What would be the 'best' Sansui amplifier for sound quality?

[fojica]

@gammi

Thank you for sharing pictures and impressions.

Regarding the bias settings that you mentioned - you may be aware or not, but:
- 28mV means ~127mA bias per each output pair
- 35mV means ~159mA bias per each output pair. This is +25% more current relative to the spec.

From my perspective, having more bias than "normal" brings no benefit other than more energy/heat wasted and shorting the life of the outputs and drivers.
But, as always, I may be wrong.

Regards

 

[gammi]

Thank you for sharing pictures and impressions.

Regarding the bias settings that you mentioned - you may be aware or not, but:
- 28mV means ~127mA bias per each output pair
- 35mV means ~159mA bias per each output pair. This is +25% more current relative to the spec.

From my perspective, having more bias than "normal" brings no benefit other than more energy/heat wasted and shorting the life of the outputs and drivers.
But, as always, I may be wrong.

Regards

Thanks for the info.

I measured at all four bias points hot and cold, left and right and set all four to 28mV.
Is this not correct? Your post seems to imply I did something wrong. They were all 35mV when I first opened it.

By the way, I just bought an AU-X11 as well, I've certainly been bitten by the Sansui bug. Now my job is to find a list of all the capacitor values for that so I can order and have them ready to replace.

 

[fojica]

I measured at all four bias points hot and cold, left and right and set all four to 28mV.

Then it should be my misunderstanding that you let them biased a bit more (at 35mV), as you found them when checking.
You did nothing wrong, adjusting to 28mV is correct.
Please excuse me for the confusion.

 

[gammi]

Perhaps this isn't the right place to ask, but it didn't feel like it was worthy of a new thread. This is what I ordered to refresh the AU-X11 I just bought, does anyone want to double check me on this? Am I missing anything? I ordered the parts based on the attached image of a driver board from one of the restoration threads. Quantity indicated is for both driver boards total.

silver mica:
33pF x 2
10pF x 4
47pF x 4
22pF x 2

electrolytic:
220uF 80v x 12
100uF 35v x 2
4.7uF 50v x 8

trimpots:
100ohm x 2
1kohm x 2

diodes:
1N4150 x14

 

[JimEGR]

Perhaps this isn't the right place to ask, but it didn't feel like it was worthy of a new thread. This is what I ordered to refresh the AU-X11 I just bought, does anyone want to double check me on this? Am I missing anything? I ordered the parts based on the attached image of a driver board from one of the restoration threads. Quantity indicated is for both driver boards total.

silver mica:
33pF x 2
10pF x 4
47pF x 4
22pF x 2

electrolytic:
220uF 80v x 12
100uF 35v x 2
4.7uF 50v x 8

trimpots:
100ohm x 2
1kohm x 2

diodes:
1N4150 x14

You will get the best response if you start your own thread (and help keep this thread on topic) . Also, anyone in the future looking for this information will be able to more easily find it. Try a thread title like "AU-X11 restoration component help". Or something like that. Key words "AU-X11" and "restoration".

 

[gammi]

My bad, I'll make a new thread

 

[Sui-Yogi]

Perhaps this isn't the right place to ask, but it didn't feel like it was worthy of a new thread. This is what I ordered to refresh the AU-X11 I just bought, does anyone want to double check me on this? Am I missing anything? I ordered the parts based on the attached image of a driver board from one of the restoration threads. Quantity indicated is for both driver boards total.

silver mica:
33pF x 2
10pF x 4
47pF x 4
22pF x 2

electrolytic:
220uF 80v x 12
100uF 35v x 2
4.7uF 50v x 8

trimpots:
100ohm x 2
1kohm x 2

diodes:
1N4150 x14

It’s good to start a new thread , you will get better response.
Did you receive my email with the SM ? Is pretty accurate for BOM .
If needed I can indicate where is a mismatch SM vs PCB….

 

[fojica]

As for sound? I'm struggling to put the difference into words. I feel like the way it presents itself is different. Like it stages a little differently and feels fuller perhaps? That was on headphones (Susvara), on my speakers the thing I noticed was it felt more 3D. I'm not sure which I like better yet.

