Cable capacitance with NVA preamp

[Giubanix]

Looking for any thoughts on a problem I seem to be having with an NVA P90 passive preamp.

I just received the P90 today, so I'm still trying to track down the cause, but I'm getting some light distortion when everything is hooked up. Apologies in advance, but this needs a rather long winded explanation...

I wanted to use the P90 because my hearing is slightly quieter in my left ear than my right. Not so much that I'd normally be aware of it, but listening on headphones, any time there are centred vocals, it's obvious that the vocal is shifted a little to the right, so I wanted to use the P90's dual volume controls to drop the right channel just enough to have everything properly centred again.

I've got three headphone amps, so the P90 seemed ideal - a pre out to each headphone amp, allowing me to correct for my hearing imbalance, plus a tape out to the main amp, which I don't use too much nowadays, having started
using 'phones probably 90 percent of the time.

At first I connected my rega dac to the NVA's direct input. With it connected like this, there was really obvious distortion if I switched to any other input (the direct input bypasses the source selector, so you hear the direct input playing regardless of the input switch position). If I remove the cable from the tape output to the main amp, the distortion seemed to disappear, but after a bit more listening, I can hear that there's still some light distortion, just a kind of subtle fuzziness that crops up on a couple of tracks I've listened to so far. The fuzziness is gone if I connect the dac straight into the headphone amp for comparison.

I know that NVA recommend using their own cables with all their products, so I'm wondering if the capacitance of the interconnects I'm using is could be the problem, or am I just trying to do something that's likely to result in distortion regardless of the cables used?

The interconnects are QED Performance Audio 2 (1 to each headphone amp) and a Chord Cobra Plus from dac to P90 and P90 to the main amp. Also, the distortion is there whether the amp is on or off.

I'll contact Richard at NVA to ask his advice of course, but I wanted to have a fiddle around first to make sure I'd tried every possible combination before doing that.

Any advice from people here would be appreciated in the meantime. :scratch:

[Marco]

Hi Ian,


I'll contact Richard at NVA to ask his advice of course, but I wanted to have a fiddle around first to make sure I'd tried every possible combination before doing that.


Just in from the man himself (RD):


The direct input is for use as a single source and as it is always in circuit if you connect other inputs then it interacts with them. Sometimes this if fine sometimes it is not, it sounds like the DAC is screwing up everything else. Answer multi source then ignore direct, single source use direct. I thought everyone who has bought from us would know this before buying.

All direct does is give you best from single souce as it takes the selector switch out of the signal path.


If you have any other problems, he's asked you to contact him directly, or via his forum: http://thehifisubjectivist.noadforum.com/index.php

:)

Marco.

[Giubanix]

The dac is the only source connected at the moment. I did have a phono preamp connected to another input at first, but removed it when I started trying out other methods of connection. I've tried the dac into the cd input as well as the direct. Doesn't seem to make any difference.

The fuzziness is subtle and I can only hear it on the odd piece of music here and there, but if I put the dac straight into the headphone amp and listen to the same bit of music again, the difference is clear, even with my dodgy hearing.

I'm still listening to see if I can find any common denominator between the bits of music that seem to highlight the problem. Will contact R if I have no success in the next day or so.

[Reid Malenfant]

Are you sure it isn't the CD itself? I have quite a few CDs where the mastering leaves a lot to be desired :(

Once you get a sufficiently open system you'll start hearing the recording much more clearly, this often leads to disappointment :eyebrows:

I'm pleased I generally listen to music that isn't exactly commercial, so while I can hear CDs which have run out of headroom, they are not that common in my music collection thankfully.

[Giubanix]

Are you sure it isn't the CD itself? I have quite a few CDs where the mastering leaves a lot to be desired :(


The first recording I noticed it on, was a track from the Chesky HiFi Test and Setup CD. I guess all the music tracks on that disc should be of pretty high quality as far as mastering goes. Heard it when some backing vocals came in behind the main vocalist. Then I heard an obvious distortion on another track from the same disc featuring an upright bass soloist. It distorts a bit on a couple of loud plucks of the strings. Sounds perfectly clean straight from the dac.

