Not acccording to the manual.
In Pure direct mode signal processor is off so what would be the logic in converting signal to digital when you can't process it?
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Review and Measurements of Marantz AV8805 AV Processor
- Thread starter amirm
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Not acccording to the manual.
In Pure direct mode signal processor is off so what would be the logic in converting signal to digital when you can't process it?
That makes sense. Since, turning off some video (but not HDMI inputs) might help on the margins, it is really a marketing feature. Not quite as bad as the copper base
.Oppo manages to achieve excellent performance measurements with the video on. They also have a Pure mode but it serves the purpose of turning off the front panel display that uselessly scrolls "screen saver" which using the DAC in.
I could never convince Oppo to remove scrolling "screen saver" from the front panel, it only has value when the screen is off
- Rich
Look at the violet part, this is how they implement "Direct" mode on pretty much all AVRs. Signal from analog inputs is routed to the relay (IC717), then to volume control (IC706), tone control (IC709) and to the opamp output buffer (IC712). As you can see Multi input FR and FL signlas are routed through the exactly same path (path for FL shown in blue):
That is not correct. The Double bass function does not need ADC/DAC or DSP. Yes, in pure direct you can select "double bass", that is LFE+Main but in actuality, it really isn't LFE anymore once you are in direct/pure direct mode because the bass management functions are disabled in those two modes.
I read the schematics more than once just to be sure too. There is a selector to select "go direct to the preamp/vol control ICs, or through ADC path. The schematics does not show what control the selector positions, but it is logical to think that it is done via the mode selection of stereo, direct and pure direct.
Think about a simple analog only integrated amp, you can hook it up to power a powered subwoofer too just the same.
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Thanks, I wish I could post the ones for the Marantz/Denon schematics but I am not sure about the copy right thing. The AV8805's are downloadable by anyone who cares to search and it clearly shows how the line input signal "could" be routed directly to the preamp/vol control IC via a multi-selector IC.
Since it is easily searchable on the www so I see no reason why it can't be linked here. If not, I am counting on our moderator to delete it for me.
Page 50 is a good starting point as it is in block diagram form so Rich can easily follow.
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"Sound recorded in source is played as is. "
This really says nothing substantive.
This really says nothing substantive.
Here is a link to the AV8805 service manual, so help yourself - it should be a piece of cake for Stereophile Senior Contributing Editor.
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What is the double bass mode, I'm not familiar with it?
Working my way through it.
Here is a link to the AV8805 service manual, so help yourself - it should be a piece of cake for Stereophile Senior Contributing Editor.
If it is still about pure direct/direct not going through ADC, start with page 50, that is a simple block diagram and you will see the two paths, one go to ADC, the other straight/"direct" to preamp/vol control, via the NJU72750 analog switch.
You can freely post a snapshot of the schematics here as I did with Rotel as Marantz published schematics publicly on their web site so there is no copyright protection.
Sounds logical, I kept thinking about hifiengine.com's, but this one is indeed directly from Marantz.
Yup. I saw that.
OP
- Thread Starter
- #457
They publish schematics? If so, kudos to them.
Did you find the hardware present to route the mains to the subs with double-bass enabled?
Is there hardware that also avoids DSP's when bi-amp is enabled?
Clearly, the XLR inputs can be without A/D but with Pure Direct, but it is unclear if other functions trigger A/D conversion. It seems like that would be the simplest implementation.
- Rich
Great link - and a very complex unit. First time I see the schematics of the HDAM.
I would like to compare this incarnation of HDMA with the one in my old AV7701, but I couldn't find a link (except to shops which sell). Any idea where to get one for free?
With its signal switching capabilities all things are possible in the AV8805. Testing of these various signal flows is even included in the service manual. Unfortunately based on the AV8805 user manual, all 2ch (not 7.1 external inputs) playback goes through the attenuation/ADC/DAC chain.
ADC/DAC Signal Chain
Specifically this chain is -8.5 dB attenuation of the analog signal using an active opamp circuit with NJR (NJM2115) opamps and +/- 2.5 rail voltages(!) and less than great specifications. This gain reduction is to fit the signal within the 1V capabilities of the just OK AKM (AK5358B) ADC. After the ADC the signal goes to the NJR CMOS switches and CMOS volume control. This is no way to treat a nice analog signal.
2ch Playback
In the AV8805 user manual Page 240.
o "Select the method for ... 2-channel Playback direct and stereo playback modes - No distinction between digital and analog is given
(in other locations in the manual, direct and pure direct are given as the same in this area)
o Speaker size can be set
o SW Mode seems indicate digital processing
o Distance can be set which is hard to do in the analog domain
Page 50 of the manual is does not provide a clear answer, it just shows levels with digital or ADC signals inputs. Note the -8.5dB mentioned above.
The fact that this signal flow is not made clear in the user or service manuals also suggests that the ADC system is used. Higher-end users won't be happy with this design.
XLR Inputs
XLR inputs first go to a three opamp circuit that reduces the signal level by 6dB and converts it to single-ended. The resistors used in these circuits are 5% tolerance with means that common mode noise reduction from the differential amplifier function won't be great. The resistors are also thick film surface mount units that have extra noise (over Johnson noise) and distortion. As an overall note: Newer units such as the AV7705 use 1% thin film resistors in key locations, such as the differential amplifiers after the DAC's, which don't have these drawbacks.
There is no indication that XLR inputs take any different path in the AV8805 than stereo inputs.
Why would Denon/Marantz treat analog signals in the manner? My guess, YMMV, is that D/M is worried about what some users will connect to the analog inputs. Tube preamps often have high RCA output levels as do other components. The switches and volume control in these units are CMOS based. CMOS is great except it doesn't like high voltages. The voltage supply to these CMOS units is 7V DC, which is likely about all they want so see anywhere. A 6V AC sine wave input would have 8.4V peaks for example, which might causes damage. The signal input limit of the volume control is just over 4V, so care is necessary.
The 8 (7.1) external inputs are an exception, this is likely because the assumption is that the 8-channel RCA outputs feeding these inputs are from say a Blu-Ray player than will have about a 2V maximum output on each channel. In addition, 8 ADC circuits would be required instead of just 2 and that would cost money. In the user manual the 7.1 channel input is labeled for use by a Blu-ray player, DVD player, etc, not stereo.
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