Gain vs Volume....a question?

Thanks all for your help and education!!!!

Wow, what a great set of responses. Very informative. Good question Rwd!

Just to add a couple more simplistic thoughts to the already excellent discussion from an absolute layman’s perspective, "volume control" generally can be achieved by two basic means, either attenuating (that is reducing) the signal that comes into the control or by amplifying it (which I have understood as adding gain). An active preamp is called that because the volume control can do both of these things--it can both reduce the signal from the input level towards zero and it can (because it has an amplification stage) amplify the signal above the input level. A "passive" preamp, on the other hand, is passive because it can only reduce the input level -- it will not have an amplification stage at all.

For most sources, the output level of the signal (which is the input at the preamp) is relatively high. Which is to say that at zero gain at the preamp (no attenuation or amplification of the signal) the volume level will be relatively loud. (Which is how passive preamps/volume controls can work -- based on the assumption that the volume associated with zero gain will be louder than you ever want or need, therefore attenuation or reduction of the signal level can provide all of the volume control range you would ever want).

Compared to just about every other source out there, however, the output signal that comes off of a vibrating pin scratching across a rotating platter of vinyl is tiny. So tiny that, without additional amplification, the signal would be too weak for a volume control designed to provide a useful range for things such as CD players to do much anything useful with at all. Thus, in order to jack the tiny output from a typical phono cartridge up into the range the your average preamp volume control was designed to operate in, you need some additional amplification. This is why a phono preamp is a separate or additional piece of equipment (or stage in your existing preamp) from your plain vanilla preamp -- it independently amplifies the signal coming from the cartridge up into a range useful for your average volume control. The gain level of the cartridge dictates how much more work the phono stage will have to do to get the signal up into this useful range. Did my layman’s understanding screw that all up horribly?

In simple terms, gain is a ratio and volume is what you hear. For example, say that "gain =10". Take two sounds - a gunshot and a whisper. If you multiply each by 10, the whisper will have a higher volume and be easier to hear whereas the gunshot will have enough volume to seriously damage your ears. Both sounds are increased by the same proportion or gain. But a gain of 10 will not take a whisper to that of a gunshot - you will need a series of gain stages in between.

Front end audio equipment is a series of gain stages. The cartidge has a gain setting, but not enough to drive an amplifer, and in most cases not even a preamplifier. So the chain is cartridge, phono preamp, preamp, and amplifer.

The volume control adjusts the gain within the preamp from zero gain to the maximum gain of the preamp. The strength of the source signal will ultimately determine the audible volume for a given volume (gain) setting.

Sugarbrie;

Thanks for the post. It looks like you did a lot of work for us as I think you had to copy it, word for word.

Rick,

Gain setting is like a car’s transmission box. Preamp volume control is like the gas pedal.

I might disqualify to answer but English was never my strong suit & I don't follow instructions too well either! :-)

>>cartridge gain settings
The amount of gain you will be providing to the signal coming from the cartridge. You can multiply the cartridge output signal level by this gain number (not in dB but after you convert it to a linear number) & this will tell you the max. signal that you will able to feed your phono pre with.

>>the actual volume control on the pre-amp
The portion of the total available gain that you are actually using to listen to music. In most cases, the user rarely uses all the available gain in his/her system to listen to music at reasonable volume levels.
It is important to have much more gain than you are going to use as this ensures that the signal is within the linear operating range of the electronics being fed with this (music) signal. I.E. you are above the min. sensitivity of the electronics.

Hope that this complements TWL's post.

There is the aspect of hitting the max. input level of the electronics. You didn't ask for that, so I won't answer either.

This information was posted by Blue Circle's Gilbert Yeung in the Blue Circle forum.

"This is a topic I have been thinking about posting for a long time and never had a chance to do it. But now’s the time.........

In order to understand what I am going to tell you and learn something from it, you must have an open mind. Forget everything you have ever learned about the three terms Volume Control, Attenuator and Gain or you are just going to be confused more and more and use the wrong terms every time.

First, let me tell you my interpretation of the above three terms related to audio use.

VOLUME CONTROL: A device which will allow the operator to adjust the sound level of the system. The sound level can be increased or decreased depending on the direction the operator turns or slides the control.

ATTENUATOR: A device which will decrease or increase the level of signal. The term attenuator usually suggest the decrease of signal. However, negative attenuation means increasing the signal.

GAIN (in this case, we are talking voltage GAIN only): The amount of amplification of a given device. Gain in audio is usually understood as an increase of signal. However, gain can also be used in a negative way. If negative gain is applied, the level is decreased. The unit of gain is usually expressed in dB (decibels).

Why do we need a volume control in a preamp?
Because a preamp has a gain stage and usually it has a fixed amount of gain. Therefore, the signal must be attenuated (decreased in this case) before being fed to the input stage. The volume control in this case can be also called an attenuator. Volume control in the digital domain may not work the same and cannot be called an attenuator, however, we will stick to an analog volume control and preamp at this time.

These days preamps usually have a range of gain from 0dB (passive preamp) to 35dB. Some of you know people that are using a passive preamp with a power amp and have plenty of gain. And then there are others using an active preamp that’s supposed to have 25dB of gain but they have to turn the Volume Control up to 2 or 3 O’clock before they can obtain any reasonable volume. WHY?

