Input Levels: Hotter on the Right

zs941 wrote:
think what you want, professor but you're wrong. you may not be able to hear any difference but you have lost data. it is not the same data you sent it because bits have been removed.

So educate me ol wise one. What sort of data did I lose?

I know you said that you don't want to sample from your SPDIF outs of your sound card....I wouldn't either. No point in moving a sample from your computer to the MPC just to return it to the PC. But if someone wants to do that they CAN. Regardless if you dislike the fact that you would lose your 'data', which is only true if you are sending a sample into the MPC that was recorded at a higher sample rate. As far as my own personal set-up...my mixer can 'dither' audio to be sent to my MPC without pitch changes or loss of 'data'.

I am far from a tech head. But all this talk about zeros and ones and capturing an audio signal without losing data....its so funny. First it was 8bit..12 bit....16bit...20bit...24bit..32bit....When will it stop When sampling recorded material, you are (I assume) trying to faithfully re-capture/reproduce a sound. At one time 16 bit was the shiznit. 20 bit and then 24 bit came, which was said that it captures sound more faithfully. Now we have 32bit that claims to do even better...not to mention all the higher sample rates. So please educate a brother....I don't want to lose my precious data....Should I record everything at 36bit/92khz to prevent my data from being lost? Will this add data to my signal So when I record a sample at higher rates...it is not the same because data has been added

zs941 wrote:
apparent and actual are two different things. you've actually lost data but apparently you can't tell. which is fine. it's all about the ears, right, so do what your ears tell you is good. seriously. but don't kid yourself or others into thinking that pitch-shifting a f*cked up sample either dithered or replaced the data you lost.

Hmmmm. Just because I had to pitch-shift the sample recorded at a higher bit/sample rate..it doesn't mean that it is F Up. Don't kid yourself into believing that.

The Jay-Z vocal I tested was ripped from a CD recorded at 44.1khz. I imported it to a track set at 48Khz. Yes, the pitched was changed when sample rate was converted. Sounds as good/better than the original...even when I went back down using the MPC..whether data was lost, added, subtracted, multiplied, or whatever...still sounding the same. I guess I should say to my ears. But, I could do a blind test on my family

zs941 wrote:
i never said you can't record different bit depths or sample rates into the MPC (i actually said you can). the MPC will record what you send it, no doubt, but what you get is not a digital copy as you may expect. what is very UNTRUE is to claim that the MPC correctly records that data, that is has a bit converter, that it has any form of dithering, or that the data is there and you just need to pitch-shift it. You clearly understand very, very little about digital audio so do everybody a favor and hit the books. of course i'll post my finding in the forum but discussing this with you is a waste of time because you keep claiming to know all sorts of stuff that you clearly don't. just admit you don't have a clue, ask some quesions, do some reading, or shut up. For somebody who gets so uppidy when somebody makes false claims about the MPC it's odd that so far in this thread you've made at least four.

Twan...don't get mad

With you here in the forums, I will glady be your pupil and learn everything about digital audio., because I don't know that much..just a little. I do get confused reading all the zeros and ones in the data streams of the samples I record.

As far as being 'uppidy ' I am from the inner city streetz..never been called that before But I will always reply when someone doesn't know how to use their MPC and post some nonsense.

About the 'dithering'....I may have used the term incorrectly..or loosely. I do know the fact that when your record audio at greater than 44.1khz, that you WILL have to 'dither' the recorded material one day if you want to burn to CD and play in standard CD players. (I GUESS you will be losing data huh? ). My software DAW and my mixer has the ability to 'dither'. I had no idea what 'dither' was until I bought my first highend digital mixer. In plain English, dithering was converting a signal recorded at higher sample rates to be used in a standard CD player. I used this term loosely when talking about the 2500. Because the fact remains that the MPC will still capture the audio signal and convert it to 44.1khz/16bit. I have no plans to test the audio to see how much data, if any, was lost. But since you are the expert, don't be uppidy..and share your knowledge.....................................without hiding it in a PM.





