Hi All,
I currently use a Pass F5 clone that I made and am considering building an F4 clone. As many of you are familiar the F5 has a gain of 5.8(15.2dB) and the F4 has a gain of 1. I currently use a passive attenuator in place of a pre-amp and wanted to know if I would need a pre-amp with the F4. Not that I would mind building one, just wanted to know.
My initial thinking was that when I listen to music my attenuator is set to -20dB and since the F5 has a gain of 15.2 I should be ok with the F4 and have a few dB to spare.
I then started to analyze the situation more closely to see at what wattage am I running the F5 and then could I achieve that same wattage with the F4. Much to my surprise I calculate that I am running the F5 at 0.22 watts! This volume is plenty loud enough for me and fills my listening room just as I like it. My current speakers are rated at 91dB sensitivity but my previous ones were rated at 89dB and my attenuator settings weren't too much different with them.
What I'm wondering is, it really possible that I'm running the F5 at 0.22 watts and getting complete enjoyment out of it? My calculations are as follows...
assume CD output is at rated 2Vrms (my phono stage is spec'd at 1.3Vrms but lets use 2v)
speaker spec'd at 6ohm nominal (reduces to 2ohm at 20khz)
-20dB attenuator setting is a gain of 0.1, so F5 input is 0.2Vrms
F5 gain is 5.8 so speaker is driven with 1.16Vrms
e=(V^2)/R
e=(1.16^2)/6
e=0.22 watts rms
Does anyone see anything wrong with the above?
Considering the F4...
attenuator setting to achieve the same 0.22 watts would be -4.37dB
So given the above I still have about 4dB to spare with the F4 which is consistent for my initial thinking.
Just was quite a surprise to me that my listening level which is quite loud in my room only requires 0.22 watts of power.
I do understand there are other things to consider such as instantaneous power and also the fact that my martin logan planer speakers do increase to 2 ohm load at 20khz. Not sure if these need to be factored in to my analysis if the F4 will be OK with no additional gain stage. Maybe I am looking at this whole thing too simply.
Phil
I currently use a Pass F5 clone that I made and am considering building an F4 clone. As many of you are familiar the F5 has a gain of 5.8(15.2dB) and the F4 has a gain of 1. I currently use a passive attenuator in place of a pre-amp and wanted to know if I would need a pre-amp with the F4. Not that I would mind building one, just wanted to know.
My initial thinking was that when I listen to music my attenuator is set to -20dB and since the F5 has a gain of 15.2 I should be ok with the F4 and have a few dB to spare.
I then started to analyze the situation more closely to see at what wattage am I running the F5 and then could I achieve that same wattage with the F4. Much to my surprise I calculate that I am running the F5 at 0.22 watts! This volume is plenty loud enough for me and fills my listening room just as I like it. My current speakers are rated at 91dB sensitivity but my previous ones were rated at 89dB and my attenuator settings weren't too much different with them.
What I'm wondering is, it really possible that I'm running the F5 at 0.22 watts and getting complete enjoyment out of it? My calculations are as follows...
assume CD output is at rated 2Vrms (my phono stage is spec'd at 1.3Vrms but lets use 2v)
speaker spec'd at 6ohm nominal (reduces to 2ohm at 20khz)
-20dB attenuator setting is a gain of 0.1, so F5 input is 0.2Vrms
F5 gain is 5.8 so speaker is driven with 1.16Vrms
e=(V^2)/R
e=(1.16^2)/6
e=0.22 watts rms
Does anyone see anything wrong with the above?
Considering the F4...
attenuator setting to achieve the same 0.22 watts would be -4.37dB
So given the above I still have about 4dB to spare with the F4 which is consistent for my initial thinking.
Just was quite a surprise to me that my listening level which is quite loud in my room only requires 0.22 watts of power.
I do understand there are other things to consider such as instantaneous power and also the fact that my martin logan planer speakers do increase to 2 ohm load at 20khz. Not sure if these need to be factored in to my analysis if the F4 will be OK with no additional gain stage. Maybe I am looking at this whole thing too simply.
