nemoid
Seeker Of Truth
Posts: 3
|
Post by nemoid on Aug 6, 2019 2:38:47 GMT -5
Good morning to you all,
i have recently been been looking into upgrading the power amps in my system and honestly the more I look into gain matching etc the more confused I become.
Currently I have an arcam 390 which arcam recommend to use a power amp with a gain of 31db . Arcam have communicated that “The nominal output of the pre-outs on the 390 is 1V RMS at 560R. This is a variable output that can raise far above 1v”. So my question is if for instance I purchased an amp like the Emotiva xpa DR3 which has a gain of 29 dB and input sensitivity of 2v would I still get full rated power?
In modern amps and receivers does gain matching matter as much? Tbh the whole subject is all rather confusing and not clear cut to simpletons like me .
cheers
|
|
KeithL
Administrator 
Posts: 9,938
|
Post by KeithL on Aug 6, 2019 9:06:16 GMT -5
You really don't need to worry about it... it will work just fine.
While there isn't an actual standard, most home power amps have a gain between about 28 dB and 32 dB, and need somewhere around 1V to 2V to reach full power... And, in general, all preamps and processors are designed to work with all of them. The same is true for the pre-outs on most home theater AVRs - the ones that have pre-outs. (Speakers do tend to vary quite widely in terms of efficiency...)
In the old days you would hear serious discussions about "optimally matching output levels, input levels, and gain, to get the best possible S/N ratio".... Today, while that still matters with very low level signals like phono and microphone inputs, it just isn't important any more with line level signals, like the one between a preamp and a power amp. (It would be like worrying whether your car would run on one particular brand of gas.)
Furthermore, surround sound gear always has level trims you can use to match levels exactly between channels. And, for anything that has any sort of automatic room correction, that will set the trim levels for you.
Good morning to you all, i have recently been been looking into upgrading the power amps in my system and honestly the more I look into gain matching etc the more confused I become. Currently I have an arcam 390 which arcam recommend to use a power amp with a gain of 31db . Arcam have communicated that “The nominal output of the pre-outs on the 390 is 1V RMS at 560R. This is a variable output that can raise far above 1v”. So my question is if for instance I purchased an amp like the Emotiva xpa DR3 which has a gain of 29 dB and input sensitivity of 2v would I still get full rated power? In modern amps and receivers does gain matching matter as much? Tbh the whole subject is all rather confusing and not clear cut to simpletons like me . cheers |
|
|
|
Post by garbulky on Aug 6, 2019 11:43:31 GMT -5
You really don't need to worry about it... it will work just fine.
While there isn't an actual standard, most home power amps have a gain between about 28 dB and 32 dB, and need somewhere around 1V to 2V to reach full power... And, in general, all preamps and processors are designed to work with all of them. The same is true for the pre-outs on most home theater AVRs - the ones that have pre-outs. (Speakers do tend to vary quite widely in terms of efficiency...)
In the old days you would hear serious discussions about "optimally matching output levels, input levels, and gain, to get the best possible S/N ratio".... Today, while that still matters with very low level signals like phono and microphone inputs, it just isn't important any more with line level signals, like the one between a preamp and a power amp. (It would be like worrying whether your car would run on one particular brand of gas.)
Furthermore, surround sound gear always has level trims you can use to match levels exactly between channels. And, for anything that has any sort of automatic room correction, that will set the trim levels for you.
Good morning to you all, i have recently been been looking into upgrading the power amps in my system and honestly the more I look into gain matching etc the more confused I become. Currently I have an arcam 390 which arcam recommend to use a power amp with a gain of 31db . Arcam have communicated that “The nominal output of the pre-outs on the 390 is 1V RMS at 560R. This is a variable output that can raise far above 1v”. So my question is if for instance I purchased an amp like the Emotiva xpa DR3 which has a gain of 29 dB and input sensitivity of 2v would I still get full rated power? In modern amps and receivers does gain matching matter as much? Tbh the whole subject is all rather confusing and not clear cut to simpletons like me . cheers But you would not get full power right? |
|
DYohn
Emo VIPs 
Posts: 18,347
|
Post by DYohn on Aug 6, 2019 11:45:45 GMT -5
Matching amplifier gain is only important when bi amping loudspeakers, and even then it can be moot if you get acceptable results for your usage.
|
|
nemoid
Seeker Of Truth
Posts: 3
|
Post by nemoid on Aug 6, 2019 13:57:24 GMT -5
Brilliant that puts my mind at rest a bit, thanks for taking the time to reply guys.
|
|
KeithL
Administrator
Posts: 9,938
|
Post by KeithL on Aug 6, 2019 14:32:13 GMT -5
There seems to be an awful lot of confusion about the relationship between output voltage, gain, and power. First, to answer the question:
Yes, you will be able to reach full Volume on any channel.