I'm quite certain that the problem is entirely to do with my setup, not the P90, just want to determine exactly what it is and find a way around it, because I really want to have the balance adjustment for the headphones since I listen that way most of the time now.

[MCRU]

Looking for any thoughts on a problem I seem to be having with an NVA P90 passive preamp.

I just received the P90 today, so I'm still trying to track down the cause, but I'm getting some light distortion when everything is hooked up. Apologies in advance, but this needs a rather long winded explanation...

I wanted to use the P90 because my hearing is slightly quieter in my left ear than my right. Not so much that I'd normally be aware of it, but listening on headphones, any time there are centred vocals, it's obvious that the vocal is shifted a little to the right, so I wanted to use the P90's dual volume controls to drop the right channel just enough to have everything properly centred again.

I've got three headphone amps, so the P90 seemed ideal - a pre out to each headphone amp, allowing me to correct for my hearing imbalance, plus a tape out to the main amp, which I don't use too much nowadays, having started
using 'phones probably 90 percent of the time.

At first I connected my rega dac to the NVA's direct input. With it connected like this, there was really obvious distortion if I switched to any other input (the direct input bypasses the source selector, so you hear the direct input playing regardless of the input switch position). If I remove the cable from the tape output to the main amp, the distortion seemed to disappear, but after a bit more listening, I can hear that there's still some light distortion, just a kind of subtle fuzziness that crops up on a couple of tracks I've listened to so far. The fuzziness is gone if I connect the dac straight into the headphone amp for comparison.

I know that NVA recommend using their own cables with all their products, so I'm wondering if the capacitance of the interconnects I'm using is could be the problem, or am I just trying to do something that's likely to result in distortion regardless of the cables used?

The interconnects are QED Performance Audio 2 (1 to each headphone amp) and a Chord Cobra Plus from dac to P90 and P90 to the main amp. Also, the distortion is there whether the amp is on or off.

I'll contact Richard at NVA to ask his advice of course, but I wanted to have a fiddle around first to make sure I'd tried every possible combination before doing that.

Any advice from people here would be appreciated in the meantime. :scratch:

why post at all as it's not fair to highlight a problem with someone's gear in public when you should ask the maker first surely? :)

[Giubanix]

why post at all as it's not fair to highlight a problem with someone's gear in public when you should ask the maker first surely? :)

Actually, I did regret posting for that reason, I just didn't think first. I was hoping someone would point up something that would avoid me having to contact Richard to have him waste his time dealing with some silly mistake on my part. As I said in a prevoius post, I'm sure the issue is nothing to do with the NVA unit, but something to do with my other gear.

After a bit more investigating, I've found that for some reason I get distortion when I connect the tape out to my Yamaha amp, which I've been using because it has a remote for the volume. When I connect it to my old Cyrus Straight Line instead, there doesn't seem to be any distortion, so it looks like the problem lies with the Yamaha amp somehow.

I'm perfectly happy if Marco wants to delete this thread for the above reason.

[Marco]

The decision is yours Ian :)

Either way, I think you should speak with Richard.

Marco.

[Giubanix]

The decision is yours Ian :)

Either way, I think you should speak with Richard.

Marco.

Well, I've switched back to the Cyrus amp and from what little listening I've had time to do so far, the distortion seems to be gone. For some reason, connecting the P90 tape output to the yamaha amp caused the distortion to appear on the headphone amps if the yamaha was in standby or switched off completely. If I switched the yamaha amp on, the distortion disappeared. No such problem with the Cyrus.

I was leaning towards going back to the Cyrus anyway, since I liked the extra weight to the bass compared to the yamaha. I only bought the yamaha because I wanted a remote control, but since I don't listen on speakers very much now, the lack of remote is less of a problem.

It definately seems like the problem was with the yamaha though. I'll drop Richard an email tomorrow to see if he has any idea why the yamaha amp would add distortion, but it clearly isn't an NVA issue.