BLAH BLAH
Super Member
Yeah but what about my AU-D11?!?!?Loving this discussion... especially the bits about my personal favourite amplifier, the AU-D11 II
How to best the Sansui X-Balanced amps?
- Thread starter toneriderMUC
- Start date
Regarding Sansui NRA series - just found some nice photos for AU-A607NRA, including the pcb side for driver boards.
It puzzled me why on the driver board there were 12 transistors instead of 8 as in MR series. At first look I suspected that they added some cascodes, but seeing the pcb side it was obvious that this wasn't the case. But, there is clearly something different to the MR series - in AU-A607NRA what I call VAS transistors (kQ6,7,8,9 in AU-A607MR) are "doubled" - similar with output stages where multiple devices are in parallel.
Otherwise the circuit around the input JFET's is identical with MR series, as I suspected.
Maybe this helps somebody around.
Regards,
Tibi
It puzzled me why on the driver board there were 12 transistors instead of 8 as in MR series. At first look I suspected that they added some cascodes, but seeing the pcb side it was obvious that this wasn't the case. But, there is clearly something different to the MR series - in AU-A607NRA what I call VAS transistors (kQ6,7,8,9 in AU-A607MR) are "doubled" - similar with output stages where multiple devices are in parallel.
Otherwise the circuit around the input JFET's is identical with MR series, as I suspected.
Maybe this helps somebody around.
Regards,
Tibi
Cosmin2000
Active Member
Greetings, Tibi! I was tempted to purchase at some point the Sansui AU-Alpha 607NRA or the improved Sansui AU-Alpha 607NRA II (this has an extra transformer in the front for the preamp?), but bought something else instead. Now if I want to buy a less expensive Sansui I will focus on AU-607 Mos Premium model because I have noticed it has much better construction and components. The looks are on the side of 607NRA though...
Could you be kind to post those pictures with the inside of 607NRA?
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JoseHH
Super Member
Hello Tibi and @Cosmin2000
In case that you did not know the Amp8 site, a very interesting site indeed. You can also see here some pictures. There are also some for a couple of other bigger alpha models.
In case that you did not know the Amp8 site, a very interesting site indeed. You can also see here some pictures. There are also some for a couple of other bigger alpha models.
To add something for JoseHH, regarding japanese series of Alpha amplifiers 
Found some pictures with AU-D607X (1984) - as far as power amp is concerned, to my eye it's 99% identical with AU-D77X and AU-G77X (not AU-G77X-II !!). Looks like having the same driver boards (spotted 1 cap different), same protector boards, just a bit different pcb on main/power-amp pcb (board F-4295), same speaker output board, same output transistors. However, for some reason the protector boards are only half-populated, compared with AU-D77X (or maybe only on later Decade models ?). No idea why.
There are different control/flat-amp board, phono/EQ board and main power supply board.
On main power supply board there are 2 bridges and 2 main (smaller ?) caps instead of 2 dual diodes +1 big cap, so a dual-mono design instead of shared power-supply as in AU-D77X/AU-G77X.
And also "classic Sansui" voltage regulators with zener + darlington config, instead of "basic" R + zener like we see in AU-D77X/AU-G77X.
Personal conclusion - strictly for power-amp adjustments most probably service manual from AU-D77X / AU-G77X can be safely used also for japanese model AU-D607X.
Found some pictures with AU-D607X (1984) - as far as power amp is concerned, to my eye it's 99% identical with AU-D77X and AU-G77X (not AU-G77X-II !!). Looks like having the same driver boards (spotted 1 cap different), same protector boards, just a bit different pcb on main/power-amp pcb (board F-4295), same speaker output board, same output transistors. However, for some reason the protector boards are only half-populated, compared with AU-D77X (or maybe only on later Decade models ?). No idea why.
There are different control/flat-amp board, phono/EQ board and main power supply board.
On main power supply board there are 2 bridges and 2 main (smaller ?) caps instead of 2 dual diodes +1 big cap, so a dual-mono design instead of shared power-supply as in AU-D77X/AU-G77X.
And also "classic Sansui" voltage regulators with zener + darlington config, instead of "basic" R + zener like we see in AU-D77X/AU-G77X.
Personal conclusion - strictly for power-amp adjustments most probably service manual from AU-D77X / AU-G77X can be safely used also for japanese model AU-D607X.
smurfer77
Super Member
Can confirm, the AU-Alpha607NRAII does have a little transformer hidden up front to drive the preamp (and a few other bits). The AU-X111MOS Vintage has a similar preamp stashed in a similar position.
