Threshold Stasis 3, should I recap?

[marcomariutto]

Hello, I am the lucky owner of a Threshold Stasis 3 amplifier.
I love how it sounds, but I am aware it is getting old and some of its components (electrolitc caps in particular) might be out of specs due to aging.

Question for the experts:
Do you think I would gain something in terms of sound quality from a recap or would I only risk to negatively affect the sound?

Thank in advance for your suggestions,
Marco

 

[Zen Mod]

as I see it , there is not so much to choose ....... you can only delay a moment ....... unill you hear buzzing



recap it with decent quality caps , and enjoy in it next 15-20 years

 

[Eric]

I would agree - recap it before old caps cause problems that are harder to fix.

 

[marcomariutto]

Thank you guys for the suggestion.
One step at the time, I would start from the PSU.
I see it's using 2x15000uF 100V 85C capacitors.

Low ESR and long life is a must. I was also considering the option of going for a higher filter capacity (eg 22/33 kuF). For sure it would reduce 60Hz ripple and less voltage drop on the current peaks, but is it worth? I cannot see any real negative side effect aside from the fact that I might need a bridge rated for higher current (inrush current will be higher when switching on the main supply). Am I underestimating any risk/side effect?

 

[Zen Mod]

naah ........

just go for it

 

[marcomariutto]

) EPOCS, Vishay ?

 

[Zen Mod]

of these two - easier to get and/or cheaper

can't do wrong

 

[marcomariutto]

Ok, so the final choice is EPCOS 33kuF 100V 6mohm@100Hz 12000hrs@85degC. It's good stuff, a bit on the expensive side but I want the mod to last for many more years.
Also I am going to replace the bridge with a 400V 50Amp one.

I am gonna setup a scope and a dummy load to evaluate 60Hz noise amplitude and square wave response before and after the PSU restoration/upgrade. I am curious to see what the instruments say..

 

[Eric]

Just work carefully and methodically and you should be fine. Photograph EVERYTHING before you take parts out, it will save you headaches later on if you are replacing a large number of caps.

 

[marcomariutto]

Today I replaced two fuses that sits between the input board and the power section, and I immediately noticed that the volume is now more equal between the two channels (before one of the channel was +3dB higher than the other) and the mid-bass sounds more controlled and punchy.
Could just the replacement of a fuse give such an improvement?? The fuse itself looks ok.. maybe it's just my ears getting used to the amp..

 

[Zen Mod]

or it was oxide , either in fuse or between fuse and holder

 

[marcomariutto]

The fuse looks actually quite funky, like the conductor is not broken but it's been stressed...it's resistance is probably higher than it should be. The enigma is resolved!

 

[Zen Mod]

no actual enigma

fuses are parts which we need to exchange periodically , in critical positions

 

[Extreme_Boky]

or it was oxide , either in fuse or between fuse and holder

..."or between fuse and holder"

It happens all the time, especially with old equipment and spring-loaded fuse holders - ones that you twist-turn to lock - like in the TASCAM 85 that I just fixed for a friend of mine. The whole thing can even measure very close to okay, but as soon as you let some current run through (I'm taking 14A in case of this outstanding reel-to-reel machine...), it starts to arc due to oxidation. Tricky to fault-find.

 

[marcomariutto]

Replaced all the electrolitcs and set the bias to its correct level. It sounds suave.

 

[Zen Mod]