SD1300.5 Subwoofer Output

[dwnrodeo]

I decided to test the sub output of my SD1300.5 using an O-Scope and DMM. Now the SD sub channel is rated at 800 watts into 2 ohms so I should be seeing about 40 volts of output.

Tested in car (no power supply) running at 13.9 volts verified by DMM and RMD voltage display using a 60 hz test tone. Headunit is a Kenwood X994 and was tested to verify that it does NOT clip at full volume. Gains were turned up until just below clipping on the O-Scope and then voltage was measured using DMM set to volts AC. No loading. The amps crossover can NOT be bypassed so I set it at the maximum level 250 hz @ 18db/oct.

Results show 28.6 volts of ouptut. I know that is not at 14.4 volts, the crossover can not be bypassed, but does this seem kinda low? That only equates to about 400 watts @ 2 ohms. Did I do this correctly or am I missing something? Sorry for the crappy Ipod pics, it's all I had at the time.

[Eric D]

Your amp is indeed a 5-channel, not a 6-channel, correct? Assuming so, there is a good chance the sub output is bridged, which may be affecting your measurements. Some o-scopes (old ones like yours looks to be) require a good ground signal, and won't work differentially. In extreme cases, these scopes can damage the amplifier as well (I killed a few RF amps with an old o-scope I had, and then bought a scope with a floating ground, no more dead amps).

It is possible the negative lead of your scope is pulling down the output signal of one channel on the sub output. I would measure the sub out using the center tap on the output of the transformer for the negative lead, and then the positive on each sub terminal (one at a time).

Also, you may be getting some issue since these amps are Class D (I think they are Class D). Although I doubt it, you might need a load on the amp for it to behave correctly.

Or, maybe the amp just plain won't do what it is rated. I doubt this too, but would never rule out the possibility.

[dwnrodeo]

Thanks for the reply Eric. Yes, the amp is a 5 channel class D amplifier. The O-Scope belongs to a friend of mine who was kind enough to let me borrow it because I'm hesitant on spending money on a scope right now. Excuse my ignorance, but I'm not sure on what you mean by center tap on the output of the transformer for the negative lead.

[Eric D]

Almost all car audio amplifiers can be bridged. To make an amp able to do this, one channel is inverted 180deg, and then the labels on the outside of the amp are reversed. This allows the two channels to sum together. Each separate channel has its output signal, and a ground. To connect an o-scope to it, you need to use the "live" terminal, and one a ground terminal. If you connect the "live" terminal to the o-scopes ground (because on the outside of the amp it is labeled as a (-) terminal, but really is the positive terminal internally), you can kill the amp.

In some mono amps, they are internally bridged, so both output terminals are "live", and are 180 deg out of phase of each other. Now, if you connect an o-scope to the mono amp, you are correctly connecting one lead to the "live" signal, and then incorrectly connecting the negative (ground) of the o-scope to the other "live" signal. Instead, you need to take the amp apart, and connect the negative of the o-scope to the ground reference of the amplifier which would be the center tap of the secondary output on the main transformer.

If you have what is known as a differential o-scope, or an differential scope probe, you don't have to worry about things like this. You just connect it to both outputs on the mono amp, and it will compute the difference internally.

If this makes no sense, I apologize. It is far easier to show somebody this, than it is to explain it too them.

I guess the bottom line here is if you are using an older oscilloscope, and don't understand these concepts, you can damage your amp (I know, as I damaged an amp this way prior to learning about my old oscilloscope). If you use a more modern scope, these issues are almost non-existent.

[dwnrodeo]

So by connecting the scopes probe to the - and + terminals of the mono channel and turning up the gains until I see clipping, will that still let me know the maximum gain setting of the amp? Even though the output voltage on my DMM states 28.6 volts, can I assume that the O-Scope is correct in the gain setting where the signal begins to clip? That would make sense if I was seeing roughly half of what the amp is rated for if only one "live" terminal was being measured.

[kg1961]

i don't know what to say. but reading some of the performance and sound mags it seem like pg amp(new one) don't get to the rated power will 1ohm but this was in the mono amps?
that would sure suck if you didn't get close to rated sorry don't know the amp what is rated not peak numbers?

[dwnrodeo]

It is rated to do 800 watts RMS @ 2 ohm, 1000 watts dynamic @ 2 ohm. I haven't checked the 4 channel section yet to see what the numbers are. I'm not very experienced when it comes to testing amps, and the equipment I'm using isn't the greatest, so I'm not jumping to any conclusions just yet.

[stipud]

So by connecting the scopes probe to the - and + terminals of the mono channel and turning up the gains until I see clipping, will that still let me know the maximum gain setting of the amp? Even though the output voltage on my DMM states 28.6 volts, can I assume that the O-Scope is correct in the gain setting where the signal begins to clip? That would make sense if I was seeing roughly half of what the amp is rated for if only one "live" terminal was being measured.

