Au-919
- Thread starter phatster
- Start date
Not exactly unnecessary, but not needed for all sources. It should have the effect you describe, but on the AU-919 it isn't as noticable as on some other amplifiers.
You mention to AU-X901 - a prime example, I have its lesser brother the AU-X701 and I can definitely hear a difference using the 'source direct' mode.
You mention to AU-X901 - a prime example, I have its lesser brother the AU-X701 and I can definitely hear a difference using the 'source direct' mode.
rasenthiran
Well-Known Member
Hi John,
Does bypassing Tone control in vintage amplifier such as AU 717/719 works the same as "source direct mode"??
Does bypassing Tone control in vintage amplifier such as AU 717/719 works the same as "source direct mode"??
Not really, but it might have been the idea that started all the 'jump' and 'source direct' switching ideas.
The AU-919 has a secret regarding it's tone controls, discovered by ConradH...
_mano
Well-Known Member
So many secrets, not sure which ones! I was curious about the tone controls in various Sansui amps, because they seemed to change the design across many otherwise similar amps. Bench tests suggested that no perfectly flat setting was possible. I put the various circuits into a simulator and concluded that by accident or design, "flat" was indeed not possible. Now, I'm talking very small deviations here, but I have to wonder if it was intentional voicing on their part. If you look at the tone controls on even most cheap receivers, they do zero to flat, and we know Sansui designers were pretty good. It's unlikely they forgot how to design tone controls on their best amps. If you use the defeat switch you do get flat response.
On the jump switch, I can't hear the difference and it would scare me to use it in the out position, only because I'd be afraid of hitting it by mistake and blasting myself with headphones or waking the dead with speakers.
On the jump switch, I can't hear the difference and it would scare me to use it in the out position, only because I'd be afraid of hitting it by mistake and blasting myself with headphones or waking the dead with speakers.
That was my first thought, but what the sim showed was that the topology doesn't produce flat response no matter what part values are used. I'll repeat though, these are very subtle deviations.
barclay t.
New Member
I'm having an AU-919 restored at this moment, so I'm following this thread with interest.
To those who think the 919 benefits from a careful choice of speakers, do you have any specific suggestions, or advice on what speaker characteristics I should look for? Or for those who own a 919, what speakers have you matched it with which you've found work very well? I've been looking at a few different floor-standing types, but the layout of my apartment precludes any floorstanding models from being set out very far from the wall. Bookshelf speakers would work much better in my room, but if I went that route I'd still be after something with a good bass response.
Along those lines, I wondered whether I might perhaps make use of the 919's A+B speaker outputs together, to power the main bookshelf speakers with "A" and augment them with a separate sub run from "B". I do presently have an NHT sub with its own amplifier, but I'd like to be able to run the Sansui to the main stereo speakers directly, and not through a sub's amp and crossover, which might colour the sound.
To those who think the 919 benefits from a careful choice of speakers, do you have any specific suggestions, or advice on what speaker characteristics I should look for? Or for those who own a 919, what speakers have you matched it with which you've found work very well? I've been looking at a few different floor-standing types, but the layout of my apartment precludes any floorstanding models from being set out very far from the wall. Bookshelf speakers would work much better in my room, but if I went that route I'd still be after something with a good bass response.
Along those lines, I wondered whether I might perhaps make use of the 919's A+B speaker outputs together, to power the main bookshelf speakers with "A" and augment them with a separate sub run from "B". I do presently have an NHT sub with its own amplifier, but I'd like to be able to run the Sansui to the main stereo speakers directly, and not through a sub's amp and crossover, which might colour the sound.
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This might not be the best way to power a sub from the AU-919. You should know that the A & B speaker outputs come from the same place - so it is as if the A terminals are presented at the rear panel twice - if that makes sense.
Having speakers and a sub connected in this way might present too much load to the AU-919, I recommend you consider a sub fed from low level outputs, like the "pre-out" connections for example.
Having said this if you choose the right speakers you won't need a sub, the AU-919 has tons of bass if you need it.
Having speakers and a sub connected in this way might present too much load to the AU-919, I recommend you consider a sub fed from low level outputs, like the "pre-out" connections for example.
Having said this if you choose the right speakers you won't need a sub, the AU-919 has tons of bass if you need it.
barclay t.
