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Cambridge Audio 840A V2 Volume Levels

timtaylor10

Standard Member
I have recently purchased a V2 840A and am having trouble getting my head round the -db volume control display.

On my unit I am not getting a meaningful output until the display is showing at least -50db and find that dependant on source I need to run it at anything between -45 to -35db to achieve a good sound.

This implies that I am using half the available output before getting anything from the speakers, can this be right or is it a characteristic of the class XD design ?

It is hooked up to a pair of Mission 773e's which my previous NAD C352 drove without a problem with a useable output from almost the first "crack" of the volume control.

I would be grateful to hear what volume levels other owners owners find they are using to gauge if I have a faulty amp or not !

Having said that, when it's cranked up to -35db the sound is awesome, its just that with an output rated at 120 watts into 8 ohms I would have expected it to rattle the windows much earlier in the power curve.

All experiences welcome and appreciated.
 

skazz

Active Member

Ed Selley

AVF Reviewer
Having said that, when it's cranked up to -35db the sound is awesome, its just that with an output rated at 120 watts into 8 ohms I would have expected it to rattle the windows much earlier in the power curve.

Further to Skazz's comments, the volume control isn't a "pot" like the NAD and most other amps but a resisitor ladder. The increase in output (and the balance) is absolutely linear. With the NAD, I imagine that after the initial burst of grunt, the upper reaches of the pot (in fact much after half way) didn't do very much. The 840A volume will work all the way around. It can feel a bit odd and seem that you are overdriving the amp but I assure you that this isn't the case.

There is another volume mode in the settings menu which ramps the level a bit differently that might be worth a try as well.
 

timtaylor10

Standard Member
Thanks Guys, I did think that I may be overdriving the amp to get a satisfactory output but your explanations have put my mind at rest.

It is a great sounding piece of kit, would recomment to anyone.

Thanks to Richer Sounds at Leeds who when they could not find the V1 they had reserved for me did me a hell of deal on a V2.
 

scorpion88

Active Member
Thanks Guys, I did think that I may be overdriving the amp to get a satisfactory output but your explanations have put my mind at rest.

It is a great sounding piece of kit, would recomment to anyone.

Thanks to Richer Sounds at Leeds who when they could not find the V1 they had reserved for me did me a hell of deal on a V2.

I have a 640aV2 @ 75watts which sounds brilliant so can only imagine what the 840 must sound like when cranked up.:thumbsup:

Cheers

Scorpion
 

BlueWizard

Distinguished Member
Thanks Guys, I did think that I may be overdriving the amp to get a satisfactory output but your explanations have put my mind at rest.

It is a great sounding piece of kit, would recommend to anyone.

Thanks to Richer Sounds at Leeds who when they could not find the V1 they had reserved for me did me a hell of deal on a V2.

This odd linearity in the 840A volume control has come up before. I believe a representative of Cambridge or Richer Sound even acknowledged it.

Most Potentiometer volume controls, meaning a single variable resistor have something know as a Audio Taper. Meaning the change is resistence for a change in the position of the knob is not linear, it attempts to mimic human hear in response to volume change to make changes in the Volume Control appear to be linear or even.

As mentioned the 840A uses a gang of resistors, but to make the resistive ladder or gang, the had to calibrate the individual resistor pairs to control the perceived change in volume. Cambridge admitted the that calibration of the overall resistor network was a little off. Not agressive enough in the beginning, and perhaps too aggressive at the end.

However, since the volume output is referenced in DB rather than by position of the control, you can somewhat ignore the position, and use the db dial as an indicator. -50db to -30db don't seem all that loud to me. Especially when you consider that in terms of measured output, many home cinema system are jumping up to or near 0db.

Keep in mind that while each 3db is only a slight change in the sound level, it represents a doubling of the power. So, to double the perceived volume by increasing the level by 10db (as previously mentioned), you have multiplied the power by 2 x 2 x 2 and more. In short, the power has increased by more than 8 times.

Though I don't have any direct experience, what you are experiencing doesn't seem out of the ordinary for this amp. So, for the most part, ignore the position of the volume knob and let you ears be your guide.

Just one man's rambling opinion.

Steve/bluewizar
 

scorpion88

Active Member
Interesting thread. I have the Cambridge Audio 640aV2 @ 75 watts and also the Harman Kardon HK 980 @ 80 watts.

FWIW in terms of absolute volume the CA 640 at 12.00 to my ears appears equal in volume to the HK 980 at about -5db using similar CDP's and Speakers (see sig).

Just an observation.

Cheers

Scorpion
 

skazz

Active Member
My Densen has a similar clattering-relay volume control to the Cambridge as it happens. But Densen decided to go with 200 steps rather than using the -dB system. Each step is a different relay, so they clatter like mad when you go through the scale quickly.
The scary thing is that you get audible music at 20 already, but the steps are all pretty small so between 70-110 is normal listening volume in my room, and 130-140 is seriously loud. And no matter which setting I pick on the relay ladder, I can't hear any change in background noise levels even with ear-to-tweeter.

The -dB scale is more logical but in the end any arbitrary system is usable, you just need to get used to it.
 

scorpion88

Active Member
My Densen has a similar clattering-relay volume control to the Cambridge as it happens. But Densen decided to go with 200 steps rather than using the -dB system. Each step is a different relay, so they clatter like mad when you go through the scale quickly.
The scary thing is that you get audible music at 20 already, but the steps are all pretty small so between 70-110 is normal listening volume in my room, and 130-140 is seriously loud. And no matter which setting I pick on the relay ladder, I can't hear any change in background noise levels even with ear-to-tweeter.

The -dB scale is more logical but in the end any arbitrary system is usable, you just need to get used to it.

Totally agree, it's important how the sound is to your ears more than anything else,

Anyhow, hope you enjoy the 840; can't see how you can fail to frankly as I reckon it is one of the best stereo amps in it's price range - even better if you got a decent deal.

Cheers

Scorpion:)
 

GloopyJon

Distinguished Member
I too have the 840a v2, connected to a pair of ProAc Studio 130s. Not being an electronic engineer, I find a negative volume scale (using db) rather confusing so I switched to the alternative scale (which just goes from 0 to 96 or 100, I'm not sure which as I've never been there).

I usually listen to music at around 45-55 on this scale and once tried pushing it up, but I live in a flat, and didn't dare going higher than 75. If this scale is logarithmic, as the db scale (and I guess it's the same one just with different numbers), and max volume would be another six times louder, that would be earth- (let alone ear-) shattering!

Interesting to read this thread, I too had wondered why I don't seem to get any sound much below about 40.

Jonathan

PS I'm actually fairly good at maths and can understand the concept of negative numbers :) (my bank has helped me with this in the past) but I don't like complicating my life more than necessary, and I fear the impact on prospective girlfriends who may come back to my place and ask "Why does the volume number go down when I press up?" :suicide:
 

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