Amp for Acoustic Zen Crescendo 2 ?

You are correct Al as usual.  

@almarg ,

I have a question for you. The Lyngdorf does use a very small inductor and .47uf cap on the output just before the speaker binding posts. How important do you think the quality, sound wise, of the cap is in this position? Since the entire signal, it is in the signal path, is going through the cap I would think this is not a place to skimp on a $2 cap? 

This assumes ones thinks caps sound different. I do 😁

Hi Bill,

I’m one who certainly agrees that capacitors can sound different, to a greater or lesser degree depending on the circuit application, of course.

In this case I assume the cap is in parallel with the output, rather than in series, and therefore it may tend to be somewhat less critical than say a coupling cap that is in series with a signal. On the other hand, though, at 20 kHz a 0.47 uf cap would have an impedance of about 17 ohms (while having a proportionately higher impedance at lower frequencies), which means that within the audible frequency range its impedance is not high enough to be considered to be negligible in relation to the impedance the speaker presents to the amp.

So my speculative guess is that an upgrade stands a good chance of being worthwhile, but of course it’s hard to say with any kind of certainty.

Best regards,
-- Al

Thanks Al.

Here is why I ask. I mod lots of gear and usually hear differences. I have modified this unit removing those Wima .47uf caps at the output. I replaced them with some decent Jupiter HT caps. I did hear an improvement and that is fine. However, I then decided to add the new Duelund silver foil bypass caps .01uf. Ok, now the improvement is VERY noticeable. So much so I had to ask you this question. The improvement across the board is very obvious and good. Trying to get an objective basis for my subjective experience.

I loved the unit before the mod and now I am smiling even bigger. We read a lot about expectation bias and I wonder sometimes. I felt I was open minded during this mod. Right now am hearing a considerably improved sound. It is very easy to hear the differences, but I have to wonder why the builder did not try and improve on that Wima part. I know it costs etc...I looked inside the unit and that particular part/position just stuck out.

It never ceases to surprise me of the level of sound refinement and improvement that can be had on highly regarded and reviewed gear with just a couple of nice upgrades. Or is it expectation bias? 😕 

I have completed mods that I did not like and many that I have.  

Hi Bill,

Clever idea trying the 0.01 uf cap in parallel with the 0.47 uf.  That would presumably cause the filtering provided by the cap combo to become more effective at the RF frequencies corresponding to the switching that occurs in the output stage.  As you no doubt realize, as a general rule of thumb a smaller cap such as 0.01 uf will tend to act more purely like a capacitor at RF frequencies than a larger one such as 0.47 uf.

And I see no reason to doubt that the improvements you perceived were real.  Perhaps the reason is that the greater amount of RF garbage that was previously being put out by the amp had been finding its way to some other point in the system, or even some point earlier in the signal path within the same amp, resulting in effects at audible frequencies via intermodulation or AM demodulation or other such effects that can cause inaudible frequencies to have audible consequences.  Although I suppose it's also conceivable that the RF had been directly affecting the speaker's sonics in some manner.

Best regards,
-- Al