[Yifang]

I know part of your issue is using extremely sensitive headphones or IEMs along with the RCA inputs. Some good power conditioning or an isolation transformer could definitely be beneficial, but there may still be some residual noise if you're using the same RCA DAC and IEMs.

I believe you are located in Australia? PuraSound in Brisbane carries Keces products. It might be worth seeing if they will offer you a trial period on one of their small isolation transformers like the IQRP-800. Or perhaps they might have something else they carry that they would suggest trying to see whether or not this reduces or eliminates the noise you are experiencing.

My issue isn't with the IEMs having noise and I have accepted the fact that this will be something I can't fix regardless with these sensitive IEMs. Needless to say if one is using sensitive IEMs with an amp this powerful then that would be quite silly, but it is important for people to also know that there is a significant change towards frequency responses & damping factor on low impedance 1-3 modes regardless of if you are using IEMs or headphones, especially dynamic driver headphones which don't have flat impedance curves. If that alteration is an enjoyable presentation for you, great! In my case, not so much.

My issue is with the headphone itself still having noise floor using XLR output on high impedance (which is the only mode I consider viable as I do not enjoy the effects of low impedance 1-3 options). The only fix in this case would be to switch my DAC to one with XLR out, or a headphone that is less sensitive. Obviously if one had headphones more difficult to power than the Meze Elite, then this is something to be ignored and just enjoy the amazing amp. If one had an XLR based DAC, then the same can be said. Most people should fall into one of these categories, or both.

However, it definitely wasn't something I personally was aware of being a user of the Chord Qutest (which only has RCAs) and Meze Elite (a relatively easy to drive headphone). If I knew about this case initially, I would have reconsidered my amp options as I had no plans of changing the DAC or headphones. I am looking into getting an XLR based DAC now, but I'm sure if others ran into this situation they would be a little frustrated too, especially if they do not have the ability to make another purchase. I'm sure you wouldn't be too happy getting an item like this only to find out afterwards that your previous gear aren't good enough to match it and need more unplanned changes. Wish there can be a fix in this case because the pairing between all 3 of these units (Silver Fox/Qutest/Elites) is unreal, the noise floor is the only thing stopping it from being perfect. Once again, the noise floor is also extremely inaudible and only people like me with OCD towards the smallest imperfection noticeable will ache over it.

I hope this doesn't blow out of proportion and make people turn away from the amp, this is easily the best amp I have ever heard. I don't have much experience with amps however...

Not sure about the small isolation transformers however, those seem way too expensive compared to what I'm willing for pay for them and I would rather just use that budget to find a superior DAC with XLR and just use parallel mode (even if the DAC just costs much more).

 

[ArthurPower]

My issue isn't with the IEMs having noise and I have accepted the fact that this will be something I can't fix regardless with these sensitive IEMs. Needless to say if one is using sensitive IEMs with an amp this powerful then that would be quite silly, but it is important for people to also know that there is a significant change towards frequency responses & damping factor on low impedance 1-3 modes regardless of if you are using IEMs or headphones, especially dynamic driver headphones which don't have flat impedance curves. If that alteration is an enjoyable presentation for you, great! In my case, not so much.

My issue is with the headphone itself still having noise floor using XLR output on high impedance (which is the only mode I consider viable as I do not enjoy the effects of low impedance 1-3 options). The only fix in this case would be to switch my DAC to one with XLR out, or a headphone that is less sensitive. Obviously if one had headphones more difficult to power than the Meze Elite, then this is something to be ignored and just enjoy the amazing amp. If one had an XLR based DAC, then the same can be said. Most people should fall into one of these categories, or both.

However, it definitely wasn't something I personally was aware of being a user of the Chord Qutest (which only has RCAs) and Meze Elite (a relatively easy to drive headphone). If I knew about this case initially, I would have reconsidered my amp options as I had no plans of changing the DAC or headphones. I am looking into getting an XLR based DAC now, but I'm sure if others ran into this situation they would be a little frustrated too, especially if they do not have the ability to make another purchase. I wish there can be a fix in this case because the pairing between all 3 of these units (Silver Fox/Qutest/Elites) is unreal, the noise floor is the only thing stopping it from being perfect.