New Member
Thanks! Yes, that does make more sense. And the NHT's amp does allow for that kind of connection.
http://www.nhthifi.com/site/pdf/sa_2Man.pdf
If I were to go that route (Sansui pre-amp out to the NHT amp's low level line in), how would I set the Sansui's Pre-amp/Power Amp switch, seen at the bottom of this picture?
I agree -- which is why I'm open to suggestions and recommendations.
Over to the right, which should be separated & capacitor coupled. (you will need to use a 'Y' cable to feed the pre-amp output to the '919 AND the Sub).
(use capacitor coupling just in case there is any DC on the input of the sub - there may be none - but this is the safe option).
I think it depends just how much bass you want to hear, I have tried mine with Mordaunt Short MS30's (stand) and KEF iQ7's (floor) - both fine to my ears, not a great selection, and neither are modern speakers. You'll probably want speakers with the lowest possible LF rolloff frequency, however this isn't the whole story and only auditioning will show you how much bass you can get from a pair of speakers.
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ilimzn
Well-Known Member
The AU-919 is the first amplifier which implements Sansui's DD-DC front end circuits. This was later branched out into a 'separates' version, the BA-F1/CA-F1 combo, and developed into the AU-X1 - and also slightly simplified for the AU-519/719 amps. Also, some of the large receivers from the same time might have used similar circuits.
They do indeed sound rather different than the older amps, a transition to a more analytical sound from the older BA2000/3000 AU9900/11000 sound, via the AU517/717/710.
Sansui AU-D9/D11 are descendants, using almost exactly the same DD-DC front and a power stage with a feedforward error corrector stage added. The interesting part is that both use only one pair of output transistors (though much more beefy).
The AU-X1 is a far less 'souped-up' design than the X1 and suffers much less of the X1's problems. There is also only one major revision of the 919, though there might be differences to the Japanese market equivalents. When buying stock, getting a 919 is surely a better idea than buying an X1, although the black flag capacitors WILL eventually send the 919 power amp section to little transistor heaven
The critical bits, aside the ubiquitous Sansui glue problem and semiconductor degradation due to corroded pins (mostly this applies to multi-junction 'bead' diodes), are the black flags, and the main filter caps. The latter will degrade well below tolerance if the amp is operated at todays 115/230VAC while being set to 110/220V, which is almost invariably the case. I've had a few 919's to restore and the 15000uF/63V caps usually measure 10-12000uF. Replacing them is not impossible but it IS difficult, and I would not recomend putting in NOS ones even if you could find the peculiar oval originals, because the 63V maximum working voltage is underspecified as it is. Replace with 75 or 80V if at all possible. Keeping the original arrangement requires the original caps to be carefully opened and the innards replaced by two standard caps in parallel, or the whole lot of 4 has to be replaced by 4 pairs on carrier boards with provision made to emulate the original screw terminals, because the whole power supply board bolts directly onto them.
The black flags need to be replaced by silver mica or ceramic C0G/NP0 caps. DO NOT try polystyrol because they are generally inductive, and the black flags are invariably used for frequency compensation, and when they fail open, as they do, the amp tends to turn into an oscillator and will fry itself and sometimes tweeters connected to it.
Regarding the original output transistors, DO NOT if you have any choice, replace with ONsemi slow MJ types. This MAY work but the amp will not sound right and the compensation will be off, making it marginally stable. Also some care should be taken when choosing the driver transistors. Do NOT change with MJE15030/31 and similar because it used far too little current for these to operate in their ideal region, reducing the bandwidth and gain significantly. Smaller and faster (1-2A) types with gain optimized for tens and not hundreds of mA should be used. There are many types still available. As for the outputs, the only TO-3 parts once made by ST microelectronics have been discontinued even though they only lasted about 2 years on the market. In essence they are a cousin of the Toshiba 2SC2500/2SA1943 in a TO-3 case. Unfortunately, as it is, the only way to put replacement transistors into the original arrangement with TO-3 sockets, implies filing off a corner of a TO-3P descendant of the originals, OR removing the sockets and rewiring for transistors fitted directly to the heatsink. The amp will work beautifully with 2SA1115/16 2SC2921/22 pairs (needs rewiring and fitting the transsitors directly to the heatsink, or 2SA1294/2SC3263 and even better 2SA2223A/2SC6145A. The later can, with some work, be adapted to fit the original sockets but in order to fit the heatsink one corner needs to be filed off or it will impact a heatsink rib which will tear up the mica or silicone insulation (whatever you use). I normally implore owners to do this change because the original transistors are so tight on spec especially for 4 Ohm speakers, that an upgrade to the replacements which are capable of withstanding 25-30% more voltage and almost double the current, not to mention VASTLY improved safe operation area, is well worth the not so high price even at roughly half the speed. Keep in mind that even though ONsemi parts are even more robust, they are slower by a factor of ~18, which is a HUGE difference. The same parts may be used for the AU-X1 (though less filing ) although a slight adjustment of the compensation is well advised (not necessary for the latest version with all the bugs fixed).
