Gain mismatch? - When to use in-line attenuators?

[Rja4000]

A lot of measurements here.

Amongst those data:

Input sensitivity (maximum volume, XLR)

285mVrms

So, if you push 4V from your DAC, you may attenuate by 23dB, and you'd still get the maximum power if you turn the amp volume fully to the right.

You may do that with the amp volume knob and control your volume through the DAC, or you may set your DAC volume to -23dB, or anything in between.
(I'd personnaly go for the first option.)

You may as well insert your -20dB attenuator.

Balanced input impedance is also measured, by the way :

Input impedance (line input, XLR)

19.0k ohms

(It's a shame Music Fidelity doesn't provide proper detailed specifications, by the way. I own an M6PRX myself and that's the same issue.)

 

[Rja4000]

By the way, yesterday, I was evaluating the benefit of a passive attenuator vs the digital volume in my RME ADI-2 Pro fs R.

The passive attenuator is this one:

I plotted SINAD vs attenuation (in dB) for the 2 options
(There are also 2 fixed attenuators: a H-PAD attenuator at around -60dB and a transformer-based passive DI at around -40dB).

Interestingly (but not surprisingly), the behaviour of the passive attenator is not linear :
It becomes really more efficient than the DAC attenuation below -23dB or so.
So you may probably as well attenuate the DAC output.

(Of course, this measurement is only valid for my very context)

 

[tonapo]

I am not as experienced with the type of gear you're using. So bear that in mind as you read my comments/suggestions. I think trying RCA to RCA might help to isolate whether the issue is in the XLR connections, or somewhere else in the setup though. (Since RCA is the standard in home setups, I think it might be somewhat less likely to find errors in the implementation of those connections than with the XLR ins/outs. Not sure about that though.)

I dug out some RCA to RCA cables and managed to connect to aux 2, although they were hard to push on, and its always fun reach behind an equipment rack! Anyway, once on, I activate RCA and XLR on the DAC (just XLR before) and I was able to play some tracks and switch between the two inputs. The RCA input is noticely quieter, although I am not sure what that means.

The specs on the Reference 1 suggest an amp in the 50 to 200 Watt range btw. While your amp is 220 Watts, which is a bit higher. And I saw no way to trim the gain on the amp, other than using the volume control. So perhaps this amp is just a bit too powerful for the speakers you're using?

Time to get a benchmark then! (joke!)

I wonder if there are any controls on the speakers themselves that will allow you to trim/dial back the gain there. And also wondered if you were using any kind of EQ that could be effecting the output levels on your player or DAC.

No I don't think so.

For volume control : Adjust M6si amp volume fixed slightly above max listening level and adjust with D90 dac volume control down to desired level

I could try this as a possible solution, but might degrade performance?? I could potentially swap out the Topping for my desktop DAC if needed, its a RME ADI-2 DAC FS, that may be complicating things at this stage.

 

[tonapo]

Thanks for the reply RJA4000, I think you were replying as I was to a previous post.

A lot of measurements here.

Thank you. I found this myself yesterday but I confess most went over my head.

You may do that with the amp volume knob and control your volume through the DAC, or you may set your DAC volume to -30dB, or anything in between.
(I'd personnaly go for the first option.)

You may as well insert your -20dB attenuator.

Balanced input impedance is also measured, by the way :

Input impedance (line input, XLR)

19.0k ohms

(It's a shame Music Fidelity doesn't provide proper detailed specifications, by the way. I own an M6PRX myself and that's the same issue.)

Interesting, so it might be worth putting the attenuators back in.

How did you find the Sat 2?

 

[Rja4000]

How did you find the Sat 2?

I use it to attenuate level before device for measurements.

It's working good.
It's also rock solid (as any Radial Engineering device. Those are designed for live tours, for users that are not exactly pampering their hardware)

There are cheaper options though, and the knob is way too small, making it difficult to adjust accurately.
I have it and I keep it.

 

[DonH56]

I had the genesis of an article on this a while ago, and switched gears a bit (from Mathcad to SPICE) to finish it off since the subject seems to be reasonably popular. You can see it at https://www.audiosciencereview.com/forum/index.php?threads/attenuator-bandwidth.34268/

HTH - Don

 

[AnalogSteph]

By the way, yesterday, I was evaluating the benefit of a passive attenuator vs the digital volume in my RME ADI-2 Pro fs R.

