TOPIC:

I have the 88A connected using balanced cables. The 88A is configured for 8V output. There is a slight hissing sound coming from the speakers. While it is not noticeable from the primary listening spot, I would still like to understand whether there are steps I can take to reduce or eliminate the hiss. I have followed the calibration procedures to the letter, paying close attention to making sure both output volume and input gain are adjusted properly in the DLCT. In other words, I don't think the hiss is being caused by a procedural error on my part.

The only configuration option I have, as far as I know, is the output voltage, which I could reduce from 8V to 4V. It is not clear to me whether this change will make things better or worse. According to the manual, I will lose 6dB in output volume. And, of course, I would need to re-run the measurements. Can someone who understands the relationship between the output voltage and noise from the speakers comment on whether changing to 4V output is likely to make things better or worse?

BTW, my speakers are reasonably efficient (90dB), but not overly efficient.

It might help to determine where the hiss is coming from. Have you tried unplugging your receiver and everything upstream of the DSP to see if the hiss is going away?

In fact I would unplug everything. Leave only your amps connected to the speakers and turn them on with no input. Is there any hiss? If not, then plug in your DSP. Does it start hissing then? Be sure to turn off the amp before making or breaking any connections, BTW...

Once you find out which component is creating the hiss, it may be easier to find out how to solve it. I suspect that lowering your output voltage will only make it worse because then you will have to turn up your amps that much more to compensate. But I could be wrong. You may have an EQ setting off. Maybe your highs are boosted too much. Start by isolating the component and then work from there.

I have three possible sources of the noise: a Marantz 8801 pre-pro, the 88A, and an Emotiva XPA-7 power amp. I turned off the 8801, and there was no change in the noise. I turned off the 88A, and the noise volume went down considerably, but didn't go away completely. I could replace the balanced connectors with un-balanced connectors as a final test, but this would not be very easy. As I said in my original post, the noise is low enough that I don't hear it at the MLP, so if there are no other suggestions, I think I will live with it.

I guess it is also possible that the balanced wiring into the Phoenix blocks could be causing an issue, but I was very careful, and think my workmanship is good.

Lower the output volume of the 88a, and raise it on your Prepro. Also, maybe go unbalanced to 88a (that Marantz Prepro had junky balanced outputs) and balanced from
88a to amp. Also, Emo amps tend to have high gain and older ones weren't 6dB lower gain from the balanced outs. So unbalanced may be a better way to go for you.

May be worth experimenting, thanks.

@ Jerry,

8Vrms is really high (20dBu which is more ProAV levels), in a typical home theater setup (unless it's a sub), we don't see how you can easily get an optimized gain structure with this knowing you'd have high sensitive drivers (i.e. don't need much level at all). Our guess is somewhere down the chain (knowing the high level of 8Vrms compared to typical sensitivities of amplifiers), one amplifier has lower levels and you're therefore running close at a poor SNR ratio configuration. Just a guess..

What DS21 is suggested is exactly what we'd do.
1) Put your unit in 4Vrms or lower your levels.
2) Just raise the level of the amplifier.

DevTeam

Thanks for confirming DS21's recommendation. It is certainly something that is relatively easy to try, and I plan on doing exactly that early this week. I will report back the results of my test.

I have re-configured the 88A for 4V output on balanced connections, reset to factory defaults, and re-run the measurements. There is no change in the very slight hiss from the speakers. I don't feel that the issue is significant enough to try switching to un-balanced connections, which would be a significant project.