Jl Audio Adjust Gains
Most everyone that has ever purchased an external amplifier is at least familiar with the term voltage gain. Simply, it is the degree to which an amplifier actually amplifies the input from the preamplifier/processor. Often overlooked by those unaware of its importance, this one parameter can have significant implications on actual performance when an amplifier is introduced into an AV system. Understanding the impact that different levels of voltage gain can have in your system can very well be the difference between poor sound and getting the most out of an external amplifier. Sowhat is voltage gain exactly?When you think about it, an amplifier has a pretty straightforward job: to take an incoming voltage signal from a pre/pro and make it bigger.
The amount by which the incoming signal is amplified is given in decibels (dB). Every 6dB of gain equates to a doubling of voltage; as such, a hypothetical amplifier with a voltage gain of 30dB will increase voltage by 2^5, or by a factor of 32.
For unbalanced inputs, the THX standard gain level is 29dB; utilizing balanced inputs decreases this to 23dB, though naturally the output of the preamp is boosted by 6dB under this scenario (i.e. Voltage output of the preamp is doubled). For example, in the Audioholics review of the, the unbalanced outputs were measured to deliver 7Vrms; via the balanced outputs, the Integra delivered 15Vrms!
Sounds easy enough, but why does it matter?Naturally too much or too little of anything can present a problem, and the ideal amount of voltage gain can vary depending on a few factors. Utilizing a receiver with poorly implemented preamplifier outputs for example can be a problem when coupled to a high powered amplifier with relatively low voltage gain and consequently a high input sensitivity, which is the amount of voltage needed from the preamp to drive the amplifier to full unclipped power. Suppose you have a receiver that can deliver 1 volt RMS from its preamplifier outputs before clipping; if you pair this receiver with a high powered amplifier expecting a huge boost in headroom, you might be sorely disappointed if its voltage gain is a below average 27dB.Fig. 1: Unclipped sine wave versus a clipped sine wave.A gain of 27dB equates to a 22.6x increase in voltage, meaning our amplifier will be putting out 22.6 volts RMS, or a whopping 64 watts into an 8 ohm load before our AVR’s pre-outs run out of gas. Even if the amplifier is rated to deliver 1,000 watts, all you’re going to do when you push harder is get garbage as your AVR clips the signal to the amplifier or potentially trip its protection circuits.
The gain adjustment control on an amplifier is one of the most misunderstood concepts in the car audio world. Well, basic concepts that is. The purpose of the gain control is to level match the head unit’s output voltage to the gain structure of the amplifier so that the input is not overdriven which would introduce clipping.
Long story short: if you want to add power to a lower end receiver with pre-outs, you probably want something with a better than average amount and a low input sensitivity.Fig. 2: QSC GX Series Amplifier DatasheetAbove is the voltage gain and input sensitivity specification for the QSC GX series professional power amplifiers. Irvrobinson, post: 1110941, member: 6847As you might have expected of me, PENG, I read the specs before ordering. I suspect the problem is one or more of the following:- The 975 doesn't have an output level problem; it has an input sensitivity problem, and has substantially less than unity gain.- The 975 has an unusually low input impedance, perhaps because of a design defect, and is somehow stressing the cheap output devices of certain components, like the cheap Sony BD player. (I doubt this is the reason, but I don't know.)- The 2V output spec is simply incorrect, or wasn't met in the first version of the product, which I have. (I suspect this is the real reason.)- The ATI AT602 gain is not 28db, it is only 24db, which is woefully low. If you look at the ATI web site, which was my reference, gain is listed at 28db.
If you read the owners manual, I just noticed it is listed at 24db. 24db, if correct, is the lowest gain I've ever encountered for a power amplifier.
(24db of gain in conjunction with less output from the 975 than advertised could be a double whammy.)So, I'm thinking this is a genuine case of components that are just incompatible, especially when the electronics chain is pair with a set of JBL speakers that are probably 82db/2.83v/m, sensitivity-wise. And I'm also thinking that y'all ought to consider the silliness of being so dismissive of a situation that when discussed gets an immediate match from an audience with such a small population.I did expect you to read the specs, that's why I asked for explanation instead of doubting you.
