Jason,

You can see my measurements (using REW) as posted on page 1 of this thread. It's a link to the Home Theater Shack, where I posted a number of plots of the 990's frequency response for the various modes.

I think the response that Scott gave is with respect to someone's (Kris, I think) assertion that since there is some time delay from input to output, then there must be some A/D/A conversion going on. It's slightly different than the bypass bass management problem that is the focus of this thread.

As you will be able to see from my original plots, there is indeed some type of high-pass filtering going on, but it's constant with respect to the varying crossover settings. It starts at about 100 Hz, IIRC. Also, although there is some type of strange filtering going on, we can't assume that it's a digital filter (nor can we assume it's not). It's just a filter at this point.

Thanks, Otto - I appreciate the clarification. I have no idea if it's happening in the analog or digital realm, but it's certainly quite audible and easily avoided by using the "Large" speaker setting.

Hopefully Scott's comments to me last month (on my birthday no less) that an updated firmware that fixes this issue is forthcoming were accurate.

Fingers still crossed...

- Jason

Hey LCSeminole. Haven't seen you around here in a bit.

I initially didn't plan to reply to your post because I didn't feel that it would aid the discussion in question. I also haven't been to Emotiva's site or forum in months - things got real busy last fall, around the time that Doug917 made a first pass at updating the LMC-1's manual, and by the time I got my head above water I just never got back to their site to see what was happening. I glanced at their site just now and didn't see any sign of a newer version of the manual than I saw last fall or of a FAQ for the LMC-1. Based on the assumption that the LMC-1's status is unchanged from when I lost track of it last fall (some time before it was discontinued), I'd take some exception to your comments here. True, Outlaw is overdue on getting a patch out for the 990 on this issue. Also true, Outlaw had a very difficult time with the 970's "no audio" bug. It's worth pointing out, however, that Emotiva's fixes for the LMC-1 (which took over a year and a half) only fixed some issues - others were "fixed" by labeling them features. A couple of quick examples might help. Signal acquisition time was "fixed" by achieving a two to three second delay (eliminating an intermittent 10 to 15 second delay experienced by some users), even though that two to three second delay is roughly double the one to 1.5 second delay found on processors like the Model 950 and Rotel's 1066 (both of which used the same DSP chip as the LMC-1 and were released back in 2002). Surround mode memory was fixed by saying that per-input memory was impossible due to hardware limitations, and even then I was never able to get a definitive answer on how the global memory worked - even after asking countless times in e-mails, at AV123's forum, and on Emotiva's own forum. That means that not only was the issue not fixed, it wasn't even explained in any complete fashion. For that matter, it would appear that Emotiva has also still not documented exactly how the LMC-1's bass management breaks when using Pro Logic II/IIx with Dolby Digital sources, even though the firmware that produces that break has been in production since June of 2006.

Just to be clear, I am not making this post to excuse the delay in a firmware update for the 990. I am making the post to suggest that posts comparing the issue under discussion with the LMC-1's mis-adventures is of no use to the discussion. In fact, they really feel like nothing more than trolling. Now, back to the discussion at hand (including Jason's very good question)...

Well, I did some testing tonight on my 990 and here's what I've found...

Testing with pink noise, even using the same 30 second snippet of pink noise designed to have very regular distribution results in some anomalies that suggest that testing with test tones may be easier. However, the data appears significant enough to draw some conclusions.

I ran three tests. I used the IASCA 1995 competition CD, track 27 which is pink noise, and a Sound Devices 744t recorder set to analog input at 16-bit, 44.1kHz with levels ~ -1dB peaks. I recorded the first 30 seconds of the pink noise track while playing back from my CD player:

First: CD Player RCA outputs > Sound Devices 744t
Second: CD Player > 990 set to Large speakers, bypass mode > RCA L/R line outputs > 744t
Third: Same as Second but with Small speakers.

I opened up the recordings and did a spectral analysis of the same section of audio (Blackmann-Harris with Fast Fourier Transfer size of 8192 samples.) The Second recording (990 Large) looks very much like the First in the bottom 2.5 octaves. But the Third run shows some dramatic dropoff in the lower registers. It's not so even and regular looking that I can absolutely identify the crossover type or slope, but extrapolating through some data, I would guess that it's a 12dB/Octave slope with a -3dB (crossover point) of 70Hz.

Some interesting data...
- down ~ 26dB at 20Hz
- down ~ 17dB at 40Hz
- down ~ 10dB at 50Hz
- down ~ 3dB at 70Hz

Hopefully we can all agree this is a VERY audible filter. I can't say if it's digital or analog, but it's there... and it's not supposed to be.

More tests if feedback warrants.

- Jason

JasonR,

thank you very much for your measurements, but, you know, no good did goes unpunished .
Is there any chance you could run a similar test in stereo mode by applying tone controls? I am curious to see whether the bass rolloff pattern seen in the "bug" matches the crossover and slope of the analog bass tone control.

My thinking is that if it does, then the bug might act totally in the analog domain, and it simply messes up the tone control settings. This doesn't make it any less of a bug, but since you are on this path of tracking it down, this might come across as of interest.

Just a thought...

I believe that in stereo mode (not bypass) with analog inputs, the signal is digitized and all equalization or tone control is handled in the digital realm. With digital signals, the EQ is digital.

I believe everything going into 990 regardless small, large, digital, analog is more-less digitized and all x-over filters, lips delay, etc. are handled in the digital realm. The volume control is digital right?
Regards
Kris

The volume control is applied in the analog domain, not digital. Crossovers, tone control, channel trims, channel delays, and AV sync are all digital domain. In most cases, analog signals are converted to digital, but not always. Bypass mode is supposed to preserve the analog signal all the way through, although some users are reporting behavior that makes them question if that is operating as intended.

It is digital potentiometer not analog right? So if it digital how it could be in analog domain?
Kris

I’m no audio electronics expert, but I know there are wholly analog circuits that can be used as volume controls where the audio signal is not run through an exposed resistive conductor with a sweeping arm moving along the conductor.

The digital operation of the 990 volume knob or remote control could, for instance, be converted to a controllable, steady analog voltage of say zero through one volt dc and then that dc voltage used to govern an analog circuit through which the audio signal is passed when in ‘bypass’. I don’t know if that’s actually the case, but it’s possible.