AVR input levels from DAC

[walt99]

So I have a Denon A110 which is basically the same as the 8500. The Denon analog input spec states 200mv and when I inquired to Denon support they said the same thing.
I have the X16 at 0db and previously the node2i at fixed volume plugged in and have not heard any signs of distortion/clipping, I believe they both output around the 2v level.
So what's the right answer, is 2v ok? It appears to be, but I still wonder how close I am to overloading the input.
I can attenuate the output of the X16 via the volume control, or adjust the input level of the Denon if need be via the input setup menu.

My question to them:
Using an outboard DAC to 'Media Player' analog input, what is the maximum input voltage that may be applied without overloading the input. The DAC output is adjustable via the volume control but prefer to run at 0db as recommended.

Their answer:
We would not recommend inputting more than 200mV to avoid clipping or distortion.

 

[RayDunzl]

Semi-educated guess:

The volume knob on the Denon attenuates the analog input level. That should regulate whether or not you are overloading the later circuit stages.

200mv is 20dB lower than 2V, so you get full amplifier output at -20dB on the volume knob, if it is so marked.

That would equate to an audible "twice as loud" reduction (-10dB) two times.

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On the other hand, you say the Denon volume knob is at 0dB without stress, so, don't worry about it.

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The only solution to your question is to take a measurement.

 

[walt99]

I may be wrong but I'm pretty sure all analog inputs would have their own buffer amp prior to reaching the volume control.

 

[bigguyca]

I may be wrong but I'm pretty sure all analog inputs would have their own buffer amp prior to reaching the volume control.

For pure analog inputs, that is without going through an ADA process, the analog inputs go first to a CMOS switch that has a very low impedance and then an 8-channel volume control. The outputs from the 8-channel volume control are the preamp outputs. There a no output buffers. There are of course internal opamps in the volume control IC. The gain/attenuation process is implemented around, and using these opamps. Marantz unfortunately has the HDAM output buffers that significantly worsen measured performance.

In an X8500H/A110 an opamp input buffer would be essentially just an extra component in the analog signal path. This is especially true of the very modest opamps and low supply voltages generally used by Denon/Marantz in AVR's/AVP's.

The volume control is actually quite good for all it does. At least in the X8500H, the A110 hasn't been measured, the attention to signal routing, power supplies, etc., must be quite good to get essentially the specified performance of the volume control as the measured output.

 

[walt99]

For pure analog inputs, that is without going through an ADA process, the analog inputs go first to a CMOS switch that has a very low impedance and then an 8-channel volume control. The outputs from the 8-channel volume control are the preamp outputs. There a no output buffers. There are of course internal opamps in the volume control IC. The gain/attenuation process is implemented around, and using these opamps. Marantz unfortunately has the HDAM output buffers that significantly worsen measured performance.

In an X8500H/A110 an opamp input buffer would be essentially just an extra component in the analog signal path. This is especially true of the very modest opamps and low supply voltages generally used by Denon/Marantz in AVR's/AVP's.

The volume control is actually quite good for all it does. At least in the X8500H, the A110 hasn't been measured, the attention to signal routing, power supplies, etc., must be quite good to get essentially the specified performance of the volume control as the measured output.

Thanks very much for the detailed description of the inputs, so based on what you say then is it safe to assume a 2v input (from x16 DAC) would not overload anything? The reason I'm asking is Denon spec's a 200mv max input for the analog inputs. I'm currently running the X16 at 0 db with no signs of distress.

 

[bigguyca]

Thanks very much for the detailed description of the inputs, so based on what you say then is it safe to assume a 2v input (from x16 DAC) would not overload anything? The reason I'm asking is Denon spec's a 200mv max input for the analog inputs. I'm currently running the X16 at 0 db with no signs of distress.

First, a 2V input will be fine and is what an X8500H (A110) "wants" to see.

The output from the AKM DAC circuitry is 2V internally in a Denon AVR and Denon equipment takes 2V as a reference. In Amir's measurements of Denon equipment you'll note that 82.5/2.5 on the volume control is 2V output from the preamp outputs if the unit is being run pure direct and without Audyssey. At 80.0/0 the output of the A110 should be about 1.5V with a 2V input, assuming I understand your setup. This is with no Audyssey, offsets, etc.

Based on the Amir's measurements an input of 4V or so maximum should be OK although it's hard to see why 4V input on an RCA input would be used. The 4V limit also fits with the internal design of the upper level Denon equipment, but it's good to have actual measurements.

The Denon/Marantz User's Manuals are nice, but can be a bit confusing. The 200mV specification relates to the 1.2V output specification. That specification means that with a 200mV input, the output preamp output can be 1.2V with the volume control set appropriately, in other words, at least 6X or a bit over 15dB of gain is available. In today's world, with a lot of equipment having 2V outputs, that gain specification is typically irrelevant. Normally the preamp of an AVR is attenuating a preamp signal, not providing gain.

 

[walt99]

Thanks bigguy, great info and very helpful, to bad Denon can't offer the same level of tech rather than just repeating the specs when you ask them a question!