Topic: putting line transformers inside a batt box -- please help (DPA4061 related)

[dklein]

Just curious - what's the cap value on the small one?  And how about the resistor?
It'd be nice to file away a powering scheme for the 4061s.

[Nick's Picks]

I'll slap on another +T for your ideas and efforts.
4061s...I dont know.
far to "un sensitive" w/o some sort of gain that you can add.

imo, the one to get is the 4070.  built in roll off and more sensitive.

but, that doesnt' help, does it.

I think maybe gutting the BB and building it in a different sized project box might do the trick.  But then again, the Oade mod M1 would solve everything, wouldn't it.

[pfife]

even the 4060.  As macdaddy has.

[jamonyorke]

Just curious - what's the cap value on the small one?  And how about the resistor?
It'd be nice to file away a powering scheme for the 4061s.

Here are the values:

R= 10K
C (small) = 2.2uF
C (big) = 0.15uF

(thanks JK for deciphering the caps values for me a while ago)

The bass rolloff filter (small C) is suposedly designed for mic-in impedance (4,7K), but applying the formula gives me a cutoff freq. of 226Hz.
This somewhat contradicts what's written on Coresound's Page (120Hz).
Maybe he considered the mic-in impedance as 10K?

[dklein]

Here are the values:

R= 10K
C (small) = 2.2uF
C (big) = 0.15uF

(thanks JK for deciphering the caps values for me a while ago)

The bass rolloff filter (small C) is suposedly designed for mic-in impedance (4,7K), but applying the formula gives me a cutoff freq. of 226Hz.
This somewhat contradicts what's written on Coresound's Page (120Hz).
Maybe he considered the mic-in impedance as 10K?

Interesting...exactly the same as the standard CSB box - same powering as the Panasonic capsules

Remember that when you use that formula you get the -3dB point (on a 6dB/octave slope).  CS says it's down 6dB at 120 Hz - I would think the -6dB point is somewhere near 167 Hz.

[relaxing]

Did this actually work?  I'm considering doing the same thing, all homebrew.

It'd be better to not kill a pair of hosa's - do you know the specs of the transformer?

Would something like radshack #273-1380 work? ("Audio Output Transformer 1,000-ohm center-tapped primary, 8-ohm secondary. Many uses including audio output and low-level impedance matching.")

[zhianosatch]

the 4060s would be the much easier solution here, but good job for doing what you're doing!

[relaxing]

the 4060s would be the much easier solution here, but good job for doing what you're doing!

The 4060s really put out enough signal to get a good recording on the jb3?   

In any case, the 4061s are cheaper and easier to find, so I really want a solution like this.

[pfife]

yeah, the 4060's are higher sensitivity.

[SparkE!]

Would something like radshack #273-1380 work? ("Audio Output Transformer 1,000-ohm center-tapped primary, 8-ohm secondary. Many uses including audio output and low-level impedance matching.")

The voltage gain is going to be the square root of the impedance ratio.  You're talking about an impedance ratio of 125, so the voltage gain will be 125 ^ .5 = 11.18.  If you express that in dB, you'll have 20 log 11.18 = 20.97 dB gain.  You'd run you mic signal into the 8 ohm side and get your boosted line level signal on the 1000 ohm side.

[relaxing]

Would something like radshack #273-1380 work? ("Audio Output Transformer 1,000-ohm center-tapped primary, 8-ohm secondary. Many uses including audio output and low-level impedance matching.")

The voltage gain is going to be the square root of the impedance ratio.  You're talking about an impedance ratio of 125, so the voltage gain will be 125 ^ .5 = 11.18.  If you express that in dB, you'll have 20 log 11.18 = 20.97 dB gain.  You'd run you mic signal into the 8 ohm side and get your boosted line level signal on the 1000 ohm side.

Excellent!  I'll try to put something together tonight.

Thanks SparkE!  I'd +T you if I could!

[relaxing]

Would something like radshack #273-1380 work? ("Audio Output Transformer 1,000-ohm center-tapped primary, 8-ohm secondary. Many uses including audio output and low-level impedance matching.")

The voltage gain is going to be the square root of the impedance ratio.  You're talking about an impedance ratio of 125, so the voltage gain will be 125 ^ .5 = 11.18.  If you express that in dB, you'll have 20 log 11.18 = 20.97 dB gain.  You'd run you mic signal into the 8 ohm side and get your boosted line level signal on the 1000 ohm side.

ok... so what do I do with all these wires? 

one side, labeled "8 ohms",  has red and white wires.  the other, labeled "CT" (center-tapped?), has blue, black and green.
by sides I mean the diagram goes    =3||C=

I found combinations that didn't work, and some that did, but none gave me a huge boost in sound.  I'm using a pair of transformers after the battery box, with just a plain signal/shield stereo pair to a 1/8 mini plug.

hope that makes sense.

