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Old 26th October 2003, 07:06 AM   #1
DomKo is offline DomKo  Canada
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Default JLH 10 Watt class A amplifier

Hi,

I want to build a JLH 10W Amp.
Where can I buy the heatsink from the web having a good price?

Thank you.
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Old 26th October 2003, 02:51 PM   #2
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Try the trading posts on this forum. Peter Daniel is selling his 11x11 heatsinks that are suitable for the JLH. He is located not far from Toronto.
Hope this help
Chris
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Old 27th October 2003, 11:25 AM   #3
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Hi Domko,

I have deleted your e-mail by mistake without reading it first. Please resend it if you don't mind.

Sorry,
Chris
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Old 29th October 2003, 11:30 AM   #4
Mike L. is offline Mike L.  United States
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Domko,

I also built (and currently use) the JLH 10W amp, 1969 version. The original heatsinks I used were obtained from Jameco. They are extruded anodized aluminum about 4" x 2" x 2" and inadequate.

I just obtained new heatsinks, Wakefield 423-A's, that measure 5" x 6" x 2.5" and keep things nice and cool. Three of them came from electronicsurplus.com (that's all they had) and the fourth was obtained from Newark Electronics (newarkinone.com).

Newark doesn't list this particular heatsink in their printed catalogue, but a search of the site found quite a few in stock for just over US$16 each (which isn't a bad price for heatsinks of this size).

Which version of the amp do you plan to build? I would like to try the version for dual supply rails found in the design notes article.

If you haven't yet decided on which power supply to use with your amp, I suggest the Capacitance Multiplier PS from the Elliot Sound Products site. I built a single rail version of it for each channel powered by a single Hammond toroid transformer. There is absolutely no hum.

Another tip that just came to me is that the chipset is very important to the sound. I have tried several of the suggested substitutes before settling on the following: TR1/2 - MJ15003, TR3 - 2N1711 and TR4 - 2N3906.

Good luck. It is a great little amp.

Mike L.
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Old 29th October 2003, 04:57 PM   #5
DomKo is offline DomKo  Canada
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Default JLH 10 Watt class A amplifier

Hi Mike,

My plan is to build 10W amplifier using 2003 Aug Feedback Cap verion. PS will try to use CRC
Topology and 15V x 2 dual supply with dual 160VA transformers.

I have got four 1000000uF 35V Cap from Nippon Chems for 5 years. I will test with double RC filters in 1 ohm and 4700uF. The ripple is simulated under 10mv. I will also test with Elliot Sound Products cap multiplier later.

I will follow your suggestion for the transitors to build this amp.

There is differnce between 10W & 15W on design.
One question I concern is 10W amp whether is enough or not for a room 200 sq. ft. Otherwise, I will build 15W. Is there any suggestion?

Thank you very much.
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Old 29th October 2003, 06:00 PM   #6
paulb is offline paulb  Canada
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I wouldn't have thought the Wakefield 423A would provide enough cooling. What supply voltage and bias current are you set at?
Maybe I can get by without a fan....
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Old 29th October 2003, 06:18 PM   #7
Mike L. is offline Mike L.  United States
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Paul,

The supply voltage is 28.5 volts. I don't know what the quiescent current is at this time; I never bothered to recheck it when I replaced the 2N3055's with the MJ15003 devices.

I changed the transistors at the same time as the heatsinks and noticed that both the transistors and the rectifiers(?) are running cooler. It could be that I was just about to loose the output transistors when I made the change.

At this time, I'm able to touch the transistor can without any discomfort. With the previous heatsinks/transistors 4 or 5 seconds of contact resulted in pain.

Also, I apologize for the oxymoron at the end of my last post. I should have written that the JLH is a wonderful little amp.

Mike L.
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Old 30th October 2003, 05:30 AM   #8
DomKo is offline DomKo  Canada
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Default JLH 10 Watt class A amplifier

PS will try to use CRC Topology and 15V x 2 dual supply with dual 160VA transformers.

I have got four 100000uF 35V Cap from Nippon Chems for 5 years. I will test with double RC filters in 1 ohm and 4700uF.

Four 100000uF 35V E. Cap. is used instead of 1000000uF for dual supply.
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Old 30th October 2003, 11:32 AM   #9
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Default Re: JLH 10 Watt class A amplifier

Quote:
Originally posted by DomKo
Hi Mike,

My plan is to build ............
There is differnce between 10W & 15W on design.
One question I concern is 10W amp whether is enough or not for a room 200 sq. ft. Otherwise, I will build 15W. Is there any suggestion?

Thank you very much.
Hi,

It depends on what you like to listen to most. I used to like the sound of my 100W Meradian mono blocks pushing the Tannoy Super Red Monitors with the volumn set at 1'o clock. I used to sweat listening to Private Investigation in a 150 square foot room.
Now I don't do that kind of stuff any more.
My last JLH 1996 was loud enough for me with my Morrison ELAD set at 10'o clock pushing 89db Mirage speakers in a 12 X 47 room with me sitting 15 feet from the speakers.

Hope this helps,
Chris
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