[GeoD]

I was wondering if someone could help shed some light on a situation I'm experiencing. I just picked up a RudiStor NX-33 amp and have it running off of a Pico for my source. I initially plugged my phones in the SE jack and get a pitch black background, all the way up until full volume, then I hear the faintest background noise. Immediately as soon as I changed to balanced, volume off on the amp, I experience more background noise than the SE output.

Would this have to do with my source being SE and it's converting to balanced output? Would getting a balanced source fix this?

I'd like to think it's not a cable issue, especially when it sounds pitch black when I run it off SE at the volume setting I'd normally listen at.

My headphones are low impedance Denon's, would that have anything to do with it?

Any input would be greatly appreciated.

The amp is incredible I must say, completely opens up the Denon's in a way the little Pico simply couldn't. I just sat here listening in awe for the past 4 hours, hearing new things in songs I thought I knew inside and out. I was completely floored how this amp took control of the bass. To me, the RudiStor highlights how good the Pico DAC is. I want to pair this up with a Lavry DA-11 if I go fully balanced.

Thanks in advance.

 

[aasat]

Yes, it's normal when you use SE, ballanced source fix this
In ballanced mode signal is more dynamic and highest volume level.
also you don't hear faintest background noise.

I never tired use IC SE to ballanced, probably this fix this problem.

sorry for my poor english

Quote:

Originally Posted by GeoD /img/forum/go_quote.gif I was wondering if someone could help shed some light on a situation I'm experiencing. I just picked up a RudiStor NX-33 amp and have it running off of a Pico for my source. I initially plugged my phones in the SE jack and get a pitch black background, all the way up until full volume, then I hear the faintest background noise. Immediately as soon as I changed to balanced, volume off on the amp, I experience more background noise than the SE output. Would this have to do with my source being SE and it's converting to balanced output? Would getting a balanced source fix this? I'd like to think it's not a cable issue, especially when it sounds pitch black when I run it off SE at the volume setting I'd normally listen at. My headphones are low impedance Denon's, would that have anything to do with it? Any input would be greatly appreciated. The amp is incredible I must say, completely opens up the Denon's in a way the little Pico simply couldn't. I just sat here listening in awe for the past 4 hours, hearing new things in songs I thought I knew inside and out. I was completely floored how this amp took control of the bass. To me, the RudiStor highlights how good the Pico DAC is. I want to pair this up with a Lavry DA-11 if I go fully balanced. Thanks in advance.

 

[shamu144]

Hi GeoD,

Sorry to hear that

Your question is indeed very interesting for all NX-33 owners.

Well, I am no expert, but like aasat mentions, it could be due to the amplificated noise introduced by the internal splitter opamp used to balance the signal received through the RCA inputs.

In this case, maybe using a true balanced source would get rid of this background noise.

Another option, if you want to stick with an unbalanced source, would be the use of a high quality RCA to XLR transformer to balance the signal. I have been seriously considering this option myself to use with my Sony SACD player, before finally moving to a computer based playback system and going the full balanced road.

Using my first USB DAC (a Keces DA151 mk2) with unbalanced RCA outputs, I remember I could already easily detect some background noise when plugging my Creative Aurvana Live (clone of Denon D1001, with exact same impedance at 32ohms) into my NX-33 SE outpt. I am surprised you don't notice that as well in SE mode with your Denon. I have to say I never detected any background noise before with my other headphones in SE mode (K501 and HD650, not even ATH-AD900)...

I will listen with my Lavry DA11 in balanced mode and let you know if I get noise in SE mode with the Creative Aurvana Live. However, I guess in this case the signal has to be converted from balanced to unbalanced at some stage to feed the SE output, and that could affect the results as well. I have unfortunately no low impedance balanced headphone to sort it out.

My gut feeling is that usually, balanced topology is more indicated for high impedance phones (providing more voltage swing) and in this specific case, the balanced topology is degrading the "already insufficient" NX-33 response when using RCA inputs with low impedance headphone.

It would be also very interesting to know how other RudiStor model (i am thinking to the NX-03 and the RPX-100) handle low impedance phones (32 ohms and below) when using the RCA inputs.

