- Joined
- Dec 12, 2019
- Messages
- 14,144
- Likes
- 31,736
After I posted that
-- I did, indeed, note that you even used the same emoji in response to @antcollinet's quip! 
Sorry for veering perilously (although not unpredictably, for me) off topic!
-
Welcome to ASR. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
Are passive volume controls totally transparent?
- Thread starter Miguelón
- Start date
-- I did, indeed, note that you even used the same emoji in response to @antcollinet's quip! Sorry for veering perilously (although not unpredictably, for me) off topic!
OP
- Thread Starter
- #62
So fun! I’m from Spain: here when we start a debate or a conversation we never know where we will go and end…After I posted that
View attachment 428096
View attachment 428095
Sorry for veering perilously (although not unpredictably, for me) off topic!
Branching is the national sport in my country
OP
- Thread Starter
- #63
Speaking about things out of topic: some ancient colleagues at the conservatory and me we’re thinking about make a very homemade little recording studio for chamber music.After I posted that
View attachment 428096
View attachment 428095
Sorry for veering perilously (although not unpredictably, for me) off topic!
We think about purchasing Neumann KH 120 ii as main monitors, and a sub, I’ve seen that can be connected either by digital source SPDIF or analogue XLR and reconverting to digital on the internal AD for precessing on the DSP.
Do the late process affect sound by this double conversion in a negative sense?
Is better to use SPDIF connection directly from the source? If yes, do any RCA cable be adequate or digital needs a special cable? Sorry for this trivial question but I never used SPDIF…
antcollinet
Grand Contributor
I would always use a digital connection where possible. In reality though, the extra DAC/ADC step will be transparent to human hearing.
Coax/RCA SPDIF needs a cable designed for it. Specifically it needs to be 75ohm characteristic impedance. RCA cables designed for analogue audio are more often not.
- Joined
- Feb 23, 2016
- Messages
- 23,575
- Likes
- 44,235
Extra conversion is no issue for concern. Did you see the 8th generation loopbacks I presented in the past? You can listen for yourself.
I too like antcollinet would use digital anytime it is available. What you need are 75 ohm coax RCA cables. RG 59 or RG 6 based cables. RCA video cables are this. As long as it says it has 75 ohm impedance it should be fine.
OP
- Thread Starter
- #66
Thank you both @antcollinet and @Blumlein 88 for your advices!
Let me abuse a little bit more, this time for subwoofers to my home 8030C setup:
-1 7050 8inch subwoofer (deep in lows, advised by Genelec to 8030)
-A pair of 7040 6,5 inch subs (not so deep but more homogeneous low frequencies distribution, less SPL individually but think is ok for a combined pair)
Let me abuse a little bit more, this time for subwoofers to my home 8030C setup:
-1 7050 8inch subwoofer (deep in lows, advised by Genelec to 8030)
-A pair of 7040 6,5 inch subs (not so deep but more homogeneous low frequencies distribution, less SPL individually but think is ok for a combined pair)
- Joined
- Feb 23, 2016
- Messages
- 23,575
- Likes
- 44,235
I think it depends. If there is somewhere in the room where one sub has pretty even response the bigger sub would do fine. If not, two might allow you to create a smoother low end, but they'll probably not be symmetrical in their placement.
A bit of work, but you probably could figure it out with your speakers. Just send them low frequency signals, don't over do it. Measure with REW and find out if a spot has a smooth low end or if you need to find two spots. The response you are looking for isn't even and flat as your speakers are rolling off. But one where they roll off smoothly almost in a way similar to what the Klippel measurements show.
OP
- Thread Starter
- #68
I will do it.
Our living room is mixed with a kitchen, in proportions is approximately square form.
But we have a kitchen bar that divides partially in two uneven rectangles: the larger one is about 4 m x 6 m and our sofa is on the smallest side (not worried about SPL and distance because we listen quite low and even a pair of 8020 fill the room in our perception of loudness).
Given that we are in a longitudinal axis of a rectangle, and by ear I detect the “hot spot” of bass response quite centered (It doesn’t change so much from left to right but it changes from close to far from the speakers line) may the single sub will be enough…
OP
- Thread Starter
- #69
Correction, bass is not as symmetrical as I thought: apparently the bookshelves and a column at right of the speakers is making a bass tramp…
I’m not using REW measurements and the mic is not trustable but at least should be consistent:
Left speaker correction from WiiM, around 4.5 dB spike at 70 Hz, others are above subwoofer
Right speaker: 8.5 spike at same frequency, huge difference! The spikes at middle range are caused by reflexion on a TV screen placed on the long side at right of the speakers; when I leave it they barely disappear
Of course this may not be correct values but for instance may suggest to put our future sub at left side to not oversaturate low end?
Last edited:
welwynnick
Addicted to Fun and Learning
- Joined
- Dec 26, 2023
- Messages
- 553
- Likes
- 683
If you're considering using a passive volume control (which can have good fidelity) can I suggest using a low cost high performance headphone amplifier as a pre-amp instead?
If you chose the right one it will be objectively indistinguishable from the best passive control, and will have some key advantages - high input impedance and low output impedance.
I'd suggest considering the SMSL SH-6, Topping L30, L70 or Sabaj A10h. Some of them even have relay switched R2R volume controls.
OP
- Thread Starter
- #71
Thanks for the suggestions!
Finally I barely did that, time ago I bought second hand an Ifi Zen DAC signature, without realizing that it hasn’t any headphone output.
