Banana Jack Amps: No-Solder, All-Tube Guitar Amp Kits

[FUZZZZzzzz]

https://www.kickstarter.com/projects/1335354839/banana-jack-amps-no-solder-all-tube-guitar-amp-kit

I like how some people just wonder of in their minds and come up with this kind of stuff

[mth5044]

Couldn't watch the video, but I didn't see in the description if there was HV through those free, easy to pull out and touch banana jacks?

[italianguy63]

It's a teaching tool.  How all the parts "fit together."  I see value from a "teaching" standpoint.  But that is about it.

Last time I checked.  Banana jacks were not cheap.  You still have to "solder" each of the modules together... it's very misleading...

As MTH5044 pointed out-- potentially dangerous too.

[wavley]

Couldn't watch the video, but I didn't see in the description if there was HV through those free, easy to pull out and touch banana jacks?

Yeah, that was my first thought too.

[bool]

... gzzzzzzzttt ...

[italianguy63]

Wavley sez:

"Hey, hot wife.. hold this..."

[Luke51411]

Wavley sez:

"Hey, hot wife.. hold this..."

Secret to mad toan??? Use hot wife to make connection from B+ 

[petemoore]

  Colorful !
  Plexiglass looks cool, easy to see in there...I wouldn't try this at home.
  I'd have to drill holes between the sections and point to point solder it anyway.

[R.G.]

The repeated "Without Soldering!!" seems to be the only real advantage.

The ABC blocks approach is a good mental exercise, and good in a classroom, but unless there's some way to solidify it agains real world knocks and dings, it's going to be pretty fragile.

Fragility, version 2: woodworking is even more difficult to learn than soldering, so "a cabinet of your own design" may be a much tougher job than the amp. And woodworking can not be done without tools. 

And there's that high voltage and safety thing. I had thought that perhaps they had buried B+ and ground busses in some kind of rail or module-to-module connector system outside of the bananna hoses that could not be accessed. Nope. The pictures of the modules and the schematics and the bottom of the one module show pretty clearly that the DC high voltage is on the external wires.

The AC wiring seems to be two different modules. There's an AC power input module, then a power transformer module, making two of the nine module types. It's possible, I suppose, to make the AC input module and the transformer module individually meet safety standards, but the connection between them sure won't. I'm not sure exactly how I'd make clear plexiglass meet the flammability standards.

Then there's output tubes. Anybody here ever touch a nicely warmed-up and running 6L6? The surface of a power tube and and does get to well over 100C if everything is working well. The tube data books warn designers to keep them below 200C for best life. 200C is 392F, and well into the deep-frying range. They're a clear and present burn hazard.

Presumably the modules will be made in large quantity and from those pennies-for-a-part sources they mention. So they might be cheap. But I can't imagine the disclaimers and releases needed to sell these on the internet to some 14 year old metal maniac that wants MORE GAIN!!  without having to learn to solder.

[Gerry Rzeppa]

Couldn't watch the video, but I didn't see in the description if there was HV through those free, easy to pull out and touch banana jacks?

Hello, folks! I'm the inventor of Banana Jack amps. Sorry you couldn't watch the video -- it's one of the best parts! And yes, there's both 120 and 240 volts in those banana cables -- but only when the amp is operating, of course. And they're not that easy to pull out -- it's surprising how much oomph it takes (unlike the jacks on, say, a well-used multimeter). In any case, we figure they're at least as safe as extension and dryer cords, especially since both prongs are exposed on extension and dryer cords (while our banana cables only expose one line at a time).

[Gerry Rzeppa]

It's a teaching tool.  How all the parts "fit together."  I see value from a "teaching" standpoint... Last time I checked.  Banana jacks were not cheap...

The banana jacks and plugs are one of the most expensive parts of the kit; fortunately, there are a lot of them in each amp so we can buy in large, wholesale quantities.

You still have to "solder" each of the modules together...

Actually, no. The modules are pre-assembled; no soldering is necessary. We are considering an "advanced kit", however, where the student would solder up his own modules.

