Hi all,
I recently put together 6 class D amps to power a pair of 3-way array speakers. After much troubleshooting (thanks again) it was determined that the inputs could not share a ground without introducing noise from unaligned switching currents. The solution I found was using input transformers (Monacor FGA-40HQ) to float the ground on inputs. Two questions:
1. I am assuming the best placement of potentiometer will be on the secondary, not in front of the primary, right?
2. These xos have 12k/12k Ohm impedance. What resistance pots should I be considering. I have usually used 50k or 100k, but is there a protocol around determining this so as to maximize fidelity across the frequency range?
I should add, the source is a Behringer DCX, which lists output impedance as 160 Ohms at 1kHz.
Thanks for your help.
Gary
I recently put together 6 class D amps to power a pair of 3-way array speakers. After much troubleshooting (thanks again) it was determined that the inputs could not share a ground without introducing noise from unaligned switching currents. The solution I found was using input transformers (Monacor FGA-40HQ) to float the ground on inputs. Two questions:
1. I am assuming the best placement of potentiometer will be on the secondary, not in front of the primary, right?
2. These xos have 12k/12k Ohm impedance. What resistance pots should I be considering. I have usually used 50k or 100k, but is there a protocol around determining this so as to maximize fidelity across the frequency range?
I should add, the source is a Behringer DCX, which lists output impedance as 160 Ohms at 1kHz.
Thanks for your help.
Gary
Last edited:
I would place pot before the transformer, assuming your preamp is of good quality and can drive them without any issue.
Transformer has much higher output impedance, thus much poorer in driving your pot, and next stage input.
Transformer has much higher output impedance, thus much poorer in driving your pot, and next stage input.
To drive a 12k transformer you want a low impedance. Pot is variable impedance depending on setting. The Beeringer can drive a 5k pot which will be 1.25k worst-case, probably as good as it gets.