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

Descartes

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Marantz CINEMA 70s AVR has been recently reviewed by @amirm here and I had it purchased online a couple of hours prior to the above review to be published on ASR. Also, audio.com.pl had it reviewed earlier as well.

View attachment 337062
Front side with the Inputs selector

View attachment 337063
Front side with the Volume rotary knob

I bought it for improving movies listening experience in an audio surround environment, for its PRE-OUT outputs for all its 7 channels, but also because it was the only AVR with a low height I’ve seen on the market at a reasonable price. I paid for it 646 EUR on amazon.de with free shipping, so it’s an OK price I’d say. I had it connected to a couple of Canton GLE 496 as Front speakers, one Magnat S 14C as Center, a couple of JBL Control 28-1 as Surrounds, a couple of JBL Control 23-1 as Front Height / Atmos and a SVS SB-3000 subwoofer.

View attachment 337064
Rear view with the PRE-OUT outputs

For those willing to read the Datasheet can have a look here or to the infosheet here, while the Owner’s Manual can be read here while its PDF version can be download from here.

I did like the way it was packed inside, very organised and all items were safely arranged in there, without using a lot of cardboard, but also protecting just fine the inside equipment and accessories. The corners were also perfectly protected and the cardboard was of a good quality and hard to bend. The new design of the CINEMA series is definitely better than the old one that I have known for a couple of decades. A TV attached would be needed to set everything up, as the AVR will not operate otherwise, not even as a stereo amplifier. So, all relays will remain open until the setup gets finished.

View attachment 337061
Top shot of the packaging

The startup takes about 30 seconds, probably a bit longer than I was expecting, but this is something normal for all contemporary AVRs that are filled with several chips inside and each chip has its own startup time, then they all need to sync together and work in such a way a central microprocessor tells them to.

The Setup menus are similar to other’s AVRs from the market, with lots of settings from where you can set up both Audio and Video, but also the ubiquitous Audyssey settings from where you calibrate your audio setup, but you can also manually modify the calibrated audio measurements as per your liking. An ADC chip, I wasn't able yet to identify it, is handling the analogue Mic-input for the Audyssey microphone, so the AVR to be able to calibrate its sound by reprogramming the settings inside the DSP chips to modify the audio coming from each speaker in a way to make for the listener the best audio experience for its home theatre. It basically corrects phase issues, timing between channels, volume levels, 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

View attachment 337067
Very accurate distance measurements, except for the subwoofer where it's not 4.74 m, instead it's 3.80 m

View attachment 337068
Speakers levels after Audyssey calibration can later be modified if needed

View attachment 337069
High pass filters for each set of speakers can also be adjusted by the user

View attachment 337002
Bass LFE crossover can be adjusted later if needed

View attachment 337070
Bass can be extracted from the Front channels as well and the crossover frequency can be manually altered when needed

View attachment 337066
Audissey EQ curve from my CINEMA 70s in my living room

The Power On Level can be set to a desired value between 1 and 98 or to Mute or to Last, but it can also be set to a hard limit between 60 and 80 which might be a good thing if you don’t want someone else to increase the max. volume past this level. I set it up myself to 80 which is a reasonable high value for my living room and this way will ensure that the amplifier itself will not overheat and our hearing will not be damaged at the same time.

When I want to listen louder I connect the PRE-OUT of the Front channels to my Yamaha A-S701 external amplifier, this way the internal power supply of the CINEMA 70s will be able to deliver more current to the remaining five channels achieving lower distortions for the output stages. The volume level for the A-S701 I need to set it up to precisely 12:30 o’clock to match the exact output level of the CINEMA 70s, then I set master volume through the CINEMA 70s’s volume knob that will change the volume on all the five channels and on the two Front PRE-OUTs connected to A-S701 at the same time.

The case is not grounded and the power plug is also a 2-pin model, so the amplifier is an IEC Class 2 device, more details here. However, there is a dedicated grounding screw on the backside, but this is most likely to get all the audio sources to the same potential in case of hum noises.

View attachment 337014
Bottom part of the mains plug

An audio DSP chip made by Cirrus Logic CS49844A-CQZ is located on the main board. As per manufacturer wrote: “The DSPs support all legacy DVD audio codecs and all Blu-ray Disc® audio formats, along with enough DSP capacity to support a wide variety of concurrent post processing algorithms all in a single chip without need for external memory”, so I suppose it’s used to decode all 70s’s audio formats for music playing.


Another chip marked R5F564MJCDFC, from the RX64M family of MCU’s manufactured by Renesas, is a 120-MHz 32-bit RX MCU with on-chip FPU, a 3 Mbytes internal flash memory and 512 Kbytes RAM. It seems to be taking care of Ethernet communications and USB communications too.

