Waveform problem - PLEASE HELP

[Busman Audio]

Thanks for your support guys. There is always more to learn. I am happy to provide this service and I would not let a few issues get in the way. Things happen and those things will get fixed. We will overcome these issues and move on in our quest for great sound at a price that is affordable.

Thanks and +T  to all of you.

[stirinthesauce]

In a seperate issue,  I wasn't aware that a stock UA-5 shows signs of clipping at -3 dB.  I realize the light is programmed to light up at -3 dB per the manual but does anyone have a stock mod UA-5 that they've verified this on and could show some wav captures?  I've looked at a lot recordings made with my stock UA-5 and never noticed.  I always try to keep my levels high.  I easily could have missed some rounding of the peaks in the -3 dB to 0 dB range.  I'll go through  a few of my stock original wavs tonight to see if I can spot it.

Here is the thread I was referring to.http://taperssection.com/index.php?topic=57630.0Never run a stock unit so I can't comment and have never done any testing with sine waves on my unit.  Maybe Richard can chime in with some of his experience with the stock units.

[poorlyconditioned]

In a seperate issue,  I wasn't aware that a stock UA-5 shows signs of clipping at -3 dB.  I realize the light is programmed to light up at -3 dB per the manual but does anyone have a stock mod UA-5 that they've verified this on and could show some wav captures?  I've looked at a lot recordings made with my stock UA-5 and never noticed.  I always try to keep my levels high.  I easily could have missed some rounding of the peaks in the -3 dB to 0 dB range.  I'll go through  a few of my stock original wavs tonight to see if I can spot it.

Here is the thread I was referring to.http://taperssection.com/index.php?topic=57630.0Never run a stock unit so I can't comment and have never done any testing with sine waves on my unit.  Maybe Richard can chime in with some of his experience with the stock units.

Yep, that's me

OK, *I believe* there are two separate issues here.
- the UA5 shows significant distortion (eg., 1% THD), when driven above -3 or -6dB.  I *believe* this is due to the ADC and not the opamps.
- the observed distortion (clipped/assymetrical sinewaves) is different.  I *believe* this is an opamp problem.

I think the first is a *defect* in the design of the UA5, but I cannot explain why or how to fix it.  For comparison, driving something like a Minidisc with the same signal (line in, up to -1dB) does *not* produce the same distortion.  This unit it *broken* in my opinion!  A cheezy workaround is to run at -6dB always.  Never let the clip light turn on and you will get better sound out of it, even if you have to add that 6dB back in post.

The second is *probably* an opamp problem.  I've experienced this before on swapping various opamps.  It could be defective amps, connections broken, or just the wrong opamps.  I hope Busman2 can track this one down.  I would not even know where to start!

OK, +T to all of you for isolating and tracking down these problems.  It is not easy!  And +T to Chris for great service.

  Richard

[beanstalk]

hmmm
I have been real happy with my Bm2p+ mod I have not noticed this problem with mine. I don't recall which # mine is .

I have not run any full tests on it I will have to try and run some for a comparison but everything has been real clean for me, with the exception for some crackling which I am 99% sure it is my left mic cable.

note to self get some decent cables

Same here. No problems at all. #11 (I believe)

[jeromejello]

Echoing terrapinj's comments, turnaround time was great in getting this mod, clear communication, top notch work.  Have made many great recordings in the past 8 months with this box.  I think this community is really priveleged to have someone offering these mods to us at such reasonable prices.

QFT

i also went ahead with my bm2p+ due to the overwhelming kudos for the sound and service busman delivered.  i have no intentions on putting chris on the spot, i was just trying to facilitate a dialogue with some of the other users of this box to see if there was anything in the commonality that could help everyone with one of these things.

+t to the bm2p+ team 

[morningdew]

Stirthesauce,

Excellent link, I just learned a ton.

Poorlyconditioned,

Thanks for chiming in!  Learn me something though  .  Throughout the thread you seem to be assumming that the JB3 does nothing to manipulate it's line out?  Is this true?  And this also leads me to the question, why do we trust the soundcard?  I'm assumming you go straight from your sound card to line-in on the JB3 to line-out of the JB3 to the RCAs or the XLRs of the UA-5.

Aren't soundcards from computers notoriously crappy?  Could the soundcard or the JB3 be introducing this harmonics?

This is why I have been actually recording the sound (sine waves) coming out of my speakers.  I thought I would be eliminating a lot of signal processing by doing it this way.

