building etiquette

[andresound]

Not amp related, but here is a pic of a distribution board from a home we were called on to integrate with CRESTRON automation. Naturally.... we declined and ran away!!

[pompeiisneaks]

As pointed out by others, most peoples experience with PCB amps have been commercial, value engineered pieces of crap. Maybe a new sub-forum could be started here to explore well executed PCB designs and develop some best practices.

I think it would be cool to develop some standard boards for power supplies, tone controls, etc and do group purchases...

I'm okay creating that, I had a decent amount of push back when I thought of expanding a while back, since many other good forums seem to be dying, it may be good to absorb some of those types of interests, but anyway, maybe start a post in general discussion with your suggestion and see if people are amenable to it @stephenl

~Phil

[R.G.]

The stuff on geofex was developed in part by visiting amp techs and asking them what NOT to do. They were not subtle in their replies.

One tenet of all good engineers is that you should try to make it last forever (within what your boss will let you make it cost); but if you just can't make it last forever, at least make it easy to repair. That gets lost in an MBA-Disease ridden world.

Guitar amps live a tough life. They share the same enclosure or air space with speakers producing shaking at all audio frequencies and up to nearly jet-engine levels. They are dropped, fall off speaker cabs, and tossed into the backs of U-Haul trailers in the wee hours of night, sometimes by people NOT their owners.

Hand wired amps get by this (mostly... ) by having excess flex in all the component leads. Wires wandering around in 3-space can flex, and tend to only break at discontinuities - the ends. They're mostly spring mounted, leaving out the metal-lump transformers.

You can't do that with PCBs. The designer has to support the PCB so it doesn't flex beyond its elastic and fatigue limits. Fortunately, fiberglass is a better spring material than copper or steel wire. You just have to know how to use it. And support it.

Hand wired amps put the controls off on flying wires, which is good for servicing. You need to replicate this in PCB amps. The MBA practice of putting all the controls, jacks, and switches on the edge of a PCB will inevitably result in cracking PCBs or cracking solder joints. Not to mention what I remember fondly of a bearded and grizzled amp tech who pointed out a M@4$@LL head he was working on. He described in detail taking all 20 knobs off the pots, taking the nuts and washers off all 20 pots, four switches, and four jacks, removing the six PCB mounted connected cable plug ins, unscrewing the six screws holding the 18 x 3" PCB down, and wiggling the PCB out of the tight-fitting enclosure past the back panel and transformer to get at the parts. He pointed out that once he thought it was fixed he had to put it back in to test it.

If you do a PCB amp, put the PCB where you can run the pots, switches and jacks off on flying wires. In the Workhorse amps, dropping off the back panel had pots, switches, and jacks on wires right inside the back panel. The PCB didn't even have to come out for testing, as it was all visible and probe-able with only the back cover off. Replacing a pot required unsoldering three wires, removing one knob, nut, and washer, the putting the replacement pot in place, replacing washer and nut, and soldering three wires to test. Same for all controls, switches and jacks.

The PCB was 0.090" thick - we couldn't get 3mm/ 0.125" in time for production - and had two-ounce copper, as well as two copper plated steel stiffeners soldered down the length of it in about 12 holes for each stiffener. The stiffeners were grounded, so they served as a local clip-point for grounding scope probes. The boards were held into the chassis with sixteen screws - which didn't have to be removed from the chassis for access to the back/solder side of the PCB to replace parts on the PCB. A cover panel over the back of the PCB let you get to the back side of the PCB without removing the PCB from the chassis.

... but I digress.

[Rockwell666]

You know...I'm a new builder (hobbyist mostly). I don't know which camp I'd be in, honestly. My Bassman build may look as bad as the Jim Kelly amp to some of you, but I was proud of it as my first amp. I'm very green admittedly, so I don't know everything I should about lead dress, grounding, etc.

To be honest, I don't consider myself to be OCD by any stretch about it. My first goal was to make an amp that worked #1, and sounds good #2. Time will tell. I'm more about function than anything, and consequently I am drawn to simpler amps. Thinking about wiring up a feature laden amp with 12 knobs has no appeal. I think I'll end up being neater because I like simple things.

Here's a shot of the amp I made. I can admit that it looks to be on the sloppy side, but I do hope to improve over time. As a side note, the amp sounds fantastic!

that's clean for a build. my original point was that if your going to sell a product, straighten the leads, spend the time to make it look half organized.

[Rockwell666]

I started building my amps on PCB's when I realized it's much easier and cheaper to design a PCB and order it from China than to buy a tag board and eyelets and hammer them in place. Unfortunately the interiors of my builds haven't become any neater than with eyelet boards, because now I end up cramming more stuff in to a smaller space.

This may look messy, but for how much you got crammed in there its more impressive!!! I am a point to point kinda guy and it requires some degree of art to bend and shape the components into a quiet, good sounding amp.

[fevzay]

You know...I'm a new builder (hobbyist mostly). I don't know which camp I'd be in, honestly. My Bassman build may look as bad as the Jim Kelly amp to some of you, but I was proud of it as my first amp. I'm very green admittedly, so I don't know everything I should about lead dress, grounding, etc.

To be honest, I don't consider myself to be OCD by any stretch about it. My first goal was to make an amp that worked #1, and sounds good #2. Time will tell. I'm more about function than anything, and consequently I am drawn to simpler amps. Thinking about wiring up a feature laden amp with 12 knobs has no appeal. I think I'll end up being neater because I like simple things.

Here's a shot of the amp I made. I can admit that it looks to be on the sloppy side, but I do hope to improve over time. As a side note, the amp sounds fantastic!

that's clean for a build. my original point was that if your going to sell a product, straighten the leads, spend the time to make it look half organized.

Thanks, it turned out to be a great amp!

Understood and fair point. When purchasing an amp, I'd certainly expect better lead dress than my own. LOL!

[Rockwell666]

As pointed out by others, most peoples experience with PCB amps have been commercial, value engineered pieces of crap. Maybe a new sub-forum could be started here to explore well executed PCB designs and develop some best practices.

I think it would be cool to develop some standard boards for power supplies, tone controls, etc and do group purchases...

I see this in the hi-fi community alot. great idea

[pompeiisneaks]

As pointed out by others, most peoples experience with PCB amps have been commercial, value engineered pieces of crap. Maybe a new sub-forum could be started here to explore well executed PCB designs and develop some best practices.

I think it would be cool to develop some standard boards for power supplies, tone controls, etc and do group purchases...

I see this in the hi-fi community alot. great idea

Seems seconded, but I'd love to have a few more people chime in saying they want it, if so I'll spin one up.

[xtian]

Do it, Phil!

[dorrisant]

I 2nd that!

[pompeiisneaks]

Okay here in the Shop Talk section I've added a new forum section called "PCB Design" that people can use to post PCB files, and discuss design etc.

Let me know if anyone thinks I should add more to it than that.

~Phil

[dorrisant]

Phil, I don't see a way to post a new topic there. Am I missing something?

[xtian]

Yeah, man, permissions are harsh.

You do not have the required permissions to read topics within this forum.

[pompeiisneaks]

Gah let me look.

[pompeiisneaks]

I don't see how to set the settings, but I did see I could copy another forum's permissions, so I copied over from the Tech Discussion one. Can someone try again?

~Phil