I'm suspecting as I first did that the impedance range being higher means the previous models would be as noisy at the same range.  It's confirmed as not being mains hum from the unit as the behaviour is the same on a battery powered laptop.

I'd still be interested to hear from other users that were having trouble with signal to noise ratio whilst using a guitar or something else that actually requires Hi-Z though.

As I say the entire internet seems remarkably quiet about it which I don't think would be the case by now if there were real issues here.

I may yet be wrong of course...

Jonbouy


I'm suspecting as I first did that the impedance range being higher means the previous models would be as noisy at the same range.  It's confirmed as not being mains hum from the unit as the behaviour is the same on a battery powered laptop.

I'd still be interested to hear from other users that were having trouble with signal to noise ratio whilst using a guitar or something else that actually requires Hi-Z though.

As I say the entire internet seems remarkably quiet about it which I don't think would be the case by now if there were real issues here.

I may yet be wrong of course...

Yeah, that seems logical to me. The curiosity in me would still like to understand why the Hi-Z hums rather than hisses like the Hi-Z on my other interface, but all in all I guess (for me) it doesn't really matter. I've found that if I keep the knob at 12 o'clock or less it's not noticeable, and I typically have the pre set in the 10 or 11 o' clock range. If it ever does become a issue for me I also have an external pre/di so I can just go line in. My interest in this topic has been more a question of: "Should it do that?" rather than "This isn't acceptable"

Yeah it is pretty quiet. I haven't found any mention of this elsewhere either. The only thing I could even relate to this in anyway is a video review of the Octa-Capture (which I understand has the same pres) where the reviewer mentions that the pres are slightly noisy when phantom power is on. 

But as far as Hi-Z is concerned, I think most people won't notice this or if they do notice it they won't think it's out of the ordinary. I know I didn't until I found this thread and started testing things out.

The tech who replied to you is assuming the buzz is being picked up over the cable to an instrument, or the input is open circuit. A higher input impedance would in this case cause more sensitivity to interference.

However, as I said, the buzz is there when a shorted jack is inserted (impedance = 0). The buzz source is therefore internal.

Besides, the older Edirol units have NO buzz at all at Hi-Z, not just 1/3 less buzz.

The reason this is not widely noticed yet may be because the switch is now somewhat hidden on the back of the unit. My guess is few guitarists even know what it does and simply run their guitars low-Z.

audiyo

...a video review of the Octocapture (which I understand has the same pres) where the reviewer mentions that the pres are slightly noisy when phantom power is on.  

Thanks for that info, audiyo. This again is possibly overlooked because most condenser mics are high output. But one that is somewhat lower output may run into this problem. 
 
Do they say what kind of noise? (Hiss, buzz)

JazzSinger


The tech who replied to you is assuming the buzz is coming from an instrument plugged into the Hi-Z input, or is open circuit. A higher input impedance would in this case cause more sensitivity to interference pick-up.

However, as I said, the buzz is there when a shorted jack is inserted (impedance = 0). The buzz source is internal.

Besides, the older Edirol units have NO buzz at all at Hi-Z, not just 1/3 less buzz.

The reason this is not widely noticed yet may be because the switch is now somewhat hidden on the back of the unit. My guess is few guitarists even know what it does and simply run their guitars low-Z.

I agree, the buzz source has got to be something internal.

I don't think think the guy reviewing the Octa-Capture specified whether it was hiss or buzz. Just noise. 
I'll try to find a link to the video.

Edit: Here's a link to the Octa-Capture review: http://www.youtube.com/watch?v=Cx8Ou_Q0_uw

Hi guys. New to this forum but I have been reading about the quad capture with a view to buying (newbie to the whole recording scene)Not sure if it is of any use but I read a couple of user reviews from Amazon US/UK that had mentioned the noise problem. Quotes from the reviews below. "I found that anything above 0 volume on the analog outputs actually INCREASES INPUT NOISE. So I got myself a pair of Behringer MS40 with digital inputs. Then I found out the hard way that the digital outputs do not support 192 kHz, only 96kHz. So i can't monitor with reasonable input noise while the unit is operating in 192kHz. So effectively, this is a 96kHz unit if you want about 8 dB lower input noise." "The only issue I've had is too much USB noise in the form of high pitched hum & other weird artifacts. Went through all the troubleshooting you could imagine, analyzed my jacks for ground loops, etc. I solved it by disconnecting the Quad from the computer & plugging it into a powered USB hub instead. Instant relief."

Does anyone know if the OctaCapture also has this issue?  I am just about to pull the trigger on one....

Has anyone tried this with the Octacapture?

Just wanted to chirp in:  The buzz (background dial up modem sounding chirps when you lower screens, move the mouse etc) is a ground issue.  
 
I had this issue, tried everything under the sun (new balanced cables, powered usb expander, shielded USB cable, new graphics card, drivers, bios, everything on one outlet etc etc etc) and the only thing that worked was a Ebtech Hum X plug attached to the PC power cord.
 
They carry them in guitar center and they price match.  If you are pulling your hair out, pick one up from GC and if it does not work for you, then you can get your money back.
 
Now it is so quiet it I have to keep checking if the volume is turned up at all.  Happy days.  It also comes in handy when using two amps in stereo etc which has always given me the ground hum issue in the past.

I know the Octa-Capture has a ground terminal on the back. (not the Quad-Cature though) I've read where some guys have had good success silencing the Octa-Capture by grounding the unit. Might be worth a try on the Quad-Capture.