Banana Jack Amps: a KILLER Amp ... literally

J M Fahey

Member
Messages
2,409
For those who are tired of life and might want to end it with a flash, search no more, https://www.kickstarter.com/projects/1335354839/banana-jack-amps-no-solder-all-tube-guitar-amp-kit are here to stay.

A seemingly nice and original idea when drawn on a paper napkin, HORRIBLY put in practice by Mr Gerry Rzeppa .
https://www.kickstarter.com/project...der-all-tube-guitar-amp-kit/widget/video.html

The idea is that you have 9 pre built (soldered, of course) modules and you interconnect them to build and mod amps "without soldering".
LEGO style of course.


Problems:

1) banana jacks are used for interconnection (duh !!!)

as it's easy to see, all have a thick 3/4" exposed ... er .... "banana" on the end, which of course is metallic and is used to carry voltage and current.

We all know the kind of voltages which are used in TUBE amps :omg

2) as shown, this amp has input on left, power to the right, with mains to the extreme right, and sequence follows classic Tube Amp signal path .

Now IF you connect left to right, the exposed tip banana you are holding in your bare hand, carries no voltage, because voltage comes from the right.

BUT if you plug any right hand banana, and hold the left in your hand while reading the leaflet or whatever, you WILL have voltage.

How much voltage?

Well, the rightmost box is directly connected to mains, so those grey banana jacks carry live :omg and neutral 120V (240V in Europe). (0:34 in the Video).
Which you can grab when fiddling with the banana.

They go to the Power transformer.

Now it starts getting better:

The PT boosts to 300+300VAC , and dutifully sends them to the rectifier tube ... through another pair of bananas, again grey but now sporting some 600VAC end to end.

Just what I needed for my homemade


I think you already got the idea.

The rectifier supplies more than 300VDC to the Output Transformer, the preamp tubes get their share (think 250V DC) , always through nice exposed end bananas.

3) By the way , even if using shrouded bananas (which he already said he won't, because they cost almost 6$ each instead of less than a buck apiece) , the flimsy plastic boxes can be opened without tools (sic).

4) don't forget to check the actual SOUND of this execution device:

https://d3mlfyygrfdi2i.cloudfront.n...mlfyygrfdi2i.cloudfront.net/cc3a/kickskin.swf

Comments ??
 

Gerry Rzeppa

Member
Messages
3
The idea is that you have 9 pre built (soldered, of course) modules and you interconnect them to build and mod amps "without soldering".
Correct as far as it goes. The design goals were three:

(1) Produce an educational kit, that
(2) Results in something interesting and useful and that is more than a toy, and that
(3) Is built entirely with "basic" or "fundamental" electronic components (like resistors and transformers rather than op-amps and microprocessors).

Problems: 1) banana jacks are used for interconnection.
I think that should be listed under "Features" rather than "Problems".

We all know the kind of voltages which are used in TUBE amps
That's why our instructions include cautionary warnings, in bold, colored, eye-catching text, on every page.

And of course our voltages are no different than any other small valve amp kit. For example, in assembling these popular kits (http://www.s5electronics.com/thome.html , http://www.modkitsdiy.com/kit/mod_102_guitar_amp_kit) the student manually cuts and strips high voltage transformer wires and solders them to the rectifier circuitry with a hot iron; with our kit, the student connects the transformer module to the rectifier module with a few color-coded banana cables. In both cases, perfectly safe operations if the thing is not plugged in; in both cases, dangerous if the thing is plugged in.

...Now IF you connect left to right, the exposed tip banana you are holding in your bare hand, carries no voltage, because voltage comes from the right. BUT if you plug any right hand banana, and hold the left in your hand while reading the leaflet or whatever, you WILL have voltage.
Only if you're fool enough to plug the thing into the wall and turn it on -- contrary to the warnings on every page of the instructions -- before you build the thing! And again, the same dangers are present in every other tube amp kit.

How much voltage? ...120V ... 300+300VAC ... 600VAC
Actually, the highest voltages carried on a single cable in the current prototype are 120 vac and 240 vdc.

By the way, even if using shrouded bananas (which he already said he won't, because they cost almost 6$ each instead of less than a buck apiece)
It's true that we've had trouble finding an affordable source for shrouded banana plugs and jacks. But we haven't stopped looking. And we're thinking of offering "cabinet, panel, and speaker kits" to compliment our modules and to support more permanent installations where the cables, once connected, would be out of reach inside the cabinet. See the photos below of a similar product from our Coppertone line.

the flimsy plastic boxes can be opened without tools.
I wouldn't call our plastic cases "flimsy"; they are precision manufactured and 1/8-inch thick. And the fact that they open, easily, is a feature -- especially in an educational product -- not a "problem". We want the student to have access to the basic components so he can study them. And for the third time, I don't see how this differs from other amp kits where the student can poke around in the open chassis any time he pleases.

Note that we hope to offer a variety of modules in addition to the nine Mr. Fahey mentions: various tone stacks, gain controls, alternate power amps; and voltmeter and ammeter and perhaps even 'scope modules as well.