View attachment 337024
The microcontroller that seems to take care of Ethernet and UCB communications

A Pango PGC1KG 6CFBG256 programmable chip is part of the Compa series of FPGA chips (see also https://www.audiosciencereview.com/forum/index.php?threads/understanding-fpgas.249/) “suitable for system configuration, interface expansion and bridging, board-level power management, power-on sequence management, and sensor fusion. and other application requirements, it is widely used in communications, consumer electronics, drones, industrial control and other fields”. It supports 1276 LUT4 operations and 1595 flip-flop numbers.

View attachment 337022
The FCPGA chips that takes care of main board operations

A Panasonic MN864788 integrated circuit is most likely handling the remote control operations, but it’s hard to find the datasheet for this chip, nor schematic examples using it. However, it appears to be widely used in Denon / Marantz receivers.

View attachment 337025
The microcontroller that seems to take care of IR remote operations

Four PCM5102A and one PCM5100A DAC chips are handling digital to analogue audio streams decoding for all the 7+2 channels.

View attachment 337028
The DAC chips that handles Digital to Analogue conversion of the audio streams
View attachment 336993
PCM510xA DAC chips specs differences

The mains AC voltage that comes from the transformer is regulated by a 25A D25XB60 bridge rectifier followed by a couple of 6800 uF / 63V @105C electrolytic capacitors.

View attachment 337044
The two 6800 @ 105C filtering electrolytic capacitors following the AC / DC bridge rectifier

There are a few 3-pin fixed linear regulators, manufactured by KIA Semiconductor Technology, following the above bridge rectifier, like 7805 for the +5V rail, 7807 for +7V and 7907 for -7V, that along with many other smaller regulators from the electronic boards are providing power to all the stages of this AV, but also to the relays and to logic components from the main board.

View attachment 337029
The AC / DC bridge rectifier and the linear regulators around


View attachment 337045
A couple of fuses that located around the bridge rectifier

The output power stage is built around seven pairs of complementary Darlington transistors: SANKEN 2SB1560 being PNP and SANKEN 2SD2390 being NPN. These are 10 A and 150 W powerful transistors used in many AV receivers, some of them having twice CINEMA 70s’s power, so at least in theory, with a beefier power supply and with active cooling this AVR could be transformed into a more powerful one, tough some say that the on-die biasing resistor might get damaged in case of overheating. Not just Denon / Marantz are using these transistors models, but also Pioneer, Onkyo, Cambridge Audio and perhaps other manufacturers too.

View attachment 337031
A pair of SANKEN 2SB1560/2SD2390 Darlington transistors from the output stage

Below there is a schematic with the amplifier inside the Onkyo A-9010 AVR that is built around the same 2SB1560/2SD2390 pair of transistor, that seems to have a similar output power as the reviewed one:

onkyo-a-9010-amp-jpg.649206

Onkyo A-9010 Audio Video Receiver ampilfier schematic

There is an Auto Power Off feature implemented in CINEMA 70s that takes care of two zones independently: Main zone consists of five internal amplifiers 5ch+Sub1, while Zone 2 consists of the remaining two internal amplifiers 2ch+Sub2 from Surround Back R+L, but it can also take care of all 7.2 channels, depending on the settings we choose from the Settings menu. This will ensure that when we're listening to 5.1 environment the remaining couple of channels could get into a stand-by mode and vice-versa, when we listen to Zone 2 stereo speakers the remaining 5 channels will get into a low power state according to the Power Off settings we set up. Basically, if the AVR is not going to be used for the no. of minutes/hours that was setup earlier then it will automatically shut off entirely or only one of the two Zones.

Another energy saving feature is also the Eco Mode that allows energy saving when set to ON. With Eco Mode set to OFF I measured an idle power consumption between 25.8-27 W, while with Eco Mode set to ON it got lowered to 18.5-19 W, so quite a low idling power consumption for an AVR. Exactly the same 18-19 W value I was getting while listening to a low power level late evening. Compared with my stereo amplifier (Yamaha A-S701) that has an idle power consumption of about 20-25 W, the CINEMA 70s with its 27 W seems resonable to me, especially the 17 W value with Eco Mode turned ON).

Eco Mode setting turned to OFF

View attachment 337035
Eco Mode setting turned to ON

For those willing to use this AVR on moderate levels for watching movies I think they might experiment with different power levels until they find the “sweat spot” that will better blend energy consumption and output power. However, below are a few Eco Mode ON vs. OFF measurements and my 2 cents thoughts as well.