I guess the RME's "Auto Ref Level" function was not turned on for this, right? It may be interesting to record a third set of measurements with this enabled, chances are it'll wipe the floor with the other two options.

Why do you reckon does the SAT-2 lose out to the bare output at first - high source impedance?

 

[Rja4000]

I guess the RME's "Auto Ref Level" function was not turned on for this, right? It may be interesting to record a third set of measurements with this enabled, chances are it'll wipe the floor with the other two options.

In general, you're right.
But here, 0dBFS is 4dBu, so the lowest output range on the RME.

(I published this plot with dBFS as X. I have the same with X in logarithmic voltage. Unfortunately, I was not able to have Excel building a polynomial trend on a logarithmic plot, so I chose to publish this one.)

Why do you reckon does the SAT-2 lose out to the bare output at first - high source impedance?

I didn't say that.
I said I was not surprised that the behavior with the passive potentiometer is not linear.

 

[Rja4000]

I guess the RME's "Auto Ref Level" function was not turned on for this, right? It may be interesting to record a third set of measurements with this enabled, chances are it'll wipe the floor with the other two options.

Speaking of the different ranges on the RME, here are my best performance plots for each level (in mono loopback mode)

Note the dashed line:
Level is set with the SAT-2 attenuator on +4dBu 0dBFS output signal.

An interseting topic is that, for sine wave tests, the RME may also output more than 0dBFS.
I kept only the highest performance plots for each ADC input level.

The SINAD in Loopback (so summing the noise and distortion of the DAC + the ADC) remains above 112dB (unweighted) from 0.6V to 12V (a 26dB range)
Quite a performance !

 

[Mart68]

I had the genesis of an article on this a while ago, and switched gears a bit (from Mathcad to SPICE) to finish it off since the subject seems to be reasonably popular. You can see it at https://www.audiosciencereview.com/forum/index.php?threads/attenuator-bandwidth.34268/

HTH - Don

This again says there's no real impact on FR.

In my own use case it was a tube pre-amp, output impedance <300 ohm into a power amp with input impedance 10,000 ohms. Should be fine but - subjectively - it wasn't.

 

[chips666]

I just got a Rupert Neve RNHP amp - best settings on RME ADI-2 fs? (Page 1) — ADI-2 & 2/4 Pro series, ADI-2 DAC series — RME User Forum

@tonapo This could be useful

Enjoy...

 

[DonH56]

This again says there's no real impact on FR.

In my own use case it was a tube pre-amp, output impedance <300 ohm into a power amp with input impedance 10,000 ohms. Should be fine but - subjectively - it wasn't.

I do not know exactly what resistor values are in the Rothwell attenuators. Nor all the parameters of the cables, input capacitance of the amp, etc. Does not matter since you've found a solution that works for you.

10k is actually a fairly low load for a tube preamp.

 

[AnalogSteph]

The SINAD in Loopback (so summing the noise and distortion of the DAC + the ADC) remains above 112dB (unweighted) from 0.6V to 12V (a 26dB range)
Quite a performance !

Not to mention that input dynamic range at low levels extrapolates to a total of 122 dB, rather beating the spec of 119 dB unweighted. That's input noise levels only about 8 dB from a decent microphone input (and only about 2 dB worse than e.g. a Tascam UR22). Basically you could add an external phantom power supply and use a condenser mic perfectly fine.

 

[Rja4000]

That's input noise levels only about 8 dB from a decent microphone input

I agree that the performance is excellent...

EDITED
You refer, I guess, to EIN for mic preamp.
EIN is given in dBu, typically A weighted, for a known input impedance (150 ohm is common).

Here, the 122dB are dBFS, or dB below the maximum input level, which is 4dBu for the lowest range.
So we speak of an EIN of around -118dBu (un-weighted), which is 10dB lower than the average Mic preamp using That chips.

Let's measure it
To illustrate, I measured the RME ADI-2 Pro fs R ADC as I would do for a microphone (Range 4dBu, Mono mode)
Gain is 0, so we get an EIN (A) of -120,7dBu (A Weighted, with a 150 ohm load, between 20Hz and 20kHz)

The same with the E1DA Cosmos ADC (A Grade) :
The E1DA seems to give 3dBFS better SNR, at 1.7V range
But as the range is higher (1.7Vrms = 6.83dBu vs 4dBu), the EIN (in absolute level - dBu) is finally the same

As YOU said above, we are around 8dB behind a good Mic Preamp at max gain

But, of course, a Mic Preamp doesn't achieve the same result at lower gain either:
Here is the EIN (A) vs Gain I measured for the Millennia HV-3C, a top range Mic Preamp.