Phil
It's quite possible yes... and its easy to get a really good approximation too.
http://www.diyaudio.com/forums/soli...er-do-you-really-need-domestic-listening.html
and this one has test tracks you can download and use,
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
http://www.diyaudio.com/forums/soli...er-do-you-really-need-domestic-listening.html
and this one has test tracks you can download and use,
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html
Knew I'd posted it somewhere. The SPL meter 
http://www.diyaudio.com/forums/mult...wer-do-your-speakers-need-19.html#post2893167
http://www.diyaudio.com/forums/mult...wer-do-your-speakers-need-19.html#post2893167
Willamp - your numbers look good, you've just overlooked one thing. 2V RMS is the highest level your CD player will provide. Or 2.82 volts peak.
But the average level of music is going to be about 15-16dB below that, or even lower on dynamic recordings. Given your overall voltage gain of about -5dB (-20 +15.2) the average voltage to your speakers are getting is probably about 0.25 volts.
So you may be listening to just 10 milliwatts, average. That ain't much! I think I run my horns higher than that. (I'll check).
You still need peak power, and that's going to be up around 1/2 watt on the peaks at your volume setting - right there were you figured it.
The answer to your question "Am I really listening to my F5 at 0.22 watt?" would be "No". You are listing to it at 0.01 watt average, 0.5 watts peak (per channel).
But the average level of music is going to be about 15-16dB below that, or even lower on dynamic recordings. Given your overall voltage gain of about -5dB (-20 +15.2) the average voltage to your speakers are getting is probably about 0.25 volts.
So you may be listening to just 10 milliwatts, average. That ain't much! I think I run my horns higher than that. (I'll check).
You still need peak power, and that's going to be up around 1/2 watt on the peaks at your volume setting - right there were you figured it.
The answer to your question "Am I really listening to my F5 at 0.22 watt?" would be "No". You are listing to it at 0.01 watt average, 0.5 watts peak (per channel).
Thanks Mooly!
Knowing that the vast majority of recordings are mastered at an average level ~18dB below peak helps you know what's going on.
Will doesn't even have to measure because he knows the voltage of his source and the overall gain of his system.
Neither, really. You do want to know that you have enough power (voltage and current) not to clip your amp. And you'll want some headroom above that, too.
Knowing that the vast majority of recordings are mastered at an average level ~18dB below peak helps you know what's going on.
Will doesn't even have to measure because he knows the voltage of his source and the overall gain of his system.
The answer to your question "Am I really listening to my F5 at 0.22 watt?" would be "No". You are listing to it at 0.01 watt average, 0.5 watts peak (per channel).
Wow, what a revelation.
I've already began parts collection for the F4 and I'm guessing I won't 'need' a pre-amp gain stage but who knows maybe I'll try one someday.
i'm gonna figure a way to measure the instantaneous power used in an amplifier over the course of a very high dynamic range piece and graph it vs. time
listening to a favourite song of mine, "Enter the Dog of Pavlov" (by Soilwork), at a loudness i find almost loud enough (i'd like quite a bit more but it is 10pm now) the oscilloscope says 0.5Vrms (edit: at one speaker)
listening to a favourite song of mine, "Enter the Dog of Pavlov" (by Soilwork), at a loudness i find almost loud enough (i'd like quite a bit more but it is 10pm now) the oscilloscope says 0.5Vrms (edit: at one speaker)
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Seems that you will not need any voltage gain. But you may need some current gain, depending on how hard the F4 is to drive. I'm sure someone here knows.
F5 is 100k input impedence. F4 is 47.5k as spec'd in the store's schematic. I think either is fine for my sources.
The 47.5k comes from an input load resistor to provide a path to ground when there is no signal attached, I believe. It might be possible to increase it's R value. I could check into that if necessary.
Yes, I agree but I listen to my system a lot and I've never wanted to crank it past the -20 point. Usually I'm a few dB below that. If I find myself wanting more someday I have no problem building a pre-amp. There's plenty of room inside my current passive-pre to add a gain stage.
cheers
cheers
Attachments
I usually keep an oscilloscope around, and with my 92 dB drivers I find
that I can stay within the "4 watt window" which is where the top of the
screen is +8V and the bottom is -8V, corresponding to the range of an
amplifier that delivers 4 watts rms - peaks of 8 watts.
With music, the average figure will be less than half a watt, and this is
pretty loud.
that I can stay within the "4 watt window" which is where the top of the
screen is +8V and the bottom is -8V, corresponding to the range of an
amplifier that delivers 4 watts rms - peaks of 8 watts.
With music, the average figure will be less than half a watt, and this is
pretty loud.
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