CA1000 and tantalums

[Trnsfmr]

Hi, I usually am on the Sansui thread, but occasionally rebuild a Yamaha or two.

I am rebuilding a CA1000 and have noted that it has tantalum caps in the signal path. That would figure, as Tantalums were new in '73 and design engineers wanted to use the coolest new parts. Over the years, though, it's been found that tantalums sound terrible, even worse than disc ceramics and bi-polar electrolytics.

So, needless to say, I have replaced all the signal path tantalums with Mylars, or with a mylar and electrolytic in parallel for the one that was 33uf.

Any body else have experience with this? The CA1000 was considered a great sounding amp for its time, what about with the tantalums replaced?

 

[jheu02]

I replaced the tants in my CA-800 with film or low-leak (UKL) 'lytics. Sounds great to me.

 

[Trnsfmr]

Were you able to listen to your CA1000 before you replaced them? Do you have any sense of a before and after?

 

[jheu02]

Shortly after getting the amp, I heard a "frying bacon" sound which was the micro switches on their way out. So, though I did listen to the amp on tantalums, it was not for long and several years ago. When I went about the restoration, they were removed since I was in there anyway. The most recent iteration of the restoration was a teardown and physical cleaning of the switches, replacement of the variable loudness pot, and replacement of the small signal transistors like the 2SC458s and their compliments.

The sound is very detailed now and absolutely no more scratchiness. Dead quiet too.

 

[ConradH]

AFAIK, tantalums were around way before '73. The old ones tend to break down and leak or get noisy more than the newer ones. In theory, if they're large enough that no signal voltage appears across them, they shouldn't affect the sound. In reality, I always get 'em out of there and often the sound quality improves.

 

[gslikker]

I did see unlinear behavior on one type of old (NOS) drop shape tantalums I have. The LCR meter did not reveal it but the huntron tracker did. Although "measuring" method probably was invalid. I did put pictures somewhere on AK

 

[Trnsfmr]

Thanks for your interesting experience guys. I also found while rebuilding this CA-1000 that it has two bipolar caps in the signal path, on the amp driver board. I still have not found an actual schema for the CA-1000 but am looking at a CR-1000 which seems to have the same schema except for the Class A.

C601 is the input coupling cap to the driver board, and C603 is the cap to ground in the feedback circuit to the inverting side of the differential pair. Both of these caps will have a huge affect on sound quality. C601 is a 2.2uf and I replaced it with a Mylar 4.7uf. C603 is 47uf, and I added a 4.7 uf Mylar in parallel with it.

In my opinion the only thing worse than a bipolar for sound quality is a disc ceramic or tantalum.I don't know so much about the history of Tantalums, but didn't they either get improved, or available in reduced size or cost, or something, around 1970? There were a lot of designers who put them in audio gear around that time, and the results were uniformly horrible.

I used to have a little Sphere 16 X 4 mixer that had tants everywhere in it, and it was really bad. It sounded flat and lifeless. Sphere had a reputation for excellent sounding pro gear. I replaced every tantalum in it and it was then studio quality sound, like any other Sphere mixer. Huge difference.

GSlikker I would be real interested to hear about your testing method.

 

[avionic]

http://www.analogalley.com/m_yamaha.htmery Very HQ pdf files.

 

[gslikker]

@Trnsfmr: Not really a method...I just found a visual proof of a real bad tantalum. Note it was tested using low frequency low impedance AC current. Here are the pictures of the test. http://members.quicknet.nl/gerard.slikker/badtantalum.htm

As I have a lot of metal style tantalums, I use them anyway. An interesting read on this would be post 27, here http://www.electro-tech-online.com/threads/tantalum-capacitors-in-audio-applications.37619/page-2

Remember , in audio there is a lot of hearsay, so do not hesitate try things yourself (in old amps, you might encounter the so-called have-to-go transistors good and other ones bad....).

Now anybody has then highly regarded high-end seventies preamps full of tantalums, they are worthless so put them on my doorstep...(and I replace the small ones using films, too....)