Al's AK78 microphone project...

[alk509]

Well, this one turned into an actual build, so I guess I might as well post about it in here... This is a little site I'm making about the mic I first proposed in the Drawing Board thread "Al's pseudo-C800/G7 mic idea...":

http://home.comcast.net/~alkoury/AK78/AK78.html

Peace,
Al.

 

[Kev]

Good work Al.
:thumb:
perhaps an addition to the mic meta is warranted



I think Gus may have done some C800 work at the old place ??

 

[Marik]

Cool!:thumb:

I can feel your anticipation of firing it up. :grin:
I have an idea--bypass the regulator circuit, make additional stages of RC filtering, and then make a switch, engaging whether regulated or unregulated supply. This way you will get two completely different mics in one body for different purposes.

As for power transformer. I had a good experience with a 9V toroid, using (in US) its second 110V primary with voltage doubler, as a secondary. I got one from Avel, with current twice as needed.

 

[alk509]

Thanks for the nice comments, guys!

[quote author="Kev"]I think Gus may have done some C800 work at the old place ??[/quote]

Yup, I did a search for C800 and Gus' C800-based mic popped up. No matter what mic you try to build, Gus has already been there! Twice! :green:

[quote author="Marik"]I have an idea--bypass the regulator circuit, make additional stages of RC filtering, and then make a switch, engaging whether regulated or unregulated supply. This way you will get two completely different mics in one body for different purposes.[/quote]

Another PSU arrangement to try... Thanks Marik! It's funny, I'm doing more experimenting with the PSU circuit than with the mic itself!

Peace,
Al

 

[alk509]

Power supply tested, and it looks good! Details here.

Peace,
Al.

 

[alk509]

Minor update / shamless bump. Details here.

Peace,
Al.

 

[alk509]

Added some details about the body construction process. Details here.

Peace,
Al.

 

[AudioJunkie]

Hey Al,

Quick question. How do you get the bottom of the window cut further down the body? I gave up trying to cut my own because i could do the top and sides fine, but then wouldn't get close enough to perpendicular to get a clean cut on the bottom of the window.

I bought one of those right angle attachments, but it never got to high enough speeds with the attachment.

Daniel

 

[Gus]

When I cut the openings for the vertical grill sides I first drill holes above the marked line (like the preforation used with paper) . I first cut the horizonal and then cut the spaces between on one side of the vertical and snap the other side off. Next steps, a big file then a smaller file.

If you are careful you can drill larger holes in the corners of the cutouts for nice corners in the cutout.

 

[asm]

hey al, just so you know, that site is about 13mb of pics. they are all large pics you just changed the height and width parameters of, if your going to keep them at that size, might as well re-export them smaller. that 400k pic could be about 20k instead.
ive got cable and it took about 10 sec for me, so i dont care, i just know alot of people with dialup will be sitting there all day. 13mb is alot.

 

[alk509]

[quote author="asm"]hey al, just so you know, that site is about 13mb of pics.[/quote]

Damn it! I've been uploading the wrong (larger) files all along...

Thanks for the heads up, asm! I'll fix it up later today.

Peace,
Al.

 

[asm]

np man. project looks good btw :thumb:

 

[alk509]

[quote author="AudioJunkie"]How do you get the bottom of the window cut further down the body? I gave up trying to cut my own because i could do the top and sides fine, but then wouldn't get close enough to perpendicular to get a clean cut on the bottom of the window.[/quote]

I don't use the flexshaft, right angle attachment or any other accessories to get the cutting wheel perpendicular to the pipe, I just go in at a slight angle.

It seems from your question that you're trying to get a clean-looking, finished cut with the cutting wheel... Don't even bother - that's what files are for! :wink:

Peace,
Al.

 

[ToobieSnack]

Hey al and all
your site/project looks great!
Of course the mic is nice but I just had to comment on your power supply
mann that thing looks nice...
I have been thinking of using this neumann CMV7156 (capsule and trafo only) and retro-fitting the mic with some different/better electronics.
The continuosly variable pattern is exactly what i want.
The CMV has such a minimal amount of electronics it's ridiculous.
I think I would much rather have the pattern control and an electronics update.
BTW thanks so much for going into detail at your site...explaining all the various functions of the components and reasoning for their placement.
I really actually learned a lot from your site.

the purity of the information and the simplicity of the explanation are without paralell
......thank you ...thank you......thank you

looking forward to seeing your project finished up (and mine starting up)
good luck
ts

PS are these the torriods we have been talking about ($5 torroid)?
If not can you post info/link for them?
ALSO: went to cinimag site and couldn't find pricelist.
what are these trafos going for?...pricelist link???
thanks again
ts

 

[asm]

TS,

the transformers he is using, the 2510's are 41.36$ i think each.

also, on your CMV, didnt they have a massive problem with hum because of the transformer in the body was placed wrong or something like that. maybe im wrong.


taylor

 

[alk509]

[quote author="ToobieSnack"]your site/project looks great![/quote]

Why, thank you! Glad you like it.

[quote author="ToobieSnack"]Of course the mic is nice but I just had to comment on your power supply
mann that thing looks nice...[/quote]

Thanks again. It's actually two power supplies in one box, of course (one for the heaters, one for the plate). The circuits are straight out of each Vreg's datasheet, so nothing new there. Gus and Marik have both given me so much helpful advice on how to make this PSU better, though, that I doubt this will be the final version.

[quote author="ToobieSnack"]BTW thanks so much for going into detail at your site...explaining all the various functions of the components and reasoning for their placement.
I really actually learned a lot from your site.

the purity of the information and the simplicity of the explanation are without paralell
......thank you ...thank you......thank you[/quote]

You're very welcome! It really means a lot to me to know that somebody is finding my little crappy site helpful. :thumb:

Come to think of it, ALL the information there, I learned either here, at some of our members' websites, or from books that members here recommended. So Paul, Jakob, Ethan, Gus, Marik, Chae, CJ, Rafa, NYDave, Soundguy Dave, Kevin, Joe, Fabio and everyone else that makes this place so kick-ass... THANK YOU ALL! :thumb:

[quote author="ToobieSnack"]are these the torriods we have been talking about ($5 torroid)?[/quote]

Nope. They're Amvecos from Digi-Key. Search their site and you'll find them (they're the ones that go from about 14 bucks to 20-something bucks a piece).

Peace,
Al.

 

[alk509]

OK, I've uploaded the smaller picture files to my AK78 website (except for those pictures that people might actually use in a build, like schematics, component placements and PCBs). It's at 3.4Mb, down from 13Mb. Hopefully it'll load a little bit quicker for those on slower connections, but the site is still pretty photo-intensive.

Once again, thanks for pointing this out, asm!

Peace,
Al.