I read some theories that the 607NRAII was released to fix a flaw in the 607NRA, but I've seen no evidence to support that theory.
I also read another theory that they just had parts left over at the end so they used them... this was the last amp released. But that doesn't really seem Sansui's style either.
I've yet to compared to my AU-Alpha607MR, but one day I will put them side by side and see what happens!
JoseHH
Super Member
When i adjusted my AU-d707X i used the manuals for the AU-D11 mkIi, and also that for the AU-G90X. But latter on a partial manual for the AU-D907X Decade was kindly made available, so i also looked at that. Member @Ronito6 in this forum translated and posted this procedure for adjusting the AU-D907X which is very useful for x-balaned amplifiers.
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Ronito6
Super Member
It was my first translation helped mightily by Google translate.
My life in Japan has made me very good at understanding and correcting
the strange results you can get from machine translation.
That said, a thread here on AK someone mentioned that the procedure as described had a mistake.
I will find the thread and post it here.
Edit: it was actually JoseHH here who found the flaw. KUDOS!!
Below is his correction to my work.
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Continuing the discussion about different topology/schematic variations on Sansui amps in time....discovered another one which have the DD block and VAS cascoded, similar with AU-X1111 MV. The aforesaid it's AU-A907i, including also its AU-A907i MOS Limited version (which has MOSFET outputs instead on LAPT bipolars). Comparing with AU-X1111 MV, the AU-A907i has only a single (non-cascoded) input JFET (2SK389), while in AU-X1111 MV that one it's cascoded with another 2SK389.
But interestingly, for the input JFET (+) supply side (+27V usually) instead of simple R + zener (the most used version) it has a series pass BJT as voltage regulator, which receives the reference voltage from the zener, which in turn is supplied from the V+ rail by a JFET CCS (FT3 on the amp board). This circuit part is similar (or maybe even identical as values) with B-2201/B-2301. As far as I remember, it's the only integrated where I saw this similarity until now.
Regards,
Tibi
But interestingly, for the input JFET (+) supply side (+27V usually) instead of simple R + zener (the most used version) it has a series pass BJT as voltage regulator, which receives the reference voltage from the zener, which in turn is supplied from the V+ rail by a JFET CCS (FT3 on the amp board). This circuit part is similar (or maybe even identical as values) with B-2201/B-2301. As far as I remember, it's the only integrated where I saw this similarity until now.
Regards,
Tibi
I think the word 'balanced' was just 'marketing speak' for a feature of the power amp topology being promoted at the time. Balanced inputs are provided on professional gear for noise rejection purposes in professional setups where long cables (more liable to pick up noise) are often present.
It is true that some later models were provided with balanced inputs as well as unbalanced. Mainly I think, to appeal to 'gear heads' who, it was thought would like the 'idea' of professional connectivity options, rather than their being much practical use in the domestic (household) market.
....if I can add my experience with AU-X 701 and its modern replacement....
I've got the AU-X used some 5 years ago (and yes, it still has the old logo) , and it is powering MA Silver 300 speakers..... althought it is working quite perfect, and I' ve been very satisfied with how it sounds, I was having a thought that after 35 years it would be good to send it for a refreshment.....so I started to look for something modern to replace it, at least temporarily.
.....and I've found an amp that everybody raves about, especially teamed with my speakers. Two days ago, I've gotten myself a mint Roksan K3 integrated, two years old, still under factory warranty.....and it has left me puzzled....I really don't know if I should be disappointed with Roksan, or proud about my old, glorious AU-X......Roksan does play very well, but I feel there is less timbre and much less space in what I hear. It seems like the sonic third dimension is much shallower than with 'sui!
I will continue to try it out for the rest of the week, and only then will decide to keep Roksan or not.....but for now, I cannot say I have high hopes for that....
I've got the AU-X used some 5 years ago (and yes, it still has the old logo) , and it is powering MA Silver 300 speakers..... althought it is working quite perfect, and I' ve been very satisfied with how it sounds, I was having a thought that after 35 years it would be good to send it for a refreshment.....so I started to look for something modern to replace it, at least temporarily.
.....and I've found an amp that everybody raves about, especially teamed with my speakers. Two days ago, I've gotten myself a mint Roksan K3 integrated, two years old, still under factory warranty.....and it has left me puzzled....I really don't know if I should be disappointed with Roksan, or proud about my old, glorious AU-X......Roksan does play very well, but I feel there is less timbre and much less space in what I hear. It seems like the sonic third dimension is much shallower than with 'sui!
I will continue to try it out for the rest of the week, and only then will decide to keep Roksan or not.....but for now, I cannot say I have high hopes for that....
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