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Great replacement for O scope to set gain structure?

post #1 of 44
2/8/13 at 10:16pm
Thread Starter 
I ran across one of these when they were in the prototype stage a couple years back and am thinking this might be a great way to set a gain structure without an oscope or guessing. It was designed with the car audio world in mind, but don't see why it wouldn't work for HT as well.

What are everyone's thoughts on this? It's pretty inexpensive in the grand scheme of things, and looks to provide accurate information without requiring any fancy tools or degrees.

DD1

Manual
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post #2 of 44
2/9/13 at 12:27am

I own a DD1 and a CC1 and they are amazing pieces of test equipment.

 

On home audio use I haven't used the DD1 to "peak" the gains on my Crown XLS 2500 amp yet,

 

 but I did use the 0 and -5 db tracks of 40hz and 1khz played on my Onkyo C-7030 to test the limits of my 709's  preamp outputs.

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post #3 of 44
2/9/13 at 2:09am
I looked them over awhile back too. Meade is on top of things cause nothing exists in the car world until he came along. Especially multiple amps sharing subs in the same enclosure they need to be balanced.

Anyways YES the device can help gain structure easily detecting "overtones" for the pre amp out of the AVR to find max output. As most will find it's no where near max volume and probably 20-30% of the total volume number. To those that think zero on the volume knob is "reference".

Wayne at HTS describes it here http://www.hometheatershack.com/forums/home-theater-receivers-processors-amps/35677-gain-structure-home-theater-getting-most-pro-audio-equipment-your-system.html#axzz2KOUL8XPb

using a multi meter and "listening with a test speaker for overtone" but I like the meter better

Other than that unless you have amps sharing coils or subs of same enclosures or not knowing where your xover's are set that to me ends the functionality for HT.

Beyond knowing the AVRs max voltage, some of us use a BFD or similar in the signal chain. We drive the BFD(using the indicators looking toward the AVR signal) to just before yellow lights with heavy bass reference discs. This ensures no clipping signal to the amp.
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post #4 of 44
2/9/13 at 8:26am
Thread Starter 
Quote:
using a multi meter and "listening with a test speaker for overtone" but I like the meter better

I do too. I have pretty good ears, but prefer to see the data. smile.gif
Quote:
Other than that unless you have amps sharing coils or subs of same enclosures or not knowing where your xover's are set that to me ends the functionality for HT.

I might be down the road. I'm running 3 drivers per cab, each cab wired to a 4,000. If the power isn't enough I might combine the subs in a 2,2,2 setup off of 3 EP4000's which would leave 2 running off 1 amp, with the 3rd running off another amp.
Quote:
Beyond knowing the AVRs max voltage, some of us use a BFD or similar in the signal chain. We drive the BFD(using the indicators looking toward the AVR signal) to just before yellow lights with heavy bass reference discs. This ensures no clipping signal to the amp.

Yup, I liked the DCX and BFD for that reason. My SMS1 doesn't have the ability, but sure would be nice if it did.

I'm thinking the DD would work great for setting the gains on my 3009 and SMS1, and then I could set the gains on the EP's via the clip lights. It's either this method, or I can try and snag an Oscope from my friend who owns an audio shop. I like the DD1 as I would own it, and am sure would be used multiple times throughout the tuning process as I tweak the eq.
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post #5 of 44
2/9/13 at 8:51am
Why not just get a little DSO Nano oscope for less than that device and set the gain? Mine worked fine for doing this.


This is a comparison video of the nano against a expensive scope.
http://www.youtube.com/watch?v=Ajl21ne6JaU

James
Edited by exojam - 2/9/13 at 9:01am
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post #6 of 44
2/9/13 at 9:19am
Thread Starter 
Quote:
Originally Posted by exojam View Post

Why not just get a little DSO Nano oscope for less than that device and set the gain? Mine worked fine for doing this.