Here are a couple of pictures of our prototype Coppertone amp kit, to give you an idea of how our modules (mounted to the back of the copper panels) might be enclosed:



 

Seegs

Member
Messages
10,173
Creative...interesting and most certainly educational...I don't know if the tone is the clip is representative of how they really sound but that clip sounded like a transistor radio to me thus making it more of a toy and novelty than an amp I would use for anything...

The song in the KS video also supports my novelty theory...

Chow,
Seegs
 

teemuk

Member
Messages
3,180
I remember electronics learning kits / modules built similarly. They were either discrte parts or complete circuits, interconnects made with banana plugs.

In my days they were, of course, outdated by modern "breadboards", which were more suitable for building the modern stuff that largely was based on integrated circuits.

I wouldn't prototype or experiment with concepots of a tube amplifier using a modern breadboard though, so as a learning kit this seems like a good idea. Naturally it never makes a reliable or compact amplifier. Should be evident to anyone.

If people don't understand the concepts of high voltage and current then the kit is obviously not for them. Simple as that. There will be people contesting for yearly "Darwin Awards" with every kinds of appliances, no matter how "idiot proof" you build them. That is, IMO, their problem, not ours.
 

Mox

Member
Messages
26
This may be true, but I would want an army of lawyers behind me, before I market this to musicians.
 
Messages
826
This may be true, but I would want an army of lawyers behind me, before I market this to musicians.
I agree. Guitarists are not the best at 'reading the instruction manual' and are quite used to plugging and unplugging jacks when things are powered on. I think those banana plugs could be lethal.
 

Gerry Rzeppa

Member
Messages
3
Okay folks, let's see if we can put this "safety issue" to rest by comparing apples to apples. Here we have:

Top Left: An assembled Banana Jack chassis, ready for testing, further mods, etc.

Top Right: An assembled Mojotone Bassman chassis, ready for testing, further mods, etc.

Bottom Left: A Banana Jack chassis installed in a user-designed cabinet.

Bottom Right: A Mojotone Bassman chassis, installed in a user-designed cabinet.



I really don't see why anyone would think the stuff on the left is more dangerous than the stuff on the right. Seems to me, at the chassis level, the Banana Jack kit is much safer than the Mojotone Bassman. And once they're each fully enclosed, well, they're fully enclosed.
 

loudboy

Member
Messages
27,335
That's why our instructions include cautionary warnings, in bold, colored, eye-catching text, on every page.

Only if you're fool enough to plug the thing into the wall and turn it on -- contrary to the warnings on every page of the instructions -- before you build the thing!
Which no one will read...

Hope you got a good legal team.
 

dangeroso

Member
Messages
4,492
Okay folks, let's see if we can put this "safety issue" to rest by comparing apples to apples. Here we have:

Top Left: An assembled Banana Jack chassis, ready for testing, further mods, etc.

Top Right: An assembled Mojotone Bassman chassis, ready for testing, further mods, etc.

Bottom Left: A Banana Jack chassis installed in a user-designed cabinet.

Bottom Right: A Mojotone Bassman chassis, installed in a user-designed cabinet.



I really don't see why anyone would think the stuff on the left is more dangerous than the stuff on the right. Seems to me, at the chassis level, the Banana Jack kit is much safer than the Mojotone Bassman. And once they're each fully enclosed, well, they're fully enclosed.
I agree completely with your logic and comparison as stated above. Your kit does not appear to be any less safe than a build from scratch. (although it might be argued that a banana clip might at some point pull loose, whereas a soldered connection may be less likely to, but I don't think that is what anyone here is getting at).

I think the concern is that the banana clip kit will appeal to someone with much less training and skills than a schematic diagram, and box of standard electrical components will. Heck, that's part of your business model. As your Kickstarter page states:

If you can plug a toaster in the wall, you can build your very own Banana Jack Amp.
I think that most people are reacting to the idea that high voltage electronics experimentation by people with little training is a very dangerous idea, regardless of level of warnings, instructions, and disclaimers that might be included. Encouraging people to plug and play indiscriminately is implied by your page, but may not be reinforced in your instructions. I think that is also a huge risk, beyond the basic shock risks.

Don't get me wrong, I like the idea in concept. But I think it is unrealistic to assume that someone who is not willing to solder will be willing to custom build a headshell, especially one that requires sweating of copper pipe for structure. At a minimum, you might want to include a headshell kit as a protective measure.

Good luck!
 

Gerry Rzeppa

Member
Messages
3
I think it is unrealistic to assume that someone who is not willing to solder will be willing to custom build a headshell, especially one that requires sweating of copper pipe for structure.
We use expanding Gorilla Glue to fasten our copper pipes: glue in the fitting, water on the pipe, insert, twist, done. Remarkable stuff.

At a minimum, you might want to include a headshell kit as a protective measure.
We've got two updates on Kickstarter now offering different combo enclosures. Head-only enclosures are on the way.

Thanks!
 




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