DIY Factory - NTK mods

DIY Factory

DIY - NTK Mic Mods
A project brought to you by Gus
Updated 10 October 2004

Gus presents an NTK mic mod project

Bluebird at “The Lab” stated he had a NTK that he wanted to improve. I offered to help. Instead of shipping the whole microphone, power supply and cables he shipped just the board. I then drew the schematic and picked what
parts should be upgraded.

I found three ceramics C10,C7 and C8, five electros, one film C9 that I would change. I tested the Hitano electros and did not like the readings.
C10 is a compensation cap for the open loop gain of the circuit. C9 looked like an unmarked film of some kind, I guessed PET because of the size it is
an important cap because it is the feedback cap.

C7 and C8 were made .0056uf polypros at 100V

C10 was made a Silver Mica >200V

C9 was made a .1uf 250V polypro

The five electros were replaced with better electros that would fit.
Stock 47uf at 160V measured 13.19mm D, 20.98mm H.
Stock 220uf 16V measured 8.18mm D, 12.13mmH.
Stock 47uf at 50V measured 6.50mm D, 11.37mm H
I replaced C1,C2,C3,C4,C5 with low Z electros
Pick what brand and type you like.

C9,C1 and C2 are the most important to change.

Looking at the circuit I would use the NTK with Phantom on so C2 will stay formed. Electros without forming voltage are what give electros a “bad
name” IMO.

C10,C9,C7 and C8 are surface mount so you need to be carefull removing and replacing them.

At this time 10-10-2004 the stock 6922 (6DJ8) will be used changing to a different tube type might follow The board is going to be shipped to bluebird to compare to a stock NTK.

From looking at the circuit the tube should have less of an impact on the sound than some of the stock caps used IMO.

Gustav Smalley

Gus' hand drawl schematic