This is a comparison video of the nano against a expensive scope.
http://www.youtube.com/watch?v=Ajl21ne6JaU

James

Well, I've always been nervous about the accuracy of those really cheap O scopes. That video makes me feel a little differently about them.
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post #7 of 44
2/9/13 at 10:24am
Pretty cool, didn't realize they made pocket scopes that small. Trying to download this vid here in the stan but it's killer slow maybe by morning I'll view it lol

deleted vid post it was horrible ..

damn more info on REW i've yet to fully mess with the software like I should.....SWEET!
Edited by autox320 - 2/9/13 at 10:50am
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post #8 of 44
2/9/13 at 10:46am
Why can't you use REW to measure sub output directly? Set the gain at 1% THD or whatever you find appropriate.
Ricci posted a great walk through on gain structure set up. Much shorter and more to the point than Wayne's IMHO
http://www.avsforum.com/t/1442255/alpine-swr-1223d-diy-sub-build-for-ht#post_22663392
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post #9 of 44
2/9/13 at 1:13pm
Thread Starter 
This does bring up another point however.

Most SMS users recommend setting the sub out level on the receiver to around -5 to prevent clipping the input on the SMS (even though it has supposedly been remedied with the latest firmware). At -5 there should be no issues with clipping the output on my Onkyo, and according to others, there is no chance of clipping the output on the SMS1 either, regardless of it's volume.

So why wouldn't this method work?

1) Set sub out to -5
2) Put in 0dbs 60hz track, and while playing continue cranking up output level on SMS until clip lights light up on EP's.

This should ensure EP's are getting full signal while not clipping output on receiver. If there's a better way I'm all ears. smile.gif
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post #10 of 44
2/9/13 at 4:45pm
Quote:
Originally Posted by bass addict View Post

This does bring up another point however.

Most SMS users recommend setting the sub out level on the receiver to around -5 to prevent clipping the input on the SMS (even though it has supposedly been remedied with the latest firmware). At -5 there should be no issues with clipping the output on my Onkyo, and according to others, there is no chance of clipping the output on the SMS1 either, regardless of it's volume.

So why wouldn't this method work?

1) Set sub out to -5
2) Put in 0dbs 60hz track, and while playing continue cranking up output level on SMS until clip lights light up on EP's.

This should ensure EP's are getting full signal while not clipping output on receiver. If there's a better way I'm all ears. smile.gif


this should work. You may want to measure SMS output for distortion just to be safe.
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post #11 of 44
2/9/13 at 10:19pm
Thought this one was kinda neat. https://www.youtube.com/watch?v=np0lpIiSesU
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post #12 of 44
2/9/13 at 10:29pm
Thread Starter 
Yeah, other than the fact he contradicts himself in it.

"It looked perfectly clean to us"

"I can see it in here a little bit but I've been looking at these waveforms for like twelve years" cool.gif
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post #13 of 44
2/10/13 at 12:10am
Quote:
Originally Posted by autox320 View Post

Thought this one was kinda neat. https://www.youtube.com/watch?v=np0lpIiSesU
Could have used the FFT function on the scope to see the distortion. I don't know about the pocket scopes but most regular scopes have FFT math functions.
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post #14 of 44
2/10/13 at 8:48am
Nothing wrong with Ricci’s way but you will need a soundcard that can handle some voltage (and anothing against Ricci since he helped me set my gains up). His is shorter than Wayne’s since Wayne’s takes you through the how – why stuff. If you search for DSO Nano, there is a thread I started and I believe A9X has another way to do this. Many ways, pick which one is best for you.

James
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post #15 of 44
2/10/13 at 10:58am
True many ways to get same results. Long as keep it basic to see what is being accomplished by following signal 101. Source first and go toward the speakers. The dso nano has some pretty mixed reviews and horrible factory firmware, but there are fixes for it. I even saw one hooked tandem with a SMD DD-1 and not really any difference at all. Main vids I liked where the DD-1 detects distortion in tandem with a scope just showed clipping. One vid had the sides of the sinusoidal out of shape (head unit clipping; pre gain) but the peaks were perfect. The DD-1 showed distortion the whole way trying to tell the head unit was a problem. Then ran across the sonicelectronix showing for car audio gains by ear. Yup that's exactly the way we did it in the day is listen to overtone change lol. Standard multimeter for matching amps etc. Just brought back memories on that one.
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post #16 of 44
2/10/13 at 11:16am
Thread Starter 
I grew up doing the same thing as you with car audio. Overtone and MM accomplished most everything you needed to setup your system properly.
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post #17 of 44
2/10/13 at 4:32pm
Quote:
Originally Posted by exojam View Post

Nothing wrong with Ricci’s way but you will need a soundcard that can handle some voltage (and anothing against Ricci since he helped me set my gains up). His is shorter than Wayne’s since Wayne’s takes you through the how – why stuff. If you search for DSO Nano, there is a thread I started and I believe A9X has another way to do this. Many ways, pick which one is best for you.

