A better amp Prototyping platform

[austinb]

What do you think about a versatile " card cage in back " tube amp platform. What I am thinking about is 3 channel amp with a vertical card cage that uses card fingered connectors. One card between each pair of 12ax7's. First card will be a 4 effects card, second card preamp 1, third preamp 2, fourth card preamp 3, fifth card splitter, output, summing, master gain, and boost, sixth card switching, seventh card power supply. The switching card to use standard Protocall IC's for "MIDI or serial RS422 or USB " to encode and decode switches. Then the switching card be static ram configurable from computer. Because everyone don't have axcess to a programmer. You will have to have some computer interface firmware tho. So each preamp card can be what ever amp you want with a standard card edge connector and pin assignment. Those with programing experience can create programs for control of switching and tone stack calculator to calculate cap value to use standard value pots when converting a preamp design to this amp platform. Those with different skills can help design and come up with the standard connector pin assignment to be the most versatile platform. I'm thinking a 3 bit code on preamp board to select a table lookup of switching control. That way a person could change a amp card to be a different amp at gig and the lookup would be in place for its special control needs. The time and money savings for different amp building would be tremendous after the platform is built. Those that like eyelets can do eyelets on the pc board. Just need the fingers and standard size pc card. This could be group forum effort if the idea is liked by enough people.

[CaseyJones]

Great idea. Except that Bruce Egnater holds the patent on it. Which is dumb because card frames were used for all sorts of apps way before Bruce used them.

[austinb]

This not to sell. Its a bonified breadboard that will look like a finished amp for hobby amp builders.

[drz400]

Geeese why is everyone so slap happy patent crazy.
The Duncan amps had removable PC cards as well with the tubes on them.
The problem is I don't have faith in any connectors, connectors corrode and oxidize. The Egnater thing is a great idea but boy are those some heavy amps.

[CaseyJones]

Geeese why is everyone so slap happy patent crazy.

'Cuz dammit if I'm gonna work I'm gonna get paid.

You're right, the Duncan amps pre-date Egnater's use of the concept so the patent is probably worthless.

It's a great idea. I'd use some heavy duty connectors like what Tektronics used in their '50s or '60s scopes. Lots of nice parts in those. The digital section can be its own thing. Laptops take a beating. Some of them even last a while.

[Wayne]

I think ax84 tried some sort of modular design a while back, but without the control circuit - pwr supplies, preamps, and PI/poweramps of standard physical dimensions that pinned out the same on a 12 pin molex connector. I think the deal was that if you wanted to build and carry a few different modules, you could configure for just about any situation. Dunno how it worked out, I haven't looked around over there for ages.


W

[iknowjohnny]

The problem is I don't have faith in any connectors, connectors corrode and oxidize

Boy did you ever get that right ! I would NEVER use any kind of connectors in a quality amp. It's bad enough having to use switches and jacks which can corrode and oxidize, but connectors that aren't plugged and unplugged on a regular basis is downtime at a gig just waiting to happen. Any connector thats not used regularly will w/o a doubt oxidize sooner or later, usually sooner.

[Phil_S]

Patent issues aside, there are a few crusty old guys who just like a flat chassis, a soldering iron, and terminal strips. This is an idea that I don't think will appeal to the average hobby builder. Back to the the patent issues, without deep pockets, you will have a hard time getting such a thing into production.

Now, setting aside all that negativity, just 'cause it doesn't float my boat doesn't mean a thing. If you really hatched this idea on your own (or even if you got it from looking inside a computer), you deserve credit for looking at this from a different perspective. I like inventive minds and intellectual curiosity. Such is the foundation of all the good things we have today. Inventors tend to fail many times before they get it right, so just keep pushing ahead and see where it goes.

There is, in my view, no way to know what is on the path no one has taken before, so it is as much about the journey as the destination.

[chromaticdeth87]

sounds to me you are techno savvy enough to pick up some DSP coding, that is what I'm looking into now. Yeah, yeah, it's digital, but soon they will have them in pedal form, like line 6 and others are trying to accomplish. The only thing I see where Duncan failed and where (eventually, in my honest opinion) Randall and egnator fail are to truly incorporate the average Joe into their products. Like this, I don't want to spend 250 to 300 for a module anyway, pro or not, and be limited to a three channel or the four channel preamp, that I can't have a schematic for and be actively involved in creating in modern terms "patches" that I can trade and sell with friends. Yes I know Friedman does mod these things, but what about starting from scratch? Customizable, unique modules/patches that could be the next great thing in guitar tone history. Things like hardware that are capable of loading VSTs and other programs without a laptop and could be had by almost anyone. A virtual environment with no High voltage risks and a pedal that you could cart and feed into a PA anywhere. I think hardware is iportant there is nothing like selling new tolex and feeling a knob twist in your hand, but what if you just want to prototype and then build something without costly R&D? Well go to a virtual platform throw an EF86 preamp into a low headroom PI and out into a 15W 6l6 power amp and hear what it might, *might* sound like if you built it from the ground up.Throw that onto the web and see what another amp guru might have to say and tweak about it.