I really enjoy these exchanges. My wife is looking at me crazy wondering why I am smiling writing/posting in this forum.

You got ta love it.

Peace.

Who got next

I agree it not simple, but I suggest the following rule:

Dithering applies to converting bit depth. Like going from 24 bit to 16 bit. When you convert bith depth "dithering" is an optional post-processing that prevents a harsh quantization noise from occuring.

Changing sample rate (like going 48kHz to 41kHz), is not called dithering, it's something different.

Can we agree on that? or am i wrong?

jahrome wrote:...In plain English, dithering was converting a signal recorded at higher sample rates to be used in a standard CD player. I used this term loosely when talking about the 2500. Because the fact remains that the MPC will still capture the audio signal and convert it to 44.1khz/16bit. I have no plans to test the audio to see how much data, if any, was lost. But since you are the expert, don't be uppidy..and share your knowledge.....................................without hiding it in a PM.

No, that's not it. Sleepersriddle gave the exact definition below. Maybe you should go read that 02R manual. zs was going to PM me that stuff cause we're both interested in the results but it's off topic, and this thread's already been dragged off too many times. Just let it go.

sleepersriddle wrote:I agree it not simple, but I suggest the following rule:

Dithering applies to converting bit depth. Like going from 24 bit to 16 bit. When you convert bith depth "dithering" is an optional post-processing that prevents a harsh quantization noise from occuring.

Changing sample rate (like going 48kHz to 41kHz), is not called dithering, it's something different.

Can we agree on that? or am i wrong?

sleepersriddle, you're 100% right, dithering is a process to change bit depth. Changing sample rate is called sample rate conversion, it involves interpolating data down, using more maths.

I did error. Dither drops the bit rate. But it is correct that you have to dither down to 16bit in order to record to a commercial CD. Sample rate is completely different..but you will have to convert a song from 48K to 44.1 if you want it to playback in your home stereo.

Is is not OPTIONAL if you want to record to a CD and play it back on a home system.

And no....I will never leave anything alone.


And getting back to the thread....is my system/set-up the 'anamoly' or what? Does anyone else have an MPC 2500 that is doing fine in this regard

OK, you're nearly there. Sleepersriddle said dithering was optional, he didn't say sample rate conversion was optional. In fact nobody did.

Dithering IS optional. You can just truncate each high bit depth word down to low bit depth by chopping off the least significant bits, which isn't dithering, but works anyway. It's kind of like rounding your change to the nearest dollar just by ignoring the cents. So $5.06 becomes $5 but $4.99 becomes $4 it's not really accurate but in some cases it'll do.

So you get it? Dithering and sample rate conversion are two different processes that sometimes happen at the same time, but can happen seperately and don't do the same thing. The MPC doesn't dither or convert sample rate. If it dithered you could load 24 bit files from the flash card. If it did sample rate conversion it would play your 48k samples without changing the pitch.

Right, so I reread all the analogue input stuff, by the sound of things it's a tolerance problem in the line amps on the analogue ins on your mpcs. Cause all components have slightly different values you have to have trimpots in there to get the values the same. Sounds like Akai are having problems calibrating the MPC2500, that's fairly normal for a first production run, the workers and QC guys need to learn the ins and outs of the new thing they're making and it takes a while to get the hang of it. I'd email akai if I were you, they can probably recalibrate the inputs for you but you'll have to send it off. Then again they might just tell you bad luck.

One thing I was wondering though, you guys said the difference in the two levels wasn't as bad when you dropped the input gain down. Were you increasing it on the output of the 02R/machinedrum so it was hitting about the same level as it was with the input gain up high? Just want to discount the possibility it only looks like a smaller difference cause you're right down the bottom of the graph.

morgan wrote:

OK, you're nearly there. Sleepersriddle said dithering was optional, he didn't say sample rate conversion was optional. In fact nobody did.

