Home |
Search |
Today's Posts |
#1
|
|||
|
|||
Turning up the Gain
What is actually happening when the gain on an amp is turned up and
down? Is it throtteling down the power of the, amp, reducing the preamp signal? |
#2
|
|||
|
|||
"Sub_Lover" wrote in message oups.com... What is actually happening when the gain on an amp is turned up and down? Is it throtteling down the power of the, amp, reducing the preamp signal? It is decreasing the sensitivity of the amplifier, with it turned way down the amp can still make full power, it just takes more input to do so. Chad |
#3
|
|||
|
|||
On 16 Mar 2005 12:42:17 -0800, "Sub_Lover"
wrote: What is actually happening when the gain on an amp is turned up and down? Is it throtteling down the power of the, amp, reducing the preamp signal? Adjusting the gain control adjusts the level of the input signal. This allows you to adjust the amplifier so that it can be driven to full volume regardless of what your head unit's preamp voltage is. "Gain" is just the ratio of the output voltage divided by input voltage. So, let's say that an amp's maximum output is 20V, and it can achieve this output with an input of 1V. This amplifier would therefore have a gain of 20 divided by 1, or 20. You could also describe this amplifier as having a gain of 13 dB, using the formula (10 * log (output/input)). Now, let's say that instead of a 1V input, we give the same amplifier a 4V input. The maximum rated output of the amp is still 20V, so we have to reduce the gain from 20 to 5 to keep from overdriving the amp. Now, a 4V input and a gain of 5 still gives us 20V at the output, so the amp is still being driven to full volume, even though we've turned the gain knob "down". So, the only purpose for the gain control is so that you can match an amplifier to a variety of head units. The only reason you don't see very many gain adjustments on home stereo amp is that almost all CD players, VCR's, DVD players, and receivers use a standard pre-amp voltage. Since the amplifier manufacturers know what the preamp voltage from the source will be, they don't need to include a gain adjustment on the amp. (Some do anyway, just to give you more flexibility). -- Scott Gardner "Evolution is a harsh mistress." |
#4
|
|||
|
|||
The amps power is the same regardless of the gain.
The main function of that control is to match it with the head units output. I remember years ago (10 maybe) Kenwood head unit had a very low output and it was hard to match different brands with them. Other brand amps you had to turn the gain all the way up to get descent volume out of them. on the flip side, Kenwood amp's played louder with different brands and you had to turn the gains down. I don't know if that is still the case with ken, but I don't recall any problems like that recently -- The Clown Prince of Car Stereo "Sub_Lover" wrote in message oups.com... What is actually happening when the gain on an amp is turned up and down? Is it throtteling down the power of the, amp, reducing the preamp signal? |
#5
|
|||
|
|||
On a related note, my Nakamich CD-35 head unit's preamp out has fairly low output which feeds my Rocford Fosgate 4600x 4-channel amp. I have to turn the amp's gain up quite a bit in order to drive the amp to near or full power. I do have some room to spare on the gains, but when I turn them up, more engine whine noise is introduced, so I compromise and lower the gains a bit to where the engine noise is still there but very tolerable when listening at normal volumes. What would happen if I put a line level controller in front of the amp and raise the gain on it so that the amp is getting a higher level signal than the head unit normally outputs, and then lower the gains on the amp slightly to allow a lower volume on the head unit to drive the amp to the same volume as before at a higher head unit volume? I'm hoping that by lowering the gains on the amp, that less engine whine noise will be there. |
#6
|
|||
|
|||
I think if your moter noise is coming from the head unit, then the line
driver is not going to help much. If the noise is coming from the Amp, then the line driver will help. -- The Clown Prince of Car Stereo "Bob" wrote in message ... On a related note, my Nakamich CD-35 head unit's preamp out has fairly low output which feeds my Rocford Fosgate 4600x 4-channel amp. I have to turn the amp's gain up quite a bit in order to drive the amp to near or full power. I do have some room to spare on the gains, but when I turn them up, more engine whine noise is introduced, so I compromise and lower the gains a bit to where the engine noise is still there but very tolerable when listening at normal volumes. What would happen if I put a line level controller in front of the amp and raise the gain on it so that the amp is getting a higher level signal than the head unit normally outputs, and then lower the gains on the amp slightly to allow a lower volume on the head unit to drive the amp to the same volume as before at a higher head unit volume? I'm hoping that by lowering the gains on the amp, that less engine whine noise will be there. |
#7
|
|||
|
|||
Isn't the reason for having higher pre out voltage is to be able to
drive the amp cleanly before the source starts to distort? |
#8
|
|||
|
|||
|
#9
|
|||
|
|||
Ok gotcha.
