Class A sand amp.

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pre65
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Class A sand amp.

Post by pre65 » Mon May 11, 2015 2:20 pm

I have got some JLH PCBs from Ray, with the object of building a pair.

But now I see Colin Wonfor is doing something similar, so I may wait and see how that progresses.

Anyway, I'm starting to accumulate a few parts.

1) Two large alloy finned heatsinks 300mm x 200mm x 73mm.

2) Four Kemet 22000uf 63v caps 105 degree C. 75mm dia x 105mm high.
Type PEH169MT5220QB2

Both were Ebay bargains, but took a lot of time to find. :wink:
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Post by IslandPink » Mon May 11, 2015 6:16 pm

Good stash - heatsinks are surpsisingly hard to find cheap or s/h !
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Post by pre65 » Fri May 22, 2015 3:46 pm

The heatsinks came yesterday, but one is damaged. The Ebay seller has agreed to replace it.

And today I got the 10 caps (4 + 6) and they are HUGE. About the diameter of a Coke tin and 2/3 the height.
People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within
Dr Elisabeth Kubler-Ross

G-Popz THE easy listening connoisseur. (Philip)

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Post by pre65 » Sat May 23, 2015 12:43 pm

Picture of the heatsink and cap. The CD case is for size reference. :)

Image
People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within
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Post by Mike H » Sun May 24, 2015 3:33 pm

See what you mean about big caps!
 
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Post by Paul Barker » Sun May 24, 2015 5:02 pm

Nice Bahco 4" shifter.
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Post by jack » Sun May 24, 2015 5:54 pm

This is really interesting - I built one of these are uni in the late '70s - it cooked. Can't recall what became of it - probably caught fire like a lot of the other stuff I built at the time. My constructional skills were then most certainly "in need of some improvement" :)

Are you building the original 1969 (Wireless World) or the updated 1996 (Electronics World) one? He died in 2004, so the "Updated 2005" variant is with mods from others - how does it differ? (EDIT: found the schematic at http://www.siliconray.com/catalog/produ ... mage/3575/)

I've always wanted to build the later one - never got round to it yet...

(both articles attached for those interested)
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jlh-1996-update (1).pdf
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jlh-1969-amplifier.pdf
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Post by jack » Sun May 24, 2015 6:32 pm

Damn you, Phil - you spurred my interest in this again!.

I located "The Class A Amplifier Site" (TCAAS) which has moved several times.

What's referred to as the "2005" version seems to be actually a 2003 update by a chap called "Tim Andrews" which can be found at http://sound-au.com/tcaas/jlhupdate.htm. All interesting stuff...

I do remember the original being extremely sensitive to PSU noise & hum - a super-regulated PSU is a must...

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pre65
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Post by pre65 » Sun May 24, 2015 6:34 pm

I'm also considering a Colin Wonfor class A amp, but waiting for details of the PSU PCBs.
People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within
Dr Elisabeth Kubler-Ross

G-Popz THE easy listening connoisseur. (Philip)

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Post by Tony Moore » Sun May 24, 2015 9:24 pm

Those are some serious heatsinks. 8)

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Post by Tony Moore » Sun May 24, 2015 9:26 pm

And I have to say I've been really pleased with my class A MOSFET amp. It has come as close to what I need right now as I have any right to expect.

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Post by pre65 » Thu Jun 11, 2015 8:06 pm

Tony Moore wrote:Those are some serious heatsinks. 8)
Indeed. :)

I've finally got the replacement for the damaged one.

I've lost interest in all things hi-fi at the moment so they will be packed away with all the (ever increasing) other bits.
People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within
Dr Elisabeth Kubler-Ross

G-Popz THE easy listening connoisseur. (Philip)

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pre65
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Re: Class A sand amp.

Post by pre65 » Thu Jul 30, 2015 8:22 pm

I've just ordered a pair of SECA (single ended class A) amplifier printed circuit boards from Colin Wonfor.

Watch this space.
:)
People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within
Dr Elisabeth Kubler-Ross

G-Popz THE easy listening connoisseur. (Philip)

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pre65
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Re: Class A sand amp.

Post by pre65 » Sat Aug 01, 2015 9:19 pm

The PCBs (2) came today. I've already got two toroids, four power supply caps and the large heatsinks.

I'll go through Colins BOM for the parts to populate the PCB and order them, no hurry but at least they will be there when the enthusiasm strikes.

I have a design in mind, so will do some detailed drawings once I have an idea of where all the bits fit.
:)
People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within
Dr Elisabeth Kubler-Ross

G-Popz THE easy listening connoisseur. (Philip)

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pre65
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Re: Class A sand amp.

Post by pre65 » Mon Aug 17, 2015 5:59 pm

I've got a sheet of FR4 (2mm) to build a CF power supply, but the turret tags I ordered are far too small for me to work with.(my fault)

I've now re-ordered some larger turret tags from Modus.


http://modulusamplification.com/CIRCUIT ... 42116.aspx
People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within
Dr Elisabeth Kubler-Ross

G-Popz THE easy listening connoisseur. (Philip)

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