I hope this doesn't blow out of proportion and make people turn away from the amp though, this is easily the best amp I have ever heard. I don't have much experience with amps however...

Not sure about the small isolation transformers however, those seem way too expensive compared to what I'm willing for pay for them and I would rather just use that budget to find a superior DAC with XLR and just use parallel mode (even if the DAC just costs much more).

I can't blame you for wanting to spend your money on a better DAC. How about a matching Cen.Grand DSDAC 1.0? I know once you go down the rabbit hole this hobby can consume all your money fast.

 

[Yifang]

I can't blame you for wanting to spend your money on a better DAC. How about a matching Cen.Grand DSDAC 1.0? I know once you go down the rabbit hole this hobby can consume all your money fast.

Can't deny I am interested, but I also trust in the Chord sound given my experience with Mojo2 & Qutest. Wish I could demo the DSDAC first before I make any more decisions here. I'm now looking to see if I can find a used TT2 locally as the upgrade but if nothing shows up then perhaps I will cave into a DSDAC...

 

[ckhirnigs113]

@Yifang I still recommend trying those XLR adapters. I think that might solve your entire issue. It’s also the cheapest option as well. If it doesn’t work, you won’t be out much money, but I can’t see why it wouldn’t work. I recall now that people did this with the ECP DSHA-3F amp. The amp was balanced in and out only, but some owners successfully used single-ended DACs with adapters.

 

[Yifang]

@Yifang I still recommend trying those XLR adapters. I think that might solve your entire issue. It’s also the cheapest option as well. If it doesn’t work, you won’t be out much money, but I can’t see why it wouldn’t work. I recall now that people did this with the ECP DSHA-3F amp. The amp was balanced in and out only, but some owners successfully used single-ended DACs with adapters.

I have already ordered two of them and confirmed the viability with @cengrand. Will report back on Monday when they arrive!

 

[ckhirnigs113]

You’re saying BTL mode is unavailable with RCA inputs, but I tried that specific combination out tonight, and it was by far the lowest noise floor of the 4 output modes. I used High Impedance Mode, the 4-pin XLR jack, and RCA input 1. The other 3 output modes (Parallel, Active G, and Normal) all had a substantially higher noise floor. How can you explain the much lower noise in BTL mode while using an RCA input and balanced output? Did I misunderstand you when you said,

Also, you say BTL is preferred. Is that for all headphone types? I’ve been using Parallel with my Meze Elite because that mode has no noise floor. Should I stick with BTL for a specific reason? Does BTL have better dynamics/driving force for planars? It’s my understanding that the main difference between BTL and Parallel modes is higher gain in BTL. Is this correct?

I’m using the Little Silver Fox if that matters.

 

[Yifang]

You’re saying BTL mode is unavailable with RCA inputs, but I tried that specific combination out tonight, and it was by far the lowest noise floor of the 4 output modes. I used High Impedance Mode, the 4-pin XLR jack, and RCA input 1. The other 3 output modes (Parallel, Active G, and Normal) all had a substantially higher noise floor. Did I misunderstand you when you said,

Also, you say BTL is preferred. Is that for all headphone types? I’ve been using Parallel with my Meze Elite because that mode has no noise floor. Should I stick with BTL for a specific reason? Does BTL have better dynamics/driving force for planars? It’s my understanding that the main difference between BTL and Parallel modes is higher gain in BTL. Is this correct?

I’m using the Little Silver Fox if that matters.

Thanks for joining the conversation @cengrand!

No, he is stating BTL mode would not work via an unbalanced signal (RCA) and, therefore there is an internal conversion circuit in order to the unbalanced signal become balanced. Only that way BTL mode works, and hence why RCA by default has higher noise (conversion circuit cannot be bypassed).

