Dec 31

Solving Sneaky Audio Issues

Over the holidays, I’ve spent quite a bit of time tackling some very tricky audio issues in the rock lab. Issues that have been plaguing me for quite a while, but I didn’t have enough dedicated time to solve.

I have intentionally created an all-digital studio, and although I also have a turntable and LP’s because I love the sound of warm dynamics of analog, for the jams and recording that I do, the digital realm is infinitely more convenient…but it has it’s own set of challenges. 🙂

Challenge 1: Quiet Strat
Strat sounds awful via POD HD 500. My Red Strat (a Squier Stagemaster from the 90’s) is a Humbucker / Single / Single guitar, and has always sounded lovely and hollow like a typical Strat. But connected to the POD HD, it sounded weak and sad. I tried everything I could think of in the patch settings on the POD to get it to sound halfway decent, and it just never did. So I put it aside, and pulled out the Fretlight – it has fancy Shelby Designs pickups, so I figured it should sound fine. Nope. Same issue. I spent hours searching for pickups and such to find something decent…but just didn’t have the $$ to try it on a whim. So, I pulled out the blue Stagemaster (an Ibanez RG clone, Humbucker/Humbucker), on which I’d installed a Alumitone Deathbucker pickup. Sounded OK, but there were still issues. I put the whole thing aside for a couple days, and then came back and pulled the POD out and set it up out from under the desk. And lo and behold – the “Input Pad” switch was on. There was a similar switch on my old POD X3…and I had it on most of the time, but I hadn’t seen it on the HD500. They’d moved it to the top of the unit, I didn’t notice it since it was under the desk. I flipped it off of Pad and lo and behold everything sounded wonderful. Must be a stronger DB reduction than the X3 version was. Great! Except for this strange high-pitched ringing after every note.

Challenge 2: High-Pitched Ringing from POD HD 500
I have the POD connected to my MOTU 896mk3 via a S/PDIF digital cable. It saves me running more audio around, and bottom line the POD and the MOTU are both all-digital inside, so if I ran analog from the POD to the MOTU, it would be going Guitar (analog) -> POD (digital) -> Audio Cable (analog) -> MOTU Input (analog) -> MOTU mixer (digital). Saving a few A/D->D/A steps makes sense. Plus I get stereo with only one cable, and can record at very high sample rates if need be. However, there are some tricks to making S/PDIF sound right. Trick #1 is to make sure that the POD Output and the MOTU input are set to the same settings. Which I had done when originally setting it up. And if you don’t have it right, typically you hear nothing but horrible digital noise – so pretty obvious. In this case however, the settings on the MOTU side had changed (probably when I did a full reset on it a while back), and it was just slightly off – the MOTU side was at 44.1khz sample rate, and the POD at 48k. I flipped the MOTU to 48k, and voila – high-pitched ringing was gone. Looks like it was a subtle form of digital distortion. To figure this out, I listened to the guitar direct into the MOTU – no noise…I listened to the headphone output from the POD – no noise. So pretty much had to be the digital cable – checked both ends, and voila. Also, when the POD is not on (power unplugged), but the mixer is, I get whooshy digital noise coming into the cable. So I have to mute that input if the POD is unplugged.

One thing that kept eluding me here – since I run the Mac’s digital audio out into one of the ADAT ports on the MOTU via a TOSLINK cable, you have to use the Audio/MIDI Setup application on the Mac to make sure your sample rate from the Mac matches the MOTU as well, otherwise IT will have the strange distortion on it as well. Everything has to match! In my case, I set everything to 48k.

Challenge 3: DVI Audio Whine From Yamaha THR-10
I love the tones and feel of the Yamaha THR-10 – and it does have a USB output – but that output doesn’t play well with the MOTU mixer…unless I run some routing on the Mac side to take the USB audio and route it back into the mixer. Which I’ve done…and it just doesn’t sound right. So I’ve been running the headphone output of the THR into an analog input on the MOTU. When I run it with the power supply plugged into the THR, I hear the DVI Audio Whine from the various computer equipment through the headphone output. If I wasn’t having to amplify the output of the THR a bit (with the gain knob on the MOTU input channel) to get the levels to match, you’d probably never hear it, but with things turned up, it’s super-annoying. Bottom line, I need to run a balanced cable from the output of the THR into the MOTU to shield it from the RFI. However, the stereo headphone on the THR won’t support that. So I’ve ordered a unbalanced->balanced converter to try as a last resort. It will also be useful for connecting my turntable to the MOTU at some point, so it’s not a one-trick pony. 🙂

So there you go, three ‘simple’ problems that took me a dozen hours of hair pulling to sort through…I hope if you had any of these issues that this helped you!