Sansui AU-777A vs all contenders

[smurfer77]

Nice write up.

I had one of those Sony VFET amps, and it did sound very good.

Rob

Surprised me those little Sony units. Aside from the unobtainium factor of the VFETs it's also worth noting that I did have to play around a bit with the power supply (voltage doubler) and the VFET positions/matching (very different pinch-off voltages, but I have two VFET amps so I could measure and match output devices a bit) to get nice & clean output on the scope. As I says, they are a bit 'specialist' . Can't wait to get this TA-5650 up and running and see what that does.

 

[smurfer77]

I guess there should be pics of every amp I compare to. Here are some pics of the Sony amp. A bit naughty in the Sansui forum I know . Notice the "VFET" on the front. Very serviceable as the chassis opens up like a clam with the front and rear tilting. What else... oh there is a voltage doubler on the power supply board that sees some hard work, and it supplies the gate voltages to the VFETs (without any voltage between gate and source they are full throttle). This voltage doubler is a section I will rebuild (I've already seen one hard working cap in the voltage doubler on my other Sony VFET (TA-5650) vent hard).

I promise I will compare to more Sansui soon, but I am finding it very exciting to find models in other brands to get excited about (I know there are many, but I haven't found many personally, but hey, I'm a Sansui guy!)... but there might be a comparison to a very cool Yamaha CA-1000 soon. This model has come up lately in some other discussion in this forum, with respect to the AU-999 mods as some of the mod adjustments are built in adjustment on the CA-1000. More on that later; actually I'm listening now to the yammy, but the amp is a new purchase and I need to check it over before I do the proper A/B... but I can tell you already it's a serious amp! Can you say "Variable loudness knob!"? (not something I have seen on sansui, but have on pioneer and others too.)

 

[smurfer77]

Did a fun comparison today. I stacked up the usual rack of AU-777A / AU-9900A / Sony TA-4650 / Eight Deluxe versus my ST-70 with VTA high-gain driver board. It is an amp a built from one of the Bob Latino kits when I first got interested in audio DIY a few years back. Now it is running soviet 6p3-se tubes (a kind of military high plate voltage EL34). The imaging and top and clarity and sparkle of that ST-70 has always been outstanding, but it can't compete on the mids and bass to the sansui units. So today I paired the ST-70 up with a Marantz SC-6 preamp. That sure helped the ST-70 along. Not quite the bass or mids of the AU-777A but very very good, no doubt.

Oh and my AU-9900A has started having that leaky cap noise.... so listening to it in stock form has come to an end and it get's moved out of the rack and replaced by something else (probably a Yamana CA-1000 I'm working on) for a full recap.

The news I was hoping to share today was the comparison of my rebuilt AU-777A to a stock unit. I grabbed a very clean one recently.

It is not mint, but has very minimal signs of use; the best unit I've seen. It is meant to be working properly, so I brought it up and sure enough there was sound on both channels. So I biased it up - all good. But when I went to adjust the main amp centre voltage I can see there is a problem. As you can see, if you inspect the oscilloscope, one channel is not 'pulling' no matter the adjustment... the 'pull' just doesn't turn on. As mentioned, biases up ok, and output transistors have just been pulled and nothing seems bad. So I wont be doing the stock/rebuilt comparison today, and I'm leaving on a work trip for a few days... so it might be the weekend after this when I get to poke around this 777A. The goal is to get this, and another stock AU-777A I have up to spec, and then compare the three; with new motorola output transistors in one of the otherwise stock units.

On a final note, I think this makes it about 5% for the "fully working" amps I've bought to be actually working properly. How do non-technical folk survive?!

 

[avionic]

Wait till you go through the 9900a
-Lee

Or your favorite 9900Z...

 

[smurfer77]

How or what would an average owner hear/identify "leaky cap noise"???

In this case kind of like an alien yawning or someone opening and closing a rather large creaky door. Failing transistors can sound like that too....

 

[bsandovalb]

Smurfer, what differences do you find (sonically) between the au-777 and au-777a? I havebeen amazed by the little brother (au-505), and eas wondering how each compare against the other in music reproducton.... thanks!

 

[smurfer77]

Smurfer, what differences do you find (sonically) between the au-777 and au-777a? I havebeen amazed by the little brother (au-505), and eas wondering how each compare against the other in music reproducton.... thanks!