Dithering IS optional. You can just truncate each high bit depth word down to low bit depth by chopping off the least significant bits, which isn't dithering, but works anyway. It's kind of like rounding your change to the nearest dollar just by ignoring the cents. So $5.06 becomes $5 but $4.99 becomes $4 it's not really accurate but in some cases it'll do.

So you get it? Dithering and sample rate conversion are two different processes that sometimes happen at the same time, but can happen seperately and don't do the same thing. The MPC doesn't dither or convert sample rate. If it dithered you could load 24 bit files from the flash card. If it did sample rate conversion it would play your 48k samples without changing the pitch.

Ok. I knew setting the sample rate and bit rate are 2 different processes. There was never any confusion there. I was inmcorrectly calling both 'dithering' because I always set them together when recording/rendering audio ready for CD.

So you said DITHERING IS OPTIONAL?? So if I am recording a track at 44.1Khz (sample rate) and at 24 bit depth rate..I can burn this audio file on CD and play it back on my home stereo??

morgan wrote:
'You can just truncate each high bit depth word down to low bit depth by chopping off the least significant bits, which isn't dithering, but works anyway. '

What do you mean by this?? Truncate/choppinmg?? How and with what?


As far as the analog input stuff
I am the only one (I think) that is not having this problem..the anamoly. As stated earlier, I get the same results whether I use my MPC 2500, Fantom XR or Fantom X6.

jahrome wrote:Ok. I knew setting the sample rate and bit rate are 2 different processes. There was never any confusion there. I was inmcorrectly calling both 'dithering' because I always set them together when recording/rendering audio ready for CD.

So you said DITHERING IS OPTIONAL?? So if I am recording a track at 44.1Khz (sample rate) and at 24 bit depth rate..I can burn this audio file on CD and play it back on my home stereo??

Honestly, I'm not sure it it would play at all but my guess is that it wouldn't but I'm not sure about that. You could definitly carry out that experiment and let us know. I would be sort of interesting.

jahrome wrote:What do you mean by this?? Truncate/choppinmg?? How and with what?

Truncate simply means to reduce in size by removal. So, if you gave me a 24 inch board and I chopped off (truncated) 8 inches of that you now have a 16 inch board. The same thing happens with digital audio but it happens to bits and a bit is just a 1 or 0 and there is a string of 24 or 16 of them in a row that represent a number. You can represent a bigger number with 24 bit (see a previous post for the actual numbers if you're curious) so you get a greater degree of resolution per sample. Now, wether or not that is usefull...that's a whole other thread for a completely different forum...

jahrome wrote:As far as the analog input stuff
I am the only one (I think) that is not having this problem..the anamoly. As stated earlier, I get the same results whether I use my MPC 2500, Fantom XR or Fantom X6.

Well, the reason I even asked about an anamoly in your setup was that you're seeing it on all of your gear but I'm not. I certainly didn't mean to say your setup is wrong but there could have been things you would know about like, "the electrical wiring in my studio is really old", "i live near a radio tower", "i've had conditioning problems", "my audio cables are getting old", etc. Then again, you may have something setup wrong but that wasn't my assumption.

zs941 wrote:
Well, the reason I even asked about an anamoly in your setup was that you're seeing it on all of your gear but I'm not. I certainly didn't mean to say your setup is wrong but there could have been things you would know about like, "the electrical wiring in my studio is really old", "i live near a radio tower", "i've had conditioning problems", "my audio cables are getting old", etc. Then again, you may have something setup wrong but that wasn't my assumption.

I am not the one with the problems. I don't have any channels that are hotter than the others...in any gear. The anamoly was refering to the fact that I am the only one that doesn't have the problem

I am anxiously waiting for Morgan's response to my earlier post.

jahrome wrote:From my experience with MPCs, this is common.