BTL mode works on RCA because it is converted internally to balanced, you can't bypass this, and BTL would not work if this wasn't the case.

As for the sound quality issue and BTL mode being preferred or not however, I cannot comment on this. It would be pretty disappointing in that case if BTL is the one that sounds the best but has noise floor, versus Parallel with no noise floor but less SQ right?

 

[ckhirnigs113]

No, he is stating BTL mode would not work via an unbalanced signal (RCA) and, therefore there is an internal conversion circuit in order to the unbalanced signal become balanced. Only that way BTL mode works, and hence why RCA by default has higher noise (conversion circuit cannot be bypassed).

BTL mode works on RCA because it is converted internally to balanced, you can't bypass this, and BTL would not work if this wasn't the case.

As for the sound quality issue and BTL mode being preferred or not however, I cannot comment on this. It would be pretty disappointing in that case if BTL is the one that sounds the best but has noise floor, versus Parallel with no noise floor but less SQ right?

That makes more sense for sure. I would still like to understand why BTL mode is so much quieter than the other 3 modes when using an RCA input and balanced output. Seems like the noise from the conversion should be present on all 4 output modes. It’s merely a curiosity to me at this point since I won’t be using the RCA inputs moving forward.

Yes, I’d like an answer about sound quality in BTL versus Parallel. I know @project86 said he was preferring his Elite in Parallel mode. In my experience, Parallel mode completely eliminates the noise floor and only drops the gain a small amount, but we’ll need clarification from @cengrand to see if that is accurate or an oversimplification. I’m open to using BTL all the time if given a legitimate reason to.

 

[Yifang]

That makes more sense for sure. I would still like to understand why BTL mode is so much quieter than the other 3 modes when using an RCA input and balanced output. Seems like the noise from the conversion should be present on all 4 output modes. It’s merely a curiosity to me at this point since I won’t be using the RCA inputs moving forward.

Yes, I’d like an answer about sound quality in BTL versus Parallel. I know @project86 said he was preferring his Elite in Parallel mode. In my experience, Parallel mode completely eliminates the noise floor and only drops the gain a small amount, but we’ll need clarification from @cengrand to see if that is accurate or an oversimplification. I’m open to using BTL all the time if given a legitimate reason to.

I believe he said something about BTL mode being balanced and therefore cancelling out a lot of the noise. I am unsure as to how this is, and how the other modes operate in contrast.

As for sound quality, I really hope there is no difference between BTL & Parallel on XLR so we can just utilize Parallel with eliminated noise floor!

 

[ckhirnigs113]

Just plugged in my ZMF Auteur to the 4-pin XLR and kept it in BTL mode. I usually use Parallel because there is much more noise in BTL. The Auteur must be more sensitive than the Elite, because the noise floor is much higher using the same settings.

I discovered another strange behavior. My Little Silver Fox has a balanced potentiometer, and the noise floor in BTL mode is different at different volume positions. It’s pretty consistently loud from 7:00-11:00. It starts to get quieter at 12:00 and is very quiet from 3:00-4:00. The noise floor then comes back at 5:00. Even Low Impedance 3 mode doesn’t completely mask the noise floor at normal listening levels with my Auteur, which is 300 ohms and 97dB/mW. In this mode, I still don’t go higher than 11:00 on the volume knob.

Tested the other 3 modes, and Parallell is silent at every volume level, Active G has a low noise floor at any volume (it doesn’t rise or fall with volume), and Normal is silent throughout.

So should I settle for BTL mode in Low Impedance 3 as my best option for the Auteur? It sounds good and ZMFs are ok with higher output impedance in general, but Parallel also sounds good and there is zero noise floor in that mode. I’d really like a detailed description of the specific differences between BTL and Parallel modes if possible @cengrand.

 

[Yifang]

Just plugged in my ZMF Auteur to the 4-pin XLR and kept it in BTL mode. I usually use Parallel because there is much more noise in BTL. The Auteur must be more sensitive than the Elite, because the noise floor is much higher using the same settings.

