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Old 12th February 2004, 08:30 PM   #11
DomKo is offline DomKo  Canada
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Default Updated Version JLH 15W Amp

The following is the amp photo (front & back view).
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Old 12th February 2004, 08:31 PM   #12
DomKo is offline DomKo  Canada
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Default Updated Version JLH 15W Amp

The following is the amp set (Passive Preamp & Finished).
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Old 12th February 2004, 08:55 PM   #13
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Realy good work
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Old 13th February 2004, 12:49 AM   #14
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Default Re: Re: JLH 10 Watt class A amplifier

Quote:
Originally posted by DomKo
Hi Diyer,

But I have one question about the hum. If there is NO input connection on the RCA, there is not hum. If there is an input (JUST RCA cable), there is a low hum (bee) sound. Either one of the cable connected to the amp. There is a small hum sound. You need to place your ear over the speaker to hear this bee.

How can I fix these hum sound?

Thank you very much.

DKO
Hi DKO,

My last JLH-amp (the updated 2003-ESL version) is dead quiet in my home setup.

It's noisy when unconnected cables are present.

However, when several weeks ago I hooked both amps to my son's dual-cd-mixing console (setup for a big party). I HAD A MAYOR hum on one channel when connecting one or two amps to my son's device.

I cured the problem with a simple box which was just a resistor based voltage divider on both channels. Which was needed any way to prevent speaker damage as the output of this console exceeded the sensitivty of my J-Amp.

Two weeks after that I had a similar hum at a test-setup to get some metrics done on my amp.

So, probably, I've might have mixed the wiring of the toroids on both channels. (both main wires are yellow)

I don't mind the noisy part with not connected cables. I'ts not interfering with listning to music (which needs connect cables)
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Old 13th February 2004, 12:53 AM   #15
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btw this is how my amps look:

Click the image to open in full size.
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Old 13th February 2004, 12:59 AM   #16
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Default JLH-inside

Here's one inside detail pic taken during testing of the first channel.

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Old 13th February 2004, 07:27 AM   #17
DomKo is offline DomKo  Canada
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Default btw this is how my amps

Hi Dutch Diy,

Yours is Good Too.

The difference is that your amp is 'SEE THOUGH'.

I try to build it in one case. It is just enough space.
Finally, I add two pairs of cooling fan at the rear side.
I also need to adjust the fan speed to mininize the noise.
Now, the noise of the fan is hearing at about 1 feet. (It's acceptable).
I run the amp with about 12 hrs. The heatsink is kept at about 30 - 40 deg C.

I also test with signal generator from 50Hz to 22000Hz sine wave.
From the oscillograph, there is no visible distortion. I did not have another meter to test.

Enjoy with the music !
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