Art CleanBox II FR

[azjimmy]

EDIT
I re-did the measurements, and found them to be quite flat. See this post
http://www.hometheatershack.com/foru...html#post49929
Thanks
Jim


Hello all, been too long.
I've seen the Cleanbox threads, but I haven't seen anything for the CleanBox II, ao I thought I would run a quick freq response to see if it was just as bad.
I know my rig probably isn't as up to snuff as Ilkka's, but I think I got it reasonably close.
First is is the low freq only both channels, second is full frequency.






It doesn't look as bad as the Cleanbox, but it does have a bit of a rolloff, along with a rise in the mids to highs.

If it looks like I did something wrong, let me know and I'll shoot some more...

Jim

[brucek]

If it looks like I did something wrong, let me know and I'll shoot some more

Is it possible that you didn't clear the meter/microphone calibration file first?

The method would be to first clear the meter calibration file, then take a reading of a set of cables from line-out to line in of the soundcard only, with the soundcard calibration file in place. That should result in a perfect flat response.

Then add the ART into the loopback cables and take another reading. That will be the ART response.

Could you post with the same scale that Ilkka used here. It would be interesting to compare the two. I would think they used mostly the same circuits.

brucek

[azjimmy]

Can do Bruce. I should be able to get that tomorrow. BTW, I did use the method you described.
Removed the meter/mic cal file, run the loop-back, add the ART. I did have to bump the levels up when I ran the Art. Also, when I ran the full freq sweep, I added an off-set to bring the reading down to "0" to make it easier to see the drop. Is there a better way?
I am fairly familiar with REW, but this is my first foray into using it to evaluate a piece of eqipment.
Thanks as always, Bruce
Jim

Edit- When I say I added an offset, I did that post-reading in the Trace Adjustment field
J

[Ilkka]

azjimmy wrote:

Edit- When I say I added an offset, I did that post-reading in the Trace Adjustment field
J

That's exactly how I do it too.

[azjimmy]

Thanks Ilkka. I just got done reading that thread Bruce recommenced.
I've been looking at the data I got on my first run and had a few questions. As the signal reaches the 5-6Hz range, the signal starts to jump around. The loop-back has a bit of a wiggle in it, too. Am I seeing the noise floor of the sound card here, or is the ArtBox II that inconsistent at VLF?
J

[brucek]

I added an off-set to bring the reading down to "0" to make it easier to see the drop

Exactly correct....

The loop-back has a bit of a wiggle in it, too. Am I seeing the noise floor of the sound card here

Yeah, it's the soundcard for sure. One of my computers soundcards gets 'wiggly' down low too. Be sure when testing equipment in a loopback that you test at sufficient levels (using the check level routine with the device in the loop), so that when measuring and the signal starts to drop off because of the equipments response down low, that you still have real signal and aren't down in the noise (as you correctly observed). Then simply normalize to zero when finished (as you already have done).
You might try and do the coupling capacitor mod some day on the device to get better response, like others did with the other ART box.

brucek

[azjimmy]

You might try and do the coupling capacitor mod some day on the device to get better response, like others did with the other ART box.

I wasn't sure if that mod would apply, since this is an unpowered device. It really only a transformer, right? I guess I need to crack that thing open and check out whats under the hood.
I'll redo the measurements tomorrow
Jim

[brucek]

It really only a transformer, right?

Oh ya, that's the hum eliminator isn't it. Likely a transformer. The plot using the axis that Ilkka used would be a good thing to have for reference here.... thanks.

brucek

[azjimmy]

Thanks for the help Bruce.
I did as you asked and ran another measurement. I boosted the level so I could get the low end of the sweep out of the noise floor of my sound card. Its a Realtek integrated on my Nvidia mobo. I need to find my Soundblaster card for my laptop. That thing is as flat as a board. I new I shouldn't have cleaned up that room .
Anyhoo, Here it is. It's not as bad as my original ones. I rant the same graph limits as Ilkka, as you requested, even though the box didn't roll off that low. The purple trace is the loop back.



Since it is only a passive transformer, I don't think there's much one could mess with to flatten the response.
Here's the inside-





I tried to attach the mdat from this session just in case anyone wanted to peek at the raw data, but it exceeds the max size (2.8 Mb) If anyone wants, I can email it.
Jim

[brucek]

Yeah, good job. This is good to have.

The response of the transformer is better than I thought it would be. Certainly no reason to attempt any mods on that thing. It's basically flat to 4 or 5Hz. Can't ask for better than that.

This would be a good choice for getting rid of hum on a subwoofer caused by the BFD or similar device.

Thanks again.

brucek

[azjimmy]

NP, Bruce. Always glad to help. I'm surprised nobody had done it sooner.
J

[tweakophyte]

Hi-

It looks like this is the least-expensive solution that has a flat, tested frequency response. Any comments on these other specs (pulled from the product sheet)?

Frequency Response: 10Hz – 50kHz, +/- .5dB
@ +4dBu
THD: .01% Typical @ 1kHz, +18dBu,
<.05% @ 100Hz, +24 dBu
Insertion Loss: .4dB @ 100kOhm Load, 5.5dB
@ 600Ohm Load
Connections: 1/4” TRS balanced/unbalanced
jacks
Power: Passive
Dimensions: 4.5 x 2.875 x 1.5 inches

(114mm x 73mm)

I had hum with my first PC-U, but was able to dial the level down on the sub and boost the level on the receiver and basically eliminate it. My new PC-U has so much more overhead I had to do the opposite, otherwise I was clipping the signal via the BFD! The buzz/hum drives me nuts (like water torture). Does the ART box really work?

Thanks,

[Ricci]

That looks much better than the original one. Looks like it might actually live up to the name "Cleanbox". I think that I'm going to pick one of these up.

[tweakophyte]

bump... any more comments?

Thanks,

[tweakophyte]

Well... my hum is gone. FWIW, I tried putting the CBII in the signal chain in various spots. The first one was between the BFD and the sub, right by the sub... still humming. Next was between the BFD and the sub, right by the BFD.

The place that worked was when I put the CBII between the receiver and the BFD. Ahhh... silence.

For the record, the run between the BFD and the sub is about 20-30 ft long and runs in the wall. It is RG-6, which I finish with some nice compression connectors.

Hope this helps,

[fibreKid]

Just saw this thread, I've been using the clean box II for about 22 months now and I'm happy with it. It removed the hum I was getting in my sub real well. Based on this thread and my experience I wouldn't have any problems recomending it.

-john