Seventh Circle Audio

I'm a bit confused about which jumpers to short on the J99. I haven't been able to figure things out from the instructions or by searching this forum. What is the typical J1 & J2 setup for standard Large Dia Condenser mics? With "|" representing a jumper set vertically across pins and "__" representing a jumper set horizontally across pins, what is the correct setup?

| |
| |

or

__ __
__ __

or ?


Thanks,

Mar

I have the same question:

"Shorting across J1 and J2 with a single jumper selects a 1:2.5 step-up ratio, and a 1000 ohm input impedance. Use this setting for most microphones."

I'm assuming this means A or B. (J5 is shown jumpered for context.) Which option is correct?

"A" is correct. You can verify by observing that PCB traces connect those pins to T1-2 and T1-4. Jumpering as in "B" connects CONN1-2 and CONN1-3 together, shorting the input signal. Jumpering as in "C" or "D" will work, but will result in higher distortion at a given input level than jumpering both J1 and J2.

I am glad I found this post about the correct jumper setting at j1 and j2. It really should be illustrated clearly in the assembly instructions.

"shorting across j1 and j2" sure but which 2 sets of pins

Thanks zonkola and thanks tim for answering.

I guessed. The first guess was wrong (like your "B"), and I got no signal Swapped jumpers, and there we go!

Hey Hey!

I'm glad for this thread. It really helped.

Now the obvious question, I think, is has anyone modified to add a switch here so we can switch the input impedance. I've got some ribbons and would appreciate the option.

I'm thinking a simple switch in drilled through the front panel that simply opens/closes instead of this jumper would do it.

I'm thinking the challenges would be...
A: avoiding a loud pop when switching and
B: introducing noise by running a wire all the way past all the other circuitry at such an early point in the circuit. (I suppose a switch on the back or well shielded wire would help this?)

But perhaps this is in another thread already?

Archmart

Hey Hey!

Wait, no. The switch would have to open/close in three places... ?

Archmart

so to set this up for a ribbon mic I would do two jumpers? like a combination of A and B?

Unless you have an ancient ribbon mic with a 30-50 ohm output impedance or absolutely must have another 6dB of gain, set the jumpers as shown in step 9 of the assembly instructions.

So if I want the added gain I jumper
across J1 and J2 like a combination of C and D..
Brian

So if I want the added gain I jumper across J1 and J2 like a combination of C and D.

Right.