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Gain Setting Tutorial
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<blockquote data-quote="XTRProBoy" data-source="post: 2446550" data-attributes="member: 571009"><p>I dunno about this whole setting method really... I mean I tried this today on my newly acquired HCCA-D2400 and I must say this did not work out well at all.</p><p></p><p>Considering I'm supposed to be getting something near 1200W into 1-Ohm that means I should be looking for 34.64 VAC right?</p><p></p><p>So I tried that, with a 50Hz tone at 0dB (verified by the signal meter on my MD deck when I recorded it) and then I went out and tried this in the car.</p><p></p><p>Keep in mind I *just* got this amp so I hadn't even installed it doing the "by ear" method yet...</p><p></p><p>I have a few DMMs including a Fluke 77 but I used my UEI one because it has TrueRMS on it. Sure enough it indicated 50Hz cycle frequency and then I set the gain so that the output voltage was around 34V AC (RMS). And I must say when I played some music it appeared to me I had just installed a 120W amp and not a 1200W one, LOL.</p><p></p><p>Head unit was up so there were only two more "bars" before full volume (a Sony CDX-C7850 but connected to an XDP-210EQ) when I did the gain setting. I tried again, going to about 40V instead, and then reconnected everything but again to no avail. The sub sounded waaay underpowered to me with music playback.</p><p></p><p><strong>So then I remembered the way Orion used to say to do it with the DMM </strong>(back before they were taken over by DEI this info was on their website). Instead of setting the gain to some calculated voltage they said to turn the gain up until you see the voltage stop increasing rapidly and sort of level off, then turn it back a bit. I did this and it "slowed down" at around 70V and maxed out at 72.x volts before I hit the stop on the gain knob. So I dialed it back to around 68 volts and left it there.</p><p></p><p>Connected everything again and tried once more and I have to say it was sounding *much* better.</p><p></p><p>This was at maybe around 66% of the knob travel I think? With the input voltage range on the amp stated as 150mV-5.0V I believe. So I'm not sure what its set at in terms of input voltage, but I'm thinking it has to be around 1.5V or so. The XDP-210EQ is supposed to have 4V output all around, so I think I've either set a 2.5:1 gain overlap (or 2:1 if you consider that 34V figure "right" as I had about twice that voltage from the amp) <em>or</em> the whole JL audio method is messed up, lol. 0</p><p></p><p>But honestly I don't get how the root of the product of power output and impedance driven works out like that. Because say I had my sub wired for 4 ohms (instead of 1), then I would be looking at 450W from the amp and therefore it would be (1800W*ohms)^.5 = 42.42V . Why would I set the input stage gain such that the output voltage from the amp, <strong>with no load connected</strong> (as JL tells you to do), was at a higher speaker output voltage on the amp?</p><p></p><p>How does that make any sense? Because the only difference with no load connected would be me making the amp's input stage more sensitive and nothing else. I.e. All I'd be doing would be making the amp more sensitive for the 4-ohm load (42V) as opposed to the 1-Ohm load (34V). But for what reason??? The RCA level from the HU did not change, so why would I look for a higher no-load voltage on the speaker terminals if I were driving a higher impedance? I don't get that. Because gain is supposed to match the amp's input stage with the RCA level it receives from the HU. How does that have anything to do with what load impedance I'm driving? Especially considering you measure the outputs of the amp with no load connected (other than the DMM itself).</p><p></p><p>I dunno but the Orion method seems a lot better to me. However I don't remember if you were supposed dial up the gain with the load connected to the amp or not, but I just did it without since I didn't want to deafen myself, lol...</p></blockquote><p></p>
[QUOTE="XTRProBoy, post: 2446550, member: 571009"] I dunno about this whole setting method really... I mean I tried this today on my newly acquired HCCA-D2400 and I must say this did not work out well at all. Considering I'm supposed to be getting something near 1200W into 1-Ohm that means I should be looking for 34.64 VAC right? So I tried that, with a 50Hz tone at 0dB (verified by the signal meter on my MD deck when I recorded it) and then I went out and tried this in the car. Keep in mind I *just* got this amp so I hadn't even installed it doing the "by ear" method yet... I have a few DMMs including a Fluke 77 but I used my UEI one because it has TrueRMS on it. Sure enough it indicated 50Hz cycle frequency and then I set the gain so that the output voltage was around 34V AC (RMS). And I must say when I played some music it appeared to me I had just installed a 120W amp and not a 1200W one, LOL. Head unit was up so there were only two more "bars" before full volume (a Sony CDX-C7850 but connected to an XDP-210EQ) when I did the gain setting. I tried again, going to about 40V instead, and then reconnected everything but again to no avail. The sub sounded waaay underpowered to me with music playback. [B]So then I remembered the way Orion used to say to do it with the DMM [/B](back before they were taken over by DEI this info was on their website). Instead of setting the gain to some calculated voltage they said to turn the gain up until you see the voltage stop increasing rapidly and sort of level off, then turn it back a bit. I did this and it "slowed down" at around 70V and maxed out at 72.x volts before I hit the stop on the gain knob. So I dialed it back to around 68 volts and left it there. Connected everything again and tried once more and I have to say it was sounding *much* better. This was at maybe around 66% of the knob travel I think? With the input voltage range on the amp stated as 150mV-5.0V I believe. So I'm not sure what its set at in terms of input voltage, but I'm thinking it has to be around 1.5V or so. The XDP-210EQ is supposed to have 4V output all around, so I think I've either set a 2.5:1 gain overlap (or 2:1 if you consider that 34V figure "right" as I had about twice that voltage from the amp) [I]or[/I] the whole JL audio method is messed up, lol. 0 But honestly I don't get how the root of the product of power output and impedance driven works out like that. Because say I had my sub wired for 4 ohms (instead of 1), then I would be looking at 450W from the amp and therefore it would be (1800W*ohms)^.5 = 42.42V . Why would I set the input stage gain such that the output voltage from the amp, [B]with no load connected[/B] (as JL tells you to do), was at a higher speaker output voltage on the amp? How does that make any sense? Because the only difference with no load connected would be me making the amp's input stage more sensitive and nothing else. I.e. All I'd be doing would be making the amp more sensitive for the 4-ohm load (42V) as opposed to the 1-Ohm load (34V). But for what reason??? The RCA level from the HU did not change, so why would I look for a higher no-load voltage on the speaker terminals if I were driving a higher impedance? I don't get that. Because gain is supposed to match the amp's input stage with the RCA level it receives from the HU. How does that have anything to do with what load impedance I'm driving? Especially considering you measure the outputs of the amp with no load connected (other than the DMM itself). I dunno but the Orion method seems a lot better to me. However I don't remember if you were supposed dial up the gain with the load connected to the amp or not, but I just did it without since I didn't want to deafen myself, lol... [/QUOTE]
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