Marantz CINEMA 70s AVR - Teardown, personal thoughts and a few measurements

[trl]

But I am keeping the AVR turned Off for most of the time when I'm not using it. It also has Auto Power Off feature, like most electronic devices these days, so it shuts off by itself anyway. In stand-by it consumes less than 0.5 Watts/hour, I can't even measure it.

Eco Mode is a feature that simply lower the voltage that feds the output stage transistors to save energy while listening to music or movies in a quiet environment. From my measurements and listening done I've noticed that between 5 to 10 Watts per each channel the THD+N will not increase above 1%, which is fine under most circumstances. For example, during evenings or nights the Eco Mode can be kept ON while listening to low to moderate levels.

With speakers having an SPL of 90dB/1m or higher the Eco Mode can be of a real advantage for those willing to save energy when listening to low to moderate volume levels.

 

[trl]

Hi

@trl ... Above and beyond. Great review! Thanks!

Off topics:
The ECO mode is of great interest to me. I am virtually off-grid ... since the "grid" in my country provides less than 3 hours of electricity per day... if we're lucky...
Do the new Denon x800 series (X-3800 et al) provide similar energy savings, in ECO mode? My current Denon AVR-X3400 acting as a preamp only since diving active speakers, consume 65 watts .. on ECO mode



Happy holidays!

Peace.

From https://www.denon.com/on/demandware...1c55/downloads/avr-x3800-owners-manual-en.pdf, page 17:

"This unit is equipped with an ECO Mode function that allows you to enjoy music and movies while reducing the power consumption during use, and also an auto-standby function that automatically turns off the power supply when the unit is not in use. This helps reduce unnecessary power use".

 

[peng]

but it also has a parametric equalizer that corrects deeps and peaks to flatten the sound and to make it sound as good as a "reference" audio system

Merry Christmas and Happy New Year to you too. Thank you very much for a very detailed review, and the teardown, identifying several ICs, as well as temperatures measurements are very much appreciated. The ADC that you could not identify is obviously hidden below or behind some circuit boards, but based on Denon's, it is likely the AK1803A, that has very similar specs to the one they previously used, the AK5358.

Just one minor correction, if you don't mind, the C70 does not have parametric equalizers, as far as I can tell, no Marantz AVPs or AVRs have parametric EQs, I wish they do, but they don't. If it is compatible with the MultEQ X, (I think it is, just not too sure), then of course one can try to use the fake PEQ, the fake one, in my opinion is better anyway.

 

[Thomas_A]

@trl, since you measured a difference from -69.9 dB to -78.5 dB THD+N ECO mode off, it would be interesting to find out if the idle current is different on the power amps.

 

[trl]

Merry Christmas and Happy New Year to you too. Thank you very much for a very detailed review, and the teardown, identifying several ICs, as well as temperatures measurements are very much appreciated. The ADC that you could not identify is obviously hidden below or behind some circuit boards, but based on Denon's, it is likely the AK1803A, that has very similar specs to the one they previously used, the AK5358.

Just one minor correction, if you don't mind, the C70 does not have parametric equalizers, as far as I can tell, no Marantz AVPs or AVRs have parametric EQs, I wish they do, but they don't. If it is compatible with the MultEQ X, (I think it is, just not too sure), then of course one can try to use the fake PEQ, the fake one, in my opinion is better anyway.

Thank you for the updates and for the correction. I was referring to MultiEX X that is a paid application I will probably need to try it out sometimes.

@trl, since you measured a difference from -69.9 dB to -78.5 dB THD+N ECO mode off, it would be interesting to find out if the idle current is different on the power amps.

The biasing current is set up from the trimmers that are visible in the pictures, so it's not an active circuit that takes care of adjusting the current based on ECO Mode. However, by lowering the voltage rail for the output stage I suppose that automatically the biassing current will get lowered a bit as well.

 

[GXAlan]

Very nice work. Did you run a ground wire from the Marantz to the E1DA cosmos? You can just run a wire from the phono signal ground to the one of the ground pins. The grounds are tied, so if you record on the left channel, you can place your ground wire in the right. You can also use the 43V input jack and place a ground wire in the XLR female ports to ground the 43V input.

 

[Thomas_A]

The biasing current is set up from the trimmers that are visible in the pictures, so it's not an active circuit that takes care of adjusting the current based on ECO Mode. However, by lowering the voltage rail for the output stage I suppose that automatically the biassing current will get lowered a bit as well.

Yes, I was not thinking of the ECO mode on or off, but rather that the different amps gave different distortion numbers in ECO off mode. I guess the bias current will affect distortion and if the trimming is different among the amps, you will get varying numbers.

 

[trl]

Very nice work. Did you run a ground wire from the Marantz to the E1DA cosmos? You can just run a wire from the phono signal ground to the one of the ground pins. The grounds are tied, so if you record on the left channel, you can place your ground wire in the right. You can also use the 43V input jack and place a ground wire in the XLR female ports to ground the 43V input.