[bool]

[r.mckillop]

In any case, we figure they're at least as safe as extension and dryer cords, especially since both prongs are exposed on extension and dryer cords (while our banana cables only expose one line at a time).

When those cords are energized, the prongs are in the outlet, not exposed...

Also, your B+ banana cable is high voltage DC, you only need one conductor exposed.  If I'm standing with one hand touching my metal work table and grab the B+ with the other, I could be in for quite a surprise.

[R.G.]

Hello, folks! I'm the inventor of Banana Jack amps. Sorry you couldn't watch the video -- it's one of the best parts! And yes, there's both 120 and 240 volts in those banana cables -- but only when the amp is operating, of course. And they're not that easy to pull out -- it's surprising how much oomph it takes (unlike the jacks on, say, a well-used multimeter). In any case, we figure they're at least as safe as extension and dryer cords, especially since both prongs are exposed on extension and dryer cords (while our banana cables only expose one line at a time).

Gerry, I'm a veteran of getting power systems UL and European safety-law certified. The testing labs always told us that it was far cheaper to consult with them in the design phase, rather than testing safety in afterwards. For your own sake, I urge you to consult with an electrical safety advisor that is familiar with the homologized IEC and other world standards before you go ahead. This could be as little as paying for a couple of hours of talk time with a certification lab to show them your design. They won't be shy about telling what they see as an exposure.

I did exactly that before finalizing my amplifier design. It cost me $500, and was worth far more than that.

Whether you proceed with certification is your decision, of course. You're not required to in the USA, but juries have regarded not even looking at electrical safety issues as recklessness, and grounds for increased damage awards. In Europe, it is not legal to sell items that do not carry the "CE" mark. In the USA, you can assume that the first kid that gets shocked will have parents that will see you in court.

I am not a qualified safety certification engineer, but I have all these scars from dealing with people who are. Preface all I say with that disclaimer. I have only been on the side of trying to get my designs certified, not on the side of saying yes or no as to whether it meets the standard. Bear that in mind in all I'm about to say. I cannot tell you what is safe, only what my experiences suggest would be trouble spots.

All of those scars started itching when I saw the high voltage on banana plugs. 120 and 240 on the plugs is truly frightening. I know the rationale about the AC plug prongs exposing both conductors. But a lot of the safety testing involves things outside normal operation - such as there be no exposure of live electrical voltages to the user with any one user-adjustable item in the worst possible condition. Pulling out the down-stream end of any banana plug wire connected to over 42V DC or peak AC would (in my dim, limited understanding of the safety standards) leave a hazardous voltage on the removed plug. Any safety inspector I can remember would (I think... scars...) fail that in an internet nanosecond.

Advising people to put it in their own box probably won't get you off in court, either.

If you're using plexiglass, specify it with the appropriate flammability rating. Safety inspectors take a torch to plastics then time how long it takes them to self extinguish, and whether they drop flaming droplets before they do.

The exposed power tubes are a burn hazard. I had to design a perforated shield over the tubes in my amp design for that reason. The perforations had fairly detailed specifications on hole size as well.

The "single fault" principle in testing can be sneaky. A common test is to pull the line cord so hard it's ripped out of the box. If the line conductor could even conceivably touch the chassis after the safety ground wire has parted, it's a fail as that's putting live line voltage on the no-longer-grounded chassis. They'd grab and pull banana plugs almost gleefully. One of the tests involves hooking onto and pulling on any part with a force of 1.22 gigs... er, some number of Newtons, enough to part many wires. The result must never expose hazardous voltages at any point, even theoretically. There is a specific test involving cutting any one wire and then seeing if it's free to be exposed or to make accessible metal live. Banana plug wires are a TARGET to this kind of thinking.

I could go on, but again, I urge you to go consult with someone who is familiar with safety certification issues. The internet is NOT a sufficient place to do that. And even more to the point, convincing all of us and those on any other forum that you're OK won't help you in court.