Oh, and yes, I definitely second your choice for the Lavry DA11

 

[josep]

GeoD,
The noise you hear come from the opamp circuit on the balanced input side of your amp, taking the signal from SE. There is an easy solution to this, with higher perfomrance/SQ to be had: use a transformer on this inputs. You may order a couple of Lundhal/Jensen, or buy something like that...
http://www.nextag.com/Artisoft-ART-D...C7484EB316C6F6
... if you are not handy with a soldering iron or do not want to open/modifiy your Rudistor.
Aka "Isomax":
http://www.cs1.net/products/jensen_t...ers/PC-2XR.htm

 

[musicman59]

Use a pair of these Cardas adapters to connect your single ended source to the balanced inputs in your Rudi.
Cardas - Male XLR to Female RCA Adapter/pair - Connectors

 

[SleepyOne]

The cardas will work but note it will has some effect on the sound.

 

[GeoD]

Thanks for all of the answers. It's a relief to know the noise is because of the SE input and balanced out. I'll probably skip any temporary solution for the time being as I'm pretty sold on going to a fully balanced source ASAP. The noise isn't audible once the music is playing, I was just curious / concerned.

musicman59 - What source are you using? It looks as though we have a very similar setup with your modded D2k's and NX-33. Are you pleased with that combo compared to other headphones and amps you have? I'm pretty impressed by how the amp shows the Denon's who is boss, especially when using the balanced output.

Thanks again for all of the replies everyone. Cheers.

 

[shamu144]

Unfortunalely, the background noise is still audible with my Creative Aurvana Live despite the Lavry beeing connected to the NX-33 through the balanced inputs, so going the full balanced road nor the use of transformers will make that disappear.

However, the noise is not as obvious as I remembered, and you will have to pay attention to hear it. But it is possible that the balanced mode contributes to increase it. The Creative Aurvana Live are 32 ohms and 103dB/mw... Headphones with lower impedance and/or higher sensitivity are likely to produce background noise with the NX-33.

Since it doesn't seem to be a major concern for you (but I understand it might be for others), I would stick with your current set up untill you upgrade to the Lavry

 

[GeoD]

Quote:

Originally Posted by shamu144 /img/forum/go_quote.gif Unfortunalely, the background noise is still audible with my Creative Aurvana Live despite the Lavry beeing connected to the NX-33 through the balanced inputs, so going the full balanced road nor the use of transformers will make that disappear. However, the noise is not as obvious as I remembered, and you will have to pay attention to hear it. But it is possible that the balanced mode contributes to increase it. The Creative Aurvana Live are 32 ohms and 103dB/mw... Headphones with lower impedance and/or higher sensitivity are likely to produce background noise with the NX-33. Since it doesn't seem to be a major concern for you (but I understand it might be for others), I would stick with your current set up untill you upgrade to the Lavry

Thanks for the reply and helpful info once again.

The Denon's are 25 ohm & 106dB/mW so it probably will produce a tad more than the Creative Aurvana Lives. I don't mind the noise it produces now, once the music is going you definitely do not notice. If it improves even a little bit, I'd be pleased. I'm just trying to learn as much as possible about my equipment. I told myself what I'm hearing is the power running wild on this beast of an amp,

For those with the NX-33, where do you set your volume knob for regular listening? It's significantly lower than where I set my Pico, which is why I'm asking.

Thanks again for the replies.

 

[musicman59]

GeoD,
For my RP010B I am using two different sources. One is a Squeezebox going digitally to a Monarchy Audio DIP to then digitally to a Threshold DAC 1e. The second source is a Teac VRDS-10 CD transport with GNS mods going digitally to the Threshold DAC. From the DAC I am going balanced to the RP010B.

The second system has also a Squeezebox but going digitally to a Genesis TimeLens and then digitally to a Wadia 27 DAC and the second source is a Wadia 20 CD Transport going to the 27 DAC. From the 27 I am going single ended to the RPX-33.

The second system has better sources but I cannot use the RP010B in it due to lack of space where the electronics are in my living room.

The RP010B is in my bedroom system where I listen to headphones more.