[beanstalk]

Stirthesauce,

Excellent link, I just learned a ton.

Poorlyconditioned,

Thanks for chiming in!  Learn me something though  .  Throughout the thread you seem to be assumming that the JB3 does nothing to manipulate it's line out?  Is this true?  And this also leads me to the question, why do we trust the soundcard?  I'm assumming you go straight from your sound card to line-in on the JB3 to line-out of the JB3 to the RCAs or the XLRs of the UA-5.

Aren't soundcards from computers notoriously crappy?  Could the soundcard or the JB3 be introducing this harmonics?

This is why I have been actually recording the sound (sine waves) coming out of my speakers.  I thought I would be eliminating a lot of signal processing by doing it this way.

JB3 has Harmonic Distortion Output 0.1%

[bgalizio]

My UA-5 is busman #8. Never seen anything like that in my recordings. I'd be interested in the root cause, once that gets figured out!

[poorlyconditioned]

Stirthesauce,

Excellent link, I just learned a ton.

Poorlyconditioned,

Thanks for chiming in!  Learn me something though  .  Throughout the thread you seem to be assumming that the JB3 does nothing to manipulate it's line out?  Is this true?  And this also leads me to the question, why do we trust the soundcard?  I'm assumming you go straight from your sound card to line-in on the JB3 to line-out of the JB3 to the RCAs or the XLRs of the UA-5.

Aren't soundcards from computers notoriously crappy?  Could the soundcard or the JB3 be introducing this harmonics?

This is why I have been actually recording the sound (sine waves) coming out of my speakers.  I thought I would be eliminating a lot of signal processing by doing it this way.

I generate sinewaves/testpatterns in a program (like Audacity), transfer *via firewire* to the NJB3, then use line-out on the NJB3 to the test device.

Line out on NJB3 is pretty good.  Unlike headphone out, which is "scooped" (accentuate highs and lows), NJB3 is flat.  I've measured it.  Distortion might not be great, but it is certainly good enough to find 1% or more distortion in other gear!
By the way, not all line out are flat.  For example, line out on my MD is just the same shape as headphone.

Moral of the story: Assume nothing works as advertised.  Even if it sounds OK, there can be big problems.  Test everything.  I haven't got a distortion meter or other fancy audio gear, so this is all I can do.  But I can still find big/obvious problems that seem to be overlooked.  Who the hell designs this stuff with bugs in it?  Well, we know M-audio does

  Richard

[stirinthesauce]

OK, so let me see if I get this straight.  Richard, Chris or anyone, please feel free to set me straight, just seeing if I'm following correctly to what I talked a little bit with morningdew this morning via pm.

Because of the stock adc/design of the ua-5, there *will* be some distortion at under -3db or -2db.  Maybe soft clipping So this distortion will be apparant with any mod, whether oade or busman2 or anyone elses as the adc is not changed, just the opamps.

Does that statement stand to reason or am I completely missing the mark?

Great discussion folks!  

-Jon

[poorlyconditioned]

OK, so let me see if I get this straight.  Richard, Chris or anyone, please feel free to set me straight, just seeing if I'm following correctly to what I talked a little bit with morningdew this morning via pm.

Because of the stock adc/design of the ua-5, there *will* be some distortion at under -3db or -2db.  Maybe soft clipping So this distortion will be apparant with any mod, whether oade or busman2 or anyone elses as the adc is not changed, just the opamps.

Does that statement stand to reason or am I completely missing the mark?

Great discussion folks! 

-Jon

Yes, that sounds right.

- The ADC has got maybe 1% distortion (instead of 0.1% what it should be).  It *should* not have this.  Probably some setup of the ADC is at fault.  It is a defect, but I don't know how to fix it.  So, drive at -6dB or so to avoid this.

- the other problem (very obvious assymetry/clipping of inputs) is probably due to the opamps, either incorrect opamp, or some defect in the opamp or connections.  All of us (Busman, Oade, etc) are only changing opamps (and capactors, and maybe power supply, phantom parts).  As far as I know noone is changing the ADC, so the 1% distortion will persist.

  Richard

[morningdew]

Poorlyconditioned - Thanks! Great explanation I think I have it now.