If you do more A/B testing A907MR vs A907 Limited, please share your thoughts.
I don't expect that you'll find a clear "winner" between the two of them, more likely "flavours" differences. I'm just curios about those different "flavours", which of them is doing "better" from what perspective (we all know that the meaning of "better" in audio stuff is very relative and subjective).
Thank you for your time.

 

[gammi]

If you do more A/B testing A907MR vs A907 Limited, please share your thoughts.
I don't expect that you'll find a clear "winner" between the two of them, more likely "flavours" differences. I'm just curios about those different "flavours", which of them is doing "better" from what perspective (we all know that the meaning of "better" in audio stuff is very relative and subjective).
Thank you for your time.

You're in luck, I'm at my cabin for the weekend and brought along the 160lbs of amplifiers in my trunk haha. I'm upgrading the crossovers in my Magnepan LRS+ and then will be doing some critical listening.

 

[JimEGR]

 

[gammi]

Well I listened for about 5 hours today. Chain was:
Wiim Pro streamer > optical > Cyan 2 DAC > XLR > Sansui amps > Magnepan LRS+
And sometimes I added my Rythmik F12-400 sub into the mix too, running off of the RCA outputs on the DAC.

First off, let me say this setup kicks ass. I highly doubt I could build anything better sounding under $20k, meanwhile this setup runs about $4k for everything.

As for the two Sansui brothers, it was a close fight for sure. I wish I could AB them faster but it takes me about 30-45 seconds to get up, swap XLR, swap speaker cables, sit back down, hit play. That delay in switching made the comparison harder but one thing I do feel I consistently heard is the 907MR presents farther away and the 907 Limited presents closer. 907MR sounded more in the distance whereas 907 Limited was closer and as a result, more enveloping. You could also say the soundstage was wider on the 907 Limited because of this. Picture you're moving closer to a stage, as you get closer the angle from stage left to stage right gets wider. Because 907 Limited felt closer, it also felt wider in this way. I also think the 907 Limited had a bit more harmonics, strings seemed to zing a bit more, stuff like that.

But really though, they're both so good and so close, I think either is a winner. It probably comes down more to the features of the two, do you want the loudness button and tone controls on the 907MR? Do you need the extra power output of the 907MR? Do you prefer the lower power consumption/lower heat output of the 907MR? These things probably make a larger difference than the soundstage/presentation differences I heard.

Also my AU-X11 should be arriving in a few days along with all the parts needed to restore the power amp boards.

 

[fojica]

@gammi
Well, thank you for taking the time to share your impressions, much appreciated.
I neither have, had or have listened to A907MR, but regarding A907 Limited (strictly as a Sansui MOS amp) I have some experience with my own DIY Sansui having also the same MOSFET outputs (2SK405/2SJ115) and I can mirror your impression that, for some reason, these MOSFET's seem to be able to extract a bit more low-level or background details (you mentioned more harmonics). A friend of mine who heard the amp noted that he heard more "echoes" or "reverbs" for some known sounds/effects, which surprised him, somehow "fuller" sound compared to what he knew from my AU-D77X (also MOSFET converted by me, but having newer 2SK1529/2SJ200).
As for "distant" vs "closer" soundstage, possibly one reason to be the fact the A907MR has the JFET input stage "isolated" between Wilson current mirrors, which was a design change done after A907 Limited.

Regards

 

[JimEGR]

Very informative review, @gammi! Especially like reading you perspective on the fidelity value proposition of the Alpha's - "sounds like $20k". Are either the MR or Limited restored at all?

Another one for you to consider, if you aren't already, is the AU-a907NRA. This is the last big Alpha Sansui made, and there is no direct comparison to the either the AU-a907MR or the AU-a907 Limited here. The MR vs NRA comparison would be very interesting, considering they are the last two non-MOS Alpha iterations. (AU-a607 MOS Limited the very last Alpha).

Another review thread you will likely find interesting -

Sansui AU-111, 907 NRA, Alpha 907 Review 2019

Sansui AU-111, 907 NRA, Alpha 907 - Review 2019 Sansui Nutters!!!!! I have the pleasure in owning the following amplifiers from Sansui. Most of my collection is pre 1980's but i have started to get into the Alpha line from when the first Alpha's were released in the mid 1980's . This review...

audiokarma.org

Great contribution here! Fun to read and vicariously come along for the listening tests.

