3886 LRxover biamp speaker project... maybs kits, comments please.

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hi ive been lurking around here for a few years. a lot of what i know about linear design and IC audio comes from this forum and elliot sound products, in parallel with my academic studies in electronics and CNC machine tool technologies.

i have been working on this for awhile, with the intention of basing future projects off it and selling kits.

www.darkertechnologies.com/projects/darker_biamp/

the circuit boards are single sided, unclad (Milled Circuit Board, MCB, is neato stuff). they can be had for a couple dollars each, shipped, in nothing quantities (because i have a .001" capable CNC machine in my bedroom =).

having recently aquired the toroids for the projects, i simple need to design a psu board for the project before i begin testing the MCB for this project i have already. it runs in sim like youd expect any 1% filter component LR crossover to behave. (very nicely)

it occured to me there might be interests for a group buy here, for some or possibly all of the components.

this is my sites first project article. please forgive its very rough form, as it is still in progress. currently the link is a parts list, schematics, cnc early milled circuit board examples, and concept cad drawings of the cabinet design.

the design is a powered biamp speaker system. dual 5.25" woofers and dual 1" silk dome tweeters (yay dayton audio and partsexpress.com), both the shielded 8ohm varients, driven directly by lm3886 gainclones.

crossover boards are linkwitz-riley, designed with 1% polypropylene caps and a 1100Hz xover freq in mind, and include a buffer stage for impedance matching, which can be configured in NI mode or voltage follower mode. controls include master volume attenuator, and full cut attenuators before each of the L-R aligned active filter sections for bass and treble control.

power is 400VA toroids, panasonic FM and TSHA caps (or chemicon equivalents, KZE and KMH), 0.1uF tantalums for the chipamp, 7815/7915 regulators for the preamps, which are followed by more FM/KZE caps, and more 0.1uF tantalums.

comments would be appreciated. criticism is welcome, but dont be retarded. design theme is minimal, like the einstien quote.

thanks in advance, i know alot of you on here have some broad knowledge relating to the matter that you can share.
 
well, the cabinet and speaker choice is more a personal thing. i was planning on kits for the psu, preamp/xover, and the gainclone boards, after some refinement. the full project is kinda an example of what can be made with the modular parts.

i do plan on eventually selling custom reference models of my popular projects, with different enclosures and parts. cnc mill was a semesters worth of grants and loans, might as well make cool stuff with it, no?

dual tweeters was for power handling overhead, each tweeter being driven far less as hard than a single unit would be. things usually behave better when theyre not pushed as hard.

the HPF and LPF sections both have their own buffer/gain sections, so max power can be set as needed for that section of drivers.

after the buffers, there are passive attnuators, so you can adjust levels of both driver sections, down to full cut. (you know cuz sometimes when people are hanging out and everyones talking you wanna kill those highs so everyone can hear everyone else...)

the NI buffers can easily be configured for voltage follower operation with solder bridged or zero-ohm resistors, and the pots for control of the highs/lows can easily be bypassed in the same manner.
 
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hi ren,

Execellent work, I guess you've put a lot of time and effort into all aspects of this venture. It good to see you combining all your interests and studies in this unique manner.

Can you post a link to info on the CNC machine?

C10 on your PSU schematic seems way to big. Double check that.

Have you tried generating traces using the outlines generated by eagle? Not that there is anything wrong with your approach.

Have you tried generating a silk layer using your CNC machine?

I use VAF DC-X which have twin tweeters. ;)

regards
 
ooooh... yes. the big cap supposed to be 4700uF 100v. thank you for catching that, as i said the site is still in progress, and the psu is the last thing left.

cnc is a 3 axis machine, 12x5.5x6" travel on the xyz, like a badass engraver, or a cute mill, depending how you wanna look at it.

taig-tools.com is where the mill comes from...

xylotex.com is the stepper driver i have...

http://www.dakeng.com/turbocnc.html is the gcode intepreter im currently having the best luck with.

ive just recently gotten enough tooling to start doing parts i want with it. hehe, and getting used to the speeds anf feeds. we have huge Haas and Bridgeport machines at school. 1/4 HP on the taigs spindle motor isnt quite the same, really gotta take it easy.

it does step at .00025", tho =)

and ive havent tried the eagle .ulp on the machine yet. the gcode runs in sim pretty tho. when i finalize the hand CADed MCB, i wanna do designs with eagle, compare performance. i can make arguments why both would be better/worse so i figure best to just try.

copper panels are $2 at all electronics, for 4x6". i dont have to pay shipping cuz theyre a few miles down the street =D

im using a vise and some modified parallels for now as a panel fixture, but i should have some specific fixtures made up soon to make milling MCB very quick.
 
er, sorry...

taigtools.com (no dash)

they have a lathe, too. no autofeed/thread screws, tho. and i dont believe there is a common CNC setup for it yet.

google for sherline for the closest competive mill...

emc2 (realtime linux) and mach(winNT) are the alternatives to turbocnc for gcode interpretation...

gecko drivers are competitive with xylotex stepper drivers, also other companies i dont know off the top of my head.

mines an open loop machine (controller doesnt really know where the machine is, it assumes the steppers never fault, heheh...), but close loop setups and conversions arent uncommon.

if you dunno what gcode is, you can open one of those excellon format drill files PCB apps usually output along with rs274x gerber files. just use a text editor. thats spec gcode that CNC machines eat.
 
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