2 ZA3's with different max amplitude?

[erkall]

Hi,

Recently started building my Fosi system, ZA3, ZD3, Elac DB63.

I found the audio to be clean but weak and lacking substance and not very exciting. So I decided to add the second ZA3 as recommended by many reviewers.

Now I feel the audio has more substance and less of the dullness it did before and listening became a lot more pleasurable, which is great.

However, I can hear difference in audio and amplitude between the L and R channels . They are both set to max level and connected through XLR.

I was a little suspicious when the second ZA3 unit came in a different box from the same dealer, supposedly brand new. First one I got had a nice white box, this second one came in a pretty cheap dark coloured box, this tells me they might be from different series?

Is it possible to have such audible differences from the same unit and if so why is that? Is there anything I can do other than ask for a replacement?

Thanks

 

[RudydG]

To be sure, can you switch amps to eliminate all the other factors? wiring, power supply? In doubt I would ask for an exchange.

 

[Massimo]

I completely understand your concern, because I went through something very similar. I bought two ZA3 units on Amazon over a year ago, and in both cases they arrived in black packaging. I’m not sure whether the packaging has changed since then, but considering the new and very elegant white box of the ZP3, it’s quite possible that Fosi updated the product presentation over time. It wouldn’t be the first time they refined the packaging without changing anything on the technical side.

Over the past year I’ve put my ZA3 units through a lot of testing, including swapping different op‑amps: I tried Muses 02, Sparkos SS3602, and eventually settled on the Burson V7V. I kept the Sparkos on my V3 monos instead. During these tests I noticed that one of the two ZA3s played at a noticeably lower volume than the other.

After reporting the issue to Fosi Audio and running several checks with a multimeter, we found out that the problem was caused by an imprecise response from the potentiometer. Even though more than a year had passed since the purchase, Fosi replaced the entire motherboard without hesitation, so their support was excellent.

Before asking the seller for a replacement, I’d recommend doing a simple test: swap the two units while keeping the exact same cables and settings. This will immediately tell you whether the imbalance follows the amplifier or if something else in your chain is causing it. And make sure the XLR cables are fully seated on both ends — even a slightly imperfect connection can create channel imbalance.

 

[RudydG]

I just found out, that my 2 volume knobs (of different ZA3 batch), were not aligned correctly! one of the 2 was 1 teeth off. (you can pull the know off and reposition) Easy to check if you turn them both to their endstops, this is how I found out.

 

[Massimo]

perfect