Hi! No, I haven't ran any ground, because the output impedance of the amplifier is very low and I didn't thought it makes any difference. But I think I will retry some more measurements soon with different bias current settings and then I'll also try with vs. without the ground wire. Thank you!

 

[trl]

Yes, I was not thinking of the ECO mode on or off, but rather that the different amps gave different distortion numbers in ECO off mode. I guess the bias current will affect distortion and if the trimming is different among the amps, you will get varying numbers.

I do see your point now, thanks! I see that the trimmers in my AVR are in exact same position as the AVR from audio-com.pl pictures. I don't think that DM manufacturer was arranging these trimmers visually, I do hope they are actually measuring the current (voltage on the resistors), right? However, I will measure this in a few days, just to be sure, so thanks for letting me know your point of view.

 

[Thomas_A]

I do see your point now, thanks! I see that the trimmers in my AVR are in exact same position as the AVR from audio-com.pl pictures. I don't think that DM manufacturer was arranging these trimmers visually, I do hope they are actually measuring the current (voltage on the resistors), right? However, I will measure this in a few days, just to be sure, so thanks for letting me know your point of view.

Thanks, this would be very nice to see how the actual voltages vary (in a cold vs warm amp). I've seen also that all trimmers have the exact same position. Both local heat variation and some individual differences of each amp section would probably affect bias.

 

[popej]

Panasonic MN864788

Should be HDMI receiver/switch.

 

[sweetsounds]

This is an impressive review, looking into the build quality, temperature and features.

Great work!

 

[GXAlan]

Hi! No, I haven't ran any ground, because the output impedance of the amplifier is very low and I didn't thought it makes any difference. But I think I will retry some more measurements soon with different bias current settings and then I'll also try with vs. without the ground wire. Thank you!

In my experience, you usually get a few more dB of SINAD and once you start measuring stuff with the E1DA, you are shocked how common ground loops are (even if it’s below the threshold of audibility).

My CX-A5100 which is a two prong floating ground still generates a ground loop with XLR unless you ground the chassis

 

[peng]

Today I uploaded the ARCG file that was used when my AVM had FW Ver. 76, and ran REW again. You can see that it has improved:
In this comparison, the only difference is the FW version as both are from using the same ARCG files, though since the red one was one on 3rd December last year, it is possible that one of the subwoofer has been moved a little bit, but more than a couple inches in any direction because there really isn't much flexibility to move it in that location.

So, I still think somehow going from FW76, to 78 and now 80, ARCG is performing much better in the deep bass range. If I am right about this, it would explain why quite a few members had reported that they felt bass lacking, after their first run of ARCG.

 

[trl]

Should be HDMI receiver/switch.

Thanks! Seems to be used in videocameras and AV receivers too. So this integrated circuit is basically switching between HDMI inputs?

 

[trl]

In my experience, you usually get a few more dB of SINAD and once you start measuring stuff with the E1DA, you are shocked how common ground loops are (even if it’s below the threshold of audibility).

My CX-A5100 which is a two prong floating ground still generates a ground loop with XLR unless you ground the chassis

Thanks a lot, but in this case I was tiding the "minus" of the speaker-out to the "inverted" input of the XLR plug of the E1DA (to minimise the internal noise of the E1DA when measuring an unbalanced DUT) and to E1DA's GND as well, so tiding the GND of the E1DA and the "minus" of the speaker-out to the GND/case of the AVR will probably cause a short-circuit and trigger the internal protection.

However, when I'll have to measure a DUT having close or above -120 dB THD+N then I'll think more about ground loops or I'll just use the COSMOS APU that will help me gaining a few more dB's. But right now, for this AVR measurements, I could probably use a regular Focusrite interface and I don't think I would be getting worse THD values.

 

[Thomas_A]

@trl, when you measured the other channels, what setting of the AVR did you have? Multichannel?

I will solder my 8, 6 and 4 ohm dummy load during the holidays and put the amps on my NR1710 to test.

 

[GXAlan]

Thanks a lot, but in this case I was tiding the "minus" of the speaker-out to the "inverted" input of the XLR plug of the E1DA (to minimise the internal noise of the E1DA when measuring an unbalanced DUT) and to E1DA's GND as well, so tiding the GND of the E1DA and the "minus" of the speaker-out to the GND/case of the AVR will probably cause a short-circuit and trigger the internal protection.

However, when I'll have to measure a DUT having close or above -120 dB THD+N then I'll think more about ground loops or I'll just use the COSMOS APU that will help me gaining a few more dB's. But right now, for this AVR measurements, I could probably use a regular Focusrite interface and I don't think I would be getting worse THD values.

When testing integrated amplifiers.
Red speaker output to + of the XLR pin
Black speaker output to - of the XLR pin
Ground of the phono on the amp to the 0 of the XLR pin

That gets you to 10V.

If you are using 43V, you have the stereo +/- on the TRRS pin and then have ground going to the XLR 0 pin.

I have done this with regular and balanced differential output amps and the approach seems to work consistently.

 

[oupee]

Excellent work!

 

[popej]

So this integrated circuit is basically switching between HDMI inputs?

Yes, 4 inputs. Maybe audio extraction too.