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Couple of noob questions regarding amps
Couple of noob questions regarding amps
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Old 15th June 2019, 09:23 AM   #11
Zen Mod is offline Zen Mod  Serbia
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Couple of noob questions regarding amps
different Alephs are pretty much same amp , "just" scaled up , with more outputs , higher Iq and higher rails
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Old 15th June 2019, 04:55 PM   #12
Narside is offline Narside  Russian Federation
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Please correct me if iím wrong in my estimation.
Initial data
Desired SPL (dB) = 75
Distance to listener, l = 3 m
Speaker sensitivity, Е0 = 87 dB
Minimal linear impedance of speakers, R = 4 Ohm
Lets estimate the required ampís power output
1. SPL = E0 + 10lg(P) - 20lg(l)
2. SPL loss due to specified distance 20*LOG10(3) = 9,5 dB
3. Letís estimate the output power for the desired SPL. For simplicity instead of RMS lets take the peak output power: P= 3 W-> SPLDB = E0 + 10lg(P) - 20lg(l) = 80,7 dB
4. Output current: P=I^2/R -> I = SQRT (P/R) = SQRT (3/4) = 0,87 А
5. Sin input wave simulation results: output current (blue), output power (green) and input voltage wave (red)



Next step-checking node currents for transistors. Seems to be ok.


Graph THD on power for Aleph j tells us that we are in 0.1% of THD with 3W of output power.
So, to conclude the amp is capable to perform good with the initial data???
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Old 15th June 2019, 04:56 PM   #13
6L6 is offline 6L6  United States
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Couple of noob questions regarding amps
Absolutely correct.
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Old 15th June 2019, 05:05 PM   #14
Narside is offline Narside  Russian Federation
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Thank you 6l6.
And one more question that bothers me-if i double the output mosfet stage what will be the change in the THD plot?
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Old 15th June 2019, 06:06 PM   #15
Nelson Pass is offline Nelson Pass  United States
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Couple of noob questions regarding amps
Quote:
Originally Posted by Guerilla View Post
Is the speaker's minimum impedance the relevant number? I mean in this case and in general when matching speakers with amp. Oh.. I imagine dips in impedance will not be as important in those parts of frequency spectrum where music don't contain much energy?
It is one of several numbers. If it really dips down below 4 ohms you hope
that it's in an area where there isn't that much musical energy.

Good example is electrostatic loudspeakers, which often go down to
1 ohm or below at high frequencies, 10 KHz or higher, but still seem to
work OK with amps that otherwise are not rated for that impedance.
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