The Audio Path In Consumer-Grade Products

[M Code]

I can see the rationale, if the added gain was used to drive studio gear, for example. That's assuming this extra gain is applied in the pre- section and available on pre-outs.

It's still just a gain thing, though. It won't cause tonal shifts or anything of the sort.

Incorrect...
Anytime one changes the feedback loop circuit certain sonic byproducts may be audible..

Just my $0.02..

 

[PENG]

Because you said what is underlined below which can confuse some. A flat amp alone is usually about gain, not tone or loudness contours. I'll take a look at Block Diagram of your SC-7 but my guess is that the tone boards are separate. My guess is that your "bypass" operates like the Jump on the AU-919 in my example. The point being that some might think bypassing the flat amp is about tone control based on what you said below .

Good point, thanks, it indeed could be confusing simply because I omitted the word "switch". For better clarity, I should have said, "that Marantz flat amp bypass switch........." just so people know it applies to the Marantz SC-7 switch specifically, not your AU-X1. The reference to bypassing tone control is right from the manual page 9 where it cautions that when in bypass, "tone controls and filters switch in inoperative" The so called "flat amp" is by design "flat", it is just there to provide gain. The AU-X1 block diagram clearly shows the "jump" switch bypasses only the flat amp, so in that case, only gain is affected.

I'm not sure but I think your flat amp bypass switch drops the gain by -10 db. Not quite the -14 dB drop that mine has but have you ever carefully experimented with it while hooked-up to the same amp?

I have measured it. The difference between normal and bypass is about 23 dB, the gain of the X10 amp is supposed to have a gain of 20 dB (hence X10), but as explained, the SC-7's flat amp bypass switch bypasses the tone amp as well, so may be that's why it dropped another 3 dB. I am talking about voltage gain here.

Marantz recommended keeping it on the normal setting otherwise "For high-fidelity playback or for checking the equipment, switch it to the bypass position." It sounds like the boys from JBL/Harmon Kardon agree with me that there is a real difference when a change like this is made to the signal path

That's the part we obviously disagree. To me those are mainly marketing talks, its like many amps and loudspeaker manufacturers, including some expensive high end ones, will tell you how bi-wire and passive bi-amp greatly improves sound quality. Same thing about the pure direct (D&M), straight (Yamaha), even analog (Sony) selections, they all want us to believe those features provide audible SQ. I tried very hard, and could never tell a difference between those selections. I know I am not the only one who can't tell the difference. In fact, even my Umik-1 mic can't tell the difference either, at least not according to my REW graphs. Same for that SC-7 flat amp bypass switch, no audible SQ difference for me.

I have skimmed through the block diagrams and schematics of both my SC-7 and your AU-X1 briefly, I do need to spend more time on studying the schematics, but so far I do have the impression that the "jump" switch for the AU-X1 (or the bypass switch for the SC-7) is mainly there to allow the user to bypass the preamp's amp stage when using high level signals such as those from CD, DVD/BR players (typically >2V). It will be somewhat similar to hooking up a media player or DAC that has volume controls, directly to a power amp. I do not believe the flat amp switch in either case (AU-X1 and SC-7) is intended for the user to change sound quality, though in theory when you bypass any unnecessary electronics, the output signal will have less distortions and may change the output impedance. If designed properly, any such changes should be small and likely not discernible by humans. Then again, I am sure we will disagree on this one as well. Regardless, if I am using my DVD3910 or Oppo 105 to listen to CD/SACDs I will always use the bypass whether I can hear a difference or not. I always prefer to take advantage of better specs and measurements, as I know Placebo effect can be real.

 

[PENG]

Incorrect...
Anytime one changes the feedback loop circuit certain sonic byproducts may be audible..

Just my $0.02..

Are you sure the thing we are talking about changes the feedback loop though? I am not sure as I just skimmed through the info.. It seems to me that switch simply take an amp stage right out, as you alluded to before, the high level output device such as CD players don't really need the X10 amp.