I've been holding of giving comments/comparisons until I'm sure the units I'm listening to are up to spec. I do have an AU-777 but it's got some issues.... but i can tell you it IS going to be very good. in fact it was listening to this 777 in the workshop that made me go ahead and grab a 777A and rebuild it while I fix up the 777. The 505 is an amazing unit, as you probably know, most closely related to the AU-555A. I could easily live with the 505/555-A (they are slightly different but I tend to lump them together)... it has some magic. The 777 variants just have more (for me, and with my speakers at least...). It was the 555A that got me into Sansui in the first place.

 

[GPS16]

In this case kind of like an alien yawning

Hi Smurfer,

that's a cracker!!! One of those "difficult to describe, but you know it when you hear it" situations.

I remember one of the operators at work coming into the Maint Dep and asking if someone could look at the machine she was an operator for. She said it "sounded like a cow". All the engineers laughed but when I got close to the machine it definitely went "Moo"!!!! It turned out to be duff bearings on a cooling fan!!!!

GPS16

 

[Overundr1]

Will have a 555 non 'a' version in the collection once I get the time to go get it. Still has the original blue film, (one owner unit), over the front panel. After a rebuild will add my thoughts as to its sound as well against the heavy hitters, of course with the stuff lined up for service might be a while and no I do not want to tackle another 9900z anytime soon
-Lee

 

[smurfer77]

Will have a 555 non 'a' version in the collection once I get the time to go get it. Still has the original blue film, (one owner unit), over the front panel. After a rebuild will add my thoughts as to its sound as well against the heavy hitters, of course with the stuff lined up for service might be a while and no I do not want to tackle another 9900z anytime soon
-Lee

I hope you enjoy the regular AU-555. I have tried one, and also listened to my friends and it is my least favourite of the 222/555/777. In fact, it's probably my least favourite AU I've heard. Not saying it was bad, just not amazing like the rest IMO. Also, a bit bass light until you crank it up, and yet not trebly shy, which made it worse. Sounded fine at high volume though - things seemed to balance up in terms of tone. But hey, maybe both units I tried had issues that I didn't know about. (FYI, both were stock)

 

[Overundr1]

Weak output coupling caps will cause that for sure, intend to uprate them and replace along with signal transistors and caps before giving it a true listen. Happen to have a nice restored tube receiver to compare it against with Klipsch speakers. Should be interesting to add to the thread once done.

 

[smurfer77]

I finally got an amp I had been after for a while; a Yamaha CA-1000. Engineers obviously put a lot of thought into it's design and there are 10 pots to adjust during servicing! Also variable loudness. This is not just a feature to vary strength of loudness; it is used together with the volume knob, and in a way that the freq response compensation is correct at any volume. She has a dedicated MC board as well as MM board, adjustable tone rollover frequencies and so on. Even the low and high filter frequencies are adjustable (well switchable... it's not a continuous adjustment).

Here she is.

She is 100% up to spec. I had to iron out a number of annoying to find issues (on main amp board and phono/function board) to get this up and running properly. She is mostly stock except outputs are now all onsemi MJs and some of the drivers etc have been replaced. As well as bias transistors and a few resistors. All caps are original. If you want to read the train wreck that is my troubleshooting, as well as nudes, the thread is here.

How does she sound? Bloody good! She is immediately up there with the Sony TA-4650 and AU-777A. I also have the Sansui Eight Deluxe in the rack making a 4-way comparison. The Eight was again the brightest (but again, still have high hopes for this rebuilt). The Yammy was pretty much equal in bass to the Au-777A on first listening session. I couldn't quite decide if the mids and highs were actually better on the yammy! So more listening is needed. I ran tone controls flat and loudness off. The variable loudness on the yammy is very usable (like the 777A) and gives good results, not boomy rubish you sometimes get on some units. The yammy also has a bias mode operation switch... when you flip it idle consumption goes up by an amp and bias voltage across two emitters goes from 47mV to .94V. Didn't notice any difference for now so I will run in the cooler bias mode.

I am confident my AU-777A will be serviceable for another 50 years, but the Yammy will take more effort as they suffer from chassis and PCB oxidation... but still, I'm excited to find another super amp (IMO) even if it's not a Sansui (in fact, to find other brand units I like is very exciting by itself... it's not been easy to do so far!).

