Adjusting bass compensation by the number of transformer laminations

At your own risk. Take all safety precautions.


This was tried quite a long time ago on Sowter and Jensen transformers.


The wound bobbin was left in its own.


Then while singing to the microphone connected to the input transformer and listening by headphones...


Initially it is only high frequency detail that can be heard.


One E lamination is inserted. Mid high starts to increase.


Another E lamination is inserted, more.


....



Another E is inserted mid bass starts to appear.


A great parametric EQ.


It's is surprising how little sometimes laminations are needed until one arrives at a result that does not sound bass heavy. For example compensating the proximity effect.


Any combination can be made. For example 7 Es one way, 7 Es the other way until all space is filled. Acknowledging here the great hint by Brian Sowter.


Then of course one can have fewer turns or wind on ring cores.


It may be a fine balance. Sometimes too few primary turns may produce less treble results.


For example the Pleiades V5 with input transformer primary L=47mH sounds less treble extended than the V6 with primary inductance of 140mH.


But the V6 has additionally an output transformer with -3dB at around 100Hz.


The V6 sounds amazing with the Geampian DP4/L ie the 25 ohm version. The input transformer is 1:10 wound on the Magnetec 070 nanocrystalinne core. Amasing treble detail and full body sound. Almost no noise.


More investigation is needed.


Reference:


Coil Desigh and Construction Manual - B. B. baba I


Pleiades V6 Schematic