Leestereo's Restoration and Upgrade Of A Sansui AU-919

A while back, EW explained to me that the 919 was NOT completely Direct Coupled as advertised. If EW reads this then maybe he will chime in. I know the MC section isn't DC. I believe the main amp is. There are a few key places that are not and I would like to know exactly where. Those places need the best caps!
Anyone know where?
 
Essentially, the outputs of the all of the low level stages have a capacitor in the signal path, e.g., Flat Amplifer (see post #14), MM Amplifer (see post #15).
 
It looks like c43 & c44 are the 2 film caps to replace on the MM board. All electrolytics and black flags have been replaced. I just want the signal path film caps to be replaced. I have some 1.uF polycarbonate caps that would fit perfect. Can I just put those in there? You went to .47uF to 1.uF.
 
Yes, the C43/C44 film by-pass capacitors can be replaced with 1.0µF polycarbonate types. Replacing the C55/56 and C57/58 polarized capacitors in the output to bi-polar types will likely have a larger sonic impact than just replacing the film by-passes alone.
 
Yes, the C43/C44 film by-pass capacitors can be replaced with 1.0µF polycarbonate types. Replacing the C55/56 and C57/58 polarized capacitors in the output to bi-polar types will likely have a larger sonic impact than just replacing the film by-passes alone.
It's sad that electrolytics are in the signal path!:mad:
 
Lee, What do you think of this? When using one bipolar in the place of those two,...instead of using jumpers in those empty places,...use a high grade film very low value in it's place.:dunno:
Or maybe bypassing that bipolar with a film cap. Perhaps on the back side of the board?
 
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Lee, What do you think of this? When using one bipolar in the place of those two,...instead of using jumpers in those empty places,...use a high grade film very low value in it's place.
The output coupling capacitors are part of a RC high pass filter. For example, in the Flat Amplifier (with tone controls defeated), the F3 of the RC filter with the stock 50µF capacitance and 1.63 kohm resistance (R47/48 + R07/08 + R09/10) is ~1.95Hz (the pass band needs to be <5Hz to minimize phase shift in the midrange). Installing a film instead of the jumper, places it in series with the electrolytic capacitor and results in much lower effective capacitance (and increases the F3). For example, a 1.0µF film in series with the 47µF bipolar electrolytic capacitor results in an effective capacitance of 0.98µF and a F3 of 100Hz.
 
OK, I put 1uf polycarbonate caps in c43&44. The only difference in sound is the vocals are (maybe) a tiny bit clearer. The mids and highs may be a little softer. Thought you would want to know.
 
OK, I put 1uf polycarbonate caps in c43&44. The only difference in sound is the vocals are (maybe) a tiny bit clearer. The mids and highs may be a little softer. Thought you would want to know.

Thanks for the update, did you replace the polarized electrolytic pairs with bi-polar types, e.g., Nichicon ES?
 
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