[SparkE!]

Would something like radshack #273-1380 work? ("Audio Output Transformer 1,000-ohm center-tapped primary, 8-ohm secondary. Many uses including audio output and low-level impedance matching.")

The voltage gain is going to be the square root of the impedance ratio.  You're talking about an impedance ratio of 125, so the voltage gain will be 125 ^ .5 = 11.18.  If you express that in dB, you'll have 20 log 11.18 = 20.97 dB gain.  You'd run you mic signal into the 8 ohm side and get your boosted line level signal on the 1000 ohm side.

ok... so what do I do with all these wires? 

one side, labeled "8 ohms",  has red and white wires.  the other, labeled "CT" (center-tapped?), has blue, black and green.
by sides I mean the diagram goes    =3||C=

I found combinations that didn't work, and some that did, but none gave me a huge boost in sound.  I'm using a pair of transformers after the battery box, with just a plain signal/shield stereo pair to a 1/8 mini plug.

hope that makes sense.

So, you'd go mic signal between the red and white wires and the coupled signal would come out between the blue and green wires.

[relaxing]

Would something like radshack #273-1380 work? ("Audio Output Transformer 1,000-ohm center-tapped primary, 8-ohm secondary. Many uses including audio output and low-level impedance matching.")

The voltage gain is going to be the square root of the impedance ratio.  You're talking about an impedance ratio of 125, so the voltage gain will be 125 ^ .5 = 11.18.  If you express that in dB, you'll have 20 log 11.18 = 20.97 dB gain.  You'd run you mic signal into the 8 ohm side and get your boosted line level signal on the 1000 ohm side.

ok... so what do I do with all these wires? 

one side, labeled "8 ohms",  has red and white wires.  the other, labeled "CT" (center-tapped?), has blue, black and green.
by sides I mean the diagram goes    =3||C=

I found combinations that didn't work, and some that did, but none gave me a huge boost in sound.  I'm using a pair of transformers after the battery box, with just a plain signal/shield stereo pair to a 1/8 mini plug.

hope that makes sense.

So, you'd go mic signal between the red and white wires and the coupled signal would come out between the blue and green wires.

Between the wires???  Sorry, what gets connected to what?

(This must be what it feels like when I'm explaining computer things to the computer illiterate...  It's all so unintuitive to me!  I've googled and no one explains how this stuff works on the level I need.) 

[SparkE!]

Would something like radshack #273-1380 work? ("Audio Output Transformer 1,000-ohm center-tapped primary, 8-ohm secondary. Many uses including audio output and low-level impedance matching.")

The voltage gain is going to be the square root of the impedance ratio.  You're talking about an impedance ratio of 125, so the voltage gain will be 125 ^ .5 = 11.18.  If you express that in dB, you'll have 20 log 11.18 = 20.97 dB gain.  You'd run you mic signal into the 8 ohm side and get your boosted line level signal on the 1000 ohm side.

ok... so what do I do with all these wires? 

one side, labeled "8 ohms",  has red and white wires.  the other, labeled "CT" (center-tapped?), has blue, black and green.
by sides I mean the diagram goes    =3||C=

I found combinations that didn't work, and some that did, but none gave me a huge boost in sound.  I'm using a pair of transformers after the battery box, with just a plain signal/shield stereo pair to a 1/8 mini plug.

hope that makes sense.

So, you'd go mic signal between the red and white wires and the coupled signal would come out between the blue and green wires.

Between the wires???  Sorry, what gets connected to what?

(This must be what it feels like when I'm explaining computer things to the computer illiterate...  It's all so unintuitive to me!  I've googled and no one explains how this stuff works on the level I need.) 

Your mic signal wires will connect to the red and white wires (one to each).  Then your blue and green wires will connect to the output connector.  I don't know enough about the connectors you are using to tell you exactly how to wire the connectors.  I also don't know if you are balanced or single ended.  Both are shown below:


                         Red      Blue
       Mic +  o--------------. ,-------------o  Line Out +
                             )|(  Black
                             )|(-------------o    GND
                       White )|(  Green
       Mic -  o--------------' '-------------o  Line Out -
                                                                     +
                           Balanced



                         Red      Blue
       Mic +  o--------------. ,-------------o  Line Out +
                             )|(  Black
                             )|(-------------o   Unused
                       White )|(  Green
        GND   o--------------' '-------------o    GND

                         Single Ended

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