no.
As I said the source, the amp gain and the speaker determine the SPL.
The attenuator merely attenuates (reduces) the volume below maximum.
If your source puts out a maximum signal of 2.3Vac and the amplifier gain is 30times (+29.5dB) and the speakers are 88dB/W/m.
then the maximum volume will be 20 * log [2.3 * 30 / 2.83] + 88-8 +3 = 111dB at your seat (if the maximum signal has not distorted).
{2.83 converts your speaker watts to signal voltage. 88+8 -3 converts the speaker sensitivity to a pair (+3dB) @ 1m to 2.5m listening distance (-8dB)
The average level could be 20dB be below this giving ~91dB at your seat.
20dB of attenuation will give an average level of 71dB at your seat. Some folk listen at this level quite frequently.
If you want to listen at an average level of 71dB with the example given then the potentiometer must be set to -20dB.
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Hmmm I think I remember reading somewhere in de B1 pdf that NP uses a lineair pot...
Linear PEC pots are better matched. Its a precision benefit VS a practicality benefit IMHO.
My brother ask the same question. I sent him this as his answer.
http://www.diyaudio.com/forums/pass-labs/124889-b1-buffer-preamp-210.html#post2025400
Doug
http://www.diyaudio.com/forums/pass-labs/124889-b1-buffer-preamp-210.html#post2025400
Doug
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My B1 buffer amp (from post no:287) works very well, but I have a question about the maximum volume; whereas the output of a cd player can give 2 volts, which is usually enough to drive ones power amp into maximum output, this preamp, which is actually normally more working as a limiter, as I understand it, but can give a maximum gain of 2x , can only drive my power amps loud, but no more than that. (Excuse the non technical explanation!)
Is this inherent in this design or is there a mistake in the lay out?
I can live with it but want to know and understand things, and be sure I make no mistakes. I'm not very technical, just handy in he normal sense and keen on copying your ideas (ha, ha)
Ruud
Is this inherent in this design or is there a mistake in the lay out?
I can live with it but want to know and understand things, and be sure I make no mistakes. I'm not very technical, just handy in he normal sense and keen on copying your ideas (ha, ha)
Ruud
Ruudjoo,
We need to know the spec given by the manufacturer of your amp of the voltage required to drive your amp to it's full power output. This would be known as it's input sensitivity.
For example I will use two amps made by Bel Canto. The older
amp called the eVo 200.2, the spec is given this way. The input nput level for full stereo output(which is 120 watts into an 8 ohm load) requires a full 2 volts RMS, while one of their newer amps, known as the e.One S300 can achieve 150 watts into the very same eight ohm load with an input voltage of only 1.5 volts RMS. So it will depend on this input sensitivity of your amp that you are using with your B1 in combination with how well the power you are getting out of the amp drives the speakers. This is dependent on their sensitivity, or in other words how loud they will play with a given amount of power. These should be the two factors.
My suspicion is that you have speakers of low sensitivity and are not getting them enough juice with the B1 in the rig. You may be better off with a line stage that has some voltage gain, or in other words, a small amount of voltage amplification to make your speakers play more loudly than they are now. It would be worth looking at both specs.
Does this help?
Keith Lockwood
We need to know the spec given by the manufacturer of your amp of the voltage required to drive your amp to it's full power output. This would be known as it's input sensitivity.
For example I will use two amps made by Bel Canto. The older
amp called the eVo 200.2, the spec is given this way. The input nput level for full stereo output(which is 120 watts into an 8 ohm load) requires a full 2 volts RMS, while one of their newer amps, known as the e.One S300 can achieve 150 watts into the very same eight ohm load with an input voltage of only 1.5 volts RMS. So it will depend on this input sensitivity of your amp that you are using with your B1 in combination with how well the power you are getting out of the amp drives the speakers. This is dependent on their sensitivity, or in other words how loud they will play with a given amount of power. These should be the two factors.
My suspicion is that you have speakers of low sensitivity and are not getting them enough juice with the B1 in the rig. You may be better off with a line stage that has some voltage gain, or in other words, a small amount of voltage amplification to make your speakers play more loudly than they are now. It would be worth looking at both specs.
Does this help?
Keith Lockwood
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I use a UCD180 power amp now, which my other (old fashioned) pre amp can drive with a 1/16th of a turn of the knob so loud that I have to leave the room. And though I am not very technical, I am pretty certain that the problem (if there is one) must lie in the B1 buffer. If the specs say that it can give amplification of 2x max and a cd player gives out in the region of 2 Volts, it is very nice that it buffers and keeps outputlevels low if you want, with preservation of quality, but if you want it loud it must be possible I think.
I know for a fact that a number of B1 fans have discarded their B1 for this reason. Not the real electronics freaks of course, who are able to change their amps at will. I can not, by myself, may be with a little help.
Ruudjoo
I know for a fact that a number of B1 fans have discarded their B1 for this reason. Not the real electronics freaks of course, who are able to change their amps at will. I can not, by myself, may be with a little help.
Ruudjoo
The B1 is a unity gain stage. It does not do 2X gain.
2Vac from a CD player will still be 2Vac out of the B1.
A typical low gain amplifier would be the F5 which has a gain of 6X, +15db, will have an output of 12Vac for an input of 2Vac. This is about 18W and will be ~two thirds of the maximum power capability of the F5.
A 100W into 8ohm amplifier needs a gain of 15x to convert the 2Vac to 30Vac to take the amplifier to clipping. Most 100W amplifiers have a gain of >20X.
Using B1 is not usually a problem. Only in rare cases of very low gain amplifiers will extra gain be required
2Vac from a CD player will still be 2Vac out of the B1.
A typical low gain amplifier would be the F5 which has a gain of 6X, +15db, will have an output of 12Vac for an input of 2Vac. This is about 18W and will be ~two thirds of the maximum power capability of the F5.
A 100W into 8ohm amplifier needs a gain of 15x to convert the 2Vac to 30Vac to take the amplifier to clipping. Most 100W amplifiers have a gain of >20X.
Using B1 is not usually a problem. Only in rare cases of very low gain amplifiers will extra gain be required
Rudjoo,
Andrew T. is right. The B1 has no gain, meaningthat 2V RMS in =2V RMS out.
I looked for the spec that would tell me what sort of voltage it would take to drive a Hypex UcD 180 to is full output and I didn't find what I was looking for. Perhaps Andrew has a better grasp of these specs. www.hypex.nl/docs/UcD180HG_datasheet.pdf
Another issue you didn't address is the sensitivity or otherwise referred to as the efficiency of your loudspeakers.
Keith Lockwood
Andrew T. is right. The B1 has no gain, meaningthat 2V RMS in =2V RMS out.
I looked for the spec that would tell me what sort of voltage it would take to drive a Hypex UcD 180 to is full output and I didn't find what I was looking for. Perhaps Andrew has a better grasp of these specs. www.hypex.nl/docs/UcD180HG_datasheet.pdf
Another issue you didn't address is the sensitivity or otherwise referred to as the efficiency of your loudspeakers.
Keith Lockwood
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