Topic: AKG Active Project part 3

[Teen Wolf Blitzer]

I believe this is what Busman is developing as well.  Same cap style.   I hope to be running a test pair at Pickathon.   

[Chuck]

I believe this is what Busman is developing as well.  Same cap style.   I hope to be running a test pair at Pickathon.   

Nice. I am slowly becoming a fan of those capsules.
They do need some refinement, but they do sound good to me for very little money.

[illconditioned]

I cut about 1" off the end of the mic and ...

Now that's f'n hacking

I've got two sets of C4 (with cardioid caps), both loaned out.  This is a third set I obtained, just the bodies + omni capsules.  I got them because one of my original bodies died.

So now I've got a bunch of omni capsules.  I'd be interested in cheap deals on specific capsules known to fit these threads.

  Richard

[illconditioned]

To mshilarious (if you're listening, you seem to have blocked PMs):

I'm looking for a phantom power generator.  A step-up chip, to go from say, 9v to 48v @ >=1mA.  A set of my "actives" would take approx 1mA (0.5mA each channel), maybe a bit more, just to be safe.

I'm thinking of building a battery box.  It would operate in two modes.  In one mode it would operate as a standard phantom power generator, like the Dencke (sp?) PS-2.  In the second mode it would power a pair of actives, that is, it would supply +48V (or so) @ 1mA bias to the capsules, then run (unbalanced) lines into a miniplug for the recorder.  Maybe the unit could have a switch 24/48V, so it could run some mics that play nice with lower phantom voltages.

Hey, would you bulid this for me?

  Richard

[mmedley.]

Someone should contact this guy. They did a TV show on him on Science Channel called 'Ingenious Minds'. He could knock this shit out in a week I bet...seriously.


http://science.discovery.com/tv/ingenious-minds/bios/john-robison.html


John Robison


John Robison never had a high school degree, but he worked as a highly skilled mechanical engineer designing sound equipment, special effects, cutting-edge toys, nuclear test apparatus, and medical lasers.

John is a savant with Asperger's Syndrome, which has given him a preternatural understanding of mechanics, but has made his social and work life exceptionally challenging.

John is working with Harvard researchers on trying to improve his social cognition and empathy through Repetitive Transcranial Magnetic Stimulation, or RTMS. By speeding up or slowing down areas of John's brain, the researchers hope to stimulate mirror neurons, which they believe could help John understand the intentions and feelings of others.

[audBall]

^Dude worked for Kiss also when he was young designing some of Ace Fraley's live effects. 

Interesting read by him:  http://www.amazon.com/Look-Me-Eye-Life-Aspergers/dp/0307395987

/sorry for the hijack, carry on

[Chuck]

I have a version of the PFA that will provide 45V and 13V rails to the capsule.

That's what I've wanted to hear! I love that idea.

[illconditioned]

To mshilarious (if you're listening, you seem to have blocked PMs):

I'm looking for a phantom power generator.  A step-up chip, to go from say, 9v to 48v @ >=1mA.  A set of my "actives" would take approx 1mA (0.5mA each channel), maybe a bit more, just to be safe.

I'm thinking of building a battery box.  It would operate in two modes.  In one mode it would operate as a standard phantom power generator, like the Dencke (sp?) PS-2.  In the second mode it would power a pair of actives, that is, it would supply +48V (or so) @ 1mA bias to the capsules, then run (unbalanced) lines into a miniplug for the recorder.  Maybe the unit could have a switch 24/48V, so it could run some mics that play nice with lower phantom voltages.

Hey, would you bulid this for me?

  Richard

littlebox can do that, tinybox can support the active capsule directly at up to 100uA (it has a separate 16V rail that can provide several mA for the FET).  I have a version of the PFA that will provide 45V and 13V rails to the capsule.

I don't do a box without an amp because once you've got a battery, case, connectors, PCB, and DC converter, the amp section is only a few bits more . . .

I'm wondering, could I get a schematic of the littlebox?  At least the part that does phantom power?  I recall seeing you post info a while back, but I don't think you had phantom in the circuit you showed before.

As far as having an amp, I'm thinking "less is more".  I would rather just put the mics directly into a Sony PCM M10/D50.  The amp in these is just fine, even for recording quiet sounds.  My ideal setup would be the smallest possible box, just phantom and a power switch.  No levels to worry about (except on recorder), and good battery life.  I also think there would be a market for these.  Lots of people with phantom mics and flash recorders.  And the PS-2 is just too bulky, and probably not very good on batteries.

Anyway, thanks

[illconditioned]

I did post the full schematic a while back, but even on the power side there are many parts that aren't directly related to phantom.  Basically it's MC33063A with a cascoded MOSFET such that the chip's rating is not exceeded.  Get the lowest DCR inductor you can fit and a very low on-resistance 60V MOSFET.

There are more efficient converters than MC33063A, but I stick with it because it's nearly bulletproof whereas some others I have tried tend to die of unnatural causes on the breadboard.  Plus the nicer stuff is usually SOT-23-6 or smaller . . .

I really have no interest in developing a phantom supply.  The desire for simplicity is nearly always trumped by the need for a differential input amp to follow balanced output mics.  See DSatz's many illustrations of that principle when people can't figure out why transformer-output condenser mics into DS2s into unbalanced input recorders don't work.  And even mics that are happy running unbalanced . . . well, that still means they are unbalanced from the mic all the way to the recorder.  That defeats a primary advantage of professional mics; noise rejection that permits use of very long cables.