With Eco Mode turned OFF I measured on Front outputs a SINAD of 75.1 dB at about 5 W / 4 Ohms and turning this feature ON lowered the SINAD to 59.7 dB, so a decrease of about 15 dB in SINAD and also in THD+N. Similar measurements done for about 21.5 W @ 4 Ohms showed that SINAD decreases from 80.7 dB to 43.5 dB, meaning a difference of 37.2 dB, so increasing the volume when Eco Mode is turned OFF may not be a good idea, unless energy consumption matters more than audio quality.

I was able to measure at 5 W / 4 Ohms (approx. 4.5-4.6 V RMS @ 4.1 Ohms) a SINAD of 75.1 dB on the Front Right channel and about 69.9 dB on the Front Left channel, a SINAD of 78.5 dB on the Surround Right channel and 77.5 dB on the Surround Left channel. It's interesting to see that the Surround channels are a bit better in terms of SINAD / THD+N than the Front ones, kind of unexpected.

Increasing the volume a bit more, to about 22 W / 4 Ohms (approx. 9.4-9.4 V RMS @ 4.1 Ohms) improves SINAD results to 80.6 dB for the Front Right channel and to -73 dB for the Left one, while the Surround gets to -80.8 dB for the Right channel.

What's very interesting is the difference between the SINAD figures when comparing ECO Mode OFF vs. ON. For the Right Front channel there's an increase from 75.1 dB to 59.7 dB @ 5W and from 80.7 dB to 43.5 dB, so much worse than the distortions at 5 W, which is quite normal given that enabling the ECO Mode feature means lowering the voltage for the output stage. To summarise, the ECO feature does a good job for low output levels up to 10W / channel, while for higher output levels it should be left OFF or to AUTO to ensure that the distortions will not become audible. Worth mentioning that a SINAD of 43.5 dB means 0.668%, but most people don't perceive distortions if below 1%.

View attachment 337047
Front channel Right, SINAD of 75.1 dB, 5W @4Ohms, Eco Mode OFF

View attachment 337046
Front channel Right, SINAD of 59.7 dB, 5W @4Ohms, Eco Mode ON

View attachment 337049
Front channel Right, SINAD of 80.7 dB, 21.5W @4Ohms, Eco Mode OFF

View attachment 337048
Front channel Right, SINAD of 43.5 dB, 21.5W @4Ohms, Eco Mode ON

View attachment 337050
Surround Right channel, SINAD of 78.5 dB, 5W @4Ohms, Eco Mode OFF

View attachment 337051
Surround Right channel, SINAD of 80.8 dB, 21.5W @4Ohms, Eco Mode OFF
I haven't noticed a better SINAD result when using Pure Direct, though the "skirt" around the fundamental signal disappears completely with Pure Direct pushed, so the output signal is cleaner when Pure Direct is pushed, although this doesn’t change the final THD+N results.

View attachment 337052
Pure Direct on Front channel Right, SINAD of 74.7 dB, 5W @4Ohms, Eco Mode OFF


How is Marantz / Denon achieving such an energy saving with this Eco Mode feature? They added a rather big and powerful relay HF115F / 012-2ZS4A 8A/250VAC on the main board that seems to switch on-the-fly from one winding of the transformer to another one, decreasing the AC voltage that powers the bridge rectifier shown a few paragraphs above. I measured 96.5 VDC on +/- rails of the bridge when Eco Mode is turned OFF and 38.53 VDC with this setting turned ON, an unexpected big difference. What’s important is that turning the Eco Mode OFF is indeed saving a lot of energy. Another example is when I was listening to a rather compressed song to a bit over 90 dB peaks and I’ve noticed that by turning the Eco Mode ON decreased energy consumption from 96 W to 47 W maintaining the same output level; audibly it was very difficult for me to notice the increase in distortions, although focusing only on the bass I think it was a slight difference.

View attachment 337042
DC voltage with Eco Mode turned OFF

View attachment 337043
DC voltage with Eco Mode turned ON

View attachment 337037
The relay for ECO Mode setting is in the bottom-right of the image\

Below I'm posting a few pics with the internals. I find the modular design and implementation to be easier to service, at least for the authorised repair services where they simply swap the defective module with a new one.

View attachment 337036
The AC transformer is on the left, the 14 powerful output transistors are on the bottom

View attachment 337038
On the mid-left, with heatsink on top, there is the MBBVOP13082E module that takes care of wireless comms.
On the right there is the small power supply that takes care of powering the device On / Off.