I discovered another strange behavior. My Little Silver Fox has a balanced potentiometer, and the noise floor in BTL mode is different at different volume positions. It’s pretty consistently loud from 7:00-11:00. It starts to get quieter at 12:00 and is very quiet from 3:00-4:00. The noise floor then comes back at 5:00. Even Low Impedance 3 mode doesn’t completely mask the noise floor at normal listening levels with my Auteur, which is 300 ohms and 97dB/mW. In this mode, I still don’t go higher than 11:00 on the volume knob.

Tested the other 3 modes, and Parallell is silent at every volume level, Active G has a low noise floor at any volume (it doesn’t rise or fall with volume), and Normal is silent throughout.

So should I settle for BTL mode in Low Impedance 3 as my best option for the Auteur? It sounds good and ZMFs are ok with higher output impedance in general, but Parallel also sounds good and there is zero noise floor in that mode. I’d really like a detailed description of the specific differences between BTL and Parallel modes if possible @cengrand.

This can't be right as the Elites are 102dB/mW @ 32 Ohms so they are most definitely more sensitive than your Auteur...

 

[Yifang]

@cengrand has said something along these lines :

BTL mode is the bridging of two amplifiers while Parallel is the parallel output of the two amplifiers.

BTL mode can therefore output 4 times as much power while parallel cannot change the power output, only adjust the resistance within the circuit. BTL mode cancels the noise for the the two circuits when in phase while parallel cancels out out of phase.

As for sound quality, there will be a sonic difference between the modes. Different amplification processes will obviously change this, but as for what is better cannot be said.

The inclusion of various modes to begin with is so that users can have a choice for what sounds best towards their headphone given each one responds differently to settings. It's impossible to predict how each one will respond and sound to each different mode here.

Users really shouldn't stress so much over the differences here, just go with whatever sounds best to your ears.

There's still a vast unknown about what makes sound enjoyable to us as humans, you'll only throw yourself deeper into the Abyss if you get hung up over this.

From me :
In your case @ckhirnigs113 (or our case), just continue to use whatever has the lowest noise floor if you cannot tell an audible difference between BTL and Parallel. In your case, this would be parallel.

I'd personally guess in theory BTL should sound the best with more headroom, but given our super easy to drive headphones, parallel should do more than enough. I wonder if there is a capped scaling point for our easy to drive headphones in regard to this, but it'll be impossible to determine. Planars love current, but just feeding current into a headphone isn't necessarily going to make it sound better right?

If one had Susvara which is extremely hard to drive however, BTL is obviously the way to go (and there wouldn't even be noise floor on this).

 

[Yifang]

Upon further listening, I can re-confirm that the BTL noise floor is definitely noticeable on the Elite in my case, even during quiet passages with audio playback too. Parallel on XLR (no inputs) has noise floor compared to Low Impedance 1-3, but it is far less noticeable in comparison to any other mode. I think it's impossible to truly reach the 0 noise floor level on High Impedance with this headphone...

I have also noticed a slight transformer hum when in a completely quiet environment which I know the DC blocker can help as previously posted in this thread. I will give that a go tomorrow and see if that does remove the transformer hum in my case, perhaps also work some magic to remove noise floor even more?

Noise floor aside, I really don't know what magic is happening in this amplifier compared to my previous experiences but this is the most musical and emotion inducing amplifier I have tried and I can't emphasize this enough! HOW???

 

[ken6217]

I was also getting noise with HD650 using balanced interconnects and balanced headphone cable. Amp was set up to high impedance and BTL. It didn’t bother me at all because I couldn’t hear it once I play music.

The noise was proportional when turning the volume dial up.

 

[Yifang]

I was also getting noise with HD650 using balanced interconnects and balanced headphone cable. Amp was set up to high impedance and BTL. It didn’t bother me at all because I couldn’t hear it once I play music.

The noise was proportional when turning the volume dial up.

Could you please try parallel mode and see if that ends up with no noise floor?