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In the Forum: Off Air Audio
In the Thread: TU-X1 setup
Post Subject: Some aged thoughts about TU-X1Posted by Romy the Cat on: 11/29/2008
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 drdna wrote:
Honestly for now, the character of the tuner is unobtrusive enough that I notice mostly the problems I have with the preamplifier and the electricity. However, I would be interested about what you had thought at this point to be modified (I recall your experiments before and comparing your two Sansui tuners before and after, but I wonder how you feel now some time later).

Well, in my experimental modified TU-X1 at I’s best time was able to get sound identical or virtually identical to my stock version. So, it might be recognized a failure of modification objectives. However, my experimental TU-X1 did not sound as good as my main TU-X1 in stock version – so go figure… My modifications were not really modifications, but just parts swapping in critical locations of output stage. In fact I did not see anybody propose any more or less making sense modification of TU-X1, like moving the automated gain control sensor behind the second filter, instead of having it before it. (This is why the tuner inclined for easy overload). Still, flipping the part on shell be very accurate as the parts that Sansui used in TU-X1 are very good. I for instance was trying to replace the PS filtering caps but after a while I put the original caps back – trios vintage top of the line Nichicon are extremely good. My attitude with my main TU-X1 is “do not harm” as I pretty much have no complains of frustration to it’s sound and I would be pity to loose what I have now from this tuner. I have some people told me about specific mods but none of them were able to describe to me the Sonic benefits they were able to get after their mods in the terms that I would consider not idiotic. I told them about it and they stopped recommend me the modes, I wonder why…

I sold my “experimental” TU-X1. My main TU-X1 now works together with quite modified Rohde & Schwarz tuner and decoder, offering practically identical sound but slightly different quietly of reception that all together boil down in the amount if background noise. Why do I mention the Schwarz? Because it is very nice for sake of reference if one would like to have tuner “modified” to have another then TU-X1 tuner with the very same sound – it always nice to monitor how far the modification take you forward or backward. The reason I say it because sometimes in future I am planning to have one modification done with my main TU-X1. I was thinking to replace the 10uF electrolytic cap right after detector and before the decoder with wet tantalum. They worked phenomenal in Schwarz. That is all that I consider for my TU-X1.

TU-X1_Circuit.jpg

Ok, what my main TU-X1 has different from the stock version - very few mods and they mostly logical. The out pots are bypassed – there is no need for them not to mention that they add output impedance to this tuner. The DC blocking capacitors after the out stage are bypassed as well. Those caps are not necessary as it has just 45mV before them - there is no need to block it. Even in my case what I have A/D processor after the TU-X1 the very minor DC is not a big deal as Pacific Microsonics has own DC canceling input bias. I also so not use (if I rember corectly) any resistors after the Sansui’s output op-mps. They are old and “slow” type op-mps  and they might drive load without any oscillation comforting resistors, at least I do not measured or heard any oscillation in my case with my cables. Still to be on a save side I would have there 20-50R resistor. (The originals R17 of 560R is shorted in my TU-X1 as I would like to have as low output impedance as possible). The last mod that I have is the change of output feedback resistor to get more voltage out of the tuner. My TU-X1 give I think 8-9dB more then stock version. It is just a freakishness of mine – I like all my sources to have similar output in order do not use volume control too much when I switch sources….
 drdna wrote:
If you know a specialist out in this area, then let me know. I was thinking to get the tuner aligned and have a local guy, Evgeniy, recommended to me to do it. However, I have not been unhappy with the sound to really want anyone to mess with the tuner at this point.
Alignment of a tuner by a person why knows what he does is absolutely necessary and never heard. In worst case you will have juts more selectivity and sensitivity. More sensitivity – less noise, I do not think you would complain. The aliment of front end, IF and setting the separation in AMX stage shell not mess anything with tuner if the person is knows what he does. It is also very good to have you aliment alignment technical locally as you certainly do NOT what to ship the tuner after it was aligned.

The Cat

PS: If some would find for me a source where I might buy those output op-amps I would appreciate it.

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