Hi
I recently purchased a Saansui TU-9900 tuner and I am impressed. It is a great receiver ( the best I have come accross )but the audio electronics seem to let it down slightly. But I thought I can have a go at that part!
Initially I replaced all the electrolytic capacitors with ones of similar values and found an improvement.
However I found that the sound was thin in the base, light on transients and a little confused on complex passages. I guessed that the power supply reservoir was insufficient and increased the capacitance to 1000uf per rail. Things improved. I then increased in increments and found that the transients were there, the base firmer and no confusion on complex passages at 3000uf/4000uf per rail.
I also added polystyrene bypass capacitors ( 0.047uf )and that cleaned up the treble.
The sound is now very good. All I lack is some soundstage and imaging and I am hoping replacing the ic's with more modern ones will provide that.
I initially trawled diyaudio and found some threads and then I was directed to this thread by Netlist ;
http://www.diyaudio.com/forums/showthread.php?s=&threadid=46179
It explains how to change the opamp for a more modern op amp - I plan to do that shortly.
That's all the changes planned as it sounds so good already - better than my FM4 which I have liked.
Its great to listen to.
Don
I recently purchased a Saansui TU-9900 tuner and I am impressed. It is a great receiver ( the best I have come accross )but the audio electronics seem to let it down slightly. But I thought I can have a go at that part!
Initially I replaced all the electrolytic capacitors with ones of similar values and found an improvement.
However I found that the sound was thin in the base, light on transients and a little confused on complex passages. I guessed that the power supply reservoir was insufficient and increased the capacitance to 1000uf per rail. Things improved. I then increased in increments and found that the transients were there, the base firmer and no confusion on complex passages at 3000uf/4000uf per rail.
I also added polystyrene bypass capacitors ( 0.047uf )and that cleaned up the treble.
The sound is now very good. All I lack is some soundstage and imaging and I am hoping replacing the ic's with more modern ones will provide that.
I initially trawled diyaudio and found some threads and then I was directed to this thread by Netlist ;
http://www.diyaudio.com/forums/showthread.php?s=&threadid=46179
It explains how to change the opamp for a more modern op amp - I plan to do that shortly.
That's all the changes planned as it sounds so good already - better than my FM4 which I have liked.
Its great to listen to.
Don
This is the mods they did on to make it much better
http://www.fmtunerinfo.com
Sansui TU-9900 (1974, $570, front 1, front 2, back) search eBay
The TU-9900 has 5 gangs and 3 IF filters, two of which have 4 stages rather than a typical ceramic filter's 2 stages, so it's like 5 filters if we count them in the traditional fashion. The TU-9900 is solidly built and our panelists who have used it praise its sound quality and DX performance, but David "A" rates it well below the TU-X1 for sound even though Eric (a non-audiophile) felt that it was "close enough." Our panelist Bob did some mods on his: "The TU-9900 has incredible potential. At first, it just did not open up sonically, but after trying a bunch of things, I nailed it. It is there now. I removed tantulum caps in the signal path. The big gain was replacing the TA-7136P op-amps, which were limiting the sonics in a big way. They are inline 7-pin units, so I had to put in 7-pin inline sockets, and custom modify a standard single op-amp to solder onto a 7-pin header. It was about three hours' work just to make the replacements, but well worth it. I also added six polypropylene caps, along with new power supply caps. With all the mods, the TU-9900 may be one of the top all-around tuners ever built. I have talked to many people who feel that a stock TU-9900 just smokes about everything out there for distant reception capability. If your unit does not astound you, it is broken or out of alignment. It will easily surpass a stock KT-8300 by a decent amount. I think the sonics were the holdback on the 9900s, but not anymore." The TU-9900 is very sensitive and selective in stock form, better than just about any analog tuner that commonly sells for under $500 on eBay. Because it uses LC filters that are encased in metal and plastic enclosures, no one should buy a TU-9900 expecting to replace the filters. The TU-9900 offers many nice features, including a calibration tone and scope outputs. On eBay, the TU-9900 usually sells for around $450-625 but anywhere from $380-800+ is possible, depending on condition, the seller's track record, and fluctuations in demand. [DA][BF][EF]
http://www.fmtunerinfo.com
Sansui TU-9900 (1974, $570, front 1, front 2, back) search eBay
The TU-9900 has 5 gangs and 3 IF filters, two of which have 4 stages rather than a typical ceramic filter's 2 stages, so it's like 5 filters if we count them in the traditional fashion. The TU-9900 is solidly built and our panelists who have used it praise its sound quality and DX performance, but David "A" rates it well below the TU-X1 for sound even though Eric (a non-audiophile) felt that it was "close enough." Our panelist Bob did some mods on his: "The TU-9900 has incredible potential. At first, it just did not open up sonically, but after trying a bunch of things, I nailed it. It is there now. I removed tantulum caps in the signal path. The big gain was replacing the TA-7136P op-amps, which were limiting the sonics in a big way. They are inline 7-pin units, so I had to put in 7-pin inline sockets, and custom modify a standard single op-amp to solder onto a 7-pin header. It was about three hours' work just to make the replacements, but well worth it. I also added six polypropylene caps, along with new power supply caps. With all the mods, the TU-9900 may be one of the top all-around tuners ever built. I have talked to many people who feel that a stock TU-9900 just smokes about everything out there for distant reception capability. If your unit does not astound you, it is broken or out of alignment. It will easily surpass a stock KT-8300 by a decent amount. I think the sonics were the holdback on the 9900s, but not anymore." The TU-9900 is very sensitive and selective in stock form, better than just about any analog tuner that commonly sells for under $500 on eBay. Because it uses LC filters that are encased in metal and plastic enclosures, no one should buy a TU-9900 expecting to replace the filters. The TU-9900 offers many nice features, including a calibration tone and scope outputs. On eBay, the TU-9900 usually sells for around $450-625 but anywhere from $380-800+ is possible, depending on condition, the seller's track record, and fluctuations in demand. [DA][BF][EF]
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