I will be testing this tonight with a Topping DAC and SMSL VMV D3.
Cen.Grand 9i-906 "Silver Fox"
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Long report below but below is my findings (please note I am definitely not a person who listens to measurements).
Items used : Cen.Grand 9i-906 "Silver Fox", Chord Qutest (3V, iFi iPower Low Noise PSU), SMSL VMV D3, Thieaudio V16 Divinity, QDC Anole VX, IEC60318-4 (711) Ear Simulator.
Listener age : 23 & 20. I felt that this may be relevant as we may be more sensitive towards noise floors than some of the more senior people here.
I had a conversion about the noise situation with Cen.Grand and their response is roughly along these lines :
- The circuits weren't designed with the intention of chasing low noise. If low noise was chased during circuit design/implementation, part selection etc, the numbers & measurements can look very good but the actual sound may not be desirable.
- The numbers provided (I personally have no idea if these are high or low) are the Silver Fox would normally sit at 60-80uV with balanced inputs using RCA inputs will increase that to over 100uV due to the unbalanced to balanced conversion. The conversion circuit is implemented because they wanted the amp to be powerful enough to power everything, regardless of signal input, and are willing to sacrifice the noise aspects for this.
- Adding resistors in series to the circuit shouldn't change the frequency response (was not specified whether this is amp side or transducer side). Only gain will be different.
With their response in mind, I went and tested the two different input methods of XLR and RCA, even with no DAC input connected provided the same results so feel free to verify for yourself. Note that this is with no audio playback and the noise floor is inaudible during playback when on the quieter options.
- XLR is definitely the superior input method, with noise floor reduced across all different modes (BTL, Parallel, Active.G, Normal).
- Noise floor is much lower when switching from RCA 1 (no input) to RCA 2 (Qutest input).
- BTL is fairly consistent in having low noise floor, however this is no longer the option with the lowest noise floor.
- BTL on XLR inputs has the same noise floor as the Qutest.
- BTL doesn't seem to change noise floor with volume changes, while the other 3 do on RCA. I will update this again when I test XLR again.
- Using 2v or 3v on the Qutest did not make an audible difference to me, neither did using powerbank as supply. It is still not dead silent as it can be.
- Parallel has become the mode with the lowest noise floor when using XLR inputs, and is definitely quieter than BTL on XLR/RCA (which I previously mentioned to be the most quiet RCA input mode).
- I can barely notice a difference between the noise floor on XLR + Parallel between the different Impedance modes. This probably is as quiet as it gets on High Impedance, essentially inaudible. Only when going from Low Impedance 3 to High Impedance on Parallel can I hear a noise floor that shortly becomes inaudible after as my brain starts blocking it out. Within seconds, or could even be placebo entirely.
- Parallel has the highest noise floor on RCA inputs.
This by itself isn't an issue, given that there are the 4 different impedance modes available to reduce noise floor. However, given that the method of gain adjustment is to add resistors in series, this would change the output impedance, which in theory can potentially influence frequency response as well as damping factor and such. Therefore in order to verify the effects, a friend of mine measured our two IEMs (Thieaudio V16 Divinity via 6.35 SE & QDC Anole VX via 4.4 Balanced) using each different impedance mode while maintaining XLR + Parallel for the lowest noise floor.
Please refer to the graphs below :
Graph 1. Thieaudio V16 Divinity Frequency Response
Graph 2. QDC Anole VX Frequency Response
As it can be seen from the two graphs, there is quite a significant change going from High Impedance setting to any of the Low Impedance 1-3 settings. However, the differences between Low Impedance settings themselves then becomes relatively insignificant, especially between Low Impedance 2 & 3. Whether this change in frequency response is a good or bad thing is then subjective to your listening preferences as some may enjoy this altered sound (similar to why some enjoy tube amps).
How this will influence your specific transducer (headphone, IEM) will then depend on the impedance curve of that specific model. In the case of the Meze stuff though, impedance curve is flat as a ruler so there should be no changes in frequency response.
Lastly, given that the impedance does significantly boost which changes the damping factor (I believe ideally at least 8 is desired), I was concerned whether or not the headphone will then sound more sluggish or less dynamic, etc. This is something I personally place significant value on in my listening. Unfortunately there is no scientific method of determining this between the two of us, but using extremely dynamic test tracks Days of Thunder - The Midnight & Get Lucky - Daft Punk [feat. Pharrell Williams & Nile Rodgers], we did quick A/B testing between the modes and came to the same conclusion that as we progress down the Impedance modes, the Meze Elites indeed lost a bit of dynamic magic and the bass felt a bit weaker. This was most noticeable when cycling back from Low Impedance 3 to High Impedance. Note that this was not volume matched we do not rule out the possibility of placebo on the two of us.