The level trims on each channel will take care of making sure all the channels play at the same level with the same input level. The differences in amplifier gain will NOT be an issue unless you actually have a situation where the processor is UNABLE to deliver enough signal to drive the amplifier to full output. So, as long as the processor can deliver 2V, it can drive either amplifier to full output power just fine. (This is why you were reassured that "the processor could deliver a lot more than 1V if it had to".)
However, the goal of all the adjustments you make is to ensure that, when you apply the same input signal to each channel, they all play at the same level. Assuming you had the same speakers all around, and all of your amplifier channels were the same MAXIMUM POWER, the level trims would completely cancel out the differences in gain. But, if your amplifier channels are of different power, or your speakers are different, then some channels may clip before others if you turn them up.
So, for example, if you have a much more powerful amplifier on your front channels.... You may NOT be able to turn your front channels up to deliver full power.... Because, at the current overall Volume setting, your surrounds are already at clipping.... (However, this has nothing to do with the gain of either amplifier.... it's simply because "one amplifier ran out of power before the other"...)
You really don't need to worry about it... it will work just fine.
While there isn't an actual standard, most home power amps have a gain between about 28 dB and 32 dB, and need somewhere around 1V to 2V to reach full power... And, in general, all preamps and processors are designed to work with all of them. The same is true for the pre-outs on most home theater AVRs - the ones that have pre-outs. (Speakers do tend to vary quite widely in terms of efficiency...)
In the old days you would hear serious discussions about "optimally matching output levels, input levels, and gain, to get the best possible S/N ratio".... Today, while that still matters with very low level signals like phono and microphone inputs, it just isn't important any more with line level signals, like the one between a preamp and a power amp. (It would be like worrying whether your car would run on one particular brand of gas.)
Furthermore, surround sound gear always has level trims you can use to match levels exactly between channels. And, for anything that has any sort of automatic room correction, that will set the trim levels for you.
But you would not get full power right? |
|
|
|
Post by Gary Cook on Aug 6, 2019 15:41:25 GMT -5
The individual channel output trims typically allow for -10 and +10 dB, so a gain difference of 4 (28 to 32) would be easily covered. Which is the case in my system (trims around +/-2) with the XPA-1L’s versus the XPA-5 Gen 1.
Cheers
Gary
|
|
|
|
Post by patate91 on Aug 6, 2019 16:16:10 GMT -5
Gain structure seems to be more critical in active setup : 2 or 3 different amplifiers with drivers with different sensitivity.
|
|
KeithL
Administrator
Posts: 9,938
|
Post by KeithL on Aug 6, 2019 16:31:17 GMT -5
Yes and no.....
Often, when folks do what they call "vertical bi-amping" nowadays, they've got multiple amplifiers connected via passive splitters. And, in that case, you really need amps with similar gain, since most amps lack input level controls.
However, most active crossovers have individual gain adjustments on each output, along with all their other controls. (If the drivers have even slightly different gain you're going to want to adjust that individually for each of them.)
Gain structure seems to be more critical in active setup : 2 or 3 different amplifiers with drivers with different sensitivity. |
|
|
|
Post by mauriceminor on Aug 6, 2019 16:41:40 GMT -5
Gain structure seems to be more critical in active setup : 2 or 3 different amplifiers with drivers with different sensitivity. Some amplifier requirements for Linkwitz LXmini active speakers are on the website: www.linkwitzlab.com |
|
|
|
Post by patate91 on Aug 6, 2019 17:45:02 GMT -5
Yes and no.....
Often, when folks do what they call "vertical bi-amping" nowadays, they've got multiple amplifiers connected via passive splitters. And, in that case, you really need amps with similar gain, since most amps lack input level controls.
However, most active crossovers have individual gain adjustments on each output, along with all their other controls. (If the drivers have even slightly different gain you're going to want to adjust that individually for each of them.)