I understand you will not have that problem, but many others will so I just avoid the product.  It's just not a good value from my perspective when I can supply a full preamp for $40 more.  Really, it saves two pots, two ICs, and about 20 small parts.  Take away another 20 small parts for the meter.  I still need the box, switch, battery tray, connectors, PCB, DC converter circuit with its big capacitors, input capacitors, and associated several dozen small parts . . .

Thanks for the reminder, I'll look up that part.  About stability, I've noted some phantom power generators don't start up right.  For example on my Fostex FR2-LE, I notice that I sometime have to remove and replug my mics to get phantom voltage on them.  If I just hit record, the levels are really low.  When I remove and replug (with phantom on!) they come up to the proper level.  Never figured out why.  I always wonder if this hurts the mic and/or recorder, but I just live with a big "pop" at the beginning of the recording.

Re: gain.  OK, I get it.  Balanced input is an issue I had not considered.

Hmm.  I wonder if a (fixed) unity gain setting might be feasible (or maybe you've already got this?).  Either a bypass switch, or a minimum setting on the pot that is unity gain.

  Richard

[willndmb]

I did post the full schematic a while back, but even on the power side there are many parts that aren't directly related to phantom.  Basically it's MC33063A with a cascoded MOSFET such that the chip's rating is not exceeded.  Get the lowest DCR inductor you can fit and a very low on-resistance 60V MOSFET.

There are more efficient converters than MC33063A, but I stick with it because it's nearly bulletproof whereas some others I have tried tend to die of unnatural causes on the breadboard.  Plus the nicer stuff is usually SOT-23-6 or smaller . . .

I really have no interest in developing a phantom supply.  The desire for simplicity is nearly always trumped by the need for a differential input amp to follow balanced output mics.  See DSatz's many illustrations of that principle when people can't figure out why transformer-output condenser mics into DS2s into unbalanced input recorders don't work.  And even mics that are happy running unbalanced . . . well, that still means they are unbalanced from the mic all the way to the recorder.  That defeats a primary advantage of professional mics; noise rejection that permits use of very long cables.

I understand you will not have that problem, but many others will so I just avoid the product.  It's just not a good value from my perspective when I can supply a full preamp for $40 more.  Really, it saves two pots, two ICs, and about 20 small parts.  Take away another 20 small parts for the meter.  I still need the box, switch, battery tray, connectors, PCB, DC converter circuit with its big capacitors, input capacitors, and associated several dozen small parts . . .

Thanks for the reminder, I'll look up that part.  About stability, I've noted some phantom power generators don't start up right.  For example on my Fostex FR2-LE, I notice that I sometime have to remove and replug my mics to get phantom voltage on them.  If I just hit record, the levels are really low.  When I remove and replug (with phantom on!) they come up to the proper level.  Never figured out why.  I always wonder if this hurts the mic and/or recorder, but I just live with a big "pop" at the beginning of the recording.

Re: gain.  OK, I get it.  Balanced input is an issue I had not considered.

Hmm.  I wonder if a (fixed) unity gain setting might be feasible (or maybe you've already got this?).  Either a bypass switch, or a minimum setting on the pot that is unity gain.

  Richard

fwiw
i have never had my mics not power up on the fr2le
and i have been told its not a good idea (generally speaking) to plug mics into a hot 48v source

[setboy]

fwiw
i have never had my mics not power up on the fr2le
and i have been told its not a good idea (generally speaking) to plug mics into a hot 48v source

what he said ^

[igene]

I was supposed to be working on a video project today, but my project computer crapped out and won't load windows.
So I gave up on that for the day and moved onto a project I've been wanting to start.
I have AKG H98 / MK90 3 cables that went bad. The wire is so thin that it gets damaged easily.
So instead of fixing it to OEM spec, I decided to do an active cable mod.
I had the AKG connects, so I didn't have to do a ghetto job.

I had ordered new cable from Sound professionals. It came this morning.
It is 50% thicker than the AKG wire,
so I had to drill out the entry hole a bit, but no issues.
Also, I had to manage a grounding ferrel that I was initially unaware of.
Soldering and reinserting the contact rig was a bit of a challenge, but I got it.
Long story short, here is the first one finished and tested.
Works great and looks great.
I tested it with a CA-9100.
I can't wait to do the other one.

[illconditioned]

^^^ dude, you're outta control.  Hide your gear, folks, igene is in the house!

Comment by someone who has more than a dozen partially completed projects on his desk.  Each project is "on hold" in a plastic tray, with disassembled gear, parts, and schematics, all waiting to go...

Seriously, please make sure you keep the old parts in case you have to backrack.



  Richard

[Chuck]

Each project is "on hold" in a plastic tray, with disassembled gear, parts, and schematics, all waiting to go...
Richard

Richard, that is SO funny. I do exactly the same thing. When I disassemble something I use some clear plastic storage containers with lids to store everything in, including notes etc... because I can drop or forget about a project for as long as a year. I must have 5 or 6 projects in various states of repair and disassembled in those clear plastic storage boxes. It really helps me keep track of everything.

[igene]

I actually only have 3 projects on hold disassembled (neatly in it's own container)
in such a way that I know where I left off.
I never leave anything too apart so I can't go back.

1. Nak700 mod
2. 2 wire bat box
3. 3 wire bat box

Am I missing something ?

I'm doing the other cable (AKG active today) so I'm done today.
I'm actually shooting every step of the way for a AKG active mod post that's going to blow you away !

I don't know what you mean...hide your gear....
I'm doing it right, better than a lot of homemade mods I've seen.
(no duct tape here)
I also started and finished the AT power module mod in 1 day - DONE ! completed


Are you telling me that AKG cable mod doesn't look pro ?

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add >

I just remembered I have another one...

4. KORG MR-1 project
For battery upgrade and CF/SSD mod