Superampman
AK Member
Very good. Thank you, Brian. I'm assuming you meant 'small increment of volume' in your last sentence. I have a vague recollection reading about this in the past.
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1db is clearly perceptible
- Thread starter Superampman
- Start date
Very good. Thank you, Brian. I'm assuming you meant 'small increment of volume' in your last sentence. I have a vague recollection reading about this in the past.
robgmn
Super Member
Easily achieved with Audacity to create the differences (in dynamic sound like music AND with pure tones), and Foobar to do blind comparisons...
Brian
An Old Geezer
No, power as I stated. Some makers made receivers and amps with very small power increases and charged a premium when there would be no practical increase in spl as applied to most speakers. And, sometimes even this small increase would be negated as the headroom was greater on the smaller amp than the larger so the dynamic range was equal. Many times the preamps and tuners were the same or only non audio related differences in them.
Superampman
AK Member
Oh, sorry. I get it.
Lapslah
Super Member
dB by itself is really a meaningless term. dB VU? dB SPL? dB volts? Especially with a preamp, the dB markings on the volume control CAN'T be dB SPL, since the preamp only operates in the electronic realm (as opposed to acoustic) and has no idea what kind of amp or speakers it will be connected to. Would that preamp produce the same perceived volume change between two settings marked 1dB apart when connected to a 1 watt amp as when connected to 10,000 watts? Doubtful.
Those dB markings are more likely referenced to a zero point which has been established by the manufacturer as the point beyond which you risk going into electronic distortion (with a buffer). They don't have any useful correlation to dB SPL - especially when you introduce other variables like YOUR amp and YOUR speakers in YOUR room.
Those dB markings are more likely referenced to a zero point which has been established by the manufacturer as the point beyond which you risk going into electronic distortion (with a buffer). They don't have any useful correlation to dB SPL - especially when you introduce other variables like YOUR amp and YOUR speakers in YOUR room.
Superampman
AK Member
Yea, it's been alluded to. I wasn't aware of the correlation, or lack thereof.
It seems to me that changing the volume control to achieve a change in power output equivalent to 1dB would have precisely the same effect regardless of the output capability of the downstream power amp (assuming it is not clipping). Perhaps I am misunderstanding your comment?
Brian
An Old Geezer
That's would be correct if the amp output was linear to the inputs voltage to the point of clipping but, it is not. At a point compression of the output starts requiring more input voltage the increase the output power. At some point it can no longer compress and increase the output driving it into clipping.
It is linear up to the point of gain compression, which is at the far reaches of a decent amp's capabilities. But your correction is certainly valid....I should not have used the word "precisely".
The comment to which I responded suggests that the change is highly variable depending upon the power capabilities of the amp, which is misleading. Within the range of linearity, the change would be precisely the same whether it was a 10 watt amp or a 10,000 watt amp.
fred soop
Super Member
If the amp is starting to go into a non linear compression, then this IS the start of clipping, just not quite up to hard clipping.
Superampman
AK Member
Okay, now I'm really confused. How does the pre know the total output power of the amp? At '60' on the pre, whatever amp is hooked up, it's cookin. Whether it's a 40wpch, 80, 120, 150, 200, or 256. The only exception is my Leach Superamp monos with 2.40v input sensitivity. Very hard to drive those into clipping. Mind you they output 375 watts each. I think the pre would clip before they would. I've never been able to cause the clipping indicators on those amps to light up. The others are anywhere from 1-1.5v. Two completely separate but major variables. So, how can an increment ever represent a 1db or any standard increase in volume or power when the pre has a fixed attenuation scale?
Brian
An Old Geezer
Respectfully, I have to disagree. It is not the start of clipping but the none linear delta of a gain stage. While discussing this, BTW, the compression may be caused by this at any stage within the circuit, not just the output stage. Other times it is a function of the limits of the power supply.
I know we still use the hard and soft clipping terms but the distinction is a characteristic of tubes and transformers. With ss it either is on or off so it will clip or not.
It doesn't "know", nor does it matter.
While the output to the speakers at a given point on the volume knob will vary depending upon the amp being used (due to varying input sensitivities from amp to amp), the change in output as the volume knob is adjusted will be the same.
While the output to the speakers at a given point on the volume knob will vary depending upon the amp being used (due to varying input sensitivities from amp to amp), the change in output as the volume knob is adjusted will be the same.
Some manufacturers state amplifier input sensitivity, ie: x volts input will produce y watts output.
Preamplifier output voltage varies with the signal - just as the power amplifier output. Preamplifier output voltage is not fixed.
Input sensitivity is variable on amplifiers with GAIN controls.
The preamplifier has no idea what is happening after it.
Huh? Clipping may be slight, it may be severe, or it may be complete/full, or anywhere in-between. This is true of both tube and ss amps.
Brian
An Old Geezer
These preamp does not know or care about the power amp or its power rating, it just passes a voltage. The amp requires volts to provide you watts. In the linear range d% of change of the output voltage will produce d% of change on output power, assume 100% efficiency in this discussion. Amps can require the same voltage to attain max output whether 10, 20, 200, or 2,000 watts. The amp is little more than a gain multiplier of the input so, 1 amp have a gain factor of 10x and another 100x while each does it with the same preamp output voltage. This is a layperson writing, dropped engineering for accounting more years than most here have existed.
Superampman
AK Member
I get that. But my point is, or rather question, volume increase per increment on the pre must be commensurate to total output power of the particular amp. Wouldn't a higher power amp yield a greater increase per increment?
LordOfTRings
Be Cool with the Blues
Not only some people can differentiate volume level variations of half decibel (0.5dB),
but also differences in frequency response (particular areas of the audio spectrum) as small as a quarter of a decibel (0.25dB)!
- Good hearing, experimentation, long experience, and attentive listening.
Brian
An Old Geezer
If I understand you, then yes. Of the "increment" is say 10% in preamp voltage then in theory if one amp amp produced 2x the rms power of the other while the % of power increase in each is 10% the power increase in the larger amp would be 2x the power increase in the smaller.
This is simplistic but, basic theory.
In theory it should but is primarily dependent on the amplifier's gain structure.
In other words, it is entirely possible for a 10 watt amplifier to produce higher SPL (before it runs out of steam) than a 500 watt amplifier - at the identical volume control setting.
A loose comparison would be an accelerator pedal in a car - with a hair trigger as opposed as one more evenly calibrated throughout the range.
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