However, I must note that this amplifier truly sounds amazing and works magic. I can already confidently say that the sound is better than of my Burson Soloist 3X GT (no modifications) + Supercharger 5A, but this is a comparison to be written later. RCA > Low Impedance 1 > BTL is still superior to the Burson here.
My final conclusions are therefore :
- XLR is definitely the superior input and one should definitely prioritize using this input if possible.
- High Impedance setting should be used ideally for maximum sound quality and no alteration of frequency responses.
- Sensitive IEMs are most definitely not recommended to be used with this amplifier which is quite a bummer, perhaps and IEMatch by iFi could help here?
- The Silver Fox indeed lives up to the design intention of driving monster-class headphones, but as a result makes this a bit more of a difficult situation for those of us out here without the monster-class headphones and only easy to drive headphones. One may potentially have to pick between the trade-off of noise floor to frequency response alterations or loss of dynamics.
- This could all have been fixed if a proper gain system was implemented instead of adding output impedance. Poor design on this aspect IMO but maybe there is a reason behind it?
- If you are incapable of hearing a noise floor on the High Impedance mode, then count yourself very lucky and enjoy this amazing amplifier!
- The Meze Elites are still extremely enjoyable on my RCA > High Impedance > BTL as the noise floor is inaudible during audio playback. I will probably stick with this.
Happy to answer any questions regarding my findings, please note this is the first time I have ever looked into the measurements and science aspect of audio.
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Long report below but below is my findings (please note I am definitely not a person who listens to measurements).
Items used : Cen.Grand 9i-906 "Silver Fox", Chord Qutest, SMSL VMV D3, Thieaudio V16 Divinity, QDC Anole VX. I do not know the model of the measuring device.
I had a conversion about the noise situation with Cen.Grand and their response is roughly along these lines :
- The circuits weren't designed with the intention of chasing low noise. If low noise was chased during circuit design/implementation, part selection etc, the numbers & measurements can look very good but the actual sound may not be desirable.
- The numbers provided (I personally have no idea if these are high or low) are the Silver Fox would normally sit at 60-80uV with balanced inputs using RCA inputs will increase that to over 100uV due to the unbalanced to balanced conversion. The conversion circuit is implemented because they wanted the amp to be powerful enough to power everything, regardless of signal input, and are willing to sacrifice the noise aspects for this.
- Adding resistors in series to the circuit shouldn't change the frequency response (was not specified whether this is amp side or transducer side). Only gain will be different.
With their response in mind, I went and tested the two different input methods of XLR and RCA, even with no DAC input connected provided the same results so feel free to verify for yourself.
- XLR is definitely the superior input method, with noise floor reduced across all different modes (BTL, Parallel, Active.G, Normal)
- BTL is fairly consistent in having low noise floor, however this is no longer the option with the lowest noise floor.
- Parallel has become the mode with the lowest noise floor when using XLR inputs, and is definitely quieter than BTL on RCA (which I previously mentioned to be the most quiet RCA input mode).
This by itself isn't an issue, given that there are the 4 different impedance modes available to reduce noise floor. However, given that the method of gain adjustment is to add resistors in series, this would change the output impedance, which in theory can potentially influence frequency response as well as damping factor and such. Therefore in order to verify the effects, a friend of mine measured our two IEMs (Thieaudio V16 Divinity via 6.35 SE & QDC Anole VX via 4.4 Balanced) using each different impedance mode while maintaining XLR + Parallel for the lowest noise floor.
Please refer to the graphs below :
Graph 1. Thieaudio V16 Divinity Frequency Response
Graph 2. QDC Anole VX Frequency Response
As it can be seen from the two graphs, there is quite a significant change going from High Impedance setting to any of the Low Impedance 1-3 settings. However, the differences between Low Impedance settings themselves then becomes relatively insignificant, especially between Low Impedance 2 & 3. Whether this change in frequency response is a good or bad thing is then subjective to your listening preferences as some may enjoy this altered sound (similar to why some enjoy tube amps).
How this will influence your specific transducer (headphone, IEM) will then depend on the impedance curve of that specific model. In the case of the Meze stuff though, impedance curve is flat as a ruler so there should be no changes in frequency response.
Lastly, given that the impedance does significantly boost which changes the damping factor (I believe ideally at least 8 is desired), I was concerned whether or not the headphone will then sound more sluggish or less dynamic, etc. Unfortunately there is no scientific method of determining this between the two of us, but using extremely dynamic test tracks Days of Thunder - The Midnight & Get Lucky - Daft Punk [feat. Pharrell Williams & Nile Rodgers], we did quick A/B testing between the modes and came to the same conclusion that as we progress down the Impedance modes, the Meze Elites indeed lost a bit of dynamic magic and the bass felt a bit weaker. This was most noticeable when cycling back from Low Impedance 3 to High Impedance. Note that this was not volume matched we do not rule out the possibility of placebo on the two of us.