 

[smurfer77]

After living with the up-to-spec Yamaha CA-1000 in service for the last couple of weeks, I have to say I'm really still impressed. A very nice sounding amp. I wouldn't say the jump to 70W is noticeable (if anything, due to the volume pot used is seems less powerful until you turn it all the way up), but it sure does have stellar imaging and haunting mids/highs much like the AU-777A. Bass is great too. It really does it all. I couldn't really tell you that the AU-777A is much better in any particular department (and this CA-1000 is largely stock!). I'm really keen to try out the phono section on this yammy too, which looks very serious indeed, with a dedicated/separate MC board and so on. There is some nice info here on vintage knob about the topology of the Yamaha CA-1000.

Next up, we will be getting back to Sansui comparisons. I've - finally - just about finished getting an AU-70 up-to-spec, and have fully recapped it now. I have had the unit for a while but it had a few little issues that many might not notice, but I didn't want to due full comparisons (even by myself) until I was 100% sure the unit was good to go. I have now finished a FULL recap, and just need to pop the phono boards back in tonight. Oh boy, am I excited to put this one into service and see how it stacks up against the 777A and some others. Judging by headphone monitoring during repairs, it is going to the VERY interesting.

PS. what should I be working on after that? I've got an AU-111 that needs some love, AU-X11 that need (at least) driver board rebuilds, and a pair of HFV60/PR-330 waiting for essential maintenance. (more common options for next comparison include a regular Eight, Seven and a stock 777A, which all need repairs). I think the AU-X11 is probably going to need some other (time consuming) work to get fully up-to-spec, so I might start on those on the side, but get the tube amps up and running as based on initial inspection they are not going to be much work.

 

[stereofun]

Hey smurfer77 - I'd vote for the Eight deluxe to be recapped and pitted against a ditto Yammy - then you will have a same basis shoot out of three great amps from the "early transistor years", 1969-1974. The the winner should then face off with the holy grail AU-111 - and of course its tube relative the AU-70. The king from that early era - be it it tube or tranny - should then be up against some of the speedy and highly engineered late era Sansui like the AU-X11.

What a feast, that would be - even if there is no "winner", but just some fine gear to enjoy and compare........But of course it is a lot to ask

 

[The Fuxtor]

Smurfer, I am curious if you ever got around to the preamps issue of one channel being weaker in your Sansui 8 some posts back? I am working on a 555a which seems to still exhibit the same behaviour after recapping... Also uses the same transistors ( 2sc645 ??) which you had replaced with 2sc1815's . I purchased some ksc1845's for this area..... any thoughts?

 

[Styxdude99]

[HAHAHA! I had to break my first post into two posts because I discovered a 12,000 character post limit!]

Again, still not ruling out a modded Au-999, but a unit hasn't fallen into my path lately.

And the latest contender, an AU-9900A just arrived on my doorstep (and I have an AU-9900 on the way). Checking out status of that unit now! I had read that people think it might be warmer sounding than the AU-11000. And the 9900 is basically the same unit but running at lower power, which could have better long term reliability (?). Anyway, will report very soon... it's on the bench now doing essential checks and rebias before hookup.

Am also interested in the AU-717 based on high opinions of Hyperion and others.

More rambling to come.... consider yourself warned. One day the rebuilt AU-777A will be dethroned. I apologize for the no doubt numerous typos as I'm just typing these thoughts quickly. These are the thoughts i might usually keep to myself and there is no hard science (I try to stick to quantifiable facts where possible and thought about doing a similar thread with full measurements... but I aint got the time for that), but I thought someone else might get a kick out of my 'process'.

I just picked up a Sansui CR-M5 but I can't seem to find much on it. I got it for $40 bucks with a Sansui P-D10 record player they both look brand new and work great. Do u think it's worth keeping or just getting something different.

 

[smurfer77]

Smurfer, I am curious if you ever got around to the preamps issue of one channel being weaker in your Sansui 8 some posts back? I am working on a 555a which seems to still exhibit the same behaviour after recapping... Also uses the same transistors ( 2sc645 ??) which you had replaced with 2sc1815's . I purchased some ksc1845's for this area..... any thoughts?