I was confused because they use a Pentaconn balanced ouptut as line out, so rarely used the DAC. Has an attenuator onboard, I don’t perceive any tonality change (maybe a tad warmer, but not very sure).
My audio interface has also a volume knob but the DAC is not good and produces scratch noise when turning the knob (electric noise via the speakers).
Other advantage of the Zen Dac signature is balanced line outs, but inconvenient was the expensive Pentaconn to 2 XLR cables
Edited: sorry, I’ve just seen that L70 is balanced
OP
- Thread Starter
- #72
Thaks for all of you clearing me the impedance intervention in serial stages, I was confused before with a lot of (digital, analogue, input) variables to optimize a basic setup.
After a couple of experinents and reading other posts, I learned the importance of the digital dBFS scale and the SPL, letting headroom and minimizing noise floor.
The intermediate voltage outputs and inputs are relatively negligable because high impedance input of amps and low impedance DAC and preamp outputs.
The slightly different tonality I noticed was just a gently roll off from higher frequencies (smooth and totally acceptable) when connecting two identical active monitors with 10 dB differnce in sensitiviry to the same source, which volume pot produce the tonal difference.
Also it exist general agreement to set the attenuation on the amp input side if possible, and keeping higher signal, so I decided to keep my G Three because a little more on the this direction (96 and 86 dB @ 0 dBu sensitivity values)
After a couple of experinents and reading other posts, I learned the importance of the digital dBFS scale and the SPL, letting headroom and minimizing noise floor.
The intermediate voltage outputs and inputs are relatively negligable because high impedance input of amps and low impedance DAC and preamp outputs.
The slightly different tonality I noticed was just a gently roll off from higher frequencies (smooth and totally acceptable) when connecting two identical active monitors with 10 dB differnce in sensitiviry to the same source, which volume pot produce the tonal difference.
Also it exist general agreement to set the attenuation on the amp input side if possible, and keeping higher signal, so I decided to keep my G Three because a little more on the this direction (96 and 86 dB @ 0 dBu sensitivity values)
Is there any reason that a passive line level controller such as this is a bad idea for level matching in biamping situations? Will it effect noise and distortion?
www.sweetwater.com
Rolls ILC19 In-line Level Control
2-way In-line Level Control for XLR Balanced Signals
www.sweetwater.com
OP
- Thread Starter
- #74
As far as I know, should not, only a minor one depending on impedance. Don’t take me serious in my post, I’m quite obsessive in those things, it will work well.Is there any reason that a passive line level controller such as this is a bad idea for level matching in biamping situations? Will it effect noise and distortion?
Rolls ILC19 In-line Level Control
2-way In-line Level Control for XLR Balanced Signals
Having the digital volume to low is worse, in general and specially in classical music because of quiet moments, so it is good to add some minimal noise and go far from noise floor in the DAC.
I might add that this will be used on the low pass section with a 25’ run before and 3’ run after.
Holmz
Major Contributor
OP
- Thread Starter
- #77
Impedance of cables is expressed in ohms per meter? Or per feet?
I see, impedance is not dependent on lenght in usual distances, is a charachteristic value.
Why the lenght does matter in XLR balanced signals? Is the combination of the attenuator plus the cable lenght that can cause alterations?
I recently red about the common wire ground (L+R signal) resistance combined with R out and amp resistance can affect soundstage but I thought was only for headphones.
I have a quite particular output, Pentaconn balanced but this means that ground wire is shared by both channels. But my cables are 10 feet
Last edited:
antcollinet
Grand Contributor
Cables have an impedance in capacitance and resistance and inductance which are all proportional to length.
They also have a characteristic impedance which is related to the way an electrical wavefront propagates through the cable. This however only becomes relevant at much higher frequencies than baseband audio** - where the cable length becomes significant compared to the electrical wavelength.
Characteristic impedance - Wikipedia
**It can become relevant for baseband audio - again when cable length becomes significant compared to the electrical wavelength. But that needs cables 100's of miles in length - it first became an issue in the early days of electrical signalling and telephony over long distances.
Last edited:
OP
- Thread Starter
- #79
Thanks for answering, but in that case what matters in Holmtz commentary about the lenght cable and the passive attenuator is the inductance and capacitance of both devices?Cables have an impedance in capacitance and resistance and inductance which are all proportional to length.
They also have a characteristic impedance which is related to the way an electrical wavefront propagates through the cable. This however only becomes relevant at much higher frequencies than baseband audio** - where the cable length becomes significant compared to the electrical wavelength.
Characteristic impedance - Wikipedia
en.wikipedia.org
**It can become relevant for baseband audio - again when cable length becomes significant compared to the electrical wavelength. But that needs cables 100's of miles in length - it first became an issue in the early days of electrical signalling and telephony over long distances.
It is possible in passive devices to not add impedance (nor inductance or capacitance) to the system or that is only achievable in active?
Edited: thanks also for the article, quite better understood by the definition of characteristic impedance and the expression
Last edited:
antcollinet
Grand Contributor
A passive volume control is a potentiometer. This has to be a reasonably high resistance, otherwise it presents too high a load to the source.
But this necessarily means it's output impedance is high. So if you use a 5K pot as in the device linked (already low compared to typical RCA input impedance), then it also has at a 1.25k output impedance (when at -6dB) - this is around 10x bigger than the typical output impedance of an active device.
So the following cable capacitance will have 10x the effect on frequency response as it would on a typical active output. This can then become audible if the cable length from the pot to the destination device has enough capacitance.
Similar threads
