AU-D907 LIMITED vs 919
- Thread starter ghamilton
- Start date
GrisPato
Super Member
Main reason I started thinking about this was that I wanted @ghamilton to have peace of mind about his AU-919, can i say, his precious 
.
And I try to mostly verify what I learn with different sources, and as you will know, often we learn at best half truths. ( Or often context makes the difference).
So in the case of the AU-D707/907 being the first models of Sansui with the high fT devices we all assume that the drivers are fast to. But this was just the first step, in the AU-X1 ( and the D907 Limited) the next step was taken.
My guess is that the NMC/NMA devices are "just" 25-40 MHz fT, which was a big step up from the 10-15 MHz fT available until then.
The 2SC2493/2SA1068 are 70 MHz fT, catching up with the NEC transistors used by Trio (Kenwood).
That is when they switched to the Toshiba drivers with fT of 100 MHz.
.And I try to mostly verify what I learn with different sources, and as you will know, often we learn at best half truths. ( Or often context makes the difference).
So in the case of the AU-D707/907 being the first models of Sansui with the high fT devices we all assume that the drivers are fast to. But this was just the first step, in the AU-X1 ( and the D907 Limited) the next step was taken.
My guess is that the NMC/NMA devices are "just" 25-40 MHz fT, which was a big step up from the 10-15 MHz fT available until then.
The 2SC2493/2SA1068 are 70 MHz fT, catching up with the NEC transistors used by Trio (Kenwood).
That is when they switched to the Toshiba drivers with fT of 100 MHz.
ghamilton
Super Member
Hyperion, you said "the substitutes suggested, although overkill in respect of their basic specs, have the important metal tabs,"...
That's why I chose these transistors.
"overkill" specs! That means better than needed to me.
ghamilton
Super Member
Ok, sorry. Should I replace them? They seem to be great.
kevzep
Its all about the Music
2SA1068 are 50mhz
2SC2493 are 35mhz.
pete_mac
Super Member
ghamilton
Super Member
Sorry. Didn't know.It’s 3am in the morning in England - patience!
GrisPato
Super Member
This ones are difficult. I can not find an official datasheet.
The only thing I can find is this:
Japanese transistors reference guide for 2SA1068 50 MHz, confirmed by a datasheet from savant IC.
Japanese transistors reference guide for 2SC2493 gives 70 MHz and one other reference guide 35 MHz but stated as minimum.
All information I found states 2SA1068 fT 50 MHz
2SC2493 fT between (minimum) 35-70 MHz.
I can also find 2SC2492 (120V) fT 60 MHz.(edit: also 70 MHz fT is given).
For this reason I wrote the value of 70 MHz fT.
I am still a beginner at all of this and for sure don't want to claim any knowledge. I have learned most of the little I know ( you ever experienced that, that when you start learning more about certain topics you mostly find out you know almost nothing because there is so much to know) from the people here on Audiokarma sharing there experience and knowledge. At times I try to get some more information about the things I learn and try to bring that back.
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Sorry for the delay, here is a post from JoseHH who outlines the possible options for transistors that are still available (depending where in the World you are), do have the right spec' and do have the metal tab, unless otherwise indicated in the text of the post.
https://audiokarma.org/forums/index.php?threads/sansui-au-x11-repair-work.1000228/#post-15711901
^^^These^^^ are what you should seek out, but beware of counterfeits or fakes. As mentioned (in my post #4 of the linked thread) 'Ceitron' or 'B&D Enterprises' are the most likely reliable sources for the transistors.
However if you can't get any of them, then this one
https://www.mouser.co.uk/ProductDetail/Toshiba/TTA004BQ?qs=Mv7BduZupUjGQix8c1RZeA==
And this one
https://www.mouser.co.uk/ProductDetail/Toshiba/TTC004BQ?qs=Mv7BduZupUgP0/eZ2DvzIw== (No STOCK until 02 August 2022)
Can be used with a solder tag to enable the collector connection to the fixing screw.
