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Old 4th December 2012, 01:57 PM   #1
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Default Question reg. Sansui Au-D5 mod

Picked up this working Sansui AU-D5 for cheap.

Does anyone know what the mod in the picture is for?
Large resistor between left - and left + and between right - and right + of A channel. Screwed on the back to the outside of the chassis. Both (resistor)clips show the following info:
Bosch 0 227 900 001
343
1,8

Thanx.
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Old 4th December 2012, 09:28 PM   #2
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Bosch Ignition Parts for Flat Four VWs
according to this ref. they are Bosch 0.9 ohm ignition coil ballast resistors suiting Porche 924, several Volkswagen models and other German vehicles from ca. 1980.

Why anyone would want to load their amplifier with such a virtual short, is beyond comprehension, if that is in fact how the resistors were configured in use. Perhaps this wasn't the case in actual use. A quick check with a DMM set to resistance would tell you how smart or not this addition was.
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Old 5th December 2012, 07:43 AM   #3
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Wink Soldering gone wrong...

Ian,

Thanx for the quick reply.

Just removed the bottom case and it looks like a lot of sloppy soldering was done down there. Maybe someone was trying to 'upgrade' the amp .

I'll remove the additions, clean up the sh#t and see what's left.

Thanx again. Always a joy to visit the fora.
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Old 6th December 2012, 08:29 AM   #4
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Oops, my fault. I've dismantled the thing (what a mess compared to my TEAC's).
Due to the excessive soldering, wiring and +/- marker indications(!) I mistakenly swapped ground and plus :-0. So the resistors are between the (star) ground and the speaker grounds. This evidently makes more sense than what I mentioned earlier. Would this be some sort of noise dampening?
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Old 6th December 2012, 08:48 AM   #5
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Serial connected with the load. They were certainly used to adapt the Qt of some particular speaker. I would take them off as it affects the damping factor of the amplifier.
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Old 6th December 2012, 08:55 AM   #6
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I don't think it has anything to do with noise. Often, we see people messing with reducing the damping factor of an amplifier by just such an inclusion. You can Google this or read an interesting article on variable damping factor by Rod Elliott on his ESP site. Take a look at fig.1b

I think Rod paints the picture fairly about the merits of reduced damping factor. It's often debated inconclusively but it's another effect to play with. Some love it and others can't see (or hear) the benefit of it. Your choice
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Last edited by Ian Finch; 6th December 2012 at 09:00 AM.
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Old 6th December 2012, 08:57 AM   #7
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Hello friendlypersonwiththeunpronouncablename,

Thanx for the quick reply and the info.
Only waiting for replacement binding posts now. The twist-n-lock variety used on this amp really s#ck. Hope to have the thing up and running before Christmas.

Adam.
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Old 6th December 2012, 09:00 AM   #8
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Ian,

Will read Rod's article. Thanx. I'm always pleasantly surprised with the help and info one gets on this forum. Never read any "STFU" or "R U STPD or something" here which are rampant on other fora.

Regs,

Adam.
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