SMT and tube amps

[Vorg]

Hello everybody! I fear I'm opening a black hole but, just out of curiosity: what are the reasons why Surface Mount Technology doesn't catch on tube amps?
I must confess I don't know if the newest guitar amps already use SMT technology (I'm thinking to contemporary designs with several channels, midi options etc.) but I rarely see Surface Mounted components in tube amps.
I've been seeing this change through time in guitar pedals, though: legendary manufacturers such as Boss and Electro Harmonix gradually moved to SMT, but it doesn't seem to be the case for tube amps.

I can see some voltages and wattage ratings would hardly be matched by SMT components but the production is huge, nowadays, and I think many components and devices could easily be SMT rather than through-hole, still allowing to shrink the size of boards and builds in general. I suspect RF interferences may have to do with the preference for the usual through-hole technology but here's where my knowledge stops.

Is anyone willing to shed some light on this topic? Thanks in advance!

[maxkracht]

Plenty of tube amps and hybrid amps use surface mount. This can be done well but rarely is, in my experience. A large portion of the tube guitar market is recreating classic designs, or pretending to, and looks matter to crusty old guitar players. I have worked on a handful of pedals that use oversized, through hole, components on the top of the board, and smd on the bottom board, to avoid offending the aforementioned crusty old guitar players.

The general problem I find in smd is it allows the designer to lay out a PCB very tight. This often leads to ignoring what parts get hot, and how easily an amp can be serviced. This isn't exclusive to smd, but is very common.

TLDR: guitar players hate change, and surface mount is often perceived as cheap. PCB and SMD! EEk! must have point to point and giant old things or your amp sounds bad and you're not a real man. You can design around modern parts very well, but the incentives aren't always there.

[Vorg]

Plenty of tube amps and hybrid amps use surface mount. This can be done well but rarely is, in my experience. A large portion of the tube guitar market is recreating classic designs, or pretending to, and looks matter to crusty old guitar players. I have worked on a handful of pedals that use oversized, through hole, components on the top of the board, and smd on the bottom board, to avoid offending the aforementioned crusty old guitar players.

The general problem I find in smd is it allows the designer to lay out a PCB very tight. This often leads to ignoring what parts get hot, and how easily an amp can be serviced. This isn't exclusive to smd, but is very common.

TLDR: guitar players hate change, and surface mount is often perceived as cheap. PCB and SMD! EEk! must have point to point and giant old things or your amp sounds bad and you're not a real man. You can design around modern parts very well, but the incentives aren't always there.

Totally feeling this, it's true guitar players are usually VERY conservative, and yet as long as they (ehrr... most of "us", I'd say ) don't look inside, they usually won't complain, given it sounds good. This is definitely easier with pedals (a few brave ones will open them up) rather than with amps that usually have more "naked" parts, though I suspect the technology could gain space in light of the trend of low wattage heads. I wonder how recent builds like the PRS' MT15 are like: bet they actually use SMT, though I was curious as to whether there could be technical reasons to prefer through hole over SMT. Thank you for your point, mate!

[LOUDthud]

Modifying a SMT amp is quite difficult unless you have the parts. Purchasing SMT parts in small quantities from distribution can be difficult if not impossible. Need a 10K resistor, you might have to buy 100. Same goes for repairs. If you need a part, you might have to contact the factory, especially for any surface mount film caps. Don't have a schematic and a layout diagram ? Nightmare on Amp Street.

[TUBEDUDE]

SMD is great for machines to pick and place then wave solder in a manufacturing realm.
Most of the amp service, design and building world outside of that shuns them. Why? For me it means that an enjoyable part of building is changed to a more dreadful task. Small.parts and big hands.dont mix well. Ì never enjoyed hovering over optics, using a hot air rework station with tweezers to work on tiny components.
So it converts an enjoyable activity into a tedious one, not to mention the cost of the rework station etc. And modifying an amp becomes more problematic than need be.
My personal.grab and go amp has been modified multiple times since I built it thirty years ago. Added loop, added relay board, etc. Many circuit changes that would have been a huge pain in the neck on a circuit board, but would have been an absolute nightmare on a tiny card with SMD components. So for those reasons, I'm out.
Although SMD is great for circuit card automated manufacturing, it all lives at low voltage and thermal environments. Perfect for digital.amps and modelers, maybe not so much if integrating with an environment of the high voltage, high heat confines that tubes live in.