 

[gammi]

@gammi
Well, thank you for taking the time to share your impressions, much appreciated.
I neither have, had or have listened to A907MR, but regarding A907 Limited (strictly as a Sansui MOS amp) I have some experience with my own DIY Sansui having also the same MOSFET outputs (2SK405/2SJ115) and I can mirror your impression that, for some reason, these MOSFET's seem to be able to extract a bit more low-level or background details (you mentioned more harmonics). A friend of mine who heard the amp noted that he heard more "echoes" or "reverbs" for some known sounds/effects, which surprised him, somehow "fuller" sound compared to what he knew from my AU-D77X (also MOSFET converted by me, but having newer 2SK1529/2SJ200).
As for "distant" vs "closer" soundstage, possibly one reason to be the fact the A907MR has the JFET input stage "isolated" between Wilson current mirrors, which was a design change done after A907 Limited.

Regards

Yeah, I did think I was picking up on some sounds echoing a little further on the Limited, possibly contributing to its closer, more enveloping feel.

Very informative review, @gammi! Especially like reading you perspective on the fidelity value proposition of the Alpha's - "sounds like $20k". Are either the MR or Limited restored at all?

Another one for you to consider, if you aren't already, is the AU-a907NRA. This is the last big Alpha Sansui made, and there is no direct comparison to the either the AU-a907MR or the AU-a907 Limited here. The MR vs NRA comparison would be very interesting, considering they are the last two non-MOS Alpha iterations. (AU-a607 MOS Limited the very last Alpha).

Another review thread you will likely find interesting -

Sansui AU-111, 907 NRA, Alpha 907 Review 2019

Sansui AU-111, 907 NRA, Alpha 907 - Review 2019 Sansui Nutters!!!!! I have the pleasure in owning the following amplifiers from Sansui. Most of my collection is pre 1980's but i have started to get into the Alpha line from when the first Alpha's were released in the mid 1980's . This review...

audiokarma.org

Great contribution here! Fun to read and vicariously come along for the listening tests.

I was looking at the 907NRA before I bought these but some comments I had read about it seemed to feel it was a bit too detailed to the point of being harsh. I got the vibe that it being one of their last amps didn't really mean it was the best, but rather it was a victim of the company being on its way out. Perhaps this is a mischaracterization, I don't know.

I was also looking at the B-2105 MOS, the last of the "high end" MOS amps from Sansui, with the 607 MOS Limited being the last of the midrange.
I had read the 907MR was voiced with the AU-111 tube amp as its inspiration so ultimately I decided to stay in that era since that was appealing to me.

As for my amps, no, neither is restored. I just opened them up, checked for leaking caps (saw none) and adjusted the DC offset and bias back to spec.

 

[fojica]

Yeah, I did think I was picking up on some sounds echoing a little further on the Limited, possibly contributing to its closer, more enveloping feel.

In my case (DIY MOS Sansui) probably the best description that I could make it would be to say that is has a different layering or texturing of the presentation.....voices and instruments somehow more distinct in the overall envelope, but in the same time small details and background can equally be perceived as distinctive, without feeling that they are "masked" by the voices of the singer(s) for example.
Don't know if my summary is coherent enough, but hopefully you got the idea And I think it's (at least to some degree) similar with what you described about A907 Limited.

 

[fojica]

@JimEGR
Below are some comments related to 907MR, 907NRA and 907 Limited that I saved when reading a Sansui thread on Stereonet, posted by Cafad (which I think is present also here on AK). They are not necessarily in any chronological order and the initial thread was modified and merged I think, so probably impossible to locate them now exactly in the actual thread on Stereonet.
Not sure how much this helps you or anybody else, but anyway, here they are:

***
907 Limited -> A very nice beast it is too, handsome and musical in equal parts.Sound signature wise it is squarely in the middle between the XR and the NRA. It has a slightly more earthy feel to it than the XR and a light level of warmth in the upper mids that seems to increase listen-ability and banish listening fatigue even further from the room than usual. It also has some of that NRA magic in the vocals, not quite as polished as the NRA and with a little more air but certainly close enough for direct comparisons to be expected.
It also runs 7 or 8 degrees warmer than any of the other 907s.

