I have the above integrated and the volume adjustment range has always been poor in that it goes from silent to very loud within 10% of potenmiter ajustment range. In other words. If volume is 0 at 7 o’clock position, by 7.5 to 8 it’s reasonable listening levels and by 9 o’clock it is as loud as one would ever wish. Above that it’s ear splitting and clipping.
I have tried it as an integrated and with a variety of external power amps out the pre out. Including a NAD c370. The anustment is more or less the same in all cases. Slight increases in adjustment range but never being able to use more than 1/10th to 1/8 the total range. I even experimented putting a second volume control before the inputs and that was not very helpful either. Of course on amps with gain adjustment one can increase the range of the vol on the c325 as a pre. But it just can’t be “correct” . And doesn’t help if using it as an integrated.
This seems extremely strange and non-optimal. Both In terms of ergonomics and sound quality.
I am not sure if the underpaying problem is the volume pot or a larger design flaw in the preamp/line stage gain being just far to high , the c325bee’s week point seems to be its preamp section. Having tried various combos, using It just as a power amp with an external preamp (some many tines the cost of the 325) is surprisingly good! Using it just as a preamp with external power amp is always produces a hard and thin sound. Almost as if the preamp line stage is being overdrive.
Is this “normal” for this amp? Any suggestions on ways to fix this volume range?
I have tried it as an integrated and with a variety of external power amps out the pre out. Including a NAD c370. The anustment is more or less the same in all cases. Slight increases in adjustment range but never being able to use more than 1/10th to 1/8 the total range. I even experimented putting a second volume control before the inputs and that was not very helpful either. Of course on amps with gain adjustment one can increase the range of the vol on the c325 as a pre. But it just can’t be “correct” . And doesn’t help if using it as an integrated.
This seems extremely strange and non-optimal. Both In terms of ergonomics and sound quality.
I am not sure if the underpaying problem is the volume pot or a larger design flaw in the preamp/line stage gain being just far to high , the c325bee’s week point seems to be its preamp section. Having tried various combos, using It just as a power amp with an external preamp (some many tines the cost of the 325) is surprisingly good! Using it just as a preamp with external power amp is always produces a hard and thin sound. Almost as if the preamp line stage is being overdrive.
Is this “normal” for this amp? Any suggestions on ways to fix this volume range?
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Your problem is the input sensitivity of the preamp section of NAD 325BEE which is 240mV according to the manufacturer specification (see attached). This is really high sensitivity for most modern sources where line level output is more in the range of 1~2V. The amp section has sensitivity of 730mV which is not as high as that of preamp and thus should allow using passive or simply buffered attenuator with a more convenient adjustment range.
Regards,
Oleg
Regards,
Oleg
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The line inputs require attenuation. I suggest 18dB of attenuation (i.e. reducing the input signal voltage to one eighth of its value). A simple passive resistive attenuator can be wired internally across each of the line input sockets. I suggest you try 18K (R1) and 2.2K (R2) resistors wired as shown in the following calculator:
Voltage Divider Calculator
Voltage Divider Calculator
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I see now that music4cities has already experimented with a volume control in front of the inputs. Any practical suggestions on how to reduce the gain in the NAD325BEE?
The input arrangements are shown in the link below for you experts out there!
NAD C 325BEE Service Manual (Page 16 of 38)
NAD C 325BEE Service Manual (Page 16 of 38)
Wow, thanks everyone.
Brilliant observation about the input sensitivity. Why in the world would they have designed it like that?
One issue with an external volume pot before the input was indeed a negative effect on the sound quality. May in part be the pot itself. FWIW, I also tried a pair of inline RCA attenuators fixed at -12db. It helped a bit. But not enough. And again degraded the sound.
Right now I am using it with a c270 power amp, which as an adjustable gain input (an amp that I find pretty great). With amps adjustable gain knob at about 40%, the useful range of the preamp volume knob is from 7-2 o’clock. And it does help the sq somewhat since the vol pot on the pre is now in the better part of its range (less channel imbalance, less resistive track to interfere, etc)
But it still seems very odd that one would have use the variable gain input with a NAD pre and NAD power amp!
BTW, the speakers are Mirage MRM-1; a very nice small stand mount they made. A typical mirage. But the sensitivity is only around 88db. So while not hard to drive, they are not exactly high sensitivity. I tried the c325 with a set of KEF q3...useful range of vol knob even worse. Essentially it went from 0 to ear shattering in a couple degrees or rotation. All sorts of channel imbalance due to the pot. But it’s not magic.
Brilliant observation about the input sensitivity. Why in the world would they have designed it like that?
One issue with an external volume pot before the input was indeed a negative effect on the sound quality. May in part be the pot itself. FWIW, I also tried a pair of inline RCA attenuators fixed at -12db. It helped a bit. But not enough. And again degraded the sound.
Right now I am using it with a c270 power amp, which as an adjustable gain input (an amp that I find pretty great). With amps adjustable gain knob at about 40%, the useful range of the preamp volume knob is from 7-2 o’clock. And it does help the sq somewhat since the vol pot on the pre is now in the better part of its range (less channel imbalance, less resistive track to interfere, etc)
But it still seems very odd that one would have use the variable gain input with a NAD pre and NAD power amp!
BTW, the speakers are Mirage MRM-1; a very nice small stand mount they made. A typical mirage. But the sensitivity is only around 88db. So while not hard to drive, they are not exactly high sensitivity. I tried the c325 with a set of KEF q3...useful range of vol knob even worse. Essentially it went from 0 to ear shattering in a couple degrees or rotation. All sorts of channel imbalance due to the pot. But it’s not magic.
Thanks. This issue appears to be an inherent design issue rather than an isolated fault. I have searched and found no service bulletin on the issue; it’s not mentioned in the service manual either.
This model was introduced sometime after 2000...so it’s not as expectations for input sensitivies have changed that much.
This model was introduced sometime after 2000...so it’s not as expectations for input sensitivies have changed that much.
As we know, the input sensitivity of your NAD is 240mV. To put this into perspective, a broadly useful input sensitivity is 200mV, which will suit most sources. A lower value of 400mV suits CD players, but is too low for external phono stages. Naim amplifiers have an input sensitivity as high as 90mV! It appears that your NAD integrated is not atypical of the breed.
I have extracted this information from the source below, which also mentions the use of in-line attenuators.
Sensitivity
Look at the 'Tape 1' input. When this is selected, the resistors R339 (1M), R315 (470) and R345 (220k) form a Pi-pad attenuator which will also provide impedance matching between the source and the preamplifier.
The equations for calculating the values of the three resistors for unequal source and load impedances are quite complex, but it would appear that increasing R315 while decreasing R339 and R345 increases the degree of attenuation.
https://www.electronics-tutorials.ws/attenuators/pi-pad-attenuator.html
To keep it simple, you could try increasing the value of the 470 ohm resistor (R2 in the attached thumbnail) to see how that, on its own, affects the degree of attenuation.
The equations for calculating the values of the three resistors for unequal source and load impedances are quite complex, but it would appear that increasing R315 while decreasing R339 and R345 increases the degree of attenuation.
https://www.electronics-tutorials.ws/attenuators/pi-pad-attenuator.html
To keep it simple, you could try increasing the value of the 470 ohm resistor (R2 in the attached thumbnail) to see how that, on its own, affects the degree of attenuation.
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