Gain structure seems to be more critical in active setup : 2 or 3 different amplifiers with drivers with different sensitivity. The thing is that active crossover over are ajusting gain with at a digital level. And there's no impact on noise floor this way. An analogue control Will affect noise floor too. My current setup has a 13 db (14 db with amplifiers gain). I guess I can match them with the minidsp digital control, but I think I'll get better results with ab anologe attenuation (the A-100 volume pot for exemple). |
|
nemoid
Seeker Of Truth
Posts: 3
|
Post by nemoid on Aug 7, 2019 4:37:42 GMT -5
In my case I have 3 different sized speakers in my system all from the same range ,xtz cinema range, so I have m6 lcr that are 4ohm with a sensitivity of 89dB then s5 surrounds that are 4ohm with a 87dB sensitivity and finally s2 for Atmos duties which are 8ohm with 86dB sensitivity. So as there all different then the most power I can put in before clipping occurs is limited to the weakest link in this case the s2’s as these top out at 105dB based on 120hz crossover whilst the others top out at 111dB with a 80 hz crossover according to xtz anyway. In this case I presume that the height speakers are never asked to produce the same spl as the base level speakers so does that mean that the amp for the base speakers can be more powerful and I would never want to listen at 105db never mind 111db as these are just figures for peaks in the soundtrack? Even then is it still beneficial for the amp to have the most reserve power for the front 3 or equal for the whole base level? the more I read about all this sort of stuff manages to both inform and confuse me in equal measures lol There seems to be an awful lot of confusion about the relationship between output voltage, gain, and power. First, to answer the question:
Yes, you will be able to reach full Volume on any channel.
The level trims on each channel will take care of making sure all the channels play at the same level with the same input level. The differences in amplifier gain will NOT be an issue unless you actually have a situation where the processor is UNABLE to deliver enough signal to drive the amplifier to full output. So, as long as the processor can deliver 2V, it can drive either amplifier to full output power just fine. (This is why you were reassured that "the processor could deliver a lot more than 1V if it had to".)
However, the goal of all the adjustments you make is to ensure that, when you apply the same input signal to each channel, they all play at the same level. Assuming you had the same speakers all around, and all of your amplifier channels were the same MAXIMUM POWER, the level trims would completely cancel out the differences in gain. But, if your amplifier channels are of different power, or your speakers are different, then some channels may clip before others if you turn them up.
So, for example, if you have a much more powerful amplifier on your front channels.... You may NOT be able to turn your front channels up to deliver full power.... Because, at the current overall Volume setting, your surrounds are already at clipping.... (However, this has nothing to do with the gain of either amplifier.... it's simply because "one amplifier ran out of power before the other"...)
But you would not get full power right? |
|
KeithL
Administrator
Posts: 9,938
|
Post by KeithL on Aug 7, 2019 10:49:40 GMT -5
The problem is that the "official recommendations" are somewhat different than the "practical realities".
The official recommendation is that you could have a loud sound in any speaker - so you should have all large speakers and the same power all around.
HOWEVER, it's really a matter of priorities... Most people I know agree that the front three channels are both the most important and the most likely to include loud sounds...
So the front three channels should get the biggest/best speakers and the most power. Most people I know allocate the most power for the three front channels, somewhat less for the surrounds, and even less for the height channels.
(You'll notice that, in most normal installations, the size of the speakers coincides with that set of priorities as well.)
With movies important action usually happens in the front. This means that the front is where most of the loud stuff takes place. It also means that, if there's a tiny bit of clipping, the front channels are where it would be likely to be noticed the most.
Sure, your height channels could end up clipping when the mother-ship descends, likewise for the giant monster sneaking up behind you in the surrounds.... However, none of that is nearly as important or noticeable as making sure that the main action and dialog in the front is clean and clear....
A similar situation applies to music. It's theoretically possible that some surround sound music is equally distributed in all the channels... However, in reality, most of the big stuff in most recordings happens in the front.
The only real variable is in what you listen to the most.
People who do mostly movies tend to say that the front THREE channels are the most important. (The center channel actually can consume plenty of power and that's where most of the critical dialog is placed.)
However, people who listen mostly to stereo music, or who consider stereo music to be more critical, often have big speakers and amps on the front left and right speakers... And a less powerful amp for both the center and the surrounds.
There's also a matter of economics.... You're comparing the cost of an amp with five or seven powerful channels... To the combined prices of a powerful two-channel or three-channel amp AND the price of a less powerful four or five channel amp... The difference may not be as large as you think. (That's a little less of an issue if you're using an XPA Gen3, where you can mix channels of different power levels on the same amp.)