So far in this musical journey of mine I have heard several mosfet amps and my opinion of them so far has been mixed, some good, some average, and some very good in certain areas but lacking in others. But this, this is a very nice mosfet design execution, excelling in most areas and lacking in none. It does need a 20 minute warm up to sound its best but what the heck, it's 24 years old so what's a little warm up time between friends?

Did not know that 907Limited used MOSFETs. Incidentally, I have also recently acquired a B-2103 MOS Vintage which uses the same sets of Toshiba MOSFETS (in fact the same number of transistors each channel too) as this amp. Not sure how close would they be in sound, but I am liking the B-2103 a lot! The MOSFET certainly seems to have a kind of 'shine' and 'clarity' in mids and highs that I have not heard in MR or earlier Sansuis. Interestingly, the B-2103 doesn't seem to have a very deep thunderous bass that I would have expected from its weight and power rating, but the beauty of mids and highs make up for it. The bass could do with just a tad bit of slam and this could be a perfect amp
Also, the B-2103 also takes around half an hour to warm up and to get its magic going.
Edit: After some listening I have come to the conclusion that my prior post regarding the sound signature of the 907 Ltd is still relevant. I said;
Sound signature wise it is squarely in the middle between the XR and the NRA. It has a slightly more earthy feel to it than the XR and a light level of warmth in the upper mids that seems to increase listen-ability and banish listening fatigue even further from the room than usual. It also has some of that NRA magic in the vocals, not quite as polished as the NRA and with a little more air but certainly close enough for direct comparisons to be expected.

I'll expand on this a little to add that the 907 Ltd has more of an earthy feel to it with more texture to the music. This particular texture is sort of, kind of but not really related to grain but not in a way that sounds negative, more in a way that sounds interesting and slightly different. I've been trying to find a way to describe it more accurately for almost a week now and not doing very well at it. That warmth I mention is not a light and fuzzy warmth either, not like a Luxman, it is a more broad, slightly harder warmth. Warm, but not smooth, and gravelly in a similar way to Mark Knopfler's voice.
It feels a little more tactile than most music, if you can imagine listening to a song while following the music and lyrics in braille (with your fingers, obviously). That's pretty close to the way it makes me feel.
So, yes, textured, gravelly and tactile are the best I can do so far. But I'll keep trying.

Sansui AU-α 907 NRA More polish present than the other Alphas, so clean in the mid-range it sparkles, so clean in the top end it shines. Has a mild bass boost effect that is not present on the other Alphas.

The NRA has a slightly smoothed feel to it, call it polished if you wish, so it very slightly cleans off the jagged edges of rough tones. It's a subtle effect but it is there, this makes it feel just that bit less forceful than its older brothers.

It also has the ability to convey hard-worked female vocals like no other Sansui before it. On many songs this will not be noticeable as the Sansui vocal standard is very good already, however, if you are an opera lover I suspect you will notice fairly easily (but if you are a listener to commercial radio you may notice almost never) this 'effect' only kicks in when the girls really kick their voices boxes into high gear but when it does it is worth having. This is the first of the big differences, so a difference of 5%, or maybe a little more, better at vocals than its brothers.

The MR has a slight shine/light to its presentation. This makes the MR feel like a slightly bigger amp than the NRA or the XR, it feels slightly more forward (about 2 feet so not exactly a forward amp as such, just more forward than the other Sansuis) so it feels like it is trying to make more of an impression than its brothers. This doesn't really add or detract from anything much, except for electronica. I don't really have any electronica but I do have a few tracks that contain some synthesized electronica-esk style tones and the MR really makes them come out and pop. This is one of the big differences so I'd say the MR would be between 5% and 8% better at electronica than its brothers would be.

The NRA pushes its sound stage out to the sides and back further and gives much of the mids, lightly played strings especially, room to breath in a large-but-relaxed manner. Vocals are the main focus but this is only really blatantly obvious when the vocalist is actually earning their money (ie really working those vocal cords). Amy Lee, Montaigne, Enya, are really special when heard on the NRA.
The 907NRA has more of a smooth polish to its sound, it certainly doesn't seem to miss much detail when you are listening to it but compared to the C-2302/B-2302 combo I'm afraid it is. The 2302's are a little more dynamic and a bit more relaxed in their presentation as well.

