Question regarding Sansui AU-919

Glenz75

Sansui and Pioneer Freak
Hi there everyone, especially BeatleFred, I haven't been on here for ages, so I thought it was time I made an apperance again :)
I have a question for Sansui nutters like myself out there (theres no hope for us I reckon haha!) about the output transisitors for the AU919 or subsitutues/equivalents for them as I own a AU 919 and its working fine, but recently got a service manual of AG Tannenbaum and discovered I can't find any info on the outputs or specs?
They are NMA1012 and NMC1012. I've looked all up my data books etc, been on the net as well, but have come up with nothing at all.
I know Sansui did get the manufactuers to make transistors specifically for amps etc and these must be some of those 'specialist' devices.
Does anybody know of these or can give me any info so I have something for the future? :) Being a tech myself I'm curious to know..;)
Cheers
Glen
 
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Hi Glen:

Indeed it does seem to be the case that these NMA/NMC transistors were used only in the AU-919. Someone I know who replaced these transitors in an AU-919 replaced them with Motorola MJ15022 & MJ15023 and he says they work quite well.

Regards, B/F.
 
Hi there Fred :)

Hey thanks for that useful information, the other night I got curious and pulled my AU919 apart to see if the outputs had been changed and yes sure enough one channel has had replacement ouputs and I think they are the motorolas you mentioned there.. I'll have to double check on them again.
The amp sounds nice and balanced between the channels so those outputs must be suited to the 919's setup.-The Au 919 is an awesome sounding unit, especially on my new speakers which are Kef 105 Reference Series. They match up with the 919 quite well. :) :)

Cheers :)
Glen
 
The Motorola's are decent replacements... 200V, 250W, 16A. They are known to have pretty low VceSat voltage, which means less of your power is lost through the device and more makes it to the speakers, so in some cases replacing our old output devices with the newer Moto trannies may result in a few more watts output power.

The downside is that these high-power Motorola transistors have less gain and higher output capacitance, and thus lower ft frequency. Most of our vintage gear had output trannies that have a unity gain frequency of 6 to 8MHz. The Moto's are rated at 5MHz, so a heavier load is placed on the driver transistors (the gain has to come from somewhere, and if it ain't the output pair, then the drivers get to do it, but a properly designed amplifier should be fine). Then there is the argument that the lower unity gain frequency results in inferior sound quality. Not sure about that...every amp I have listened to with the Motorola devices sounded peachy.

Because of the somewhat substantial differences between the Moto devices and the originals, if it were my own amp (and even an amp that I was repairing for someone else), I'd want all the output devices to match.

But that's just me.
 
Hi there Echowars :) Ah thats quite interesting what you said there about the motorola ouptuts and the gain differences between the output stage matching etc. I totally agree with your comments about wanting all the devices matching up the same. I'm a bit like that myself when it comes to restoring old hifi and keeping it going I get the original replacment devices or find ones that are as closely matched as possible to the orginals. Interesting comment about what you said about the Motorolas sounding different and I'd tend to agree with you since thier gain characteristics are different etc, since the AU 919 uses these in one channel I've compared both channels done an A/B and I can't detect a much between them to be honest, Mind you thats with my ears and speakers, but with test gear-scopes/sig gens etc you'd see differences there. I might hook it up to my test rigs one day and have a little play.. would be interesting to see what results I get between channels. :)
I recently did up a on old Pioneer SA9100 amp that needed all outputs/drivers etc replacing and crook electros all thru it and a pleasing result came from that. The amp works great now :)

Thanks for that useful info Echo :)
Cheers
Glen
 
Very useful thread!

This is great info for a new 919 owner! (Yes, I did bite on that unit I mentioned in the earlier post. More on that later.) I really like this amp, and it's great to know what I can replace things with if I blow a tranie (or two, or ...). I'm keeping a note about the Motorolas right under my amp. Thanks guys!

I don't know what's inside mine right now. Being an occasional major league clutz, I don't like to chance scratching things or losing screws, so I don't tend to open covers on electronic gear that often -- even though I'm not really a stranger to a soldering iron. I just figure it sounds great, so I don't need to! (At least, not yet.)
 
Hi!
Just looked into my AU-D907 (said to be a Japanese analog of a 919), and the transistors that are used in mine are NMA1012 and NMA1216. So, it looks, they are somewhat different, these two models. Also, noticed that there are 4 of each type. Why so many?

Andrei
 
Widens the SAO (Safe Area of Operation) by allowing the output current to be shared between multiple output devices. Fairly common in amps with output ratings of >100 watts, or amps rated to drive very low impedences.
 
