Author Topic: Yamaha / Marantz with 7.1 Pre-outs  (Read 880 times)

Offline The Godfather

Re: Yamaha / Marantz with 7.1 Pre-outs
« Reply #15 on: January 18, 2021, 05:44:17 PM »
Que? I included Dolby's external amp's input sensitivity to highlight the fact that it extends beyond the 1.4 V threshold in this example. It's of course only a problem if what you require from your external amplification exceeds what the receiver cleanly provides
What was the input impedance of the device used in this measurement? That will have an affect on the "SINAD" results.

Eg if the device was 600 Ohms as opposed to 33kOhms typical of a power amplifier, there would be far more distortion.

Offline KenMasters

Re: Yamaha / Marantz with 7.1 Pre-outs
« Reply #16 on: January 19, 2021, 02:40:30 AM »
What was the input impedance of the device used in this measurement? That will have an affect on the "SINAD" results.

Eg if the device was 600 Ohms as opposed to 33kOhms typical of a power amplifier, there would be far more distortion.

I don't see what that has to do with a line-out measurement sweep, not that I'm any kind of expert on these things - I believe the device used to take the measurement in this particular instance is the Audio Precision APx555, if you're interested in looking into it.

Given Yamaha's lower-end AVRs' pre-outs are traditionally relatively low voltage and don't measure well in general and Marantz's op-amp tweaking, the current Denons seem the obvious choice to me for someone seeking to use an AVR strictly as a preamp. I also understand, depending on the sensitivity of the external amplification you wish to pair the AVR with, paper advantages could have little to no bearing in practice. I'm not here to argue about it either way, just passing on the information. Dolby can investigate what's right for him.

Offline The Godfather

Re: Yamaha / Marantz with 7.1 Pre-outs
« Reply #17 on: January 19, 2021, 07:45:56 AM »
I don't see what that has to do with a line-out measurement sweep, not that I'm any kind of expert on these things - I believe the device used to take the measurement in this particular instance is the Audio Precision APx555, if you're interested in looking into it.
If we term them correctly - Pre Amplifier out / Power amp out .... Electrical principle is the same.

Think about when they do THD+N measurements on a power amplifier. If a power amplifier was measured into 1 Ohm, does the voltage developed for a particular THD+N level (essentialy SINAD) not drop?

We cant really call things 'science' unless we know all of the relevant factors and how the test was setup.
« Last Edit: January 19, 2021, 07:49:45 AM by The Godfather »

Offline KenMasters

Re: Yamaha / Marantz with 7.1 Pre-outs
« Reply #18 on: January 19, 2021, 08:21:01 AM »
If we term them correctly - Pre Amplifier out / Power amp out .... Electrical principle is the same.

Think about when they do THD+N measurements on a power amplifier. If a power amplifier was measured into 1 Ohm, does the voltage developed for a particular THD+N level (essentialy SINAD) not drop?

We cant really call things 'science' unless we know all of the relevant factors and how the test was setup.

All the test is doing is comparing the incoming 1 Khz digital signal to the outgoing signal (using a floating input differential amplifier), tracking as the volume is adjusted up to 2 Volts.

Use the info, don't use it, I have no horse in this race. Dolby talked about bypassing the amp section of the AVR, the Denon and Marantz AV amps are the only ones I know of to do this. If you don't see any value in that, that's fine. I really have no driving urge to argue over this.
« Last Edit: January 19, 2021, 08:23:18 AM by KenMasters »

Offline handsome

Re: Yamaha / Marantz with 7.1 Pre-outs
« Reply #19 on: January 19, 2021, 09:37:10 AM »
The real issue is why an internal preamp cannot drive an internal power amp and another device at the same time? AP measurement system has a 100k input impedance - by today's standards that is incredibly high so hard to see how it could be loading the internal preamp. Why would a (internal) power amp offer such a drop in performance? Surely its input impedance is at least 10k. As @Hi-Phibian noted bog standard, out-of-date opamps like NE5532s or TL072s etc can easily drive ~2k. I suspect cost-cutting, there is obviously no buffering between DSP chip output and preamp outs and the internal power amo input.

Offline Zilch

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Re: Yamaha / Marantz with 7.1 Pre-outs
« Reply #20 on: January 19, 2021, 09:41:48 AM »
@handsome do you reckon it'll be worthwhile to have a custom buffer designed (to have the correct input impedance)?
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Offline handsome

Re: Yamaha / Marantz with 7.1 Pre-outs
« Reply #21 on: January 19, 2021, 10:45:17 AM »
Those pcbs i assume are very complex and surface mount - so I doubt it would be feasible for the average DIYer. If you could get in there though - it would be easy and cheap, to build a board with 7 JFET opamps (OPA2134s?) each with a gain of x2 and a nice high input impedance around say 470k or more. The gain would let you output 2V same as a CD player, the high input impedance means it shouldn't disturb the rest of your AVR internals. But whether you would hear the difference I'm not so sure....