However, I must note that this amplifier truly sounds amazing and works magic. I can already confidently say that the sound is better than of my Burson Soloist 3X GT + Supercharger 5A, but this is a comparison to be written later. RCA > Low Impedance 1 > BTL is still superior to the Burson here.
My final conclusions are therefore :
Personally, this might be my calling to swap my Chord Qutest out for a DAC that can do balanced outputs to reduce that noise floor even more... It indeed is quite frustrating knowing I may not be making the most of what this amp can do.
- XLR is definitely the superior input and one should definitely prioritize using this input if possible.
- High Impedance setting should be used ideally for maximum sound quality and no alteration of frequency responses.
- Sensitive IEMs are most definitely not recommended to be used with this amplifier which is quite a bummer, perhaps and IEMatch by iFi could help here?
- The Silver Fox indeed lives up to the design intention of driving monster-class headphones, but as a result makes this a bit more of a difficult situation for those of us out here without the monster-class headphones and only easy to drive headphones.
- One may potentially have to pick between the trade-off of noise floor to frequency response alterations or loss of dynamics.
- If you are incapable of hearing a noise floor on the High Impedance mode, then count yourself very lucky and enjoy this amazing amplifier!
- The Meze Elites are still extremely enjoyable on my RCA > High Impedance > BTL as the noise floor is inaudible during audio playback. I am still deciding between High Impedance or Low Impedance 1 as a trade-off between noise floor vs potential loss of dynamics.
Happy to answer any questions regarding my findings, please note this is the first time I have ever looked into the measurements and science aspect of audio.
Curious as to where you have your output voltage set on Qutest, 1,2 or 3V? Have you experimented with the various output voltage w/Silver Fox?
My Qutest is set to 3V and I have not experimented with the others. Maybe I should give this a go...
Just tried this, as well as using a powerbank as power supply. Both made no difference to my ears and the floor is still present as it was.
Ugh. Too bad. Maybe others have thoughts and opinions to share regarding your situation?
Best of luck.
High Impedance + BTL is the mode I will stick with for now, the noise floor is inaudible and my PC fans are probably louder than it. A bit unfortunate this is the case though given the Qutest is a perfect pairing in terms of sound signature, the main complaint of Qutest I had was the lack of weight sometimes whereas this combo now is perfect. If you have headphones harder to drive than the Meze Elite or cannot hear the noise floor to begin with, this could be a perfect match!
This now gives me an excuse to look at R26 or TT2 as an XLR option though
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ken6217
Headphoneus Supremus
I found high impedance and BTL mode the best by far for me. I think the other modes are needless bells and whistles that do not allow the amp to sound its best.
I will have to agree with you here on my RCA input mode! However, I will continue to test using XLR inputs this weekend and give more feedback. The sound on this amp is indeed amazing.
project86
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I'm intrigued by your findings because they are somewhat different than mine. I have been using my 64 Audio A18t with a single-ended cable, high impedance mode, and I get zero background noise or hiss etc using any of the four output options. Plenty of room for volume adjustments - far more than expected and more than most amps which only allow a small movement of the knob before it gets too loud to handle. I need to swap over to a balanced cable to see if that changes anything - but I'm completely satisfied with the 1/4" output in this case so it really doesn't matter much.
I've also been using my Meze Elite with balanced cable, high impedance mode, and again cycling through all four options. Again zero discernable background noise/hash/hum/artifacts/etc. I'm typically quite sensitive to that sort of thing, to the point where I expect it and am willing to forgive a small amount when using powerful amplifiers. But I'm not hearing anything from the Silver Fox nor from the Little Silver Fox.
I've also been using my Meze Elite with balanced cable, high impedance mode, and again cycling through all four options. Again zero discernable background noise/hash/hum/artifacts/etc. I'm typically quite sensitive to that sort of thing, to the point where I expect it and am willing to forgive a small amount when using powerful amplifiers. But I'm not hearing anything from the Silver Fox nor from the Little Silver Fox.
ckhirnigs113
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As a third point of reference from a Meze Elite user, albeit with the Little Silver Fox, I can hear a small bit of background noise in High Impedance/BTL modes using XLR inputs. It’s only noticeable when switching between output modes. It’s completely silent in Parallel, so I notice the difference when switching from BTL to Parrallel.
I haven’t plugged in any single-ended sources to the RCA inputs, but I did select those inputs to check the noise floor. Noise is indeed substantially higher using single-ended inputs. The internal conversion must add quite a bit of noise. Like @Yifang mentioned, strangely BTL mode is the quietest mode when using RCA inputs, which is opposite to the results when using XLR inputs.