 

[<eargiant]

I have skimmed through the block diagrams and schematics of both my SC-7 and your AU-X1 briefly, I do need to spend more time on studying the schematics, but so far I do have the impression that the "jump" switch for the AU-X1 (or the bypass switch for the SC-7) is mainly there to allow the user to bypass the preamp's amp stage when using high level signals such as those from CD, DVD/BR players (typically >2V).

Sure, the jump switch is useful in those applications but that's not the reason it's there. The engineers that designed these units in the late '70s would have had to have been fortune tellers because the units you describe were years away from being available to consumers. I see what your saying but I'll stick to Occam's razor on this one.

The X1 manual mentions nothing in relation to the benefit of engaging the Jump switch while using external units it mentions in the manual that were available at the time. Tuners, Turntables, Cassette Decks and Reel to Reel players.

 

[killdozzer]

So what you're sayin'?

 

[PENG]

Sure, the jump switch is useful in those applications but that's not the reason it's there. The engineers that designed these units in the late '70s would have had to have been fortune tellers because the units you describe were years away from being available to consumers. I see what your saying but I'll stick to Occam's razor on this one.

The X1 manual mentions nothing in relation to the benefit of engaging the Jump switch while using external units it covers in the manual that were available at the time. Tuners, Turntables, Cassette Decks and Reel to Reel players.

Cassette decks, reel to reel have similar output levels to CD players. I have a cassette deck too, so I know. Again, taking out the "flat amp" will make it more like (not exactly the same) a passive preamp, so impedance characteristics could change, but in any case shouldn't be designed to change sound quality. if it changes sound quality then between jump "on" and "off", one would't be accurate, or less accurate. I highly doubt the engineers, or designers (not sure if they were engineers, not that it matters) at the time would purposely design something that wouldn't behave as much like"wire with gain" as possible.

Edit: You brought up yet another great point, cassette players, even reel to reel players really couldn't take full advantage of the hifi quality of such amps in the 70's. Another reason why we shouldn't focus as much on amps as we do on other components in the chain, and the room. They were well ahead of their time, even from way back, relatively speaking. Speakers, source media, room acoustics are where one can strive on doing better.

 

[<eargiant]

Cassette decks, reel to reel have similar output levels to CD players. I have a cassette deck too, so I know.

Yes and they were usually 2V or less.

Both your Marantz manual and my Sansui manual suggest the the switch be in the Normal (OFF) position so I still think your original impression/assumption is incorrect.

I believe the first consumer CD player was 2V which would also have not been a problem.

Again, taking out the "flat amp" will make it more like (not exactly the same) a passive preamp, so impedance characteristics could change, but in any case shouldn't be designed to change sound quality. if it changes sound quality then between jump "on" and "off", one would't be accurate, or less accurate. I highly doubt the engineers, or designers (not sure if they were engineers, not that it matters) at the time would purposely design something that wouldn't behave as much like"wire with gain" as possible.

The switch offered flexibility and choice while giving you the option to the very best potential the unit has to offer. The very best in most applications for both our units will be the shorter signal path that circumvents the flat amp. That will produce the highest fidelity that the units are capable of and can be proven on any bench.

Another point I'd like to make is- consumer preference. Many that have these amps (mainly the more common AU-919) do not like the presentation that using the Jump switch provides. Some have described it as sounding "thin". I suppose these manufacturers were aware that many consumers prefer the dynamic punch (for lack of a better term) of the higher gain setting. That usually sells better in the showroom.

I also don't know why it's so hard to take the user manuals (these are not sales brochures) at their word especially since what they say can be measured. They're not marketing here, just stating basic facts that have held true for decades. Facts that any engineer worth his salt is aware of. Signal paths matter.

Marantz SC-7 (pre-amp):
In general, the Flat Amp switch is to remain in the Normal position. For high-fidelity playback or for checking equipment, switch it to Bypass position.

Sansui AU-X1 (integrated):
When you set the switch to the -14dB position, sounds will be reproduced without signals going through the flat amp. With this switch at -14 dB, level will be reduced by 14 dB. The switch should normally be in the off position.

The tonal quality of reproduction can change much depending on the particular signal path through which the signals flow. With your unit, you can select, by using the Jump switch, from two signal paths as follows. Make sure that the volume control is set to low when operating this switch.