[mhuss]

The other issue not mentioned yet is voltage rating. Resistor voltage rating is often related to size, and the inter-lead gaps tiny SMD resistors require means not a lot of high voltage tolerance. They could be (and probably are) used for input resistors, cathode resistors, etc., but could not in many locations. Same for caps, I'm not sure how many 400v + rated SMD caps are available.

[maxkracht]

I think most of the issues mentioned are with design, not surface mount technology as a whole. (aside from the lack of markings on caps which is a massive pain when troubleshooting, though arguably this is a design problem with the PCB silkscreen.). SMD vs through hole is another pcb vs eyelet board argument, you can make excellent pcbs and crap eyelets... High quality, serviceable, smd stuff exists in industrial, military, aerospace, etc., there just isn't much incentive for that in the guitar world.

SMD resistors are cheap, I buy sample books of all the 1% values for the common sizes.

1206 and larger are arguably easier to replace and rework than through hole. (If you have ever tried to wick that last bit of rohs solder out of a cheap double sided board with an undersized hole and solder pad you know what I mean.) I don't use a hot air station, I do work on fine pitch, 0402 stuff on occasion, just can't sneeze while holding it...

High voltage smd caps are available, though not much selection for film. I don't see this as an issue; no reason to ONLY use SMD on something. (I think board mounted power tubes are always stupid.) There is a better selection of inexpensive SMD c0g ceramics in high voltages. Sometimes I use these in amps, occasionally adding leads and dipping in epoxy. Resistors in series work for whatever voltage rating you need. Again, design problems not technology problems.

The individual parts aren't necessarily different than their through hole counterparts, the through hole stuff just has leads or is in a bigger package. You won't find fancy caps marketed to guitar players yet, but aside from that, hate on the cheap ass manufacturing practices and planned obsolescence, not whole technologies.

[Vorg]

I think most of the issues mentioned are with design, not surface mount technology as a whole. (aside from the lack of markings on caps which is a massive pain when troubleshooting, though arguably this is a design problem with the PCB silkscreen.). SMD vs through hole is another pcb vs eyelet board argument, you can make excellent pcbs and crap eyelets... High quality, serviceable, smd stuff exists in industrial, military, aerospace, etc., there just isn't much incentive for that in the guitar world.

SMD resistors are cheap, I buy sample books of all the 1% values for the common sizes.

1206 and larger are arguably easier to replace and rework than through hole. (If you have ever tried to wick that last bit of rohs solder out of a cheap double sided board with an undersized hole and solder pad you know what I mean.) I don't use a hot air station, I do work on fine pitch, 0402 stuff on occasion, just can't sneeze while holding it...

High voltage smd caps are available, though not much selection for film. I don't see this as an issue; no reason to ONLY use SMD on something. (I think board mounted power tubes are always stupid.) There is a better selection of inexpensive SMD c0g ceramics in high voltages. Sometimes I use these in amps, occasionally adding leads and dipping in epoxy. Resistors in series work for whatever voltage rating you need. Again, design problems not technology problems.

The individual parts aren't necessarily different than their through hole counterparts, the through hole stuff just has leads or is in a bigger package. You won't find fancy caps marketed to guitar players yet, but aside from that, hate on the cheap ass manufacturing practices and planned obsolescence, not whole technologies.

That's exactly what I thought when I got to the doubt that motivated me to start this thread, I'm glad I'm not alone in having thought about this!

[bepone]

nowadays, and I think many components and devices could easily be SMT rather than through-hole, still allowing to shrink the size of boards and builds in general.

This is not a option in high voltage circuits..and many more reasons..many manufacturers made this mistake..

Also tube amps still are keepin the serviceability feature with traditional layouts and components.. with SMD this is just one direction, from buying to the garbage only.