James
My methodolgy is similar, but I have a scope as well (and I'm hoping to buy an ATTEN ADS1102CAL or similar in the near future). You don't need a soundcard that can handle large signal swings, just attenuate them to a known amount before the soundcard, eg, if you need to measure 10V and your soundcard can handle 1V, a 2 resistor attenuator will drop by a factor of 10 for a few cents. There are pre made switched attenuators on ebay for about $10 that will allow a greater signal range and easy convenience switching between them. Use the lowest impedance one you can get away with.

I measure levels with a true RMS meter (Fluke 287) and use that to determine an accurate level. If what is then displayed on screen is 1.2V, then I know there is a linear scaling factor of 1.2x.

The device in the OP doesn't detect anything until 1% if I read the page correctly. That's about 2 orders of magnitude above what I consider baseline performance in audio.

The DSO nano scopes are pretty good. Old CRO scopes can be had cheap, and so long as you test them to set levels: by this I mean you use the scope as a visual display and an accurate DVM for determining level.
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post #18 of 44
2/10/13 at 5:10pm
only good to 125v wink.gif
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post #19 of 44
2/10/13 at 6:57pm
this is somewhat OT, I apologize.

What do you do if, with proper gain level on the sub amplifier, you end up with Adyssey setting sub channel at the lowest level possible ( -12 position in my AVR)? the potential problem is that it may be still too hot but there is no way to attenuate it any more. so what is a good way to address this?

And somewhat related, if during calibration Audyssey warns about sub level being too high, is it safe to ignore it? The warnings may be Denon/XT32/SubEQ specific, I do not recall sub level check with Onkyo/Audyssey XT.


thank you
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post #20 of 44
2/10/13 at 6:59pm
Quote:
Originally Posted by notnyt View Post

only good to 125v wink.gif

Yeah SMD make a special model for you notnyt. Is 200vrms enough range? eek.gif

http://www.sonicelectronix.com/item_61379_SMD-DD-1-HV-Distortion-Detector-by-Steve-Meade-Designs.html

well maybe not for a lab or anything heavyweight

voltage = sq rt ( P x R)

14000x 4ohms
236v....hmm nope

what load are your running with the clone 4 ohms right?
Edited by autox320 - 2/10/13 at 7:11pm
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post #21 of 44
2/11/13 at 4:48am
autox,

I had heard the same thing about the factory firmware, no so good. That is why I am glad it is an open source and I believe benf created new firmware for free which I had installed on mine. For what I needed the scope for it worked great and if there are any other projects I see no issues with it being used.

James
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post #22 of 44
2/11/13 at 8:22am
Quote:
Originally Posted by exojam View Post

autox,

I had heard the same thing about the factory firmware, no so good. That is why I am glad it is an open source and I believe benf created new firmware for free which I had installed on mine. For what I needed the scope for it worked great and if there are any other projects I see no issues with it being used.

James

Hey James, yes the BenF firmware 3.64 was what I was referring to for fixes(if there is newer for the V2 please link). Also the tips on proper formatting of sd cards for use of memory. I've yet to buy one but it's so small and cheap I might pick one up just for fun even though it's limited. Was looking at the simple V2. Already have a SMD DD-1 to save my ear calibrating.
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post #23 of 44
2/11/13 at 10:12am
Meade SMD DD1: "Distortion Detection trigger level > 1.0% Harmonic Distortion"

So it's useless for quality home audio.
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post #24 of 44
2/11/13 at 10:27am
Thread Starter 
Quote:
Originally Posted by A9X-308 View Post

Meade SMD DD1: "Distortion Detection trigger level > 1.0% Harmonic Distortion"

So it's useless for quality home audio.