What he's saying is that the amp may be internally bridged, so the + and - terminals are really + and +, but the second channel is out of phase.

The Ti1200.1 was like this for example. It was sold as a mono amp, but internally it was a bridged class A/B two channel.

[Eric D]

So by connecting the scopes probe to the - and + terminals of the mono channel and turning up the gains until I see clipping, will that still let me know the maximum gain setting of the amp? Even though the output voltage on my DMM states 28.6 volts, can I assume that the O-Scope is correct in the gain setting where the signal begins to clip? That would make sense if I was seeing roughly half of what the amp is rated for if only one "live" terminal was being measured.

What he's saying is that the amp may be internally bridged, so the + and - terminals are really + and +, but the second channel is out of phase.

The Ti1200.1 was like this for example. It was sold as a mono amp, but internally it was a bridged class A/B two channel.

Exactly! Now why couldn't I explain that?

The bigger point I want to make is connecting your o-scope directly to the amp could kill the amp. It all depends on the way your scope is grounded, and old ones are generally directly grounded.

[dwnrodeo]

Thanks for the explanation. Here's a better pic of the scope I'm using. The only attachment I made to the amp is the vertical input lead which has a ground on the shield of the cable. The ground(s) on the bottom left and bottom right were NOT hooked up. Sorry, no pics of the test lead.

[kg1961]

any new news? are they just not making rated power?

[dwnrodeo]

I don't really have the right equipment and definitely don't want to open the amp up to test for clipping.

[kg1961]

I don't really have the right equipment and definitely don't want to open the amp up to test for clipping.

hope its what you need i just read the ti not doing what it needs so im not a fan so far on the 5 channel pg amps

[MW3]

The sub section of SD1300.5 does about 850w at 2 ohms, 14.4 at 1% THD. I will post up the AP measurement later.

5 Channels sales across the board are up from previous years.

BTW: That post on the Ti 5 channel is weak, doesn't make any sense, someone just posting up bad/weak info and couldnt answer any of my questions.

[dwnrodeo]

Thanks Morgan. Like I said, I'm a novice at this so I wouldn't take my findings as fact.

[MW3]

No worries. Here is the RMS power output @ 1% THD and 14.4v of our "golden" SD1300.5 pre-production unit.

Front/Rear:
83w x 4 - 4 ohms
130w x 4 - 2 ohms

Sub:
537w x 1 - 4 ohms
854w x 1 - 2 ohms

I have personally used this amp to drive a single Ti2 12d4 at 2 ohms many, many times.

Its gives the single woofer more than it can handle, the sub section alone could power two Ti2 12d2's with ease.

[dwnrodeo]

Glad to hear the sub output is that high. I will test it out this weekend on my Xcon 12 and put it through the paces. I've been breaking the sub in (free air) with my XS2500 which should be near the same output as the SD @ 2 ohms, so we'll see how they compare.

[thedeal7235]

dwnrodeo, can u please post some pics of this amp in ur car???? id luv to c it, thanx, C

[dwnrodeo]

dwnrodeo, can u please post some pics of this amp in ur car???? id luv to c it, thanx, C

I have some more pics on my laptop at home I can upload, but for now you can check out my install: http://phoenixphorum.com/viewtopic.php? ... 1&start=50 .

[dwnrodeo]

Just a quick update. I purchased a newer style handheld O-scope and achieved 40 volts at the terminals without clipping.

[stipud]

Just a quick update. I purchased a newer style handheld O-scope and achieved 40 volts at the terminals without clipping.

Making the full 800 then! Nice!

Are you still only using the sub section of that amp?

[dwnrodeo]

Just a quick update. I purchased a newer style handheld O-scope and achieved 40 volts at the terminals without clipping.

Making the full 800 then! Nice!

Are you still only using the sub section of that amp?

Yes, 800 watts (I kept the gain down just below clipping) to keep it at 40 volts and a nice smooth wave. Looks like I was doing something wrong before which doesn't surprise me.

No, I'm using the front channels as well to my XS104d's in the doors. Someday I'll replace them with some newer 4 ohm subs and then bridge the front and rear channels together, but for right now it sounds good and gets PLENTY loud for me.

[Eric D]

Now I want one of these amps even more...

[dwnrodeo]

I helped my friend install his SD1300.5 and set the gains with an oscilloscope. We got just over 40 volts at the subwoofer terminal (~800 watts @ 2 ohm) and achieved nearly 21 volts on the front channels (~110 watts @ 4 ohm).

[MW3]

Very nice of you!

Bad arse little amp eh?