The Lei

 

Classic sound, tiny package

This pretty little mic packs classic sound, reminiscent of the venerable U87 into a tiny, robust package.

Options include attenuation pad, EQ/brightness change switch, or Hi-Pass filter.

We recommend limiting customizations of this to two optional switches, maximum. We have built them with three, but due to the small size of the body, switch placement becomes irregular.

The MaiTai

 

A reworking of the Lei with a different FET, and a few circuit mods.

Has the same options as the Lei, for add-ons.

NOTE: Even without the attenuation pad installed, the MaiTai will have a slightly quieter output than the Lei without one. Or the same as the Lei with one. The resistor rails of the H-pad are built into this circuit premanently, along with a couple other tweaks, resulting in a pleasant, quieter, warmer, more fluffy sound.

We recommend limiting customizations of this to two optional switches, maximum. We have built them with three, but due to the small size of the body, switch placement becomes irregular.

Lei PCB Board

The Lei is NOT for beginners. It's a tiny mic and the components go on both sides of a very small board. It's a very rewarding build, but a very difficult build. Recommend experts only. Daughterboards must be detached carefully from this board.

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Lei87:  PCB BOARD: $29 + Tax/Ship

 

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BoM:

Mouser BoM for Lei87

(NOTE: Above BoM does NOT include components for switches. See below, and add appropriate parts)

 

MATERIALS/BoM:

Resistors:
1G || 1M || 330k || 300k || 56k || 47k || 10k || 2k2 (x2) || 7k3

Trimmer Resistor:
25K

Capacitors:

33nF (NP)** || 120-180(220*)pF (NP) ||
(*NOTE the 220pf seems to work well. Higher values temper the highs.)
** In the Lei/Nano build, can best be replaced with a 68nf
470 nF (NP) || 10uf 63v (x2) || 4u7 160v || 20uF 6v || 10nF ||
1uF 160v

Transformer:

Cinemag CM2480 or sim. (10.5:1)
OR:
Neutrik NTE10/3 (NOTE! This is the one on the Mouser BoM. This transformer gets wired in reverse, swapping primary and secondary, for correct turn ratio.)

FET:

2n3819 or sim.
(FOR MAITAI: 2n4867 or 2n4867a)

 

Zener:

1N4749a

 

H-PAD DAUGHTERBOARD:

Resistors:

500r (x4) || 967r (or close. -5dB) || 470r (-10dB) || 220r (-15dB)

Switch:

1p4t (for 4-position -0,-5,-10, -15) OR:
1p3t (for 3-position -0,-5/-10/-15) OR:
1p2t (for 2-pos on/off)

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Brightness/EQ Switch Daughterboard:

Capacitors:

120-220pf (lower = brighter)
220-400+pf

Switch:

1p2t on-on

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Hi-Pass Switch Daughterboard:

Capacitors:

470nf

Resistors:

150k-180k

Switch:

1p1t (spst) on-off