You can bypass the flat amp: set the Jump switch to -14 dB. You can enjoy the purest sound reproduction with the shortest signal path.

You can use the flat amp: set the Jump switch to Off.

Edit: You brought up yet another great point, cassette players, even reel to reel players really couldn't take full advantage of the hifi quality of such amps in the 70's. Another reason why we shouldn't focus as much on amps as we do on other components in the chain, and the room. They were well ahead of their time, even from way back, relatively speaking. Speakers, source media, room acoustics are where one can strive on doing better.

No argument from me there but not all Integrated units (or combos) are created equal. Remember, I'm the guy that chooses to use a restored integrated from 1980 with my best speakers. I have auditioned many units, modern as well as from that era. Even other restored Sansui amps within the same AU series and what they did with this X1 is no marketing BS. As good as a restored AU-717 is, it is clearly not at the level of the X1.

Just because class A/B was well understood and some great units were already available back then does not mean that everything that came after was on par.

The X1 is why I was interested in the Benchmark because the design goals are very similar.

To your point about sources, my tech (who happens to restore quite a bit of Marantz gear) was blown away by the performance of this thing. He said feed this thing hi-res files and it will gobble them up like a rottweiler .

 

[everettT]

Incorrect...
Anytime one changes the feedback loop circuit certain sonic byproducts may be audible..

Just my $0.02..

Incorrect and may seem at odds. Thanks for all your insights though

 

[PENG]

Yes and they were usually 2V or less.

Both your Marantz manual and my Sansui manual suggest the Normal position to be Off so I still think your original impression is not correct.

I believe the first consumer CD player was 2V which would also have not been a problem.




The switch offered flexibility and choice while giving you the option to the very best potential the unit has to offer. The very best in most applications for both our units will be the shorter signal path that circumvents the flat amp. That will produce the highest fidelity that the units are capable of and can be proven on any bench.

Another point I'd like to make is- consumer preference. Many that have these amps (mainly the more common AU-919) do not like the presentation that using the Jump switch provides. I suppose these manufacturers were aware that many consumers prefer the dynamic punch (for lack of a better term) of the higher gain setting. That usually sells better in the showroom.

I also don't know why it's so hard to take the manuals at their word especially since what they say can be measured. They're not marketing here, just stating basic facts that have held true for decades. Facts that any engineer worth his salt is aware of. Signal paths matter.

Marantz SC-7 (pre-amp):
In general, the Flat Amp switch is to remain in the Normal position. For high-fidelity playback or for checking equipment, switch it to Bypass position.

Sansui AU-X1 (integrated):
When you set the switch to the -14dB position, sounds will be reproduced without signals going through the flat amp. With this switch at -14 dB, level will be reduced by 14 dB. The switch should normally be in the off position.

The tonal quality of reproduction can change much depending on the particular signal path through which the signals flow. With your unit, you can select, by using the Jump switch, from two signal paths as follows. Make sure that the volume control is set to low when operating this switch.

You can bypass the flat amp: set the Jump switch to -14 dB. You can enjoy the purest sound reproduction with the shortest signal path.

You can use the flat amp: set the Jump switch to Off.



No argument from me there but not all Integrated units (or combos) are created equal. I have heard several amps, modern as well as from that era. Even other restored Sansui amps within the same AU series and what they did with this X1 is no marketing BS. As good as a restored AU-717 is, it is clearly not at the level of the X1.

It's actually this amp that has made me interested in the Benchmark because the design goals are very similar.

To your point about sources, my tech (who happens to restore quite a bit of Marantz gear) was blown away by the performance of this thing. He said feed this thing hi-res files and it will gobble them up like a rottweiler .

Not going to respond point by point but would like to comment as follow.

Bench tests - They will always reveal differences between amps, as stated by many that does not always equate to audible differences, and/or the ultimate indicators.

