6.47 dB
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Topping L70 Headphone Amp Review
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staticV3
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4V setting on the E70 outputs 4.27V at 0dBFS.
From 4.27 down to 1.9 it's 20*log10(1.9/4.27)=-7.03dB
That is input required for maximum output not clipping of input stage. You can set the E70 to full volume and reduce the volume of the L70.
Yes. Just set the volume on the E70 to full and the volume of the L70 in high gain low and play a 100 Hz 0 dBFS sine and listen for distortion while turning it up. There won't be any below -13 dB.
Edit: Corrected volume setting for distortion onset. Max power at 16 Ohm balanced is 6 W so voltage is 10*log10(6*16) = 19.82 dBV. High gain for balanced is 19.8 dB and 4 V output from the E70 is 12.04 dBV so volume has to be set such below 19.82 - (12.04+19.80) = -11.98 dB to avoid distortion.
Edit2: The E70's 4 V output level is 4.27 V so volume has to be set such below 19.82 - (20*log10(4.27)+19.80) = -12.79 dB to avoid distortion.
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That makes it volume below 19.82 - (13.98+19.80) = -13.96 dB to avoid distortion.I currently have e70 set to 5V
What do you mean? Input sensitivity simply follows from maximum voltage output divided by gain. If you reduce the level using the volume control, you effectively reduce the gain.
Let me understand correctly in the end. Can I have E70 in only DAC mode with a constant voltage value of 5V and in the L70 preamplifier in high gain mode not exceed -14dB?
Are you able to look at the calculations further if I connect the L70 to Topping B200 in both low and high mode and see what the math with logarithms will show?
Are you able to look at the calculations further if I connect the L70 to Topping B200 in both low and high mode and see what the math with logarithms will show?
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staticV3
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You can plug your E70 in 5V mode into the L70 in High gain without causing clipping, as long as you keep the L70 low enough.
You can also specify a Safe volume in the L70 menu which it will revert to on startup to avoid volume shocks.
But the L70 does not support setting a hard volume limit, so during playback you could clip the L70's output at any time by turning the knob up too high.
If you want to remove the risk of clipping the L70 entirely, simply keep it in Low gain.
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Why would you ever go past -20dB on L70 in high gain? What are you trying to power...the moon?
Currently I have everything set to low gain, but I don't like this volume control, it is relatively quiet for a very long time, I can even get to -5dB from the speakers. L70 does not have a positive volume control (Pre90 has it, but I won't buy it because it doesn't have a 12V trigger, which I need for B200 and I don't want to waste money on it) Volume control in high gain is more friendly to me. Something is already happening between 50-40-30dB. I agree that the -20 level is already starting engines to the moon
Yes. That would work to avoid clipping the L70. However, the preamp has no current limiting which allows for a higher output.
Let the dBV output of the DAC be LDAC. Without clipping, the dBV output of the pre-amp with dB gain Gpre and dB volume setting V is
Lpre = LDAC + Gpre + V.
Let the dBV maximum output voltage of the preamp be Lpremax. Thus, to avoid clipping the pre-amp, Lpre <= Lpremax, i.e.
LDAC + Gpre + V <= Lpremax
and the volume thus has to be
V <= Vpremax = Lpremax - (LDAC + Gpre).
Let the amp's gain be Gamp and its dBV maximum output voltage be Lampmax. Thus, without clipping, its voltage output is
Lamp = Lpre + Gamp = LDAC + Gpre + V + Gamp.
Thus, to avoid clipping the amp, Lamp <= Lampmax, i.e.
LDAC + Gpre + V + Gamp <= Lampmax
and the volume thus has to be
V <= Vampmax = Lampmax - (LDAC + Gpre + Gamp).
Thus, to avoid clipping V <= min(Vpremax, Vampmax).
The maximum output voltage of the L70 is specified as 52 Vpp which is 20*log10(52) - 10*log10(8) = 25.29 dBV. The input from the DAC is 5 V RMS which is 13.98 dBV. Low gain is 6 dB and thus Vpremax = 25.29 - (13.98 + 6) = 5.31 dB whereas in high gain Vpremax = 25.29 - (13.98 + 19.8) = -8.49 dB. Thus, in low gain, the L70 cannot clip with 5 V input.
The maximum output voltage of the B200 is dependant on the impedance. At 4 Ohm, it is 80 Vpp which is 20*log10(80) - 10*log10(8) = 29.03 dBV and at 8 Ohm, it is 110 Vpp which is 31.80 dBV. Low gain is 11.6 dB and high gain is 22 dB. In low gain with the L70 in low gain, for 4 Ohm, Vampmax = 29.03 - (13.98 + 6 + 11.6) = -2.55 dB and for 8 Ohm, Vampmax = 31.80 - (13.98 + 6 + 11.6) = 0.22 dB. In low gain with the L70 in high gain, for 4 Ohm, Vampmax = 29.03 - (13.98 + 19.8+ 11.6) = -16.35 dB and for 8 Ohm, Vampmax = 31.80 - (13.98 + 19.8 + 11.6) = -13.58 dB. Thus, with both devices in low gain, there is enough level to get all the power from the amp. However, there is little room to increase the level for quiet recordings.
They are 22-11.6 = 10.4 dB lower volume than for the amp in low gain. Since, high gain on the L70 gives you 16.35 dB extra for the B200 in low gain, there is no need to put it into high gain.
Thank you very much for writing down my feelings in the form of numbers. To sum up, I leave E70 set to 5V, I leave B200 set to low gain. L70 has an available gain change between low and high from the remote control, so I will use them interchangeably. As I wrote earlier, I like high gain more
If it does not reduce the volume when switching to high gain, I would be careful with that as 14 dB is quite a lot and you could clip both the L70 and B200 if volume is too high in low gain.
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