Hi, be gentle, I'm trying to make the move from being a consumer buying shiny new gear, to making my own simple designs and mods...
Would be grateful for someone more experienced to audit my work - I'm making a voltage divider at the inputs to a pair of monoblock amps. The goal is to reduce audible hiss from the preamp's mosfet output stage.
The specs are:
Speaker sensitivity ~ 107dB/w/m (front loaded horns)
Desired attenuation = 15dB
Power amp input Z = 41K shunted by 47pf
Preamp output Z = 130R 'corrected' (per manufacturer)
There's a parallel load on the preamp from the monoblocks and a Velodyne SMS-1 bass management processor. I've searched the documentation and web for the input impedance of the SMS-1 but come up empty. So I'm assuming it is 'high', ~100K.
My math is based on these formula:
1) Vd = 1 + (R1 / R2)
2) dB = 20 * Log10 (Vd)
3) Zin = R1 + R2
4) Zout = (R1 * R2) / (R1 + R2)
Following are 5 R1 / R2 combinations for a 15dB voltage divider:
R1 R2 Z(in) Z(out)
4K99 1K06 6050 874
6K8 1K5 8300 1229
10K 2K2 12,200 1803
15K 3K3 18,300 2705
22K 4K7 26,700 3873
If my math is correct, any of the above R1/R2 combinations will work to attenuate the signal by 15dB. My lack of experience is around matching impedances with the pre and power amps. I'm trying to design a voltage divider with adequately high load for the preamp and low impedance for the power amp.
1) Which combination would be 'best' in this application, and why?
Much thanks!
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Topic - Voltage Divider at input to Power Amp - tetsuo 17:13:38 07/27/13 (9)
- RE: Voltage Divider at input to Power Amp - tetsuo 10:10:35 07/28/13 (4)
- RE: Voltage Divider at input to Power Amp - Paul Joppa 14:16:37 07/29/13 (0)
- RE: Voltage Divider at input to Power Amp - Tre' 14:49:24 07/28/13 (2)
- RE: Voltage Divider at input to Power Amp - TimFox 15:30:48 07/28/13 (1)
- Further clarification - Tre' 07:59:27 07/29/13 (0)
- filter already at amp input - TrustYourEars 07:32:09 07/28/13 (0)
- More calculations - Chip647 06:21:53 07/28/13 (0)
- ... and I think you are attacking the problem from the right direction - Paul Joppa 19:08:13 07/27/13 (0)
- I think you are attacking the problem from the wrong direction - bwb 18:26:38 07/27/13 (0)