Bottom line
Your estimate of 8dB is pretty much right on the money


PS:
1. Above are quite approximative measurements.
For accurate result, I'd have to measure the exact load resistance, the room temperature and the exact max input level in dBu and compensate for all that,
That may count for .1 or .2dBu

2. With almost exactly the same EIN, it will come as no surprise that the SINAD vs Level plots for the 2 devices are following the exact same trend at low level, overlapping almost perfectly.

 

[ADU]

I dug out some RCA to RCA cables and managed to connect to aux 2, although they were hard to push on, and its always fun reach behind an equipment rack! Anyway, once on, I activate RCA and XLR on the DAC (just XLR before) and I was able to play some tracks and switch between the two inputs. The RCA input is noticely quieter, although I am not sure what that means.

Time to get a benchmark then! (joke!)


No I don't think so.

I could try this as a possible solution, but might degrade performance?? I could potentially swap out the Topping for my desktop DAC if needed, its a RME ADI-2 DAC FS, that may be complicating things at this stage.

Sorry for the delay in getting back on this, tonapo. I'm doing a few minor adjustments though on some of my gear, which forced me to shut down my computers for awhile.

If you have a different DAC with XLR and RCA outs that you can try in your setup, that might be a good thing. I have not used any RME products, but have heard some pretty good things about them.

You said that you tried RCA to RCA though on your current DAC and amp, and I wondered if that corrected the sensitivity issues you were having with the volume control on your amp?

 

[ADU]

Time to get a benchmark then! (joke!)

Not familiar with this brand, but I'm assuming it's a nicer or more expensive amp than the one you've currently got. I don't think spending more is really the answer though. Because, imo, you should really be able to find gear that plays nice together without having to spend an arm and leg. And also without having to use pads, adapters, or other kinds of workarounds.

I only paid about $300 for my current audio setup, which includes a low-cost DAC from Best Buy, solid-state headphone amp from Bellari, and 250-ohm Beyerdynamic headphones, and Equalizer APO. All purchased new in the box (except EAPO, which was free to DL). And I get a nice clean, accurate signal, with no connectivity or other issues to speak of.

I spent a good bit of time researching and trying out some different gear (esp. different headphones) before settling on the above arrangement though. So I did invest some time and energy finding components that I felt would be a good fit for my particular needs and budget, that would also play nice together. (I like trying out different kinds of gear though, and really wish I had more time and $$ to do that kind of thing. So there wasn't really a downside to this in my case.)

It sounds like you were maybe trying to future-proof your setup by getting a more powerful amp than you probably needed though. And maybe found it was not an ideal fit with your current speakers?

And maybe it would be a worthwhile to speak to the either the folks at KEF, or the dealer that you purchased your amp and speakers from to see if there's another amp with XLR inputs that might play a little nicer with your current speakers. And maybe still provide enough power if you want to upgrade to some better speakers in the future.

It would be interesting to see if you get similar results (and differences in volume) with the XLR and RCA outputs on the RME DAC though.

 

[ADU]

Maybe there are some other adjustments you could make in your gear or setup that could reduce or eliminate the need for such long cables as well, including possibly the use of some components with better wireless connectivity?

I suppose I can understand why some audiophiles prefer to use equipment or gear with balanced XLR connections and cabling. But I'm afraid this is sometimes based on the (incorrect imo) assumption that it delivers a better signal or sound quality than unbalanced audio, which is frequently not the case. And also fear that the implementation of balanced connections may not be as consistent or reliable in some home audio products as it is in many pro audio components, where this type of connection is more commonplace.

I think there's also still alot of misunderstanding and general confusion about when and where this type of cabling can or should be used in home audio setups, both by the consumers of home audio components, and to some extent also the manufacturers of those components. And that there may be some manufacturers who are also trying to take advantage of some of this confusion to try to make a few extra bucks on some of their components.

I've certainly used balanced XLR and 1/4" TRS connections in some of my own setups with pro audio components. But I don't think I really have enough knowledge or experience with higher-end home audio products to properly break down when these type of balanced connections would really make sense to use in that context. And as a general rule, I try to steer clear of using them in my own home audio setups.

