Matching Treble Boosters

[audiobalm]

Hi All,

I've got a couple Dallas Rangemaster Treble Boosters here, one I built (mine) and one I bought (arangemaster). The components are virtually the same except one has an original OC44 (mine) and the other an OC76 (Arangemaster). All other components values are the same and match to the original Rangemaster Schematic.

The frequency responses of the two are quite different, mine has a peak in the upper mids I really like while the arangemaster has more treble and full frequency content which I like a lot less. (see Frequency analysis below, pink noise generator running through them).

I'm trying to figure out if it's simply a matter of the transistors being different. I would have thought that would affect the gain but not the frequencies as it hits your ear.

What troubleshooting steps should I take to see if I can get these sounding a little more similar. The arangemaster is point to point and easy enough to replace components should I need to.

Thanks!
David

[Steben]

Input impedance and therefor filtering characteristics combined with the input cap is vastly influenced by the internal Re resistance. This is linked to current thorugh the transistor etc

[antonis]

What Steben said..

If you can manage to trim both for the same Collector current the only thing remaining is components tolerance..

[Steben]

But ... if I may ask... Is one of them sounding "bad" ?

[mac]

When I built mine I tested a bunch of transistors, mostly japanese, all around hfe=70.
2sa102, 2sb175, 2sb77, 2sd72k, 2sa53, 2sa49, 2sb54...
After weeks I decided to use the first one because it has a bit more highs than the rest.

mac