TOPIC:

Hi Guys,

So I’m thinking about trying to use the DDRC-24 to control volume despite the lack of display.

My amp will achieve full output power if it receives a 0.75v input.

Is there a way to approximately correlate MV with output voltage?

Also is there any risk of the DDRC24 turning on or resetting itself to a higher dB level than previously set? For example if I was listening at MV -20db and there was a power cut or the ddrc was turned off and on, is there any chance of it coming back at say 0db and frying my speakers or my ears?!!

Thanks

I think 0 dB main volume would mean a maximum signal level of 2 Vrms. In which case 0.75 Vrms would be -8.52 dB. If a recording never gets near 0dBFS then you could have a higher main volume and still stay below 0.75 Vrms though.

You very likely don't want to send max power to your speakers though so the above probably isn't very useful.

Bear in mind Dirac Live boosts too. My above calculation assumes no boost.

When I used my 2x4 HD in the way you describe I never thought through any details like this, in the same way most people tend not to think about what position a conventional volume control on an amp could give max. output for a 2 V input. What I did do though was use some 10 dB Rothwell attenuators at my power amp inputs as a form of safety limit. How practical or beneficial this would be depends on available head room.

asx77 wrote:

Also is there any risk of the DDRC24 turning on or resetting itself to a higher dB level than previously set? For example if I was listening at MV -20db and there was a power cut or the ddrc was turned off and on, is there any chance of it coming back at say 0db and frying my speakers or my ears?!!

I realise I didn't comment on this bit. All I can say is that it didn't happen to me with my 2x4 HD in the somethng like 9 months I used it as a DAC/pre-amp as you are considering. If you had a power cut then presumably the music would stop anyway, and so give you chance to check the miniDSP setting via a USB cable priror to playing anything else?

Hi,
I think I'll assume the DDRC24 has been designed with some level of safety in mind and won't ever reset volume - power cut or not. Can't see an appropriate "fingers crossed" emoji so just imagine I've inserted one here!!

How did you work out that 0.75 Vrms would be -8.52 dB?

You may be correct... perhaps I'm over thinking this. I'm just worried (probably needlessly) that in turning down the MV I'll reduce the output quality. Any ideas when a reduction in MV has an effect on quality?

Thanks

How did you work out that 0.75 Vrms would be -8.52 dB?

Voltage gain in dB = 20*log(Vout/Vmax) = 20*log(0.75 / 2) = -8.52 dB

Michael

Thanks

asx77 wrote:

Any ideas when a reduction in MV has an effect on quality?

I suspect way below the attenuation you'll apply. Bear in mind that the volume reduction is applied within the DSP chip where the data is in 32 bit form and so has much more scope to attenuate without degrading quality.