And you did not disappoint.To add to your list of suspected causes, I noticed that the output impedance is stated as:“Output Impedance (Main-RCA) 10K. Still, when you add everything up, that Outlaw is probably only good for amps with 32 dB gains.If it has decent input sensitivity and reasonably low output impedance, even 1V can drive the 24 dB gain AT602 to its rated output but it certainly can't do anything to the ATI's larger amps.fmw may be right about in the majority of cases, but I do think it's time manufacturers be more specific about their preamp outputs. As it is now, it seems to me most of them are vague, you just can't draw conclusions without seeing bench test data. Fortunately so far any of my AVR, preamps and prepros have no trouble driving any of my power amps.
I hope that Outlaw is the only one that failed you. Irvrobinson, post: 1110941, member: 6847- The ATI AT602 gain is not 28db, it is only 24db, which is woefully low. If you look at the ATI web site, which was my reference, gain is listed at 28db. If you read the owners manual, I just noticed it is listed at 24db. 24db, if correct, is the lowest gain I've ever encountered for a power amplifier.
Jl Audio Adjust Gains Rate
(24db of gain in conjunction with less output from the 975 than advertised could be a double whammy.)Yeah, 24dB seems unlikely to me. More likely that it's a misprint.Voltage Gain (Av) is pretty easy to measure with a function generator, dummy load resistors, and an O-scope.I mentioned in another thread, when I build an amp, I typically shoot for 29dB.
That seems to be about the sweet spot from what I've seen. PENG, post: 1110934, member: 6097I just checked Outlaw website and found the 975's pre outs are rated 2V, 2.7V maximum so I don't know what it can't drive your AT602 that only needs 0.9V for the rated 60W output, according to the manual and my calculations back that up too.Did Outlaw give you any reason why their 2V is a problem? Assuming it is 2V rms I just can't see that being a problem.Outlaw never gave me a technical reason for the gain problem, and I almost sent the silly thing back, but the only alternative for a prepro in that price range was the Emotiva, and I already had a bad experience with that company. And other than the remote control design being unbelievably lame, and slower than average HDMI switching times, the 975 does perform very well within its limited output.
Jl Audio Adjust Gains Chart
It also looks good, is easy to set up, and has been reliable.As you might have expected of me, PENG, I read the specs before ordering. I suspect the problem is one or more of the following:- The 975 doesn't have an output level problem; it has an input sensitivity problem, and has substantially less than unity gain.- The 975 has an unusually low input impedance, perhaps because of a design defect, and is somehow stressing the cheap output devices of certain components, like the cheap Sony BD player. (I doubt this is the reason, but I don't know.)- The 2V output spec is simply incorrect, or wasn't met in the first version of the product, which I have. (I suspect this is the real reason.)- The ATI AT602 gain is not 28db, it is only 24db, which is woefully low. If you look at the ATI web site, which was my reference, gain is listed at 28db. If you read the owners manual, I just noticed it is listed at 24db.
Jl Audio Adjust Gains 2017
24db, if correct, is the lowest gain I've ever encountered for a power amplifier. (24db of gain in conjunction with less output from the 975 than advertised could be a double whammy.)So, I'm thinking this is a genuine case of components that are just incompatible, especially when the electronics chain is paired with a set of JBL speakers that are probably 82db/2.83v/m, sensitivity-wise. And I'm also thinking that y'all ought to consider the silliness of being so dismissive of a situation that when discussed gets an immediate match from an audience with such a small population. Irvrobinson, post: 1110922, member: 6847No, I don't. I tested the AT602 in my primary system, and that pre-amp easily drove it to clipping; the AT602 just has only 28db of gain, while most inexpensive amps these days have 32db of gain. I talked to Outlaw, and they seemed to have a procedure all ready for trying to mitigate the problem.
The Sony worked fine previously with a Sony AVR. Fortunately the problem was solved by just using much more efficient speakers, which I'm guessing are over 10db more sensitive than the previous pair.I think my case is unusual, good thing, but I also think being dismissive of the problem is incorrect.I just checked Outlaw website and found the 975's pre outs are rated 2V, 2.7V maximum so I don't know what it can't drive your AT602 that only needs 0.9V for the rated 60W output, according to the manual and my calculations back that up too.Did Outlaw give you any reason why their 2V is a problem? Assuming it is 2V rms I just can't see that being a problem.