I just duplicated this test with a sine wave coming from my O2R. When I have the sine wave coming into the ANALOG inputs of the 2500, I get varying results..the left channel was a little hotter. I used the same cables and switch the right and left channels. The right channel was a little hotter. The one thing I didn notice is that if I kept the record gain of the MPC 2500 low, I get pretty even results...as I increase the gain, I get a little boost in either the left or right channel. I did this test using unbalanced cables.

I performed the same test using the digital inputs and got even results on both the left and right channel.

ok, maybe i'm confused but i read that as you seeing the same behavior (which based on what you just wrong could be attributed to an anomaly with the cable you used)

the there was this.

jahrome wrote:
No use of complaining. It is really not that much of a difference and can't see why it would be annoying. In fact, not only the MPC does this. I have plenty of synths connected to my digital mixers. The L/R channels of these synths do not always register exactly the same on my mixers meterbridge. An I am using sytbs from Korg, Yamaha, and Roland.

I would try this test again using balanced cables..but the sound source would have to be balanced as well.

which made it sound like this was common in all or most of your gear which is [partially] how we got to the point that we're at now. are you not having the signal desrepencies you originally described?

Has anyone with this "Hot Channel" tried sampling off a cd to see if it is still hot on one channel. Maybe i'm talking out of my *** but, raw synthesis isn't going to be perfectly panned center their are to may varible. I don't know this for certiain. a cd might be a better test. Cd's on my meter bounce pretty even ( professionally mastered cd's ) just a suggestion. My fantom does always put out a even signal only a sliver but that is why you have to compress/limit your shit so it sound refined among other things but just a quick example

mrnymms wrote:
Has anyone with this "Hot Channel" tried sampling off a cd to see if it is still hot on one channel. Maybe i'm talking out of my *** but, raw synthesis isn't going to be perfectly panned center their are to may varible. I don't know this for certiain. a cd might be a better test. Cd's on my meter bounce pretty even ( professionally mastered cd's ) just a suggestion. My fantom does always put out a even signal only a sliver but that is why you have to compress/limit your **** so it sound refined among other things but just a quick example

You just saved me alot of typing

zs941, earlier in the thread, I was talking about sampling audio from any given source. Later, I used the more logical apporach by using a test tone..which gave me standard readings across the board.

Morgan...Morgan...Morgan....

So you said DITHERING IS OPTIONAL?? So if I am recording a track at 44.1Khz (sample rate) and at 24 bit depth rate..I can burn this audio file on CD and play it back on my home stereo??

I already know the answer..I am just curious to see what your reply will be today since yesterday, you said that 'DITHERING IS OPTIONAL'


mrnymms, when sampling via the digital input, the TRIM MENU shows that the L/R of a stereo sample is indentical. However, when I sample from the internal CD-M25 in stereo and go into the TRIM MENU, it shows that the L/R side of the sample were not exactly identical as far amplitude/volume. What was even more interesting, is that when I playback the samples recorded both ways through my mixer using analog outs, the mixer read the L/R channels of the incoming samples coming in at the same dB even though L/R channel of one of the samples were not identical.

ok, well in your first response (it's quoted above) you said you used a test tone which i did as well. let me also re-quote the following.

From my experience with MPCs, this is common.

also, i'm not going to discount that there may be benefit from sampling a mastered CD as a test source however that will almost undoubtibly have a signal variation (intentionally) whereas the controlled tests i've done should not.

my origninal question was more or less this: is anybody but me seeing a signal discrepency between channels?

the answer to that was yes, and then sometimes, and then no, and then some more no. so, i'm willing to just work with my setup and get things to work for me. if i find something concrete i'll let you all know but otherwise I'm happy to leave this thread unless somebody else wants to share their own experience to corraborate or give useful suggestions on what i might change or check out.

a friend just pointed out to me that arguing on the internet is a lot like the special olympics: even if you win you're still retarded. the race is all yours, jahrome. you sir, are a winner!

You are a funny guy, please don't go.

I do hope you solve all the problems you are having with your gear.