Which chassis layout floats your boat!

Arkless_Electronics

Yes it's possible to repair some SMD boards but usually it's not economically viable on consumer equipment IMHO. Others will differ in this opinion I'm sure....
It's one thing to do it if you are working for the manufacturer and have full circuit diagrams, access to hard to get components etc but another thing entirely to do it as a general repair guy. i.e if you work for "Acme" and fix their MkII amp all day long and do nothing else then yes repair of SMD boards is normal. It's yet another thing which makes it much cheaper to manufacture but much more expensive to repair!

Sporky

Arkless_Electronics said:

It's one thing to do it if you are working for the manufacturer and have full circuit diagrams, access to hard to get components etc but another thing entirely to do it as a general repair guy. 

That is an entirely fair comment.

DJH83004

I genuinely take my hat off to the guys that are repairing SMD technology boards, switch mode power supplies, class D amps etc. even with a schematic. I have a Tannoy active monitor in at the mo with a dead PSU and I just shudder at the thought of what I am going to find, on the other hand, there is a nice little Champ that needs a coat of looking at........let me think :-)   

Arkless_Electronics

I bet it didn't take much thought then!?

The commercial problem for the likes of us is that the piss easy to fix old valve amp is worth more than the very difficult to fix modern  active monitor... he says, stating the obvious...

How are other techs finding business just lately BTW? Don't know if it's the hot weather, holidays or what but it's dead up here at the moment. Much worse than the few weeks after xmas in fact! I've never known anything like it.... Maybe amps in the NE are having a "lets be 100% reliable month" or something!

mgaw

from the reverb article

The Myth: Neat wiring layouts always equate to great-sounding amps.

The Makers: On one hand, an extremely tidy wiring job might imply conscientious work in general, and that in itself is a good thing. But pure neatness in and of itself does not a toneful amp make.

“A lot of people love to see a chassis layout with wires that are real straight, and then a 90-degree bend, and then straight,” says Mark Bartel. “We used to call that ‘Manhattan wiring’ in the old days [in reference to the street grid]. I think that looks beautiful, but in two ways it is not ideal, really. From an engineering perspective, it doesn’t necessarily give you the best layout with the lowest parasitics [where noise from power lines stray into signal lines]. Just practically, it doesn’t always result in the best sounding layout. I got to talking to Bill Krinard from Two-Rock about this a lot, where we agree that sometimes the messy layouts just sound better. Of course, you can’t just make a random messy layout and expect it to sound better. The point is that wiring does have an effect on the sound, and just making it look neat on paper isn’t going to give you the best sound.”

i assume its fair to say that those guys quoted in the above really know their shit....

Sporky

I assume it's fair to say they don't make neat amps!

Arkless_Electronics

American gear made between about '40s and 70 tends to be really messy looking inside IME...... just saying...

mgaw

Sporky said:

I assume it's fair to say they don't make neat amps!

i would assume so too, dont change their pedigree though

Wazmeister

Here's the mystery... 

Poorly organised, messy wiring - yet every Carr (and equivalents) I've owned have been silent; even with my Strat leaned against them...

Go figure.

Sporky

mgaw said:

Sporky said:

I assume it's fair to say they don't make neat amps!

i would assume so too, dont change their pedigree though

Indeed. Clearly it's possible to make a good-sounding amp that looks like a robot vomited the wiring into the chassis, and obviously neatness doesn't guarantee good sound.

However, some builders clearly manage neat results and good performance, so it's definitely possible.

Arkless_Electronics

"messy wiring" in as much as if done properly to minimise signal paths, optimise earthing and prevent unwanted signals passing between the neatly loomed parallel wires, is technically the best. Messiness for the sake of it is another thing of course!
It's mainly in RF and very low noise amps etc that these things matter though and it's unlikely to have any effect on the sound of a guitar amp....

mgaw

Arkless_Electronics said:

"messy wiring" in as much as if done properly to minimise signal paths, optimise earthing and prevent unwanted signals passing between the neatly loomed parallel wires, is technically the best. Messiness for the sake of it is another thing of course!
It's mainly in RF and very low noise amps etc that these things matter though and it's unlikely to have any effect on the sound of a guitar amp....

some seem to think it does though...personally i know fuck all about it and care less...if it sounds great and is reliable i am more than happy...just dont see much point in the argument of ooh how nice and neat v ooh how nice and un neat

DJH83004

@mgaw, I have to say as the originator of the post, I think we have talked this one to death ! Especially considering the amps were rock solid, just suffering from NOS valve issues.........just don't get me started on the whys and wherefores of NOS valves :-)

mgaw

go on what about NOS valves are they any good?

DJH83004

Ha,Ha,

Just had some bad experiences, with customers paying a lot of money for their NOS valves, only to find they are microphonic or have a higher than expected hum floor or just generally quite fragile, particularly the long plate variety. Maybe I have just been unlucky, because I am sure if you get a good set they are tonally superb, but not IMHO in a gigging amp rattling around the back of a van :-)    

professorben

This thread makes me want to donate money to mental health charities.

ICBM

DJH83004 said:

Just had some bad experiences, with customers paying a lot of money for their NOS valves, only to find they are microphonic or have a higher than expected hum floor or just generally quite fragile, particularly the long plate variety.

My guess is that a lot of what are now sold as NOS valves are the barrel scrapings from lots that have been sifted, rejected, sifted, rejected, etc etc by multiple valve resellers over the last twenty or thirty years, especially of the rarer and most-hyped types.

Old-production valves were generally more robust than modern ones both physically and electrically. In fact, you may be better buying old used and tested valves than genuinely 'NOS' unless you're sure that the first state of affairs hasn't taken place.

jpfamps

mgaw said:

Does this mean that Carr Amps are inferior due to the layout......? 

I bought my first Carr Slant 6v cos it sounded fantastic..and they had a reputation for rock solid reliability, saying that when a friend looked at the chassis he was shocked at the state of it....hes an electronic engineer. But it and the Rambler both sound so good is that due to the layout or the design or the "ingredients"?

Not necessarily.

That method construction can be very robust, and allows a potentially shorter signal path (although this is spoilt in tnis chassis be having the valves at the bottom of the chassis and the controls at the top).

I've built several amps using this construction method and they were (are!!) low noise and stable. However the downside is changing components, say in the event of failure is harder.

When I started building amps, initially as a hobby, we used tag strip / point to point wiring as it seemed the most accessible method. 

However, if you've ever built an amp, then you often want to tweak it, and tag strip is not the easiest to remove components from as best practice is to crimp the component leads around the tags.

We soon moved to tag board, then turret board and finally eyelet board, using 3 mm PTFE for the board in the later two cases.

PTFE has excellent insulating properties, and is easy to machine (unlike say FR4 which not only wears tools very quickly but also produces hazardous dust).