One board amp

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Andy Le Blanc
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One board amp

Post by Andy Le Blanc »

looking at home fabrication it becomes very apparent very quickly why
modern manufactures build the way they do.

You want a more or less standard format that is quick and inexpensive.

I've been looking at a way to accomplish this basic efficiency as a cottage business.

It looks possible by combining the tube and socket and component board
and mounting the whole affair under the chassis.

The circuit can then be executed point to point between the socket and either
eyelets or terminal standoffs using modern components without the excessive lead dress
that prevails most "custom built" appliances. Nothing new of course.
Repair and upgrade becomes a board swap, a modular approach.
parts can be fabricated in house in an efficient manner, and dressed on the kitchen table.

Pros? cons?
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dartanion
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Re: One board amp

Post by dartanion »

I have never liked board mounted sockets or pots. External stress on these components stresses the boards. Especially with PCBs, this can become an issue. But, I do see what you are getting at. Anything that can speed up cottage production.
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Andy Le Blanc
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Re: One board amp

Post by Andy Le Blanc »

I have had similar experience with pcb. Your not constrained by material choice,
and point to point offers a lead flex that you just don't get with an etched board.

If you go that route, eyelets are available .219 in. and .250 in., that's a thick board.

The primary benefit is being able to do point to point with common parts.
the component leads are right on the socket pins where there supposed to be.
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Cliff Schecht
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Re: One board amp

Post by Cliff Schecht »

The biggest problem with amp manufacturers using PCB's is they almost always go cheap when it comes time to have boards made. A single-sided layout with 1 Oz. copper on standard Chinese FR4 just does not hold up to the stresses put on the PCB by tube sockets, component heating, etc.. and as many of you I'm sure have found, you end up with cracked traces and intermittent solder joints. The "correct" way to do a guitar amp with a PCB would be to use 2 Oz copper on a double-sided PCB, although the layout itself can still be single-sided. The big advantage is that the through-hole vias will give the sockets and other components a much needed strengthening and intermittent solder joints/cracked traces would be a thing of the past.

It's especially hard on an amp when it's still hot and gets bumped around by moving in and out of a show. Even the best layouts combined with what I mentioned above can't prevent certain carelessness from ruining a your PCB's..
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dartanion
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Re: One board amp

Post by dartanion »

I use 1/8" FR4 and eyelets for pretty much every build. Very sturdy board material in that thickness. I looked at using 1/16" FR4, but even that seems flimsy to me.

I would bet that mounting sockets to 1/8" FR4 would be quite bomber!
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Cliff Schecht
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Re: One board amp

Post by Cliff Schecht »

It's funny too that the price jump isn't that big nowadays from single-sided to double-sided construction. In many cases there is no price jump as every reputable manufacturer is setup to do double-sided boards at a minimum. I'd bet that the price jump from one size of FR4 to the next size up isn't too bad either, although I've never actually looked into this..
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Bear
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Re: One board amp

Post by Bear »

Speaking of PCB quality, anyone had at the insides of one of those "designed by Soldano" Jet City amps? Stock tone on the 20 watt head is workable to good, and the pics of the PCB layout look encouraging -- probably a decent PCB amp to do some mods on if the quality holds up. On-board sockets, but I suppose you could install some chassis mounted ones and fly leads to the board if it doesn't look survivable. I'm eying that to maybe recommend to people as good for the price and with hidden potential.
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M Fowler
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Re: One board amp

Post by M Fowler »

Use boards from this place like you pictured.

http://www.tubesandmore.com/
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Andy Le Blanc
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Re: One board amp

Post by Andy Le Blanc »

Well ya... but the point is to fabricate it in house, with material on hand, and
not to waste $$$ sourcing parts you can produce yourself.
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paulster
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Re: One board amp

Post by paulster »

Here's some food for thought:
[img:800:600]http://i71.photobucket.com/albums/i146/ ... rn1nw8.jpg[/img]
[img:800:600]http://i71.photobucket.com/albums/i146/ ... rn3ua6.jpg[/img]
[img:800:600]http://i71.photobucket.com/albums/i146/ ... ornti3.jpg[/img]

The key to board-mounted sockets is to ensure that the board doesn't flex under tube insertion/removal, so it needs to be anchored really firmly to the chassis at these stress points, and also if you go PCB that you use quality board material (i.e. not pressed paper) and double-sided through-hole-plated boards so that the heating/cooling cycle won't leave you with dry-soldered joints.

The other thing I'd add for board-mounted tube sockets would be that a tubes-up configuration would be preferable over tubes-down so that from a heat perspective you are dealing only with conduction rather than convection and conduction.

1/8" FR4 properly attached to the chassis is not going to suffer flexing problems so I'd have no problems using board-mounted sockets on this.
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drhulsey
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Re: One board amp

Post by drhulsey »

paulster wrote:Here's some food for thought...
Those pictures are breath-taking 8)
What a work of art :D
Tim

In case the NSA is listening, KMA!
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Structo
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Re: One board amp

Post by Structo »

Wow!
That is about the coolest looking construction I have ever seen.

Dumble did something sort of similar on his Steel String Singer amps.
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Andy Le Blanc
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Re: One board amp

Post by Andy Le Blanc »

But how much of the unit did you make or design yourself.

You can wax poetic with the wire dress or layout all you want, but it doesn't
help.

It is good looking... But the guy at the end of the bar down to the pub would say;

"So was my ex-wife" :lol:

Nice amp.
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Andy Le Blanc
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Re: One board amp

Post by Andy Le Blanc »

test fit on flat stock, made the standoff's, I like the old saying;
"make it strong enough then double it" Should have the rest of the chassis
fab'ed up tonight, it doesn't take long.
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drhulsey
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Re: One board amp

Post by drhulsey »

Andy Le Blanc wrote: ... You can wax poetic with the wire dress or layout all you want, but it doesn't help...
Larry Mann's cabs don't add to the tone, either, but they sure can make you do a double-take 8)
The guts aren't often seen, but, when they are, attention to detail is usually a positive sign.
That could be attention to electronic detail or aesthetic detail or, hopefully, both.
In the end, it's the sound of the amp that counts, as we all know.
Tim

In case the NSA is listening, KMA!
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