Tough to say. If the reviews are even remotely accurate, they claim this was picking up distortion before it even showed on the o scope.
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post #25 of 44
2/11/13 at 11:02am
Quote:
Originally Posted by zheka View Post

this is somewhat OT, I apologize.

What do you do if, with proper gain level on the sub amplifier, you end up with Adyssey setting sub channel at the lowest level possible ( -12 position in my AVR)? the potential problem is that it may be still too hot but there is no way to attenuate it any more. so what is a good way to address this?

thank you

My older Onkyo 3007 has so much sub pre-out voltage that even at -12db(lowest setting) it still will clip my EQ(BFD) at even lower listening levels. I solved this in my situation by using the higher input/output voltage setting on the BFD which is generally not recommended by bruce on HTS. Using the higher setting I can keep the sub trim to a normal setting 0db(+/- 2db). To me the bass has better resolution like this, when turned down to -12 the bass was very ON/OFF if you get my meaning. Not much in between.

However the BFD now is capable of outputting more voltage than the EP4000 needs to clip, so I keep the clip lights out with the attenuation knobs on the Berry. This works much better for me in my situation although maybe not bulletproof from a clip standpoint. I have enough headroom that I never clip the amp though. I use some 0db fs tones to set the attenuation knob and also some demo material that will tell the tale if the gain structure is not set proper.

Whats in your signal chain? If you need to lower your sub pre-out voltage at listening levels and your subs are set to -12, you can raise your level calibration on your mains which effectively lowers your sub setting at a set listening level, but may raise your noise floor. Just remember your "reference" setting is now off actual, if you believe in such a thing.
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post #26 of 44
2/11/13 at 11:06am
Thread Starter 
Quote:
Originally Posted by NicksHitachi View Post

Just remember your "reference" setting is now off actual, if you believe in such a thing.

I only use reference terminology when comparing listening impressions. The studios don't adhere to a set reference level, so it's really a moot point from a statistical standpoint.
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post #27 of 44
2/11/13 at 11:08am
Quote:
Originally Posted by NicksHitachi View Post

My older Onkyo 3007 has so much sub pre-out voltage that even at -12db(lowest setting) it still will clip my EQ(BFD) at even lower listening levels. I solved this in my situation by using the higher input/output voltage setting on the BFD which is generally not recommended by bruce on HTS. Using the higher setting I can keep the sub trim to a normal setting 0db(+/- 2db). To me the bass has better resolution like this, when turned down to -12 the bass was very ON/OFF if you get my meaning. Not much in between.

However the BFD now is capable of outputting more voltage than the EP4000 needs to clip, so I keep the clip lights out with the attenuation knobs on the Berry. This works much better for me in my situation although maybe not bulletproof from a clip standpoint. I have enough headroom that I never clip the amp though. I use some 0db fs tones to set the attenuation knob and also some demo material that will tell the tale if the gain structure is not set proper.

Whats in your signal chain? If you need to lower your sub pre-out voltage at listening levels and your subs are set to -12, you can raise your level calibration on your mains which effectively lowers your sub setting at a set listening level, but may raise your noise floor. Just remember your "reference" setting is now off actual, if you believe in such a thing.

Another owner of an Onkyo TXNR3007, BFD and Berry amp. I have to do the same thing. Wicked hot output on my LFE outs.
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post #28 of 44
2/11/13 at 11:27am
Thread Starter 
Quote:
Originally Posted by Scott Simonian View Post

Another owner of an Onkyo TXNR3007, BFD and Berry amp. I have to do the same thing. Wicked hot output on my LFE outs.

The 3009 isn't any better. smile.gif
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post #29 of 44
2/11/13 at 11:31am
Too much of a good thing! biggrin.gif
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post #30 of 44
2/11/13 at 12:40pm
Quote:
Originally Posted by bass addict View Post

Well, I've always been nervous about the accuracy of those really cheap O scopes. That video makes me feel a little differently about them.

Why does accuracy matter - aren't we just looking for clipping of the waveform?
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