 

[tonapo]

Not familiar with this brand, but I'm assuming it's a nicer or more expensive amp than the one you've currently got. I don't think spending more is really the answer though. Because, imo, you should really be able to find gear that plays nice together without having to spend an arm and leg. And also without having to use pads, adapters, or other kinds of workarounds.

I was talking about the Benchmark AHB2, which reviewed very well in Amirs tests. I was not being serious about buying one now, although I would be interested in what the company produces in the future. I did think originally that it was not powerful enough, however I now know thats not really going to be an issue with my speakers and maybe I had previously put too much store into overall power. I am also interested in Class D in the future.

I spent a good bit of time researching and trying out some different gear (esp. different headphones) before settling on the above arrangement though. So I did invest some time and energy finding components that I felt would be a good fit for my particular needs and budget, that would also play nice together. (I like trying out different kinds of gear though, and really wish I had more time and $$ to do that kind of thing. So there wasn't really a downside to this in my case.)

I generally do this too - its generally the fun bit of this hobby, and I did demo the speakers with the amp in my home. I have never come across a gain issue before, if that is what this is, so I didnt pay suffificient attention or recognise it. A bit more experience now.

I suppose I can understand why some audiophiles prefer to use equipment or gear with balanced XLR connections and cabling. But I'm afraid this is sometimes based on the (incorrect imo) assumption that it delivers a better signal or sound quality than unbalanced audio, which is frequently not the case. And also fear that the implementation of balanced connections may not be as consistent or reliable in some home audio products as it is in many pro audio components, where this type of connection is more commonplace.

I think there's also still alot of misunderstanding and general confusion about when and where this type of cabling can or should be used in home audio setups, both by the consumers of home audio components, and to some extent also the manufacturers of those components. And that there may be some manufacturers who are also trying to take advantage of some of this confusion to try to make a few extra bucks on some of their components.

Maybe, I went XLR in this instance largely down to Amir's review of the DAC. The attenuators are out of the system currently, and the system sounds excellent, I just need to be wary with over enthusiastic volume adjustments!

I've certainly used balanced XLR and 1/4" TRS connections in some of my own setups with pro audio components. But I don't think I really have enough knowledge or experience with higher-end home audio products to properly break down when these type of balanced connections would really make sense to use in that context. And as a general rule, I try to steer clear of using them in my own home audio setups.

I think this is why this website is so useful, being based on objective reviews. Amir reviewed an amp further down the Musical Fidelity range but he hasnt got around to reviewing mine yet!

 

[Tim Link]

I'm with you. They should not make any difference on the sound. This has been the stance i have taken since the get go.
However, after much experimentation, my view or stance has changed. While I agree they shouldn't make a difference, yet, In reality, i must admit they do have a negative effect.

When i first bought and tried these a few years back, I thought at first, they seemed to be affecting the high frequencies in a negative way, but my brain told me this can't be true, it's only attenuating all the frequencies.
So, a couple weeks back i decided to experiment a little more. Seeing how it has been a few years since used, I would have a fresh outlook.
First, I tried with the Rothwells (xlr) connected at the amp, Immediately, the sparkle, life, whatever you want to call it seemed to be missing, bass seemed improved. Once again, I thought this must be my imagination. So, I pulled them out and this time i added a passive preamp (xlr) to the mix.
While the passive pre of course did attenuation, there was No obvious reduction (negative effects) in the highs, bass also seemed normal, only attenuated.

So in short, I don't know why they (Rothwells) are affecting the highs as they do, but they are. I suspect, not verified, it is somehow affecting the phasing (pure speculation on my part). Oddly enough, I have tried the RCA version in the past, and noticed No ill effects. Go figure.

Serge, would really appreciate your thoughts on why this may be happening. I'm baffled as to why it is, but it is audible. I know without measurements, it's all purely a subjective observation. But that's my observation. Needless to say, they will not be used again.

I just tried some 20 dB attenuators from Parts Express on the output of my Behringer DEQ2496 and the result was a huge suprise. The soundstage became hard to hear - like it was almost mono. The music sounded very flat, dull. The tonal shift may have directly affected the perception of soundstage width. That's surprising to me. Maybe it shouldn't be. I unplugged the attenuators and set the digital attenuation in the DEQ and had a listen again. Night and day difference. My configuration is not the correct use case for these attenuators. I was eager to try these to avoid digital attenuation but it seems there's little harm in the digital attenuation but a lot from using these attenuators with the XLR-RCA cables I have.