That comparison above is while using the conventional volume pot on the C-2302, if you use the "source direct" function (which bypasses the volume pot and utilises a stepped attenuator set up instead) then both dynamics and detail improve noticeably.

In the area of hard-sung vocals the NRA is right up there with the best but when it comes to soft and delicate instruments the pre/pwr has more detail and a more natural decay.

Sansui AU-α 907 MR Very much an XR with much more subtlety on display, more resolution, cleaner background and slightly clearer vocals. Unless you get them side by side it is pretty much impossible to tell the XR and MR apart, they are very, very similar.

The MR shows much more gain than the NRA, the volume control had to be set at least one o'clock lower at all times, it once again comes across as a bigger sounding amp and it applies that spotlight effect on the entire mid range. Instrumentals come across more forcefully than they do on the NRA and you would think that with my oft-mentioned love of rock-to-hard-rock music the result of this comparison would be a no-brainer. But it isn't that simple. I do love the MR much more now that I'm using the 917 and the cd direct input to listen through and it is not an amp you can ignore easily, even when you are trying to use it for just a bit of background music but I'm not sure I would like that added spotlight effect (I think I will have to call it brightness eventually, but it is brightness of the good kind without any brittle, hard or jagged tinges to it) all the time. I may have to use it continually for a week or so and see how I feel about it afterwards. It comes across as more energetic, more flamboyant and more pumped up with harder rock than the NRA does, and it definitely has more energy in the drums, and the bass region in general, than the NRA. However, it falls behind a little if you up the ante to a truly world class vocalist.
The icing on the cake, so to speak, with the Sansui integrated amps are the MOS special editions. These models are, without exception, awesome! The 907i MOS Limited has a warm sound with an amazingly solid bass line that is just so damn satisfying to listen to. The 907 Limited has all the clarity of the normal 907 range but with a much more powerful bass presentation and a bit of an earthy (that's my claim, I'm sticking to it) feel to its sound. Generally accepted as the best integrated amp that Sansui has ever built. Then there's the 607 MOS Limited which is actually the very last '07 model amp that Sansui built. It combines the MOSFET bass presentation with some of that NRA sweetness to the midrange. Just brilliant.
***

 

[JimEGR]

@fojica Thanks for those posts from @Cafad. I hadn’t read his stuff on stereonet. Just what I was looking for.

 

[Cafad]

Present Sir!
@fojica Nicely done finding those words of mine. My 4-odd pages of Sansui work was rolled into the general Sansui Discussion over at SNA, so my 4 pages of posts are now mixed in with another 72 or so pages of posts. I've made mention of this and have been assured that my thread will return, but not the time frame that it will be returning in.

@gammi , with this latest 907MR - 907 Limited comparison, I'd love to get your impression of how the bass delivery of the two compare.

 

[fojica]

@Cafad
Jeff, it was my pleasure to read your posts back in the day, actually that's why I needed to create my account on SNA Your words helped me back then to establish some directions, as I was in the design phase on my DIY Alpha Sansui and I had a lot of questions in my mind - some of them received at least partial answers from your posts, so I can only thank you for that
And while I'm getting younger it seems that I developed a bad habit to sometimes forget some details quicker than I expect, so I tried to made another habit of saving what I find interesting at the moment That's how your words ended up being re-posted/quoted here on AK

 

[gammi]

@gammi , with this latest 907MR - 907 Limited comparison, I'd love to get your impression of how the bass delivery of the two compare.

I can't recall noticing any difference in bass but also I was using them with Magnepans, which aren't known for their bass abilities. Bass gets handled mostly by my sub.
Things more in the mid-bass range like guitar were affected by the whole "more harmonics" thing though, as in it felt a bit fuller/more complete.

It was a pretty subtle difference though, I don't think I'd be able to pick them out if I heard them on separate days, it was already hard to tell with only a minute between switching.

P.S. My AU-X11 arrives today along with my DigiKey order of a bunch of capacitors to refresh it with. Won't be able to give direct comparisons with the Alphas yet though, I left them up at the cabin with the Magnepans since I'll probably be there in a week or two again.