Marketing talks vs facts - They do say all sorts of things, in manuals, website etc. To to read on on the passive bi-amp, bi-wire, pure direct topics that I mentioned and see for yourself what they had said over the years. @ADTG found out he could drive the 802D2 (supposedly very hard to drive with his Denon mid range receiver nicely. He's been told to use amps like Classe's, but I guess he wasn't that gullible a person and wouldn't listen to them. Ironically, like me, he also owns a few preamp and amps, and some expensive ones.

Restoration/repair techs- know a couple of those too, just got mine recapped just because they were old. I was too busy to do it myself at the time. They also told me how great the pair was and that people would pay upwards of $3000 (not true) for just the power amp (used of course). With due respect, they are techs. Some are really good but it does not always mean they can be taken as the authority, they could be offering opinions from hearsay and what they read from subjective reviews.

Side note on subjective reviews

How many times you've read something like "......I was able to hear things I had never heard before..................". That, coming from experienced professional reviewers make me wonder how many times they are said, and will continue to say about products they reviewed and to be reviewed.

Back to the AU-X1

I read a lot about the Sansui AU amps and would like to spend more time on the schematics, time permitting. I am very impressed with the quality of the available information, complete with good quality schematics and some lab measurements (though not by 3rd parties). I just listened to my SC-7 and SM-7 again last night, switching the flat amp in and out using my 2V rated DAC, the system sounded wonderful either way. If I have time I will do a couple of REW plots, and I am confident the overlays of the plots will likely look like one plot, i.e. within 1 to 2 dB over the 20-20,000 Hz range.

Cautionary: Note that this could just be hearsay as I came across such talk from the internet. Reportedly, the earlier version appeared to have an issue with being "easily triggered" into oscillation causing the output transistors to blow. Since you own one so you may have read about this already.

 

[<eargiant]

Not going to respond point by point but would like to comment as follow.

Bench tests - They will always reveal differences between amps, as stated by many that does not always equate to audible differences, and/or the ultimate indicators.

Marketing talks vs facts - They do say all sorts of things, in manuals, website etc. To to read on on the passive bi-amp, bi-wire, pure direct topics that I mentioned and see for yourself what they had said over the years. @ADTG found out he could drive the 802D2 (supposedly very hard to drive with his Denon mid range receiver nicely. He's been told to use amps like Classe's, but I guess he wasn't that gullible a person and wouldn't listen to them. Ironically, like me, he also owns a few preamp and amps, and some expensive ones.

Restoration/repair techs- know a couple of those too, just got mine recapped just because they were old. I was too busy to do it myself at the time. They also told me how great the pair was and that people would pay upwards of $3000 (not true) for just the power amp (used of course). With due respect, they are techs. Some are really good but it does not always mean they can be taken as the authority, they could be offering opinions from hearsay and what they read from subjective reviews.

Side note on subjective reviews

How many times you've read something like "......I was able to hear things I had never heard before..................". That, coming from experienced professional reviewers make me wonder how many times they are said, and will continue to say about products they reviewed and to be reviewed.

Back to the AU-X1

I read a lot about the Sansui AU amps and would like to spend more time on the schematics, time permitting. I am very impressed with the quality of the available information, complete with good quality schematics and some lab measurements (though not by 3rd parties). I just listened to my SC-7 and SM-7 again last night, switching the flat amp in and out using my 2V rated DAC, the system sounded wonderful either way. If I have time I will do a couple of REW plots, and I am confident the overlays of the plots will likely look like one plot, i.e. within 1 to 2 dB over the 20-20,000 Hz range.

Cautionary: Note that this could just be hearsay as I came across such talk from the internet. Reportedly, if your unit is the earlier version, there appeared to be issues with "easily triggered" oscillation causing the output transistors to blow. So, just in case such internet hearsay were true, even to a point, be careful with how you use it. If you wish, I can try to google it again and post the link.

Awesome, thank you PENG. I know the schematic on the X1 can make heads spin (FYI the only schematic available is for the early version). Only the most qualified can work on a unit like this.

I like that you're doing your research and thanks for the heads-up (nice of you to warn me just in case)! You're absolutely correct. Due to the unique high speed of this amp, the early versions could oscillate and destroy the 12 precious outputs. The source of the problem was the early Phono boards. I have the later version with the revised phono boards so it's all good. This beast took hundreds of part replacements and we were sure to replace the problematic polystyrene caps with silver mica (the yellow ones that look like molars).