My apologies to @ghamilton for this misunderstanding, I spend a lot of time trying to make sure my posts are factually & technically correct, understandable and containing useful information. While at the same time not upsetting, belittling or undermining anyone, this is an extremely difficult juggling act I am sure you can appreciate.
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Yes you can most definitely leave the transistors in there without any concerns about safety. As for performance, you might be able to notice the smallest difference but only AFTER you have changed them to one of the above suggested alternatives. According to my experience the difference is really subtle, and apparently not everyone can hear it. And when all is said and done, any change could be the result of (obviously) checking/resetting the bias and DC offset after swapping the transistors, rather than an improvement caused by the transistors themselves.
JoseHH
Super Member
Hello everybody,
I think that the MJ15030/MJ15031 work on the AU-919. In fact, had them for a while in mine, and i later changed them with 2SC2344/2SA1011 -to my not so good ears- better sound, and better transient response. The transition frequencies of the MJ15030/31 are not all that different from those of the original drivers, 40MHz for the 2SB537 versus 30MHz for the ON parts. The junction capacitances are also comparable. No issues there so far. It is their current rating (ic=8A, Ib up to 2A), and their current-voltage response that is somewhat different from the originals 2SB537/2SD282 which rated at only Ic=1.5A designed to work with base currents of 0.3A or less. This was my understanding of what was explained in this post by member ilimzn who knew these wide bandwidth amplifiers well.
Back in 2017 there was not yet a clear consensus among the experts in this forum about what to use to replace driver transistors in the AU-919, BA-F1, AU-X1. It was still being debated, and you can see this in this and other forums. There were not many options available without getting counterfeit parts, and the advice given was the best that they could give in that context. Nothing to be sorry about.
EDIT:
I forgor to mention the parts I used to replace the MJ15030/1 in the AU-D907, which are the 2SC2344/2SA1011
I think that the MJ15030/MJ15031 work on the AU-919. In fact, had them for a while in mine, and i later changed them with 2SC2344/2SA1011 -to my not so good ears- better sound, and better transient response. The transition frequencies of the MJ15030/31 are not all that different from those of the original drivers, 40MHz for the 2SB537 versus 30MHz for the ON parts. The junction capacitances are also comparable. No issues there so far. It is their current rating (ic=8A, Ib up to 2A), and their current-voltage response that is somewhat different from the originals 2SB537/2SD282 which rated at only Ic=1.5A designed to work with base currents of 0.3A or less. This was my understanding of what was explained in this post by member ilimzn who knew these wide bandwidth amplifiers well.
Back in 2017 there was not yet a clear consensus among the experts in this forum about what to use to replace driver transistors in the AU-919, BA-F1, AU-X1. It was still being debated, and you can see this in this and other forums. There were not many options available without getting counterfeit parts, and the advice given was the best that they could give in that context. Nothing to be sorry about.
EDIT:
I forgor to mention the parts I used to replace the MJ15030/1 in the AU-D907, which are the 2SC2344/2SA1011
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GrisPato
Super Member
No, not available anymore
As stated you'll probably have to order from someone like Ceitron or B&D Enterprises.
https://www.bdent.com/nsearch.html?catalog=yhst-864421581610834172249761&query=2sc2344
https://www.bdent.com/nsearch.html?catalog=yhst-864421581610834172249761&query=2sa1011
Also apparently available from here:-
https://www.ampslab.com/components_mediumpower.htm
I can't guarantee that these are original, I'm just showing you a possible source.
https://www.bdent.com/nsearch.html?catalog=yhst-864421581610834172249761&query=2sc2344
https://www.bdent.com/nsearch.html?catalog=yhst-864421581610834172249761&query=2sa1011
Also apparently available from here:-
https://www.ampslab.com/components_mediumpower.htm
I can't guarantee that these are original, I'm just showing you a possible source.
GrisPato
Super Member
Oh no. For that price you can get 10 pairs at ampslab and share the rest with the community.
https://www.ampslab.com/trans_2sc2344.htm
https://www.ampslab.com/trans_2sc2344.htm
