Sansui AU-D707X Or Sansui AU-D907X

shojam

SHOJAM
Hello..
I just got two amps from an old friend's basement. He told me these belong to previous owner who never came back for left overs. God is great. My friend didn't hesitate while i intended to pick these. Amps were in protection mode. First was Sansui AU-D707X which is a japanese version of G90X. Second amp is bit confusing. Its D907x also japanese domestic 100 volt model with massive 160wpc.

Now the big question.

Which amp should i keep for restoration. Coz this 707x is closer to D11ii and 907X uses different power transistors (found in D9, D11 and G99x as per my limited knowledge). The problem is.... Ill have to keep only one. So i need suggestions from you guys... BTW i loved the sonic signature of D11ii and G90x (both at another friend's place who is insane sansui lover).

Recommendations must carry weight.
Thanks.
 
AU-D907X

Just guessing... 907 - with a massive 160 wpc. Power is power!

Check on availability of parts.
 
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The difference in power is not relevant unless you are trying to fill a dance hall, and even then 160W is only 1.2 dB better than 130W. Assuming that the 907X achieves its power rating by using paralleled output transistors like most of the other 907 types I am not in favour of that arrangement. Finally, very suitable new replacement output transistors are available for the 707x/D11 II should they be required.

So you know from this and other threads what my recommendation is: D707X
 
The difference in power is not relevant unless you are trying to fill a dance hall, and even then 160W is only 1.2 dB better than 130W. Assuming that the 907X achieves its power rating by using paralleled output transistors like most of the other 907 types I am not in favour of that arrangement. Finally, very suitable new replacement output transistors are available for the 707x/D11 II should they be required.

So you know from this and other threads what my recommendation is: D707X
Thanks phonomac. I adjusted the DC offset around 0mv across hot n cold terminals. Also adjusted idling current for output devices at 20mv-20.5mv. Is that right ? Coz i was not able to avail SM for 707x, so keeping in view of bias adjustment of D11ii, i performed the procedure on 707x. Its sounding more tight and precise now. My only reservation is about 20mv. Is it right or i should go up???
 
My only reservation is about 20mv. Is it right or i should go up???
There's a right amount of bias or a wrong amount of bias - for the AU-D11 II the setting is 20mV, I can only guess that for the AU-D707X it is the same. You shouldn't increase the bias just because you feel it should be more.

The AU-D11 II runs very cool when set to 20mV (for each of 4 readings) - this is as it should be.
 
There's a right amount of bias or a wrong amount of bias - for the AU-D11 II the setting is 20mV, I can only guess that for the AU-D707X it is the same. You shouldn't increase the bias just because you feel it should be more.

The AU-D11 II runs very cool when set to 20mV (for each of 4 readings) - this is as it should be.

Hyperion thanks for suggestions. Yes i have adjusted 20mv for all four pairs. Amp runs cool. Sounds perfect. Just one confusion... The hot ground adjustment is not stable. What should be done to achieve 0 at hot ground.
 
What should be done to achieve 0 at hot ground.
There is nothing you can do about this, it is an unattainable setting - just set it as close as you can to zero, however it will wander about quite a bit.

Later iterations of this design address the issue to a considerable extent, I own 3 different Sansuis with this design and they all do it to a greater or lesser degree. (AU-D11 II, B-2102, AU-X701). The AU-α907Limited I recently looked at based on the same basic design, was very good indeed in this respect.
 
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Have I misunderstood something. Thought/almost certain the AU-D907 series were the domestic version of the AU-919.
 
Have I misunderstood something. Thought/almost certain the AU-D907 series were the domestic version of the AU-919.
You got it right,.The AU-D907 is the Japan market version of the AU-919. In this thread the person that originated it was not sure if he should buy an AU-D707X or an AU-D907X. Some times in this forum the users make brief statements when it comes to mention model names and this could have caused a confusion. The amplifiers they are talking about in this thread are actually quite different from the AU-919, but very comparable to the AU-D11 II.
 
Have I misunderstood something. Thought/almost certain the AU-D907 series were the domestic version of the AU-919.

You are quite correct. Just me being lazy - I couldn't be bothered to write 907KX, 907MR, 907MRX, 907DR etc.:rolleyes:
 
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Apologies for the alarm bells. Been trying to pickup a AU-919/AU-D907/AU-X... for a while, on that Japanese auction site.
Whenever I see 907 the brain goes into auto-correct
 
707x nudies
 

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Nice amplifiers. The inside of the wood side panel was also finished!. May be you can look at this thread to see if you can rejuvenate the front panel a bit. There may be other tricks known by others.
Enjoy!
 
There is nothing you can do about this, it is an unattainable setting - just set it as close as you can to zero, however it will wander about quite a bit.

Later iterations of this design address the issue to a considerable extent, I own 3 different Sansuis with this design and they all do it to a greater or lesser degree. (AU-D11 II, B-2102, AU-X701). The AU-α907Limited I recently looked at based on the same basic design, was very good indeed in this respect.
Thats quite informative. I have another question in my mind. My current bias settings are not perfectly synchronized. Is it very necessary to achieve exact 20mv on all four points?
I can't adjust exact mv through stock trim pots. Should i use multiturn trim pots ?
 
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