Stefan1024
Member
- Joined
- Oct 30, 2021
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So I'm running the AHB2 and I'm pretty happy with it. However, it has a relatively high output impedance:
The 23 mOhm at low frequency are not too bad, but it rolls of quickly above 500 Hz. For the speaker cable I'm using a high frequency litz wire with 1050 strands of 0.1mm wire (8.24mm^2) what leads to additional ca. 8 mOhm. So there is some room for improvement.
By the way, this high frequency litz wires offer great value for a relatively low price.
Now I'm thinking about building thw monoblocks with a Purifi 1ET400A that has only one 1 mOhm output impedance to start with. Additionaly, The sense lines for the amplifier are routed seperately. Usually they are joined on the output connector of the amplifer. But I'm planing on routing the sense lines up to the speaker and only connect the sense to the speaker rigth at the end of the cable. So the amplifier would compensate the impedance of the cable and (at least in theory) also EMI.
Basically using the 4 wire measurement system idea:
So here are my questions:
1) Do you think it is worth it to reduce the output impedance?
Given the crossover has much higher (DC) resistance or sometimes even straigth up series resistors of 1 Ohm or more it feels a bit silly to improve the amplifier impedance to a few mOhms.... thougths?
2) Instability caused by remote sensing
By adding some inductance / delay into the carefully calculated feedback loop of the 1ET400A, this may cause instability. I think I'm still on the save side, but if someone has experience to share I'm interesed.
3) Noise picked up by remote sensing
I'm planning on using star quad cable for the sense lines. So again I think I should be save.
Thank you
The 23 mOhm at low frequency are not too bad, but it rolls of quickly above 500 Hz. For the speaker cable I'm using a high frequency litz wire with 1050 strands of 0.1mm wire (8.24mm^2) what leads to additional ca. 8 mOhm. So there is some room for improvement.
By the way, this high frequency litz wires offer great value for a relatively low price.
Now I'm thinking about building thw monoblocks with a Purifi 1ET400A that has only one 1 mOhm output impedance to start with. Additionaly, The sense lines for the amplifier are routed seperately. Usually they are joined on the output connector of the amplifer. But I'm planing on routing the sense lines up to the speaker and only connect the sense to the speaker rigth at the end of the cable. So the amplifier would compensate the impedance of the cable and (at least in theory) also EMI.
Basically using the 4 wire measurement system idea:
So here are my questions:
1) Do you think it is worth it to reduce the output impedance?
Given the crossover has much higher (DC) resistance or sometimes even straigth up series resistors of 1 Ohm or more it feels a bit silly to improve the amplifier impedance to a few mOhms.... thougths?
2) Instability caused by remote sensing
By adding some inductance / delay into the carefully calculated feedback loop of the 1ET400A, this may cause instability. I think I'm still on the save side, but if someone has experience to share I'm interesed.
3) Noise picked up by remote sensing
I'm planning on using star quad cable for the sense lines. So again I think I should be save.
Thank you