how to implant input and output transformers to this mic pre circuit?

Dear diy family. I have Console with circuit above. it uses ssm2017 as amplifier. I have LL1540 and LL5402 transformers around that i would like try to implant to this circuit. Thought,  why not to try how it sounds with. Problem is that I'm not sure is it safe and how to plug them in. if I'm not wrong, direct out signal (unbalanced) goes to LL5402 1:1 and after I have
balanced signal goes to audio interface. What ratio should i uses 1:1?what about input transformer, can I use LL1540? Do I simply plug it before console input? Do  I have to change some parts? Thanks for your help!

Just sticking the input transformer before the whole thing would probably work quite well.
There's no phantom power, huh? That makes it even easier.
It should be wired fully floating, balanced in, balanced out. That means that the ground should not connect through to the microphone.
Then it should connect balanced to the console.
This configuration is excellent for live sound for instance. It will eliminate the tendency of microphones to deliver electric shocks to the lips of singers.

The direct output is taken direct from the fader.. I don't think just sticking a transformer there will work very well. You'd probably need to add some buffer or something..

Disclaimer: I am much too young to have solid empirical knowledge of transformer applications.

before output what if add simple op amp buffer/voltage divider? Would it work better that way?

VictorQ said:

Just sticking the input transformer before the whole thing would probably work quite well.

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Correct.

It should be wired fully floating, balanced in, balanced out. That means that the ground should not connect through to the microphone.
Then it should connect balanced to the console.

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That means the microphone body and the cable shield would not be grounded, which is a source of noise due to RFI/EMI.

This configuration is excellent for live sound for instance. It will eliminate the tendency of microphones to deliver electric shocks to the lips of singers.

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That is true, but it's not the proper solution to the problem you describe. Electric shocks come from the fact that one (or both) the grounds of the mic/mixer and the guitar amp is not properly earthed. Disconnecting the ground as you recommend eliminates shocks but make the system noisy.
The ONLY correct solution to this issue is the have BOTH the mixer AND the guitar amps earthed, via a 3-prong plug or a dedicated earth conductor.

Oh right shielding. Sorry about that.
Guess I can't really excuse that with my age...

Unfortunately in an electrical third world country such as Denmark(!), we hardly have any three-prong outlets in residential buildings. Most equipment comes with two-prong power jacks.
In fact it can be quite dangerous if you touch the refrigerator and the plumming with different hands.

VictorQ said:

Oh right shielding. Sorry about that.
Guess I can't really excuse that with my age...

Unfortunately in an electrical third world country such as Denmark(!), we hardly have any three-prong outlets in residential buildings.

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I know about the situation in Denmark. Very surprizing from a country that was among those who formed the SEKO/DEMKO electrical safety alliance...
I believe that when you renovate a house you have to install 3-prong sockets, and you have the possibility to strap the earth pin to the neutral if a proper earth is not available. better than nothing... I wonder why there are so many unsafe electrical installations remaining in Denmark. The cost of fixing it right is not a deterrent. Maybe the authorities haven't been as insistant as they have been in Germany, France, belgium...

> dangerous if you touch the refrigerator and the plumming with different hands.

Plastic water plumbing has been a secret blessing. Inside my house I can hardly find ANY grounds except the 3rd pin of electrical outlets.

Oh, and the basement floor (concrete conducts better than people).

PRR said:

> dangerous if you touch the refrigerator and the plumming with different hands.

Plastic water plumbing has been a secret blessing. Inside my house I can hardly find ANY grounds except the 3rd pin of electrical outlets.

Oh, and the basement floor (concrete conducts better than people).

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In France, it is mandatory to have 3-prong sockets with a proper earth connection in rooms and spaces where the soil is tile or concrete.

> In France, it is mandatory to have 3-prong sockets with a proper earth connection in rooms and spaces where the soil is tile or concrete.

For several decades, most US Codes have required GFI (5mA leak detector) on most outlets within reach of dirt or concrete (as well as the general requirement for 3-pin with dedicated ground-ing conductor on most outlets).

hey guys what about output transformer? so should it work with buffer/voltage follower circuit?

Yeah a buffer would work. Make sure it is able to drive the (reflected) load. Something stronger than a TL072 would cover more ground, but assuming 1:1 turns ratio and 10 kOhm input down stream, a TL072 will work fine.

Hey guys, any fast ideas about which circuit to use for buffer?