SMD DD-1 Distortion tool, Anyone used one?

[jcyamaharider]

Mainly for @David Analog but anyone else also, have you ever used this device and what are your thoughts. I recently just purchased one and thought it is a good tool to aid in the tuning of the stereo. Relatively cheap and everything seems legit when compared to an oscilloscope.

 

[Julian]

I added a URL for the device - hopefully it is correct.....never used it....looks interesting.

 

[jcyamaharider]

Thanks Julian, yeah I should have done that but was in a hurry.

 

[David Analog]

Mainly for @David Analog but anyone else also, have you ever used this device and what are your thoughts. I recently just purchased one and thought it is a good tool to aid in the tuning of the stereo. Relatively cheap and everything seems legit when compared to an oscilloscope.

That is an excellent tool as long as you don't use it as the final word. It will accurately show the max non-clipping voltage at every gain stage in the signal path except for the very final stage. Just keep a few things in mind. You can't use a sine wave at full power to speakers so the speakers must be disconnected. The clipped voltage of a high-impedance low-current test device termination can be very different from the low-impedance high-current termination of a speaker. The electronic levels are full non-clipped before zone balancing and won't read speaker distortion. So consider these the maximum settings but not the final settings.

 

[jcyamaharider]

Very awesome and exactly why I bought it. I wanted to know exactly where my head unit clipped at and what my Max gain setting would be. I realize that I cannot leave it there I have to adjust down to meet my speakers.

On a different note I noticed that my head unit clipped at a number through the speaker terminals but when using RCA they didn't clip at all is that strange?

 

[David Analog]

Very awesome and exactly why I bought it. I wanted to know exactly where my head unit clipped at and what my Max gain setting would be. I realize that I cannot leave it there I have to adjust down to meet my speakers.

On a different note I noticed that my head unit clipped at a number through the speaker terminals but when using RCA they didn't clip at all is that strange?

No, that's not at all strange. Because you are measuring two very different paths. Some HU preouts clip @ 85% and some do not clip @ 100%. The flipside is that you could one day add a BT module with a 2 volt output that would cause your HU to clip or even saturate the Aux input.
Again, the test device is measuring the max non-clipping voltage independent of current while speakers are disconnected. And current matters. So it is accurate at a pre-level but somewhat skewed at a power level. At some point, as a final step, the best test instrument of all comes into play....your ears/brain.

 

[jcyamaharider]

Thanks for the words of wisdom.

I got to tune the stereo last night and I was shocked at the settings I started with and what I ended with. The gains on my sub amp are hardly up but it is full and clean power so it is even more crisp then last year. My highs and towers are insanely different, twice as loud as last year because I have the gains set to were they should be for the rms rating of the speakers. No clipping no distortion just clean clear music.

Thanks again @David Analog !

 

[KXCam22]

I use a scope to tune, but not everyone has one. There are some neat spectrum anslyser apps that have potential. People rarely understand clipping until you show them on a scope. Cam

 

[KXCam22]

I think you can do with a v meter as well. As you increase your gain, when you reach clipping the ac voltage stops increasing. Then back off 10%. Old-school. Assuming a sine wave input of course. Cam.

 

[David Analog]

I think you can do with a v meter as well. As you increase your gain, when you reach clipping the ac voltage stops increasing. Then back off 10%. Old-school. Assuming a sine wave input of course. Cam.

This method makes me nervous. If the voltmeter expresses AC voltage as peak then this could possibly work. However, most voltmeters express AC voltage as RMS, and you could get a much larger multiple of the non-clipped voltage before the voltage would stop increasing. Plus, once the wave form is clipped and becomes non-sinusoidal, the reading is likely far from accurate. Please get an opinion from someone other than me, someone more knowledgeable of meter operation.

 

[KXCam22]

I agree its not the best. Old school. I should try it on my truck system then put my scope on it and see how close I got. Would be a decent test. My meter has peak as well as RMS but its fancy. Cam.

 

[FloJet]

Mainly for @David Analog but anyone else also, have you ever used this device and what are your thoughts. I recently just purchased one and thought it is a good tool to aid in the tuning of the stereo. Relatively cheap and everything seems legit when compared to an oscilloscope.

My whole sound system is tuned with it. I would never go without. Tuning by ear is old school and don't recommend with high dollar systems.

 

[FloJet]

You should not get any clipping from connext until 95% for the lows

 

[WickedPorter]

I used this method: https://jlaudio.zendesk.com/hc/en-us/articles/204374120-Amplifier-Level-Setting-Guide ... would the SMD DD-1 give a more accurate tune?

 

[KXCam22]

I would say slightly more accurate. I am puzzled that the jl method ignores the head unit clipping which can be more prevalent at useable volumes. Cam

 

[FloJet]

Either way is fine. Good to use all methods. Going by ear can be tricky as many variables can be at play. Type of music, the source music is coming from, user's ear sensitivity. Good rule of thumb especially if you have a good amp is if you are half way on your amp gain you might be getting close to the danger zone. Just so many variables when tuning a unit. Not to even mention the equalizer part of things if that is being utilized. SMD tuner will help but it's not the final answer. Plus debatable if it's worth the price to some users.

 

[WickedPorter]

Thanks for the info guys ... I went ahead and bought one. It was very easy to use with clear instructions. It seems to have worked quite well, and I was surprised to see no headunit distortion at full volume with the Clarion CMD7.

 

[David Analog]

I would say slightly more accurate. I am puzzled that the jl method ignores the head unit clipping which can be more prevalent at useable volumes. Cam

Actually the HU is included in the JL Audio method. The HU is at 75% gain which ensures no significant clipping from just about any HU. Then the HU supplies the test tone signal whether by a CD or file.

 

[Rod5]

What oscilloscope would one use? Would you take readings directly from the wires like SMD DD-1 or use a mike to listen to each individual speaker?

 

[KXCam22]

Rod5,
When I use a scope I measure at the RCA outputs of the HU first to determine the max volume it can play at without clipping. This is done playing a 1 Khz sine wave test tone on a CD or other source. I then turn the volume down about 5% from the MAX setting. So if the deck clips at 95/100 then I would set it to about 90 to be safe. This is then the max volume you would ever turn to, which in most cases is far louder that reasonable. Then repeat the process by measuring the speaker outputs with the scope to determine the max gain setting before the amplifier starts clipping. On a scope screen the clipping is very obvious. Then I turn down the gain a tad for a safety margin and the setting is complete. I may test a few different frequency settings. Of course this method isn't available to everyone since a scope isn't a common household item. I few years ago I adjusted almost every auto system in my sons school. Got tired of listening to bad stereo in my driveway. Got a few sixpacks out of it. Hope this helps. Cam.