Sorry, PMing you now (had been travelling)

 

[smurfer77]

I just picked up a Sansui CR-M5 but I can't seem to find much on it. I got it for $40 bucks with a Sansui P-D10 record player they both look brand new and work great. Do u think it's worth keeping or just getting something different.

Sorry I don't know much about those models, but you could start a thread and get some nice input from those with more experience than myself with those models.

 

[smurfer77]

I've now had my Sansui AU-70 recapped and all issues ironed out for about a month now. There are lots of pics in that thread but here is a tease:

I've been living with the recapped unit for a few weeks, not wanting to blurt out my first thoughts, because frankly, my first thoughts were that nothing has improved in audio since the mid 60s (forget specs, just enjoyment, with reasonable speaker loads). So after a month, have I calmed down? Not really. This thing is good. How good? AU-777A good.

The A/B is really tough to tell apart if I run flat controls on both (tone circuit engaged, but controls flat, on the AU-70; with the tone-defeat the tone changes enough to tell the difference). All of the nuances i love about the AU-777A are here. The gripping bass, the clear and smooth mids, the detailed yet not shrill highs and surprisingly spatial separation. Perhaps the AU-777A mid is a touch more recessed in the mid, maybe not. It is by far the hardest to tell apart from all of the comparisons I've done so far. Now if you were to take two completely original units, I don't know if it would be as close... those coupling caps make quite a difference on both units (especially the 777A). And, on the AU-70 i stayed almost stock in parameters, where as the 777A goes a boost in capacitance in a few key positions. I could mention a few subtle differences in sound but I could be just kidding myself. I really find it hard to chose the winner. Any differences are slight enough changing out coupling caps would render my conclusion invalid. If you really pressure me I might say more, but for now let me say I love both machines. They are both very very special. Perhaps the AU-777 was voiced off of the AU-70?

Anyway, i think a lot of amps post 1965 should hand their heads in shame, and bow to the AU-70 (and AU-777A if they are after late 60s).

 

[stereofun]

I rarely run out of words. Suffice to say: great thread, great write up, gorgeous AU-70

 

[larryderouin]

GOOD GAWD! That AU-70 is OUTSTANDING looking! I'd put it right next to my 1000A. Which would hang it's head in shame, even if it does have the AU-70 in total watts. I WANT ONE OF THOSE!!! But would have to save up for a few years, (or sell off my FISHER gear...yeah right!).

I just noticed the Phono board box is the same shape as on the 1000A. Same Size? Is the Phono amp transistorized with 2sb381 Sony's? If you replaced them, what did you use instead as they are germanium.

 

[smurfer77]

GOOD GAWD! That AU-70 is OUTSTANDING looking! I'd put it right next to my 1000A. Which would hang it's head in shame, even if it does have the AU-70 in total watts. I WANT ONE OF THOSE!!! But would have to save up for a few years, (or sell off my FISHER gear...yeah right!).

I just noticed the Phono board box is the same shape as on the 1000A. Same Size? Is the Phono amp transistorized with 2sb381 Sony's? If you replaced them, what did you use instead as they are germanium.

I have never owned 1000A but I have read it is very good but yes, those who have owned both seem to give the nod to the AU-70. Not sure what size of the phonoboards are exactly; could certainly measure if you are interested. I think you are right about the transistor model, from memory; they were definitely Ge. I debated modifying the circuit to put in Si transistors, but when I tested the phonoboards they are really low noise for now. I probably would have only replaced with Si if the Ge was noisy.

 

[smurfer77]

Anyone noticed I have been a bit quiet lately? Well, I'm still travelling and probably will be for a few more weeks (it's not as fun as it sounds!), so no working on amps for me lately. But I have to share my excitement right now. I just had possibly the most exciting linkedin friend request. A gentleman from Japan has seen a 2015 Burning Amp video on youtube of me presenting my AU-777A and gotten in touch to request my direct contact details. Well the guy was a Sansui engineer from 72-89. (I like to imagine a bunch of sansui ex engineers emailing around the link to my video ). Apparently he is also doing some Sansui Alumni organization. He must have had a laugh when he saw the banner image on my linkedin profile is clearly a late 60s sansui circuit board!

I will definitely be letting him know about this sub-forum (maybe it's not well known in japan?), and maybe if I play my cards right we can get some answers from someone in the know.... Like was the Engineer's receiver really the Engineer's receiver.

 

[nj pheonix]

Pretty cool indeed!