E-E gain doesn't match playback gain

Question

Hi,
Since this message concerns the little USB sound device, the "Soundblaster MP3+", it probably wouldn't usually be discussed in this forum, but my question is quite technical in nature and I need to be talking to people who know what a dB is, so here goes.
Consider a line-level input, that is professional 0dB line level where that's 1mW into 600 ohms, just so we're all on the same page here. This is about 10dB higher than the little domestic Soundblaster should be expecting and indeed when recording it it's necessary to back the record levels off. It isn't clipping the inputs, it records fine, no problem.
However, when listening to this (big) signal E-E, even with the "line in" level maxed out, it's coming out of the line out RCAs at -13dB. What I would expect to see would be that the levels coming out of the RCAs would be the same as the level going in when the "line in" control was at some given setting.
I can understand that a little domestic device like this might not be able to achieve a professional zero-level output, but you wouldn't expect a 13dB drop in level when monitoring your inputs E-E. What's even wierder is that when you record some high-level input and play it back, it -does- come out at roughly the level you put it in at. What this looks like is that E-E levels have a 13dB pad, whereas record and playback levels are normal. Why is E to E monitoring so low level?
Just to summarise:
0dB in = -13dB out E to E ("line in" control at maximum)
0dB in, record into Sound Forge, playback = nearly 0dB out.
What on earth is going on?
Regards,
Phil

Answer 1

>>Does the recording level control affect the "E-E" line-in playback level?
>No.
That's really just a question to help my understanding of how the MP3+ works.
>>Does the line-in playback level affect recording level?
>Oddly enough yes. Increasing line-in level decreases the level recorded slightly - no more than about 10%. No idea what's going on here.
There's an off chance that might indicate the USB power at the device is marginal, or it might mean nothing. You could try disconnecting other USB devices you might have and/or connecting the MP3+ to a different hub to see if there is some behavior change. If the MP3+ worked like the SBLive/SBAudigy it would affect recording volume directly.
>>If you mute the line-in, can you still record it?
>Yes.
That's just another question to help my understanding of how it works.
>>Does whether recording is active or not have any effect on the "E-E" volume?
>No.
Ditto.
>>Do EAX effects like "Concert Hall" affect the "E-E" sound?
>No idea, don't have that software installed.
If you need to install software for the effects, it probably means the MP3+ itself
doesn't do them, and they likely wouldn't affect the "E-E" sound, since it sounds to me like it's probably internally routed in to out.
>The only point of comparison I have is the onboard audio for this motherboard, which is part of an Nforce 2 chipset - it acts as I would expect.
What I'm really suggesting there is getting whomever you bought it from to help you confirm the unit is OK. I about half-suspect a defective unit is what this is about.
-Dave
[email protected]
Message Edited by dwh on 03-29-200612:53 PM