I must apologize, since this is rather beginner’s question, but I am rather confused, since I’ve found opposite information on internet and this forum, and I expect my Muses chips to arrive soon for experimenting.
Looking at datasheet:
1. Diagram on page 1 shows OPAMP but outside Muses.
2. Pages 5 to 7 shows equivalent circuits behind pins, showing no OPAMP inside.
3. Block diagrams on page 8 and further shows that signal path flows only through pots.
4. Test circuits show OPAMP outside chip (recommended Muses opamps).
All this leads me to conclusion that there are no OPAMPS in signal path in Muses 72320.
BUT:
Documentation shows that Muses can work in several different regimes:
- As attenuator (0dB do -111.5dB)
- As gain module??? (+31.5dB do 0dB / 0.5dBstep) , and as
- As combination of previous two…
Definition at page 21 - Method of the volume control (D14, D15).
If there is not OPAMP inside:
- how can Muses produce gain of up to 30dB?
If there is OPAMP inside:
- why they recommend other Muses OPAMPS outside 72320?
- would setting to Attenuation method completely avoid audio signal path through OPAMP?
Thank you.
Looking at datasheet:
1. Diagram on page 1 shows OPAMP but outside Muses.
2. Pages 5 to 7 shows equivalent circuits behind pins, showing no OPAMP inside.
3. Block diagrams on page 8 and further shows that signal path flows only through pots.
4. Test circuits show OPAMP outside chip (recommended Muses opamps).
All this leads me to conclusion that there are no OPAMPS in signal path in Muses 72320.
BUT:
Documentation shows that Muses can work in several different regimes:
- As attenuator (0dB do -111.5dB)
- As gain module??? (+31.5dB do 0dB / 0.5dBstep) , and as
- As combination of previous two…
Definition at page 21 - Method of the volume control (D14, D15).
If there is not OPAMP inside:
- how can Muses produce gain of up to 30dB?
If there is OPAMP inside:
- why they recommend other Muses OPAMPS outside 72320?
- would setting to Attenuation method completely avoid audio signal path through OPAMP?
Thank you.
That's what I initially though.
How than we do get gain mentioned in datasheet?
(Gain method of volume control, datasheet page 21).
Even on other sites, on Pass Labs X30 test, someone said:
“It should be noted that Pass Labs is only using part of the IC and avoids any of its op-amps.”
Pass Labs XP-30 Reference Line Preamplifier | The Absolute Sound
real confusion..
yes, the Absolute Sound article should have been more clearly (and accurately) written.
muses makes op amps and they make this volume control IC which has no internal opamps. some designs that use muses volume IC also use muses op amps, some use muses volume ic with other mfrs op amps and some use muses volume ic with no op amps (like Pass).
mlloyd1
muses makes op amps and they make this volume control IC which has no internal opamps. some designs that use muses volume IC also use muses op amps, some use muses volume ic with other mfrs op amps and some use muses volume ic with no op amps (like Pass).
mlloyd1
> Looking at datasheet: Diagram on page 1
Link: http://www.njr.com/semicon/PDF/MUSES72320_E.pdf
> Why should one set passive attenuator to produce gain?
The external amplifier is capable of "infinite" gain.
We connect one attenuator around it in a way to control the gain. If the attenuation is 10:1, the forward gain is 10. Because we can't set the attenuation lower than 1:1, the minimum amplifier gain is unity. This part of the chip allows selection of gain from unity to around 30 (+31.5dB).
We often want to fade to silence. Another attenuator handles that part of the range. From unity down to -111dB.
The total range -111dB to +31dB is all you could want for a line level volume control.
The on-chip audio path is just resistors and CMOS switches (plus a lot of control logic). The CMOS switches have resistance which varies so potentially have distortion. But if the (external) amplifier is very high impedance, the distortion is very low. Obviously good designers using these chips are aware of this need.
Link: http://www.njr.com/semicon/PDF/MUSES72320_E.pdf
> Why should one set passive attenuator to produce gain?
The external amplifier is capable of "infinite" gain.
We connect one attenuator around it in a way to control the gain. If the attenuation is 10:1, the forward gain is 10. Because we can't set the attenuation lower than 1:1, the minimum amplifier gain is unity. This part of the chip allows selection of gain from unity to around 30 (+31.5dB).
We often want to fade to silence. Another attenuator handles that part of the range. From unity down to -111dB.
The total range -111dB to +31dB is all you could want for a line level volume control.
The on-chip audio path is just resistors and CMOS switches (plus a lot of control logic). The CMOS switches have resistance which varies so potentially have distortion. But if the (external) amplifier is very high impedance, the distortion is very low. Obviously good designers using these chips are aware of this need.
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