With the Elite and an XLR source, I can use any of the four output settings in High Impedance mode without any noise floor issues while music is playing. Up to this point, I have been using Parallel the most because it’s completely silent with the Elite, and I didn’t think BTL offered anything advantageous except extra gain, which is obviously unneeded with the Elite. Now I’m going to listen some more in BTL since some of you seem to think it’s the most optimal setting.
Side note, noise level goes up with volume when using RCA inputs and XLR output. Noise floor seems constant when using XLR input and output. With RCA input and XLR output, the noise floor from lowest to highest:
BTL < Parallel < Active G ≤ Normal
Just plugged in my Auteur in to one of the 6.3mm jacks to test noise floor when switching between RCA and XLR inputs. Turns out the noise floor jumps up even when using single-ended input and output. The internal conversion must still be taking place since the noise is still present.
*Again this is all with the Little Silver Fox, but I think the behavior is consistent between the the two models after reading Yifang’s findings.
Update: I decided to do one more experiment and plug in the RCA cables from the single-ended output of my Bifrost 2 to see if there was any difference to the noise floor of the amp versus my test with no RCA cables plugged in. Turns out there is a big difference, but only in BTL mode. The noise is drastically lower, if not completely gone, on the active “RCA 1” input vs “RCA 2” which has nothing plugged into it. I’m using my Elite plugged into the 4-pin XLR jack, and every mode except BTL exhibits the same higher noise floor as when no cables are plugged in. Weirder still, in BTL mode on the active “RCA 1” input, the noise doesn’t increase as the volume knob is turned up, or else it’s so low that I can’t hear it increasing. The noise floor increases on all 3 of the other output modes as I turn up the volume. To be clear, noise floor is present and increases with volume on all output modes, including BTL, when using one of the 6.3mm jacks with either an active or inactive RCA input.
Conclusion, for sensitive headphones it is best to use a balanced headphone cable in BTL mode with single-ended sources, at least on the Little Silver Fox. I’ll personally be sticking to XLR in/out for all my listening.
I haven’t plugged in any single-ended sources to the RCA inputs, but I did select those inputs to check the noise floor. Noise is indeed substantially higher using single-ended inputs. The internal conversion must add quite a bit of noise. Like @Yifang mentioned, strangely BTL mode is the quietest mode when using RCA inputs, which is opposite to the results when using XLR inputs.
With the Elite and an XLR source, I can use any of the four output settings in High Impedance mode without any noise floor issues while music is playing. Up to this point, I have been using Parallel the most because it’s completely silent with the Elite, and I didn’t think BTL offered anything advantageous except extra gain, which is obviously unneeded with the Elite. Now I’m going to listen some more in BTL since some of you seem to think it’s the most optimal setting.
Side note, noise level goes up with volume when using RCA inputs and XLR output. Noise floor seems constant when using XLR input and output. With RCA input and XLR output, the noise floor from lowest to highest:
BTL < Parallel < Active G ≤ Normal
Just plugged in my Auteur in to one of the 6.3mm jacks to test noise floor when switching between RCA and XLR inputs. Turns out the noise floor jumps up even when using single-ended input and output. The internal conversion must still be taking place since the noise is still present.
*Again this is all with the Little Silver Fox, but I think the behavior is consistent between the the two models after reading Yifang’s findings.
Update: I decided to do one more experiment and plug in the RCA cables from the single-ended output of my Bifrost 2 to see if there was any difference to the noise floor of the amp versus my test with no RCA cables plugged in. Turns out there is a big difference, but only in BTL mode. The noise is drastically lower, if not completely gone, on the active “RCA 1” input vs “RCA 2” which has nothing plugged into it. I’m using my Elite plugged into the 4-pin XLR jack, and every mode except BTL exhibits the same higher noise floor as when no cables are plugged in. Weirder still, in BTL mode on the active “RCA 1” input, the noise doesn’t increase as the volume knob is turned up, or else it’s so low that I can’t hear it increasing. The noise floor increases on all 3 of the other output modes as I turn up the volume. To be clear, noise floor is present and increases with volume on all output modes, including BTL, when using one of the 6.3mm jacks with either an active or inactive RCA input.
Conclusion, for sensitive headphones it is best to use a balanced headphone cable in BTL mode with single-ended sources, at least on the Little Silver Fox. I’ll personally be sticking to XLR in/out for all my listening.
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This pretty much lines up with my findings too.
The summary is :
Use high impedance + BTL + balanced output for RCA input
Use high impedance + Parallel or BTL + balanced output for XLR input, with parallel being dead silent and BTL maybe having better dynamics? Need more listening here to confirm.
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I need to know what magic you did to get 0 noise in yours!
ckhirnigs113
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Sounds like a perfect summary to me! I do occasionally try to use Active G mode, but I can’t say I’ve noticed any difference versus BTL or Parallel.
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