[Gerry Rzeppa]

Thanks for the concern regarding safety, folks.

Here's how I look at it. I recently built a MOD 102 amp kit. This is what I was exposed to while building, testing, etc:



I wouldn't let my nine-year-old near it. And it's the same with all the other tube amp kits out there: Weber, Mojotone, Ceriatone, Madamp, Torres, Guytronix, Mission, etc.

On the other hand, this is what the student is exposed to when building a Banana Jack Amp:

https://www.youtube.com/watch?v=NJF2doDu3IY

My nine-year-old puts them together with ease and just one rule: Don't mess with the wires when it's plugged in. (He's nine, so he already knows not to touch potentially hot objects like stoves and light bulbs. And he's had lots of practice plugging things like TVs and wall-warts and extension cords into receptacles -- even live receptacles.)

Comparing the two approaches, I'd venture to say that the Banana Jack Amp Kit is the safest tube amp kit ever made.

[R.G.]

It's not anyone here you have to convince.

Nobody ever said the other kits *are* safe, or that yours was as bad or worse. Or that you can't do this and get away with it for a long time, perhaps forever.

I wish good fortune and health for you and yours - and I advise you to go talk to a practicing electrical safety specialist for an hour or two for a bit of informal education. It will be money well spent, whatever you decide to do.

[commathe]

It should be pointed out that there are "safe" banana jacks for high voltage signals, as banana jacks are often used for this purpose:



Sorry for the Chinese watermark, but you can still see that the top is coated and there is a sleeve so that you wouldn't be able to touch anything conductive.

[R.G.]

It should be pointed out that there are "safe" banana jacks for high voltage signals, as banana jacks are often used for this purpose:

Sorry for the Chinese watermark, but you can still see that the top is coated and there is a sleeve so that you wouldn't be able to touch anything conductive.

Interesting. I'll remember those. I was glad to see you put "safe" in quotes. Those would be good for not having part of the actual plug exposed from a partially-inserted plug.

However, consider this: there are two ends to each banana plug wire. Let's say it's one of the deadly dangerous ones, the one with 120Vac on it from the power switch module. You have both ends inserted, turn the amp on, and there's some issue with the speaker not being connected, so there is no sound. You forget the power switch is on and start messing with plug wires and pull out the end of the 120Vac plug wire furthest from the power module, so it's still good and live. If you have good grip on the plug, the plug comes out of the socket and you have the live plug in your hand. The plastic ball cap on the ends of the specially constructed plug tips keeps you from touching the end of the plug. Good.

But if your grip wasn't so good, and your fingers slipped off the plug, catching on the wire, and the wire pulls out of the plug. Or the wire breaks right at the end of the plug, that being where the mechanical stress is. Now you have a live 120Vac wire in your hand. All you have to do is touch the end...

The safety standards explicitly call out that the unit must not expose hazardous voltages to the user even with the breakage of any wire, the worst possible positioned wire being selected for the test. In this case, that would likely be the 120Vac line voltage wire.

On the more practical side, those look like true marvels of the plastics and machining art, and may be a tad more expensive than standard banana plugs, which are already the most expensive part of the setup, we heard. There may be only one supplier, or only one supplier of compatible ones.

[commathe]

I live in China and its actually easier for me to get my hands on the safety banana plugs and jacks than the normal kind, which has been frustrating for building my modular synth. 2mm mini-bananas are also easy to come by but I've never seen them on European supplier's sites.

The safety jacks are also rated to 1000V/32A, but I take my Chinese safety standards with a pinch of salt.

[Gerry Rzeppa]

We've been looking into the "sheathed" banana jacks and plugs. Have yet to find a reasonable supplier. A standard plug, for example, in quantity, runs us about 82 cents; the cheapest equivalent in the sheathed style (that I've been able to find) is well over 5 dollars. Apparently somebody is making a bundle on safety issues. Probably the same guy who got the electrical code changed to require half a dozen smoke detectors in a 1200 square foot house.

Makes one wonder how things like this ever get approved for the home user:



Now that's scary!