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PostPosted: 10 Oct 2008, 10:15 
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Joined: 29 Jul 2008, 08:12
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Location: Wiltshire, UK
Okay, so I've been bitten. I like the JLH amplifier, and have decided to build one of the updated versions. This amplifier will run from split rails whereas my other unit ran from a single supply. It will be running on a +/- 22V supply and directly coupled at the output.

See here for additional information: http://www.tcaas.btinternet.co.uk/jlhupdate.htm

One thing I like about this particular circuit; if you need higher current capability, this can be achieved by simply adding a 0R1 resistor before the collector of each power transistor to force current sharing, and then make the necessary adjustments to the DC offset, assuming the power supply is up to the job.


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PostPosted: 10 Oct 2008, 12:19 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hi John, that looks great. Could you also share your PCB design.

Cheers

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PostPosted: 10 Oct 2008, 12:35 
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I'd be delighted to share it, I'll have to dig them out when I'm at work on Monday. It's not done on PC or anything, it was hand drawn and hand drilled but it all worked out well on the last amplifier. I'll probably draw it in software though and make gerbers/drill files available for anyone interested.

Kind regards, John.


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PostPosted: 10 Oct 2008, 12:39 
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Hi John, I could tell it was done by hand. An unscaled scan of your drawing is fine. By hand is the only way I make PCBs right now.

Cheers

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PostPosted: 10 Oct 2008, 16:06 
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Bear with me on that one. I don't have a flatbed scanner at home at the moment so will have to scan it in work on Monday. Watch this space.....

Kind regards, John.


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PostPosted: 17 Oct 2008, 07:53 
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The soldering's very scruffy and needs cleaning up, but here it is.

Kind regards, John.


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PostPosted: 17 Oct 2008, 21:37 
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Have you had a chance to try it out yet?

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PostPosted: 18 Oct 2008, 14:21 
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Location: Wiltshire, UK
Unfortunately not. At work it's gotten rather busy, so I have had to put it on the back burner for the short term. As soon as I have one channel up and going, I'll let you know the results.

We have no proper audio test instruments other than a signal generator and a 'scope. My company's test instruments are use for calibrating telecoms instruments, so work well outside the audio band. Things like distortion meters etc, are something I don't have access to, so I won't be able to give any true scientific measurements. If it sounds good though, has no hiss or hum, I'm happy.

Kind regards, John.


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