When listening loudly to music tracks on all 7 channels, the inside temperature of the hottest components from the upper board gets to 60 - 63 C, while the output stage’s heatsink reaches 53 - 56 C, with top case taken off; I expect with the case back on and with the AVR placed in small cabinet / rack or inside the furniture things to get much hotter inside, with at least 10 C more, especially when listening to music on all 7 speakers.


Given the passive cooling of the CINEMA 70s, I would recommend this AVR to be placed on a well ventilated place, same being recommended by the manufacturer as well, as per Owner’s Manual (PDF manual here):

“Power turns off and the protection circuit indicator flashes in orange approx. every 2 seconds.
  • The protection circuit has been activated due to a rise in temperature within this unit. Turn the power off, wait about an hour until this unit cools down sufficiently, and then turn the power on again. (v p. 276)
  • Please re-install this unit in a place having good ventilation.”

Marantz CINEMA 70s also has more protections in place that turns the device OFF in case of a short-circuit on the speaker cables or in case one of the speakers gets accidentally removed while playing, as per below:

“Power turns off and the protection circuit indicator flashes in orange approx. every 0.5 seconds.
  • Check the speaker connections. The protection circuit may have been activated because speaker cable core wires came in contact with each other or a core wire was disconnected from the connector and came in contact with the rear panel of this unit. After unplugging the power cord, take corrective action such as firmly re-twisting the core wire or taking care of the connector, and then reconnect the wire. (v p. 34)
  • Turn down the volume and turn on the power again. (v p. 70)
  • This unit’s amplifier circuit has failed. Unplug the power cord and contact our customer service center.”
Thank you for reading and I'm wishing Merry Christmas to all Christians and Happy Hollidays and a Happy New Year to all of us!
Did you return it?
 

formdissolve

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Great review, great details. Eco mode still burns 19 W each hour. That makes 456 W/d or 13 kW/mo or 156 kW/yr. Considering that overall (generation + distribution) each kW costs about 20 cents of a Dollar, you end up wasting almost $ 30/year for the “Eco” mode, not to mention the potential environmental cost. What is the downside of turning off the AV with a master switch on a distribution outlet? Do you loose all the AV settings?
$0.20 per kWh?! I know in Europe it's double that or more I think..

In my state:
1703649415638.png
 

eeMGee

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More detailed output stage pictures. The design is modular and the entire output stage plate can be taken out and repaired...
Great teardown tlr, but do you know what volume control chip is used?
 
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$0.20 per kWh?! I know in Europe it's double that or more I think..

In my state:
View attachment 337328
It doesn't matter the price for kWh, the idle power consumption of 18-19Wh with ECO Mode ON is probably the lowest energy consumption ever for an AVR. My two channels amplifier takes more than that when idling.
 
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Great teardown tlr, but do you know what volume control chip is used?
Hi, I can't be 100% sure, but I'd vote with R5F564MJCDFC, from the RX64M family of MCU’s manufactured by Renesas.

Here's an Application Note from the previous version of MCUs from the same manufacturer: RX63N Group Speaker Enhancement Algorithms that explains how to control the volume with it. There's also an interesting NOTE in there: "Volume control is accomplished by scaling down the PWM output, which can reduce dynamic range. For best sound quality, turn the volume all the way up (fully clockwise) and adjust volume on external speakers".
 

eeMGee

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And what about analog inputs - are they digitised/sampled?
I think that there is some analog volume chip on the side pcb between upper and lower pcb, or on the lower pcb next to the RCA pre-outs.
 

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And what about analog inputs - are they digitised/sampled?
I think that there is some analog volume chip on the side pcb between upper and lower pcb, or on the lower pcb next to the RCA pre-outs.
Analog inputs are digitised whenever you set L/R speakers to small (activating 12 dB/octave filter in the AVR that adds to a 12 dB/octave acoustic slope of typical closed boxed speakers). Setting L/R speakers to large will bypass ADC/DAC and you get full range. And I think you can use Audyssey on the subs if you also set L/R bypass mode in Audyssey and "main+LFE" on subs. The problem will be to integrate the mains with the subs if you have such. If you have small ported speakers you might get that ideal 24 dB/octave acoustic slope to match with the sub crossover at some frequency though.
 

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I'm curious if distortion measurements might improve if not connecting any speakers to the unit.

On page 202 of the USA manual, there is a setting for the speakers that allows the user to set up the unit for sending the signals to the pre-out outputs only.

"Pre-out outputs are active. Speaker outputs are disconnected for enhanced audio quality using only the pre-out terminals."

The same setting is on the stereo versionof this receiver, too. This setting appeals to me since I'm considering using one of these as a processor only.
 