|
#10
|
|||
|
|||
Scott,
Excellent information! Tony -- 2001 Nissan Maxima SE Anniversary Edition Eclipse CD8454 Head Unit, Phoenix Gold ZX475ti, ZX450 and ZX500 Amplifiers, Phoenix Gold EQ-232 30-Band EQ, Dynaudio System 360 Tri-Amped In Front and Focal 130HCs For Rear Fill, 2 Soundstream EXACT10s In Aperiodic Enclosure 2001 Chevy S10 ZR2 Pioneer DEH-P9600MP (Just gettin' started) |
#11
|
|||
|
|||
On Wed, 16 Mar 2005 19:06:45 -0800, "Tony F"
wrote: Scott, Excellent information! Tony Thanks, Tony. I wish there were a better way to express mathematical equations in newsgroups posts. It gets to be kind of a pain in the ass not having subscripts, superscripts, or all of the right symbols. I should probably do all of the equations in Word or Mathematica, save the results as web pages, and just post links to them. It really opens people's eyes when they find out what a S/N ratio of 90 dB or 100 dB really MEANS, and just how insignificant the difference between the two is. I think the pre-out voltage hype started with the original Alpine 7909 CD player. It was one of the earliest "high-voltage" preout models, with 2V or 4V pre-outs (I can't remember which right now). Anyway, it wa considered at the time to be a good-sounding unit, and was very popular, but the sound had nothing to do with the high-voltage preouts. They could have made it with standard-voltage preouts, and it would have sounded the same. In the typical car audio "more-is-better" style, it's now typical to have at least 2V pre-outs, and 4V or 8V pre-outs are becoming more common as well. The only real effect is that it makes it harder to use new head units with older amps. Have you ever tried to use a head unit with 8V pre-outs and an amplifier that was only designed for a maximum of 2V inputs? You can make it work by adjusting the gain on the amp, but with an input that high, the usable range on the gain knob is about ten degrees of rotation. *Very* annoying. -- Scott Gardner "A government that robs Peter to pay Paul can always depend on the support of Paul." (George Bernard Shaw) |
#12
|
|||
|
|||
Scott, thanks for the great info. I have a question maybe you can answer...or maybe not as it is a little odd. My Nak CD-35 head unit's specs say the preamp's output voltage is 0.8V. If I add a line level controller that adds up to 8 dB of gain to the signal, what would that same gain be expressed in volts? Thanks, Bob |
#13
|
|||
|
|||
|
#14
|
|||
|
|||
|
#16
|
|||
|
|||
In article ,
Scott Gardner wrote: :On Thu, 17 Mar 2005 04:30:50 +0000 (UTC), Bob) wrote: : :In article , :Scott Gardner wrote: ::On Thu, 17 Mar 2005 04:08:24 +0000 (UTC), :Bob) wrote: :: :: ::Scott, thanks for the great info. I have a question maybe you can ::answer...or maybe not as it is a little odd. :: ::My Nak CD-35 head unit's specs say the preamp's output voltage is 0.8V. ::If I add a line level controller that adds up to 8 dB of gain to the ::signal, what would that same gain be expressed in volts? :: ::Thanks, ::Bob :: :: ::Not an odd question at all. A line driver is just another kind of ::signal booster or amplifier. :: ::The equation for expressing gain in dB is: :: ::Gain = 10 * log (output voltage/input voltage) :: ::Re-arrange to solve for the ratio between output voltage and input ::voltage: :: :output voltage/input voltage) = 10^ (8/10), ::which gives us a gain of 6.30. This means that with a gain of 8 dB, ::the output voltage will be 6.30 times higher than the input voltage. :: ::Since the input is 0.8V, the output would be about 5.0 V. :: ::Hope this helps, :: :: ::-- ::Scott Gardner : :Thanks again, Scott. That helps tremendously. Now I am faced with the :possibility that this 8 dB gain might be too much for my amp. The :specs for it say the input sensitivity is 250 mV = 1 V. : :Bob : :That means that the amplifier is designed to be used with inputs :ranging from 250mV up to 1 V. Since the 0.8V from your Nak head unit :falls in that range, your head unit and amp seem to be pretty :well-matched. What were you wanting the 8dB boost from the line :driver for? It doesn't sound like you need it. : : :-- :Scott Gardner Scott, here is another post I made to this thread that you probably missed. I should also add that my head unit only has a single set of preamp outs so I am splitting them with y-splitters in order to feed the 4 channel amp's inputs (front and rear). On a related note, my Nakamich CD-35 head unit's preamp out has fairly low output which feeds my Rocford Fosgate 4600x 4-channel amp. I have to turn the amp's gain up quite a bit in order to drive the amp to near or full power. I do have some room to spare on the gains, but when I turn them up, more engine whine noise is introduced, so I compromise and lower the gains a bit to where the engine noise is still there but very tolerable when listening at normal volumes. What would happen if I put a line level controller in front of the amp and raise the gain on it so that the amp is getting a higher level signal than the head unit normally outputs, and then lower the gains on the amp slightly to allow a lower volume on the head unit to drive the amp to the same volume as before at a higher head unit volume? I'm hoping that by lowering the gains on the amp, that less engine whine noise will be there. As someone responded, if the noise is coming from the head unit, that noise would be amplified by the line driver, but if it's coming from the amp, lowering the amp gains might help lower the noise level. I guess I need to troubleshoot the origin of the engine whine noise and take corrective action there. I get the feeling though that the noise is coming from the amp because it is wired into the factory power and ground wires for the now not being used, factory external amp in my '96 Ford Explorer. Bob |
#17
|
|||
|
|||
|
#18
|
|||
|
|||
Scott,
Excellent information! Tony Yeah, Scott posts something worthwhile every once in a (long) while. (kidding!) |
#19
|
|||
|
|||
I get the feeling though that the noise is coming from the amp because it is wired into the factory power and ground wires for the now not being used, factory external amp in my '96 Ford Explorer. Bob The noise is most likely because you are using the factory power wires. Run your own Power and ground wire. your battery is the best noise filter in the car. -- The Clown Prince of Car Stereo |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
FS - LECTROSONICS MODULAR AUDIO PROCESSOR - EC1 EXPANSION CONTROLLER AND AP4 16 AUTO MIC PREAMP MODULES | Pro Audio | |||
Tube line and phono pre amp project | Vacuum Tubes | |||
Focusrite VoiceMaster Gain ... | Pro Audio | |||
Turner the Ostrich ?? | Vacuum Tubes | |||
What is a Distressor ? | Pro Audio |