usualsuspects wrote:
I would like to run SB2 analog out direct to my amp (Parasound HCA-750)
- my amp manual says "0.775v input for full output". At 6v on the
analog outs - I am afraid it will be way too high. Is there a simple
analog resistor network I can build that will reduce the voltage by a
factor of 10 to 0.6 volts? The input impedance on my amp is 33K ohms. I
tend to listen at low volume and having the most range in the volume
control is desired. My speakers are fairly efficient – 90db. Thanks!
Hi,
You don't actually need to reduce the output by that much.
The 0.775v figure is almost certainly a "standard" 0dBu level.
dBu measurement is referenced to 0.7746v (often rounded to 0.775v), i.e.:
dBu = 20log10(v/0.7746v)
where v is the rms voltage, 0.775v in this case (rounded from 0.7746v).
The 6v figure for the Squeezebox is a peak-to-peak figure.
Converting this to rms gives:
Vrms = (Vpp / 2) / sqrt(2)
= (6 / 2) / 1.414
= 2.12v
This corresponds to:
dBu = 20log10(2.12 / 0.7746)
= 8.75 dBu
So, to get an rms level of 0dBu you would need to reduce the output
voltage by 2.12 - 0.7746 = 1.35v rms
In actual fact, it is highly unlikely that your amplifier can't cope
with this signal level. So I would just plug it in and see how you go.
R.
--
http://robinbowes.com
If a man speaks in a forest,
and his wife's not there,
is he still wrong?
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