The phone section in this beast is elaborate and worthy of it's own thread. I believe they run Class A. The real estate that they take up inside this unit is something else. Four large boards slot into a mother board.

Design matters.

The restored MC & MM sections on Phono motherboard.

When I came across a complete replacement set of NOS Original Sanken outputs I didn't hesitate to buy them- just in case I blow the 12 TO-3 LAPTs that are in the unit now.

 

[TheWarrior]

Are you guys done exploring each other's pathways, yet?

 

[PENG]

Are you guys done exploring each other's pathways, yet?

I was, but then I got interested again when we can focus on the technical and objective side of things. Just 2 more days I will be so busy playing with something else anyway.

 

[<eargiant]

I was, but then I got interested again when we can focus on the technical and objective side of things. Just 2 more days I will be so busy playing with something else anyway.

But even if the REW plots show a difference on your units, you'll probably jump back to the subjective and say it doesn't matter because it's not audible to you . But seriously, I've never heard your units driving your speakers so I don't know that I wouldn't hear a difference either. Since they have different topologies, anything's possible. If you listen again try music that has solid mid-bass slam, something like Kraftwerk. At a higher SPL, with my unit I can even see the difference in how the speaker driver reacts (excursion) to the signal. Talk about punch! I have to go to a much higher SPL (highs & mids are clearly louder) without the flat amp to get the drivers even close to having such impact/slam.

Quick question- is there a large drop in volume when you switch the flat amp out on your Marantz combo? If so, how are you adjusting it to be equal?

I'd like to try it on my end also. Might be a good reason to get into REW. Would need guidance on mikes and set-up, etc.. Seems like so much can go wrong when making a comparison like this. Even John Atkinson blows it sometimes .

 

[Pogre]

But even if the REW plots show a difference on you units, you'll probably jump back to the subjective and say it doesn't matter because it's not audible to you . But seriously, I've never heard your units driving your speakers so I don't know that I wouldn't hear a difference either. Since they have different topologies, anything's possible.

Quick question- is there a large drop in volume when you switch the flat amp out on your Marantz combo? If so, how are you adjusting it to be equal?

I'd like to try it on my end also. Might be a good reason to get into REW. Would need guidance on mikes and set-up, etc.. Seems like so much can go wrong when making a comparison like this. Even John Atkinson blows it sometimes .

Whether or not it's audible is kind of the point isn't it?

 

[AcuDefTechGuy]

Whether or not it's audible is kind of the point isn't it?

Oh, no.

What you ACTUALLY HEAR is the least important. We don't care about that.

At the end of the day, the theories, speculations, and numbers are salient.

 

[<eargiant]

OK Heckle & Jeckle I guess you both missed the joke. PENG said "I got interested again when we can focus on the technical and objective side of things."

In case you're not aware, what you can hear is on the subjective side of things.

 

[everettT]

OK Heckle & Jeckle I guess you both missed the joke. PENG said "I got interested again when we can focus on the technical and objective side of things."

In case you're not aware, what you can hear is on the subjective side of things.

I thought they were Frick and Frack?

 

[Pogre]

OK Heckle & Jeckle I guess you both missed the joke. PENG said "I got interested again when we can focus on the technical and objective side of things."

In case you're not aware, what you can hear is on the subjective side of things.

Sorry. I have trouble telling which of your posts to take seriously. There are so many that I don't.

 

[Pogre]

OK Heckle & Jeckle I guess you both missed the joke. PENG said "I got interested again when we can focus on the technical and objective side of things."

In case you're not aware, what you can hear is on the subjective side of things.

I used to love Heckle and Jeckle when I was a kid. Part of the Mighty Mouse universe.

*The pic you edited in triggered a little nostalgia for me.

 

[<eargiant]

Sorry. I have trouble telling which of your posts to take seriously. There are so many that I don't.

At least I'm part of the conversation. You come off a cheerleader for your team.

No one is asking you to read this thread. You have no positive contribution so please leave.