Thanks, EchoWars.

It has been trying to drive my Magneplanars with their low impedance but to no considerable avail.

A.
 
Originally posted by doussia
Thanks, EchoWars.

It has been trying to drive my Magneplanars with their low impedance but to no considerable avail.

A.
I didn't quite get that... sorry...
So can you drive them Maggies with the Sansui or not?
Just curious as I got a AU-999 recently (in excellent shape I might add) and I'm considering getting a pair of 1.6 Maggies. Will I be able to drive them with my 999?

Cheers!

Bogdan
 
Bogdan,
It is driving them, all right. It is the sound that I do not like - too mechanistic and 'dirty'. Absolutely unlike the sound other members on the forum describe.

But that is MY unit. I am selling it...

Cheers,
Andrei
 
The impression I've gotten is that maggies, in general, favor tubes. Same goes for any purely magneplanar speaker. Old solid state gear may not be the best match, even if it is a Sansui. I wonder if the vintage or re-released Sansui tube gear might be a good choice.
 
John and Doussia thanks for the reply.
I was under the impression that Maggies need good 4 ohm rated power to be driven properly and that's about it. Their site certainly does not make any statements on the amp type needed to drive them.
I thought good, clean 4 ohm power is not all that easy to get with tubes however my experience with tubed gear is rather limited so I could be dead wrong.
My 999 has absolutely no trouble driving any pair of "regular" dynamic speakers that I own, but then again their impedance curve is different from the magneplanars.
Guess I'll really have to try and see...

Cheers!

Bogdan
 
John,
Can not agree with you re old SS not being able to play the magneplanars: I now have a small ( two times smaller and 3 times lighter) Revox SS amp ( ReVox A78 MkII, if you really want to know) capable of 50WPC at 4Ohms driving he maggies so much better than the Sansui, it kills me... Such an open and transparent sound... It is even TOO open nd transparent...

Would love to try them out with a good tube amp, but it is nowhere in the vicinity of my home...

Andrei
 
Well, that's why I use that really handy term, "generally".

I've just heard that, at least in most cases, tubes tend to work much better with magneplanars, which are kind of a different animal in the speaker kingdom to begin with. Of course, it also depends on individual tastes and perception. Maybe you've hit on a SS amp that works unusually well with them. Maybe the 919 doesn't, for some reason. I wouldn't know why -- I don't think that it would be an impedance problem, but who knows
:dunno:
 
Poss, you may have a point in that tubes could be less efficient for that impedance rating -- it may take relatively more power from a tube amp to drive the maggies. I believe that the logic I heard was that the magneplanars tend to be bright (at least some people think so, anyhow), and the warmer tube sound can help compensate for that. Which may not have anything to do with Doussia's problem, anyhow. This is all 2nd hand info, anyhow. I don't have first-hand experience with them, so I can't be that definite. (I'd sure like to check out Clements' new ribbon / dynamic hybrids though - if he ever releases them!)
 
John, maybe the Newforms could also "float" your boat. Some people swear for their monopolar ribbons. All the owners seem to be quite taken with Newform's extensive and deep soundstage not to mention their clean mids and highs.

For one I prefer large panels for the seamless integration of all the frequencies. I'm not sure if I could afford the largest models (mortgage + college fund + all the other bills&stuff are dampening my enthusiasm...) so I'll probably have to give up the bottom most octave on the Maggies 1.6...

OTOH the Newforms seem to be pretty well integrated. Too bad you cannot audition them at your hi-fi dealer...

Cheers!

Bogdan
 
Andrei:

Do your Maggie speakers have an extra set of terminals so that they can be bi-amped?

If they do, have you tried driving the speakers with TWO amplifiers?

I suggest trying this. The AU-D907 has a switch to make it simple to separate its pre & power amp sections. Hopefully, your other amps do too-. Why dont you try connecting one amp to one speaker, and the Sansui amp to the other speaker (vertical biamping). (Of course, you'd need extra cables for the hookup and a preamp to feed both amps).

I'd be interested to know what results you obtain. Especially if you then switch amps so that whatever amp was driving the left speaker, now drives the right, and ditto for the Sansui. Then I'm curious if the "bad" sound you claim from the Sansui amp is always heard thru the one speaker it drives.

Try different combinations for the hell of it and see what you discover. Try using the Sansui as a preamp to your other amp. Or try horizontally biamping and use the Sansui to drive the woofers only in both speakers. Perhaps you might find a sound thats more to your liking with a different arrangement.

B/F.
 
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