ruffrecords said:
The load placed across the EQ output does affect the shape of the Lo boost/cut EQ curves and the maximum boost or cut that can be obtained.
Thanks for doing that Ian
Yes I thought that the low would be the one to be changed the most and with a typical 20K:150 ohm traffo presenting 200K to primary maybe not too much to care?
ruffrecords said:
So I conclude that:
1. The load makes the greatest difference to the low frequency simultaneous boost/cut (bump)
2. The difference made by a 200K is quite small.
Yes. And if we push it a bit by adding my build out from your EQ of 15K for 215K total load, even a tiny, tiny bit less small of a difference
ruffrecords said:
3. Most people could probably live with the curves produced with a 100K load.
4. 50K load messes up the lo bump and reduces the maximum boost by over 3dB
I think you are right that 100K is even fine for Rock 'N' Roll. However, 200K is better myself but:
ruffrecords said:
I think using a FET buffer powered by phantom supply is a very clever innovation.
Thank you Ian. I would use this option myself as it costs so little and gives flexibility. Maybe add a 'buffer out' switch to provide for sometimes not having phantom?
I think using a C.C.S. on the source would be better than a resistor for a few reasons but I didn't flesh it out. I wanted to quickly throw out an idea for people.
I'll be glad to finish it and post it for anyone to use if you want? Or someone else can chime in if they have better thoughts?
Thanks again Ian for taking the time to do plots for differing loads and good for you for doing the design in the first place
Jean.
Oops, Edit: Ian, when you simulated, did you adjust upwards the original 56K so that total load for lo eq is the same as your 56K//470K = 50K?
Maybe it only makes a very small difference?