ruffrecords
Well-known member
As part of the Mark 3 development I have been looking at alternative transformers and in particular I have been looking at the low frequency distortion at high signal levels because this is one area where transformer performance can be limited. The spur for this is the desire to find an output transformer that will fit in the new 35mm wide modules.
Input transformers have little difficulty with this, probably because the power involved is very small. However, for output transformers some real power is involved. I have tested a range of output transformers from 1KHz down to 20Hz and below driving +16dBm into a 600 ohm load. Types tested range from the big old Carnhill VTB2291 used in the EZTubeMixer project through medium sized ones like the Cinemag CM2820 to as small as the Sowter 1461. As a result of this work I have come to the conclusion that all the transformers tested have low enough distortion down to 40Hz but there is great variability from 40Hz down to 20Hz. Size does play a part in this but core material is also important.
Bottom line is the transformers that fit into the new module I judge to be OK down to 40Hz but not to 20Hz. So my question is does it really matter? Is there ever any content down there? Given the lowest note on a bass guitar is just over 40Hz perhaps it doesn't.
Thoughts/opinions?
Cheers
Ian
Input transformers have little difficulty with this, probably because the power involved is very small. However, for output transformers some real power is involved. I have tested a range of output transformers from 1KHz down to 20Hz and below driving +16dBm into a 600 ohm load. Types tested range from the big old Carnhill VTB2291 used in the EZTubeMixer project through medium sized ones like the Cinemag CM2820 to as small as the Sowter 1461. As a result of this work I have come to the conclusion that all the transformers tested have low enough distortion down to 40Hz but there is great variability from 40Hz down to 20Hz. Size does play a part in this but core material is also important.
Bottom line is the transformers that fit into the new module I judge to be OK down to 40Hz but not to 20Hz. So my question is does it really matter? Is there ever any content down there? Given the lowest note on a bass guitar is just over 40Hz perhaps it doesn't.
Thoughts/opinions?
Cheers
Ian