So you took the analog signal from the POD and the digital signal at the same time into the 002r?

Wouldn't the analog signal have gone through the POD's AD and the DA conversion first and then through the AD conversion in the Digi?

Of course, I don't think this one extra step (err...2) made a huge difference, but a difference nonetheless.

Are you tied to doing your conversion tests using bass?

When I'm comparing A/D converters, I'll often use a normalled patchbay to send the same signal to both converters and then send the input into my DAW and reverse the phase. Of course, there's no way to tell which one is leaving the artifacts. (Well there is...but you have to bounce the remaining artifacts from the summed and reversed signal and then experiment by adding it back to each raw signal - phase reversed, bounce it down and then see which one causes a total cancellation....too confusing?)

I can't say I've ever done this for anything more than my own personal edification. It's interesting to hear just what is left over. What's really interesting is when you find that "inexpensive" converter that leaves hardly any artifacts when compared with one of those really expensive converters....

Cucco wrote: So you took the analog signal from the POD and the digital signal at the same time into the 002r? Wouldn't the analog signal have gone through the POD's AD and the DA conversion first and then through the AD conversion in the Digi? Of course, I don't think this one extra step (err...2) made a huge difference, but a difference nonetheless. Are you tied to doing your conversion tests using bass?

Right. I realize I can't isolate either converter this way, I have to listen to the effect of both. But, frankly it's the first time I've done a test that isolated converters from the rest of the system. I'm not tied to using bass for the test, but it is a Bass POD and I was recording bass tracks this morning. I was planning to add some electronic keyboard tracks, and I could try putting them through the POD (even thought the bass POD is mono).

Cucco wrote: ....Of course, there's no way to tell which one is leaving the artifacts. (Well there is...but you have to bounce the remaining artifacts from the summed and reversed signal and then experiment by adding it back to each raw signal - phase reversed, bounce it down and then see which one causes a total cancellation....too confusing?)...

Yes, too confusing. Run that by me again, please.

Sorry...let me explain further.

Take the original 2 comparisons (wave 1 and wave 2). Flip the phase on one of them.

You're left with the remnants of the comparison between the two (some HF stuff and maybe a single note here and there elsewhere in the spectrum)

Take wave 1 that you had and add the remnants to it. Flip the phase of the remnants (you won't hear much of a change at all - if any). Now, bounce that track down to...let's call it Track A now.

Now, load up your daw and put Track A down with Track 2. Flip the phase on one of them. If there is no sound at all, then you learned that Track 1 was the track that contained "extra" or errant information. If you hear sound, then you know that it *could* have been Track 2.

The likely scenario is, however, that both tracks contained information that wasn't in the track. However, if one AD converter appears (audibly) to contain additional HF information, this AD converter may be considered to be "brighter" or more sterile (depending upon your verbage).

The opposite could be said for the other AD converter.

These are, of course, gross generalizations but nonetheless it's what I suspect you're looking for between the comparitors.

On a different note...I'll be in the Charlottesville area Tuesday afternoon evening and again later in the month a few times recording UVA. You're welcome to come sit in on the sessions and if your bari-sax tooting daughter is interested too, I think I could make some room.

Of course, it's hard to bring a Hokie into Cavalier territory without starting a war....

PS - it's their marching band that I'm recording.

J.

Jeremy-

Tuesday will be bad for us (Alice will be down in Georgia auditioning for their music school and I'm doing senior exit interviews) but when are you recording later in the month. I will not wear any Hokie regalia, especially since we are currently tied with the Hoos for the lead in the ACC coastal division. We play them in C'ville in three weeks.

If I understand your experiment though, I would expect your mixed track to cancel track 2. Here is how I understand it:

track 1 = base signal + noise 1
track 2 = base signal + noise 2

remnants = track 1 - track 2 = noise 1 - noise 2

track 1 - remnants = base signal + noise 2 = track 2

Unless I'm missing something I don't see how it tells me anything about the relative sizes of noise 1 and noise 2.

Cool. I'll let you know the next time I'm there.

I think I'm confused now about my experiment....

Let me see if I can put some graphics to it to help out.

I think the above explanation though is over complicating it - adding noise where there shouldn't be.

Maybe my language is confusing. The way I am thinking about it, for a given analog signal there is a theoretically idea digitization - one that produces a band limited version of the analog signal exactly. I am calling any deviation from that "noise." Probably not the best term to use, maybe "conversion error"?