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@rnrmf you can use it a processor if you want; each set of channel can be redirected to Pre-Out or to both Spkrs and Pre-Out.

IMG_4627.jpg
IMG_4628.jpg
 

pma

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Very nice review, @trl , however poor amplifier results, unfortunately.
 
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Thomas_A

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Yep, even Marantz has fallen - full of garbage capacitors = dead in 5-10 years. Stay well clear.
I have the NR1506 (since 2015) and the NR1710 (since 2019) squeezed in quite small spaces and used daily. So no problems so far.
 
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Yep, even Marantz has fallen - full of garbage capacitors = dead in 5-10 years. Stay well clear.
Not sure what do you mean, could you please elaborate a bit?

I see Su'scon AU series 6800uF/63V @105V caps handling the ripple after the bridge rectifier. These caps are able to support a ripple current of 3.39A RMS and seem to be quite right for the job of smoothing the DC voltage following the bridge rectifier. As per manufacturer wrote:
"Snap-in type 105℃ 2000 hours specially designed for audio equipment
‧Select structural materials with high sound quality
‧Create high definition audio equipment with high sound quality
‧Suitable for high quality audio equipment"
"2000hours,with application of rated Voltage voltage at 105℃".


I also see many Koshin KR-3 caps, probably just fine for general use. In our case I see these caps following linear regulators, but also used as decoupling caps too. Datasheet says: "Guaranteed for 2000 hours at 85°C".

Also, several ELNA caps can be seen as well in audio circuitry.

IMG_4415.jpg
IMG_4426.jpg
IMG_4424.jpg

Given the very high number of electrolytic capacitors from an AV Receiver, I think it would be very pricey to work only with Nichicon and ELNA caps, at least not at the price of the CINEMA 70s. The most stressed caps are the two Su'scon 6800uF/63V from the power supply and the Koshin ones from around the power stage transistors, but time will tell if they'll fail in 5, 10 or more years.
 

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hi @trl , if you still have the avr open and a multimeter handy, would you mind checking if the clocks pins of the dacs are connected between the different dacs? (pins 12 13 15)
No worries if not possible. Thanks for this and your other teardowns, always learn something new from them.
(my curiosity this is a cheapish small AVR that would be ideal for me to tap the digital outputs and transform into a decoder. The low power mode is the cherry on top)
 

capslock

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$0.20 per kWh?! I know in Europe it's double that or more I think..

In my state:
View attachment 337328
In 2023, my utility charged €c 42, so about $ 0.46. It is coming down a little for 2024, like €c 35.

Still, my total monthly bill for general electricity, heating, hot water, fresh water and waste water is like € 230, thanks to LED lighting, inductive stove, efficient appliances, 10 in. of insulation, a heat pump takes heat from the ground rather than air, and photothermal panels that reduce electricity demand for heating and hot water to nearly zero for 5-6 months.
 
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I think that there is some analog volume chip on the side pcb between upper and lower pcb, or on the lower pcb next to the RCA pre-outs.
The volume on Marantz CINEMA 70s has also acceleration implemented, so a standard volume control chip was definitely not used, this is why only an MCU can operate the rotary knob from the volume AV Receivers these days.

Here's what MCU is used in Onkyo A-9010 and in other AVRs for volume control: MB9AF342NAPMC. That's why I think that a similar MCU like R5F564MJCDFC could be the one responsible for volume control in CINEMA 70s. However, if I'll ever get the front panel off, then I'll take a pic with what chips are in there.
 

eeMGee

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If 70s uses digital volume control (by reducing the bit length) before signal reaches DACs it is not optimal - PCM5102a is a low cost solution and for low level music could be resolution degradation, so it is no no for me as the pre-amp solution.
 
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@eeMGee, Amir measured a SINAD of 94 dB with volume set to 82.5. Usually the volume will stay in between 50 and 85, so I don't think the SINAD will drop so much to actually hear the difference. You may give it a try and return if you're not happy with it.
 
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hi @trl , if you still have the avr open and a multimeter handy, would you mind checking if the clocks pins of the dacs are connected between the different dacs? (pins 12 13 15)
No worries if not possible. Thanks for this and your other teardowns, always learn something new from them.
(my curiosity this is a cheapish small AVR that would be ideal for me to tap the digital outputs and transform into a decoder. The low power mode is the cherry on top)
Just opened it up again now and checked: between pins 12, 13 and 15 the resistance is higher than zero Ohms, so CLK pins are not paralleled on none of the four PCM5102A DAC chips. Same applies to the other two PCM5100A DAC chips as well, no CLK pins are tied together between chips.
 
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