SB3 mod (including DAC mod) question..

chadh · « **Reply #20 on:** 3 Feb 2006, 08:24 pm »

Why does 100W = 20dB gain? My CIAudio VMB1s are 40W and give me 32 dB of gain.

I don't think I'll ever understand this. (Unless the 100W = 20dB gain is specific to the Bryston amp in question).

Chad

ctviggen · « **Reply #21 on:** 3 Feb 2006, 08:33 pm »

See: http://www.transcendentsound.com/amp_input_sensitivity_and_gain.htm

Power = V ^2 /R (voltage squared divided by resistance). If you need 100 watts into 8 ohms, you need 28 volts. If you have a 1 volt input to get a full range output, db = 20 log (Vout/Vin), you'd get 20 log (28) = 29 db of gain.

ctviggen · « **Reply #22 on:** 3 Feb 2006, 08:40 pm »

That should be 20 log (28).

ctviggen · « **Reply #23 on:** 3 Feb 2006, 08:41 pm »

So the gain is specific to the amp in question.

95bcwh · « **Reply #24 on:** 3 Feb 2006, 09:49 pm »

Excellent explanation for newbie like me....

JLM · « **Reply #25 on:** 4 Feb 2006, 12:18 pm »

Bob,

Thanks for the link/explanation.

chadh,

The VMB-1 is designed to accommodate a low output source, like the modded SB, as Dusty believes in using passive pre-amps and putting all the gain into the power amps. So VMB-1/SB produces a good mating. (Can I say that here?

)

chadh · « **Reply #26 on:** 4 Feb 2006, 03:24 pm »

Indeed, thanks Bob for the insights on gain and power consumption.

JLM - I own an SB2, which is as yet unmodified. That's why I have my eye on this thread

So I may as well piggyback here and ask some related questions about various mod options with the SB2.

The modifications seem to fall into three categories: (i) power supply mods; (ii) mods that effect the analog out; and (iii) mods that effect the digital out. The thing is, there seem to be relatively few mods of type (iii). So...pulling on my cheapskate cap for a moment...

IF (and it's a pretty big if), people find no clear advantage to using the analog outs from the modified SB over the digital outs, and

IF there are relatively few modifications that effect the digital out, and

IF one secures an upgraded power supply, and

IF one has a pretty decent external DAC, good digital cabling, a dijittering machine etc.

then is there much to gain from having the SB modified?

I suspect that the answer is "yes", due to changes in how the power is handled internally. But I thought it was worth getting some insights.

Thanks.

Chad