5 dollar mic pre questions

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doulos24

Active member
Joined
Apr 9, 2010
Messages
32
ok so I have a couple questions I'd like to ask about this circuit first

is there anywhere I can read up on basic mic preamp theory? I really would like to know how to tap a mic pre circuits say from a mixer and impliment input an output transformers

on to the circuit first let me explain I'm just wanting to get my feet wet here. I have a lot to learn but eventually I want to understand this enough to build my own preamps.

in pic 1 we have everything but the psu ready to go which is cool, but like I said I want to kind of strip everything down and figure out what I'm doing.  

preamp1.png


pic 2 ok so I've stripped the protection diodes the dc offset loop and the phantom power circuit. I want to run this off of 4 9volts feeding a akg c1000 mic as a test bed

preamp3.png


is it safe to say c1 and c2 the 47uf 63v caps can be dropped down now since there is no phantom power to something like 1uf 25v?

later is it as simple as adding a unbalanced to balanced line circuit to the output "pin 6" and ground? to add the +6db something like this?  

converter.gif

also is it true that if i add a transformer balanced out vs active balanced out id loose the +6db?


 
doulos24 said:
pic 2 ok so I've stripped the protection diodes the dc offset loop and the phantom power circuit. I want to run this off of 4 9volts feeding a akg c1000 mic as a test bed

If you want to get rid off the phantom circuit, remove R1 & R2

is it safe to say c1 and c2 the 47uf 63v caps can be dropped down now since there is no phantom power to something like 1uf 25v?

No. Those caps form a high pass filter with R4, R5. If you are absolutely sure you will never connect anything else than your C1000, you may as well remove them. Otherwise keep them along with the protection diode.

later is it as simple as adding a unbalanced to balanced line circuit to the output "pin 6" and ground? to add the +6db something like this?  

A that 1646 or 1606 would be even simpler

also is it true that if i add a transformer balanced out vs active balanced out id loose the +6db?

Not necessarily. Depends on the transformer ratio

Axel

 
I need a simple pre(and no phantom) with 2adjustable outputs..
I was thinking something like these ina-preamps with 2x drv134  for outputs;
can i just add outputs like this( see attachment) or is there a better way to do this ?
 

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just wanted to add, and I know it's a plug, but...

We'll have pre-soldered-and-tested INA163 Mic Pre Modules available from Expat Audio in the next few weeks. (boards are enroute from the supplier, and my pick and place is impatiently waiting to assemble the boards).

You can see an early photo on the expat audio home page...

/R

 
Rochey said:
just wanted to add, and I know it's a plug, but...

We'll have pre-soldered-and-tested INA163 Mic Pre Modules available from Expat Audio in the next few weeks. (boards are enroute from the supplier, and my pick and place is impatiently waiting to assemble the boards).

You can see an early photo on the expat audio home page...

/R
nice! any info on price range? :)
 
Given that it'll be documented, manufactured and tested, it won't be super-duper cheap.
But, It'll work first time and take seconds for you to hook up!

I'm estimating $79.99 in individual units. 59.99 each for 4.
(further discount for 8).

Performance of our implementation is stellar on our initial prototypes - 0.002% THD on almost 70dB of Gain.

Cheers

/Rochey


 
Rochey said:
Given that it'll be documented, manufactured and tested, it won't be super-duper cheap.
But, It'll work first time and take seconds for you to hook up!

I'm estimating $79.99 in individual units. 59.99 each for 4.
(further discount for 8).

Performance of our implementation is stellar on our initial prototypes - 0.002% THD on almost 70dB of Gain.

Cheers

/Rochey

Rochey,

Nice! Have been thinking about building a bunch of INA163 preamps for auxiliary use, extra channels, etc. Any chance that you'll offer just the boards or board kits for those of us who want to try our hands at SMD?

Dylan
 
Dylan,

thanks for the feedback. We haven't decided on that, but it'll definitely be considered.

I'll also have some DIY SMD tools (e.g. vacuum and paste controller) for sale pretty soon.

:)

/R
 
If you choose to go that route, I would certainly be in for a few. Looking forward to your new offerings.
 
Not sure if this is he right thread to mention this but... The first dozen prototypes havevcome off the manufacturing line, and are looking good. Next step, thy'll be sent to Keith for indepth analysis. (i oly have production test facility, not the AUdio Characterization testers.

I have some documentation to make, and from there, we should be readyto rock!

Cheers

Rochey

 
just wanted to show a pic... everyone likes pictures, right?

These have been assembled here in Texas.
I have the equipment in my home right now - pick and place machine, reflow setup, rework system, audio test rig.
One day, I'll make a video of them being produced. I'm as excited about the production setup as I am about the boards themselves!

http://flickr.com/gp/66820436@N04/904242/photos/66820436@N04/8156408193/

I'll start another thread later this week, once I think of a name for the board!

Cheers

/R
 

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