The answer lies with the setting of the volume control, and NOT the gain of the preamp. When using a passive preamp, volume controls are usually set at max. attenuation 75dB to 80dB with audio taper. Audio taper volume controls have been used since way back in the 50's. You will find these audio taper controls usually give you lots of volume between 6 O’Clock and 8 O’Clock. Remember back in the late 70's, there was a receiver war and one of the major factors was the power of the receiver. Manufacturers used these audio taper volume controls so they could make the receiver sound very loud when the volume control only pointed at 8 O’Clock position. Did anyone use it up to 2 O’Clcok? Does any one know what happens when you turn these audio taper volume control up to 2 O’ Clock?

These audio taper controls are set at a non-linear increment. For example, 80dB max. attenuation at 6 O’Clock. By 7 O’Clock, it has 70dB attenuation and 65dB attenuation at 7:30. Between 6 O’Clock and 7:30, there is a 15dB decrease on attenuation or 15dB increase of sound level output. When the control pass 10 O’Clock, the increment starts to decrease rapidly. 3dB, 2dB and finally 1dB and 0.5 dB when it hits the 3 O’Clock position.

Ask yourself, when did you ever turn your receiver up to 3 O’Clock when you were older than 25 years old. Don’t answer this question to anyone becasue your answer may not be true to yourself. Keep this one for your own.

Times have changed, people have changed. Many people like to listen to their music at lower volume in their small apartment at night without disturbing their family members. Or they simply enjoy low level music in the background. Also audiophiles realize the lower part of the volume control is not as good as the upper part.* That’s why many manufacturers have started to provide volume controls which can be turned higher up without getting too loud. There are many fine settings of these type of volume controls. The most common is the linear taper. Even with linear taper, the first part (6 O’Clock to 7 O’Clock) would still be about 5 to 15 dB different. This is because when the level is down to about 80dB attenuation, to human ears, there is almost no difference between 80dB and a 78dB attenuation.

Linear taper means every step of the volume control attenuates an equal amount of dB, this usually happens when the volume control hits 8 O’Clock position. There are exceptions, like some of the digital volume controls, but again we are sticking with analog at this moment. Linear taper volume control give you a lot more fine adjustment between the 6 O’Clock and 12 O’Clock positions. To obtain the same level of volume at a 10 O’Clock position on an audio taper control, you will have to turn it up to about 2 O’Clock on a linear control. Many people have concerns about the volume control being turned too high. I say that’s great, you are actually using almost all of the volume control, you are getting your money’s worth. There is absolutely nothing wrong by turning the volume control up to 2 or 3 O’Clock. That only means you have a lot of fine adjustment on the lower setting.

However, if anyone wishes to have very loud volume at 9 to 10 O’Clock, ask for the audio taper volume control. It will give you what you need at 10 O’Clock, however, you will probably not able to use anything higher than 1 O’Clock.

All of the above is based on typical cases. Power amps having gain of 18dB to 26dB, speaker are somewhere in between 86dB to 92dB and CD player/DAC has a standard 2V output. If you throw a single-ended triode amp with only 13dB and / or a horn speaker with 104dB or even a tube amp with 40dB of gain. Then the equation has to be re-calculated. Therefore, a typical volume control may not have a range wide enough to compensate. There are solutions to this problem.

When most people have an actual gain issue to solve it’s with too high or too low gain of a power amp, or even a extra high output DAC or CD player. They blame the gain of the preamp being too high or low. Most of the time, they are wrong. The preamp is the last one to blame. The preamp is the one piece of equipment that ALWAYS has a volume control. Without a volume control, that piece of equipment cannot be called a preamp. So, what if someone has a volume control or gain control on their power amp, then what? Then adjust the volume or gain control on your power amp to suit the most comfortable level on your preamp. You are essentially adjusting the level or the gain of your power amp to suit.

If they don’t have anything else to adjust other than the preamp volume control, then what? In most cases, you are screwed. Go find something that is designed normally. Or if you’ve got a Blue Circle preamp with a Shallco attenuator, then it time to talk to me. Tell me what your problem is, then I can adjust the attenuation increments of the Shallco volume control(s) to your solve. In 99% of cases, the actual gain of the preamp does NOT need adjustment, just the volume control(s) increments.

If anyone asks whether the Shallco will change the sound of their system. My answer is no.

Why anyone would use a power amp with a 40dB of gain is another totally different issue than the volume control. But it is semi related since the whole chain in the audio path is involved in it. If anyone of you wishes to have low noise floor in your system never buy a power amp that has more than 28dB of gain. The higher the power amp gain, the more it amplifies the residual noise of the system.

* This theory does not apply to our Shallco attenuator. Since the Shallco attenuator has individual resistors at each position, there is no sonic difference between any position of the control. The only difference is the level of volume or level of attenuation."

Gilbert Yeung, President, Blue Circle Audio.

Volume level is what you are hearing.
Gain level is how much amplification is being given to the signal.
If you have a very low-level input signal, even a large amount of gain may only achieve low volume.
On the other hand, if you have a very hot input signal, you might only have to just barely move the volume knob to get quite loud volume.

Regarding cartridges, the gain setting on the phono preamp should correspond to the output level of the cartridge, so that the signal to the linestage is at a useful level for the volume control to operate in, and be at a similar level to the rest of your source equipment. Low output cartridges will need higher gain, and high output cartridges will need lower gain settings at the phono stage.

Hope that was what you were looking for.