Just so we are all on the same page, here is what busman has claimed his mods provide:

This is why I was worried my problem was cause by the "new" phantom power" caps but busman assurred this is not the case:

So here we go.
  First I have taken many hours of time and tons of research to figure out how to do this and what parts to change out and what parts should be the replacements. There are tons of great op amps out there to change the sound of a pre amp and all there is to go by is the data sheets to figure out what is the best for the application it is being used for. So to start I found a high speed low noise op amp that had a relatively fast settling time for quick dynamic changes.  Once I found a good sound I found that those didn't meet my gain requirements so I found another op amp to drive the A/D converter that would give a better gain at the  point at which it enters the ADC. The difference in noise is amazing I can crank the gain pots up to the 5 o'clock position before noticing any noise to my ears. After finishing this part of the mod I figured why not go all the way and do the capacitors like Oade does to really clean up the signal. So I went to work researching capacitors used in high end audio upgrades and decided on the brand I wanted to try. These are not film capacitors like Doug uses they are caps made specifically for audio applications and are used in high end audio amplifiers to give a totally transparent but non fatiguing sound. Again going for lower noise higher signal pass through. First I tried changing the input caps and this was very pleasing to my ears. It lent a smoother sound in all frequencies and gave the soundstage a little more clarity. Next I changed out the phantom power capacitors which there are a total of 10 this goes along the same lines as before in cleaning up the signal and gives the phantom supply a better more consistent voltage to power the mics.  I also now change out the op amp in the analog RCA input path to improve that sound for matrixes or analog patchers. These mods are done by ears for ears not specs.
     I don't claim to be an electrical engineer so don't pick me apart. I have merely provided a service that a lot of people have found useful. Also I don't claim to know exactly what Doug does to his but I am pretty positive I am on the right track. Anyone who gets this mod I hgihly doubt will be dissapointed with the results. I also don't want to claim a flavor of pre but this does lean to the transparent end of the spectrum. Please don't attempt these mods at home if you are not prepared to ruin a good pre it is not easy and does require special soldering tools other than a typical soldering iron.
   If you are interested in prices PM me and I will let you know. I hope everyone that has a stock non-Oade unit will consider this mod as it really does make a huge difference to you recordings and I know your ears will thank you, mine did.
  Thanks to all that have paid for this service I am very happy to see my handy work out there in the field.
I hope this answers most of the questions everyone has about my mods.

You hit the nail on the head.
Mine started
  BM2 mod = op amp replacement
  BM2+mod = op amps and input capacitors replaced
  BM2p+mod= phantom power caps, input caps and op amps are replaced

I have rolled all of it into one from now on it is all the BM2p+ mod because I feel the price is right and I might as well do all the work to make this thing sound as good as it can in one shot.

The reason for the 3 different mods was I was slowly working on getting the right components and yet wanted to offer what I could as I went along. I am offering good prices to those that don't have the full BM2p+ mod so they can get it upgraded the rest of the way if they like. Otherwise they can run them like they have them.

I do have a serial# system to keep track of them and what each one unit has as far as mods go.

[bgalizio]

I just wanted to confirm that my UA-5 does NOT have this problem, assuming my method was valid. It is serial number 8, if that helps Chris figure out which batch of op amps had problems. I created a sine wave, ran it from my iMac into the 1/4" inputs. Set it for when the peak light came on. The recording peaks at -2.2dB and shows a smooth sine wave when zoomed in.

[morningdew]

bg,

.  I would say no you do not have that problem.  Did you see my sine wave on the first page?

The only thing holding me back is that I haven't used the 1/4" inputs.  I don't know how all that works.  I have always used the XLR in's.  Obviously the 1/4" inputs work, I thought they were disabled with the mods.  I tried them briefly when doing the testing and couldn't get them to work but I only tried for a second and it was probably an error on my part.

I'd try again but my unit is out for repair.

[bgalizio]

bg,

.  I would say no you do not have that problem.  Did you see my sine wave on the first page?

The only thing holding me back is that I haven't used the 1/4" inputs.  I don't know how all that works.  I have always used the XLR in's.  Obviously the 1/4" inputs work, I thought they were disabled with the mods.  I tried them briefly when doing the testing and couldn't get them to work but I only tried for a second and it was probably an error on my part.

I'd try again but my unit is out for repair.

Yup, I dunno if the 1/4" inputs would cause anything to be different from the XLR inputs. I don't have a way to send a line level signal to the XLRs without hooking up my mics, which obviously wouldn't create a perfect sine wave since there would be some outside noise.

I believe the 1/4" input is disabled with Oade mods, but busman told me from the get-go that they were active with his mod.