Topic: Korg MR-1

[Colin Liston]

I may have been the one who first said "brickwalling" in another thread http://taperssection.com/index.php/topic,80867.msg1076004.html#msg1076004

I only said that b/c what I recorded sounded like what used to happen to me with my D8 long ago.  So my apologies if I have muddied the waters.  The MR-1 has a switch, "line in" or "mic in" on the top.  After further inspection it is possible that my first recording could have been V3 > MR-1 via "mic in".    My bad.

[MattH]

One thing I don't understand is who is responsible for my brickwalling when peaks reaches -3.9dB....Is it because my MR-1 has a -15dB gain setting (too low or too high) or my MixPre gain was set too high (no markings on the MixPre knobs so cannot give any value)? And also why -3.9dB and not 0dB for brickwalling?? How did the MR-1 or MixPre decide to have brickwalling when signal reaches -3.9dB and above??

Let's distinguish between "clipping" and "brickwalling".  Clipping refers to levels running too hot into the ADC, resulting in >= 3 consecutive samples at 0 dBFS, and occurs in the digital domain.  Brickwalling is overloading of an analog stage and not tied directly to dBFS levels in the digital domain.  Generally speaking, a squaring off of the waveform at 0 dBFS usually indicates clipping, while squaring off of the waveform at some level below 0 dBFS usually indicates brickwalling.  So...in this case, it seems some analog is overloading. 

I'm not familiar with the MR-1.  Does it provide for line-in and mic-in?  If so, confirm you're running line-in.  Running mic-in with an external preamp may overload the analog mic input.  If it accepts line-in, what dBu level does it accept?  Then crosscheck that with the MixPre's dBu output as a starting point for trying to track down the cause.  The MixPre's dBu output should be lower than the MR-1's input dBu spec.

I think if you add the 15dB gain you are attenuating on the MR-1 to the -3.9dB you get +11.1 dB, which is 5.1 dB higher than the +6dB max input on the MR-1.

[Nick's Picks]

= "overload clipping shitty sound"

[SClassical]

I was going line-in when the above happened. Yesterday's concert was an experiment for setting my external preamp levels with MR-1 gain setting at zero. Now I think I got the right settings on my MixPre and I plan to keep the settings...I pulled off the knobs (as Brian suggested) so hopefully it will not change. I plan to adjust the gain slightly on the MR-1 depending on how close I am on the stage, etc... I think leaving it at "0" is a good point so I have lean way both ways. Tonight I will record another concert hope I'm sorted with gain settings!

[it-goes-to-eleven]

The gain on this thing will remain a mystery until someone does some actual tests and shares the results..  I generally won't run a new recorder without doing those type of tests...

Similarly, nobody has posted a recording of the noise floor at various gain settings...

Korg shoud just send a loaner to guysonic for testing... unless they have something to hide

[SClassical]

I PM guysonic already offering my MR-1 to him to do the test - the only thing is I'll be using it until mid June..So I plan to let him test mine in mid June - if he is still interested. But I hope my DC offset problem (http://taperssection.com/index.php/topic,81258.0.html) on both channels does not affect the test.

[guysonic]

I PM guysonic already offering my MR-1 to him to do the test - the only thing is I'll be using it until mid June..So I plan to let him test mine in mid June - if he is still interested. But I hope my DC offset problem (http://taperssection.com/index.php/topic,81258.0.html) on both channels does not affect the test.

While Left channel offset does limit full scale output ability, input tests results should not be different than from units with normal or more acceptable near 0 DC output. 

However, chance is there's something in the analog processing chain causing this offset, and defective components (usually an IC or leaky coupling capacitor) like this have also been known to have less good low-noise specification. 

So maybe this DC problem is really an unacceptable defect that should be corrected by Korg under warranty BEFORE this deck is evaluated?

[guysonic]

So maybe this DC problem is really an unacceptable defect that should be corrected by Korg under warranty BEFORE this deck is evaluated?

Or BEFORE you record those upcoming shows

I agree that the offset could be caused by an upstream piece of gear, cable, etc.
I'd definitely try and record some music, white noise, etc into the unit directly and see what the offset is.  I'd try the recording in both pcm and in dsd.

Maybe test for DC making a recording with dummy load on each balanced input?  Suggest using two 100 - 1000 ohm resistors on channel's plus/minus input to ground; requires four resistors total doing the test in this manner. 

Solder one end of the resistors directly to miniplug tip/ring and then solder each other end to common sleeve terminal.  Make two of these plugs for the test.

Doing a recording with nothing else connected except a passive dummy load should settle the question of an external source causing this offset.


Let us know what you find out.

[Nick's Picks]

nice.
i'll get the parts for this tomorrow.
Thanks Q

[WiFiJeff]

Simon,

I PMed you earlier.  Converting a DSD file to 44.1/16 pcm and adding 24 dB of gain, I see no digital offset, either with the "DC cut" in AudioGate on or off.  So maybe your analog chain has an issue.

Jeff

[landshark]

I think this thread may be dead, I've also posted in another venue, but I had the same issue as Scy, regarding clipping/brickwalling.  The difference is that I was using mics directly into the inputs on the MR-1 (had setting on mics, not line).  http://taperssection.com/index.php/topic,82341.0.html

Additional note - somewhere along the way, however, something bad happend to the unit.  No physical trauma (dropping, kicking, etc.), and I don't think I severely overloaded it, but now whenever I try to set the recording levels in any of the non-PCM settings, the meters are maxed out even with no input hooked up at all, in PCM there's no signal even with gain turned up, and if I play back the samples on the unit, the sound quality's terrible and there's a wierd rythimic pulsing of the noise level.  Called Sweetwater and they conferenced in Korg technical department, who took down the symptoms and said they wanted to do some research and will call back.  Sigh.  The sound out of this thing is freakin awesome, but then I'm also comparing to a D8 and a MT <grin>.  It's a big step up from them, though.

Mike 

[SClassical]

Hi Mike,
I actually set my MR-1 gain to zero now (before it was -15dB). Now I don't get brickwalling and everything seems great. I reduced the gain on my preamp - mixpre. But I just left the gain on my MR-1 at "0". I only used it once since this gain adjustment and in that recording it sounded the best. So I'm quite pleased with it now because there is more head room at the high dB.

I'm going to do some small experiments with my MR-1 this weekend - I've got a feeling what is causing the DC offset in my recordings.

[SClassical]

nice.
i'll get the parts for this tomorrow.
Thanks Q

Hey Nick, read that you are sending your MR1 to Doug....Is he thinking of doing something with it?

Any thoughts on sending it to guysonic? I'm planning to send mine to guysonic mid June (if he's still interested).

[Nick's Picks]

no thoughts on guysonic...i'll leave that to you guys.
I just think Doug wants to play w/it for a while.

[Digital Quality]

I just nabbed one of these off flea bay.  I'm planning to run it off the analog of my V3. Do you think this attenuator Mike posted for an SMB app will work ok (except for balanced on both ends)?  http://taperssection.com/index.php/topic,56358.msg841636.html#msg841636