How to connect an XLR SM58 studio microphone to a mobile phone with Schematic

 

At your risk.

Schematic of XLR to 3.5mm to USB C adaptor.

External view of XLR to 3.5mm to USB C adaptor.

Internal view of XLR to 3.5 electret mic in adaptor.

The idea behind this is treating the SM58 as it were a condencer electret microphone. 

The SM58 has an internal transformer to step up the moving coil capsule to typicaly 300 Ohms.

The K117 gate is connected to the seconary of this transformer ie to the output of the Shure SM58.

The load drain resistor is on the device to connect to the Pleiades K117 pre preamplifier, and this device supplies the voltage to operate the K117 JFet.

This device can be an older iPhone or iPad or any device with 3.5mm electret mic input.

This of cource includes a modern 3.5mm to USB C adaptor to connect to almost any modern device!

Nice female vocals were recorded at 18in to 24in on a modern mobile phone.

Obviously the further away the microphone from singer the best it sounded as greater distance gives less proximity effect so the listener can now hear more treble detail, breath etc.

To increase further the sensitivity a good quality step up transformer can be connected between any dynamic or ribbon microphone and the Pleiades K117 XLR to USB C adaptor. A small 1:3, or 1:5 ratio may be better to avoid possible overload but it is best to experiment.

It may be worth including enerything on one box, ie input transformer, Pleiades K117 to 3.5mm and Apple 3.5mm to USB C adaptor.

Please also see much older posts on how this has evolved.

Many thanks to ny friends Lefteris and Panos for making clear the inportance of 1 stage electron tube or JFet respectively, microphone amplifiers.

On Increasing Phono Preamplifier Headroom

At your risk.

Please see previous post.

Do source bypass electrolytic capacitors kill musc?

 At your risk.

Experimenting with the Pleiades 3 K117 RIAA phono preamplifier it was found that removing a source bypass capacitor reduces gain as we know so the sound was much softer but it was also more much real. Like the real thing. For example treble detail sounded so real as when having one's ear near the stylus while playing back a record. 

If a gain at say 1st stage is reduced by 26dB, the input headroom is increased by the same amount. If the stage is low noise enough for example by low drain (JFets) or anode (electron tubes) current, it is possible that headroom is increased by removing the source, cathode electrolytic capacitor.

These experements when done by playing the LP Dromos - Mimis Pleasssas, Lefteris Papadopoulos recorded live stereo mix by Stelios Yiannacopoulos at EMI Coloumbia Athens studios:

So at this time the Pleiades K117 phono preamplifier has evolved to 3 stage K117 with no electrolytic capacitor bypassing the source resistor of any stage! The 2nd stage seems to be receiving an equal amount of low level signal as the 1st stage since the passive RIAA network follows the 1st stage. The 470K potentiometer follows the 2rd stage and then the 3rd stage inreases the signal to a louder lever to drive the output transformer which drives the Sennheser HD-580 150 Ohms headphones.

So the headroom at the input must have been increased a lot and the potentiometer protects the 3rd stage from overload.

It is a concept simillar to making nice electron tube studio microphone preamplifiers. You have to aarange the attenuator to be as close a possible to the microphone.

Same as out ears where the 3 liitle bones connected to our ear drum control gain, overload, ie increase headrrom,  dynamic range of permissible received sounds.

But the electronics have to be top quality low noise. Pleiades experiments are done with low (say 50 microamperes) electron tube anode current or JFet drain current.

The idea of not using source or cathode capacitors comes from examining the great sounding RIAA stage of the Heathkit AA-32 integrated electron tube class A amplifier.

A NAB test record was used for feeding a 1KHz signal to the Shure 75E Encore cartridge, Metz direct drive turntable.

No bypass capacitors will also allow more meaningful comparison with the Pleiades 3 stage DC90 electron tube battery powered phono preamplifier with most grids at space potential ie nothing connected to grid except a coupling capacitor.

 

Cover versions of songs

At your risk.

Few people wound make a cover version of a famous painting such a Mona Lisa.

But more would make a cover version of a song such as I wanna hold your hand.

Music Publisher:

https://en.wikipedia.org/wiki/Music_publisher

Boundary Mobile Phone

 At your risk.

Albert told me that his mobile phone sounds with more bass when placed on a table as the larger surface beacomes a soundboard.

Is the sound also more clear as the phone becomes a boundary speaker, ie the listener does not receive a delayed table reflection after the direct sound when the phone is hand held? When the phone is placed on table the listener receives almost the same direct and reflected ray (sound wave).