 02:52 PM   #364
LaZarus is offline LaZarus  Netherlands
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I made my first ever pcb layout today for the JLH 96 amplifier. I hope it is any good. Suggestions and comments are welcome.

Some notes:

R10 is off the pcb because this one gets hot.
The routes can be substantially bigger.
It isn't very neat.
Some Transistors have wrong device numbers.

But besides these points, would it work?
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Old 8th September 2003, 04:22 AM   #365
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Hi LaZarus,

You may have to give us better/clearer overlay part number in order to make any sense out of it. In my experience the R10 just get a little warm, not hot to touch, what Iq are you setting it to?

I can not see where, how the R6 connect to signal ground.

Regards,
Chris

P.S. What version of 1996 JLH are you referring to?
What is that R11 2k2?
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Old 8th September 2003, 01:05 PM   #366
LaZarus is offline LaZarus  Netherlands
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I have used this schematic, the updated '96 version.

Click the image to open in full size.

Is it better to use a ground plane on my pcb layout, which will be connected to a star ground on my chassis, or an other grounding topology?

Here is my revised pcb layout.

Click the image to open in full size.
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Old 8th September 2003, 01:35 PM   #367
sonnya is online now sonnya  Denmark
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Maybe a bit more important than a ground plane....

May i suggest wider traces, you have plenty of space.

You will get lower series inductance and lower resistance....

Sonny
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Old 8th September 2003, 02:37 PM   #368
LaZarus is offline LaZarus  Netherlands
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Ok, above is my new pcb layout, with wider tracks, place for a bigger capacitor and some other changes.

Any suggestions are still welcome.

btw, the decoupling C's still have to be added.

cheers
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Old 10th September 2003, 12:52 PM   #369
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Quote:
Originally posted by LaZarus
Ok, above is my new pcb layout, with wider tracks, place for a bigger capacitor and some other changes.

Any suggestions are still welcome.

btw, the decoupling C's still have to be added.

cheers
Hi,

Depending on your grounding scheme. The way I would do it IMO is to group the signal grounds(R2,C2,R6) and group the dirty grounds(R11,R12,C6,C7) separately. Each group then join to the star ground.

Regards,
Chris
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Old 11th September 2003, 02:57 PM   #370
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Default Feedback pick up point

LaZarus,

If you can consider R8 pick up point between Q2E Q1C and Output may be prefered to R8 pick up before Q2EQ1C as show in the schematic.

Regards,
Chris
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