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Old 9th December 2011, 04:17 AM   #31
Lo_Tse is offline Lo_Tse  Canada
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Join Date: Dec 2006
Quote:
Originally Posted by siliconray View Post
New version PCB is fab out!

Modifications:
1. connected collectors of Q8 and Q3 (which was missing on the first version)
2. modified footprint of potentiometers. Multi turn pots can also be mounted
3. fixed the bug of small hole for Q8.
4. added a 220uf cap on feedback path. In this case the VR1 should be changed to 2k. The capacitor is an optional component. If you don't need it just short 2 pins of the cap and change VR1 to 200Ohm.
5. footprint of Q1 and Q2 are modified to which TO-3PL transistors like 2SC3280 can be assembly on board directly.

Free boards keep on offering:
FREE JLH Class A Amplifier PCB

Hi, Siliconray,

Please clarify which schematic shown in the Class A Amp Site (is it fig 2, the final circuit?) that your kit is based on?

Thanks!

Lo_tse
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Old 9th December 2011, 05:15 AM   #32
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yes the fig 2. there's a capacitor in the feedback path, I suggest short the 2 pins of the cap so that to have a DC loop and 200 Ohm potentialmeter can be used as VR1
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Old 9th December 2011, 01:13 PM   #33
Lo_Tse is offline Lo_Tse  Canada
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Quote:
Originally Posted by siliconray View Post
yes the fig 2. there's a capacitor in the feedback path, I suggest short the 2 pins of the cap so that to have a DC loop and 200 Ohm potentialmeter can be used as VR1
Got it. Thank you for the prompt repsonse.

Lo_tse
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Old 3rd January 2012, 07:25 PM   #34
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Location: Newcastle
G'day,

Got my boards finished today, very stable using MJL4281, have a small cap across the feedback. Everything else per the drawing with BC560C everywhere, running with 24V rails, iq 1.7A.
Had a quick listen sounds great so far, on soak now for a few hours then give it a good listen.

Regards
Bruce
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Old 4th January 2012, 01:40 AM   #35
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Hi Bruce, you did a great job! 24V 1.7A, that's a lot of power, hot enough for frying eggs
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Old 4th January 2012, 06:37 AM   #36
polsol is offline polsol  South Africa
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Join Date: Aug 2004
Location: Cape Town and Kuwait
Default Max supply rails for this design?

Hi all,

Anybody try higher supply rail voltages (and what were they) with success on this design?
Just interested how far the design can be pushed IRO power output.
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Old 13th January 2012, 01:44 AM   #37
kp93300 is offline kp93300  Malaysia
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Join Date: Mar 2007
Quote:
Originally Posted by Assesears View Post
G'day,

Got my boards finished today, very stable using MJL4281, have a small cap across the feedback. Everything else per the drawing with BC560C everywhere, running with 24V rails, iq 1.7A.
Had a quick listen sounds great so far, on soak now for a few hours then give it a good listen.

Regards
Bruce
Hi Bruce
Any further thoughts on the sound after running in the caps ?
I am getting the parts to build soon .
regards

kp93300
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Old 29th January 2012, 10:28 PM   #38
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Join Date: Jan 2012
I have just ordered a couple of these boards to try, should be interesting to compare to the original designs and the HART design that I sell.
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Old 30th January 2012, 01:31 AM   #39
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OK, we saw it. Please post your boards and review here when they are finished.
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Old 31st January 2012, 08:50 AM   #40
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Has any body already finished the assembly? I'm looking forward to see your testing results and reviews..
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