In my case I have 3 different sized speakers in my system all from the same range ,xtz cinema range, so I have m6 lcr that are 4ohm with a sensitivity of 89dB then s5 surrounds that are 4ohm with a 87dB sensitivity and finally s2 for Atmos duties which are 8ohm with 86dB sensitivity. So as there all different then the most power I can put in before clipping occurs is limited to the weakest link in this case the s2’s as these top out at 105dB based on 120hz crossover whilst the others top out at 111dB with a 80 hz crossover according to xtz anyway. In this case I presume that the height speakers are never asked to produce the same spl as the base level speakers so does that mean that the amp for the base speakers can be more powerful and I would never want to listen at 105db never mind 111db as these are just figures for peaks in the soundtrack? Even then is it still beneficial for the amp to have the most reserve power for the front 3 or equal for the whole base level? the more I read about all this sort of stuff manages to both inform and confuse me in equal measures lol There seems to be an awful lot of confusion about the relationship between output voltage, gain, and power. First, to answer the question:
Yes, you will be able to reach full Volume on any channel.
The level trims on each channel will take care of making sure all the channels play at the same level with the same input level. The differences in amplifier gain will NOT be an issue unless you actually have a situation where the processor is UNABLE to deliver enough signal to drive the amplifier to full output. So, as long as the processor can deliver 2V, it can drive either amplifier to full output power just fine. (This is why you were reassured that "the processor could deliver a lot more than 1V if it had to".)
However, the goal of all the adjustments you make is to ensure that, when you apply the same input signal to each channel, they all play at the same level. Assuming you had the same speakers all around, and all of your amplifier channels were the same MAXIMUM POWER, the level trims would completely cancel out the differences in gain. But, if your amplifier channels are of different power, or your speakers are different, then some channels may clip before others if you turn them up. So, for example, if you have a much more powerful amplifier on your front channels.... You may NOT be able to turn your front channels up to deliver full power.... Because, at the current overall Volume setting, your surrounds are already at clipping.... (However, this has nothing to do with the gain of either amplifier.... it's simply because "one amplifier ran out of power before the other"...)
|
|
KeithL
Administrator
Posts: 9,938
|
Post by KeithL on Aug 7, 2019 10:51:38 GMT -5
Depending on where you put it in the signal path an analog control may affect the noise floor... An analog potentiometer itself generates essentially no noise... so reducing the level of an output signal before sending it to an amp won't add any noise. (The potentiometer reduces both the signal and the noise from the source equally. The noise floor of the power amp is basically fixed.) However, by reducing the level of the signal, you have "moved it closer to the noise floor".
But, when you use a digital volume control, you reduce resolution...
When you start with a 16 bit signal, and digitally reduce the level by half, you are dividing the numerical values by two. Another way of saying that is that you set the most significant bit to zero - so now you only have a 15 bit signal. Reduce it by an additional 6 dB and you're down to a 14 bit signal.
If you use analog attenuation at the output, you have not introduced any noise, and you haven't lost any bits of resolution either.
(Of course, if you're doing your math at 24 bits depth, you can easily spare one or two bits of resolution.)
With modern gear, neither should do much harm, as long as you're only adjusting it by a few dB.
Yes and no..... Often, when folks do what they call "vertical bi-amping" nowadays, they've got multiple amplifiers connected via passive splitters. And, in that case, you really need amps with similar gain, since most amps lack input level controls.
However, most active crossovers have individual gain adjustments on each output, along with all their other controls. (If the drivers have even slightly different gain you're going to want to adjust that individually for each of them.)
The thing is that active crossover over are ajusting gain with at a digital level. And there's no impact on noise floor this way. An analogue control Will affect noise floor too. My current setup has a 13 db (14 db with amplifiers gain). I guess I can match them with the minidsp digital control, but I think I'll get better results with ab anologe attenuation (the A-100 volume pot for exemple). |
|
|
|
Post by Casey Leedom on Aug 8, 2019 1:02:43 GMT -5
... But, when you use a digital volume control, you reduce resolution... When you start with a 16 bit signal, and digitally reduce the level by half, you are dividing the numerical values by two. Another way of saying that is that you set the most significant bit to zero - so now you only have a 15 bit signal. ... Sorry, computer nerd nit-picker here: In binary, which is how the data is represented, you're shifting the binary 0/1 digits "right" (down shifting). This has the result of leaving the most significant binary digit as a 0, but it's not the same thing as "setting" the most significant digit to 0. I know that you know this, but people less familiar with numerical representation systems might be mislead. Casey |
|
