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PostPosted: 13 Apr 2017, 01:54 
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This is about construction of projects over a specific type of circuit. I didn't put it in the chassis/woodworking group because it has more to do with the circuit than the enclosure.

It seems to me that people make PCBs for their audio projects. Some buy kits which come with PCBs already made and some etch their own. A few make point-to-point circuits where they glue large capacitors together and then solder the smaller components on them. The tube people are mostly point-to-point except for those who make turret boards. Tube PCBs are there but most people don't seem to prefer those.

Amateur radio guys seem to prefer "Manhattan" or Ugly construction. Manhattan is where you start with a copper ground plane (unetched PCB is fine) and glue islands on it made of pieces of PCB. Then, you solder. Everything that is grounded can simply be soldered onto the ground plane.

It works very well for RF circuitry over methods like vero-board or P2P wiring. I'm wondering why more people don't use it in audio circuits. I've seen some people make very attractive layouts using this method, such as Dave AA7EE who builds radio receivers of immense complexity. I have a power amplifier project I've been wanting to make for a long time, using TIP35/36, and a large PT I stole from a dead AV Receiver.

Ed

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PostPosted: 13 Apr 2017, 08:05 
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Labor intensive for results otherwise easily achieved.

Most power-amps are very simple and with relatively few components as compared to a receiver or tuner.
Most competent designer/assemblers, even DIY, will not rely on any sort of glue for mechanical connections. Exceptions will be speaker makers. If glue is used, it will be for tacking purposes - during assembly, but the assembly does not depend on it. I will commonly use acid-free hot-melt glue to stabilize large capacitors on PCBs to prevent vibration (and how many such caps have you seen that fail at the solder-points due to stress?).
Most competent designer/assemblers, even DIY do prefer "star-ground" systems for which a copper board or buss does nicely. But unless shielding is required, there is typically no need to make the entire base be a copper-plated board.

Cutting to the chase, and emulating William of Occam: Eschew needless complexity. PtP allows for very simple assembly without a lot of specialized parts or tools. It puts an onus on the designer to think about layout and wire-dressing to prevent interference and hum, but this is not insurmountable. Turret boards, again are less complex than etching a PCB 'at home'. and can be quite elegant in appearance. Same issues with designing and wire dressing. PCBs are most complex to achieve - except in mass production - and the materials, means and methods these days are vastly superior than they were even 20 years ago - unless you are involved with the Military or NASA. So, there is no actual penalty going with PCBs.

Comes down to 'pays you money, takes you choice'.


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PostPosted: 17 Apr 2017, 06:39 
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Do you have an image of a Manhattan?

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PostPosted: 17 Apr 2017, 07:49 
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BowToEd wrote:
I'm wondering why more people don't use it in audio circuits.


Some high-gain guitar guys do. Not often, but those with RF experience use what they know. Nothing wrong with it other than for labour intensive (and VERY difficult to change). Even the Motorola and M/A Com R&D departments use it. DC-mid GHz stability and all.

It's not conducive to HiFi simply because hum control can be a bugger. At RF, that's not an issue as it'll be shielded when done anyway. In guitar, once the "IT VERKS!" stage is crossed, it's put on chassis or PCB. Can be done for HiFi, but it's not economical compared to a plug-in breadboard where you just transfer components (breadboard is a nightmare for RF or guitar, trust me!)

Quote:
Do you have an image of a Manhattan?

https://4.bp.blogspot.com/-4Z64F0xGSXI/ ... eep103.jpg

Should be mentioned that it's more known as the "dead bug" method outside the USA.

You can even use the method for SMD:
https://i0.wp.com/cdn.makezine.com/uplo ... wimage.png

And make it artsy!
https://s-media-cache-ak0.pinimg.com/56 ... 7107f2.jpg

Cheers!

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PostPosted: 17 Apr 2017, 18:56 
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I guess I may have been there in the past. Here is a Pass BoZ built on its own output caps (10uf 100V polies).

http://mongreldogaudio.blogspot.com.au/2010/12/boz-on-cap-bozoac.html

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PostPosted: 18 Apr 2017, 12:05 
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Manhattan construction can look quite good. Some people just solder components haphazardly and some people take a lot of time and make it look amazing.

https://i0.wp.com/www.pbase.com/daverichards/image/136629753/original.jpg

https://i2.wp.com/www.pbase.com/daverichards/image/152813436/original.jpg

(source, Dave Richards AA7EE, https://aa7ee.wordpress.com/)

It's not as labor-intensive as making a one-off circuit board, and it's especially useful as a lot of circuits I build, I'm making for the first time and I'm not sure it will work. I attempted a build of the Micro 40 DSB and it failed. It's more convenient for me to be able to lay out stages quickly, test them, and then add more a little at a time.

I'd like to try again with an audio circuit like a phono preamplifier or something. If I make the box out of 100% copper clad board, it should work decently well at shielding the high-gain circuits. I'm looking at maybe trying an op-amp based preamplifier with an onboard power transformer. I have a 16v AC doorbell transformer that should give me a decent +/- 12v when lightly loaded. The phono stage for the op-amp will come easily. I can place an LM386 or even a transistor-op amp output stage to drive the cable on the output.

If that works out well, I may try my hand at a power amplifier (again) using this construction. I made one with BD139/140 last summer. It worked but there were certain things I disliked about it. I ended up chunking it in the trash.

Ed

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PostPosted: 18 Apr 2017, 14:20 
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A friend made a Le Pacific phono stage completely on a copper clad fibroblasts board. Looked junky but he was just experimenting. Phono stages and MC preamp would benefit from the this style of copper based construction as they work with such low voltages.

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Projects: "Grace" - Psvane 6SN7-SE Globe preamp | | "VoXUno" - Single driver MarkAudio 12P speaker | | "Lagoon Take 2" - Single stage tube preamp | Website: retro-thermionic


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