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PostPosted: 29 Jul 2008, 08:17 
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Joined: 29 Jul 2008, 08:12
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Location: Wiltshire, UK
After looking at this site for ages, and many others I've finally bitten the bullet and started to build a class A amp. It's a 10W design by John Linsley Hood, the prototype sounded great, now time to build the real one....I'll lre-post as soon as I've made some progress, it's a great little amp, well worth a look if you want to build a Class A power amp. :)


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PostPosted: 29 Jul 2008, 18:01 
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Joined: 06 Jun 2008, 20:12
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Location: Houston, TX
Hi John,
Welcome :)
So can you give us a link to a build or schematic ?
Ri

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PostPosted: 29 Jul 2008, 18:45 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hi John, welcome to the forum.

The John Linsley Hood designs are good. I'm sure you know, all Class A amplifier projects need a stiff power supply.

I'd love to see photos of your proto build.

Cheers,
Gio

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PostPosted: 30 Jul 2008, 03:20 
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Joined: 29 Jul 2008, 08:12
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Location: Wiltshire, UK
At the moment, I'm without a camera but will pinch one to take a photo. The prototype was built on strip board and the heatsinks were hanging loose, a right mess to be honest, but it was enough to see if it worked and how good it sounded.

The web site is a site run by a gent called Geoff Moss, and he has many circuits on this site.

http://www.tcaas.btinternet.co.uk/index-1.htm

A friend of mine etched the PCBs last night, and today I'll be working on populating them. Photo's will be on the way though. :)


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PostPosted: 30 Jul 2008, 03:54 
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The PCB in progress, the transistors aren't the right ones, but I've shoved a couple in for the purposes of the photo. This PCB also includes the additional capacitors as mentioned in the updates on Geoff's Site.


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PostPosted: 30 Jul 2008, 07:18 
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Looking very good. I recently got a PCB kit and need to try making my own PCB. Something like this that you can draw out by hand may be a good place to start.

Which version are you building and what are you doing for the power supply?

Cheers,
Gio

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PostPosted: 30 Jul 2008, 08:05 
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Location: Wiltshire, UK
The version I am building is the original 1969 version, but with a capacitor additions mentioned in a later article which I can't seem to find at the moment. In the short term for initial tests, we'll be running the amplifier on a stabilised lab power supply, but intend to build a regulated supply specifically for it later on. I'm also contemplating adding additional power transistors and the required resistors to force them to current share thus giving the amplifier more current capability.

As for making the PCBs, a friend of mine penned the layout and etched the PCB. I was doing a search recently for some layout software, and I found a respectable amount of free schematic and PCB layout tools. A couple of companies actually give away software that can be used to design and quote for the PCB, then they can manufacture them for you.

http://www.expresspcb.com/
http://www.pcb123.com/

Hope this helps. John.


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PostPosted: 30 Jul 2008, 08:26 
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Location: Houston, TX
John,
I just ripped apart a dumpster dive 8 track player and got a bunch of those little clear caps like you used. Are these just the same as small aluminum electrolytics? Can you tell me a bit about them?
Ri

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PostPosted: 30 Jul 2008, 08:39 
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Hi Ri

These are Suflex capacitors, these are just what we had to had when we built this prototype. I have been told they are very hard to come by, and are very expensive. They are spirally wound and appear to be encased in a clear heat shrink.

Other than that, I can't tell you any more, I even had to ask what they were, I scrounged them from work...perhaps I ought to take them back..... ;-)


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PostPosted: 30 Jul 2008, 08:42 
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Interesting :) Just about nothing on web about them. Anyone else know about these?
Ri

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