[austinb]

chromaticdeth87 you are the first one to get it. This is the ultimate breadboard tool to experiment with different amp designs and to tweek on before you build the real thing. It can be built up to the point that you would need to do your experimenting and leave off the parts you think that you would never use. The benefit is you can experiment with what ever section you want and the rest of the amp is already in place and working. You don't have to buy the rest of the parts if the experiment don't work out. You haven't wasted time building the whole amp to find out this isn't the sound your after.

[skipm45]

I work in "real life" in the world of hi-rel computer hardware design.

I find your concepts interesting and I personally think it would be an intriguing project. That said, I think that the firmware / driver effort would be somewhat daunting (certainly for me anyway). Probably the easiest way to acheive USB or RS422 connectivity would be to use a full blown embedded system of X86 or even RISC architecture.

Regarding connectors, you would not want to use "cheapo" connectors at all. No tin plated connectors, gold plated connectors and /or edge fingers on the plug-in cards would be the rule. Also, locking type connectors and/or a card retention system would be a requirement

We are beginning to stray outside the realm of vintage amps (we've fallen off the cliff actually) , but out of the box thinking is kinda fun

Skip
www.skipzcircuits.com

[austinb]

Everyone seems to be afraid of connectors. Do you have any idea how many connectors are in a airplane or even a car. You risk your life on those. Especially the abs brakes. Theirs connectors in almost every electronic gadget. Your appliances have high voltage, high current connectors. True a bad connector selection could give problems. The breadboard allows modular design. That's its best usage. The switching I'm talking about is only relay control from foot petal board. This can be simple design or complicated design. only one preamp slot has to have a preamp in it for simple design.

[chromaticdeth87]

To me it's really all the costs of R&D, that's really where duncan failed and egnater didn't. While the airline, car, and appliances industries spend millions on it, and while egnater probably spent thousands, this small cooperative probably has a budget of hundreds. Now if this was to be brought up in an academic community then the budget could be several thousands. I guess I take more of the DSP side of this interfacing with hardware and converting them into digital coding. Would I like to see an express,liverpool, rocket in VST form? hell yes. double hell yes. Kinda like the new Vox product interface. I like firewire better than usb, but an module with the usual copper fingers or serial bus connection could use a revamping. I would rather see, a cord coming off and into the test bed amp. I agree austinb that this has and should have always been on designers minds for a long time, and now is the best time to do it. I liked hughes and kettners as well as rockman's ideas about small tube driven pieces that could be used as preamps, but the power amp has always been an issue even for randall users, they want to mod their RM series to have more bass,less bass, more mids, a better presence and resonance control, and that is always what is most ignored, while most integral to the amp's sound. Like guys who have built the bogner ecstacy's preamp and say "wow, this is thin and buzzy what a sham" well, you have to put that in with a good hundred watt marshall power and PI and you'll see the difference right away, that amp relies heavily on a nice tight power amp. I like the THD idea of being able to use, through general bias several different tubes, and I suppose that we'll need to think about a transformer that would have to be wound to meet those specifications, as meeting the consumption needs of the preamp and a nice addition of the opputunity to choose between a solid state or tube rectifier. As I can see a transformer with a b+ that could reach up to +-600v 6.3v winding that had about 8 to 10 amps for your given choice of preamp and power amp selections, 5v 1-3 amps for a tube rectifier, and primaries of 120,220, or whatever you may need and a common. switching may take another tranny or just include another winding.

[Ron Worley]

I work in the avionics world in aviation and today's new avionics suites are all card based processors that essentially model a formerly discrete box's functionality in software. Other than some small differences, the Honeywell Primus Epic avionics rack (on a Gulfstream 550 for example) has about 10 cards that are totally identical- but their functionality runs the gamut from Navigation, Communication and surveillance applications.

I would not be afraid of rack edge connectors, but you get what you pay for. Aviation grade ARINC backplane connectors are several hundred $$ each, so they would not likely be a good choice. But the point is that aircraft have been using card / rack based systems for many years and their reliability requirements are so many orders of magnitude higher than commercial guitar amps, it's not even a comparison. So I think that your rack concept has some merit for prototyping.

Where I would be concerned would be the inability to model or see the effect that lead dress has on amps. I have always known the general lead dress was important, but when you build an Express, you really begin to understand that it is part and parcel of how the amp sounds and behaves....

I will follow this thread with great interest!

Ron

[austinb]

Finally some people that don't have only negative comments. I could use some suggestions of connector types to start with. I am now thinking a hinged top where the cards plug in from top. That way the leads are the shortest from the tubes and pots to the connectors mounted in top of the chassis. The top would hold the cards down tight. That way lead dressing wouldn't be an issue. All high voltage, high current gets more than one pin. That way if one pin fails the other or others would still be able to handle the load. As far as oxidation problems, keep the amp out of the bad humidity. If not gold plating fingers then tin them with solder then wipe with rag while still hot.