They do indeed sound rather different than the older amps, a transition to a more analytical sound from the older BA2000/3000 AU9900/11000 sound, via the AU517/717/710.
Sansui AU-D9/D11 are descendants, using almost exactly the same DD-DC front and a power stage with a feedforward error corrector stage added. The interesting part is that both use only one pair of output transistors (though much more beefy).
The AU-X1 is a far less 'souped-up' design than the X1 and suffers much less of the X1's problems. There is also only one major revision of the 919, though there might be differences to the Japanese market equivalents. When buying stock, getting a 919 is surely a better idea than buying an X1, although the black flag capacitors WILL eventually send the 919 power amp section to little transistor heaven
The critical bits, aside the ubiquitous Sansui glue problem and semiconductor degradation due to corroded pins (mostly this applies to multi-junction 'bead' diodes), are the black flags, and the main filter caps. The latter will degrade well below tolerance if the amp is operated at todays 115/230VAC while being set to 110/220V, which is almost invariably the case. I've had a few 919's to restore and the 15000uF/63V caps usually measure 10-12000uF. Replacing them is not impossible but it IS difficult, and I would not recomend putting in NOS ones even if you could find the peculiar oval originals, because the 63V maximum working voltage is underspecified as it is. Replace with 75 or 80V if at all possible. Keeping the original arrangement requires the original caps to be carefully opened and the innards replaced by two standard caps in parallel, or the whole lot of 4 has to be replaced by 4 pairs on carrier boards with provision made to emulate the original screw terminals, because the whole power supply board bolts directly onto them.
The black flags need to be replaced by silver mica or ceramic C0G/NP0 caps. DO NOT try polystyrol because they are generally inductive, and the black flags are invariably used for frequency compensation, and when they fail open, as they do, the amp tends to turn into an oscillator and will fry itself and sometimes tweeters connected to it.
Regarding the original output transistors, DO NOT if you have any choice, replace with ONsemi slow MJ types. This MAY work but the amp will not sound right and the compensation will be off, making it marginally stable. Also some care should be taken when choosing the driver transistors. Do NOT change with MJE15030/31 and similar because it used far too little current for these to operate in their ideal region, reducing the bandwidth and gain significantly. Smaller and faster (1-2A) types with gain optimized for tens and not hundreds of mA should be used. There are many types still available. As for the outputs, the only TO-3 parts once made by ST microelectronics have been discontinued even though they only lasted about 2 years on the market. In essence they are a cousin of the Toshiba 2SC2500/2SA1943 in a TO-3 case. Unfortunately, as it is, the only way to put replacement transistors into the original arrangement with TO-3 sockets, implies filing off a corner of a TO-3P descendant of the originals, OR removing the sockets and rewiring for transistors fitted directly to the heatsink. The amp will work beautifully with 2SA1115/16 2SC2921/22 pairs (needs rewiring and fitting the transsitors directly to the heatsink, or 2SA1294/2SC3263 and even better 2SA2223A/2SC6145A. The later can, with some work, be adapted to fit the original sockets but in order to fit the heatsink one corner needs to be filed off or it will impact a heatsink rib which will tear up the mica or silicone insulation (whatever you use). I normally implore owners to do this change because the original transistors are so tight on spec especially for 4 Ohm speakers, that an upgrade to the replacements which are capable of withstanding 25-30% more voltage and almost double the current, not to mention VASTLY improved safe operation area, is well worth the not so high price even at roughly half the speed. Keep in mind that even though ONsemi parts are even more robust, they are slower by a factor of ~18, which is a HUGE difference. The same parts may be used for the AU-X1 (though less filing
) although a slight adjustment of the compensation is well advised (not necessary for the latest version with all the bugs fixed).
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AUD101
Parsley The Lion!
If you find a good source for them and the price is right - got to be worth it :thmbsp:
