I'm sorry but in my mind such a device should be the most transparent thing in the chain, and having a channel imbalance defeats the evey purpose of optimization of the electrical chain for transparency.
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SPL Volume8 Review
- Thread starter amirm
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It is in your mind but not in reality. Volume control, wether it's digital, analog, passive, active, integrated, separated, will almost invariably be one of the least transparent "thing" in the chain, because it changes the gain structure, so the most direct SINAD contribution is right there, in their various implementations it will have benefits and compromises, which can be but not limited to: output impedance, digital content bit depth, hence noise floor, channel balance, distortion... You pick your poison.
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When one volume control implementation introduces 200uV of noise and channel imbalance and other 2uV of noise and has perfect channel matching over whole adjustment range, which one is more transparent?
How would I know? You just gave one spec? It introduce 2 uV under which condition, at which effective gain? Is it also your feeling that one spec tells us all we need to know about an audio device?
Agree with everything you've said, definitely all about trade offs although I personally think as of today with 32 bit, super low noise DACs digital is the way to go. I would even argue it is one of the few reasons that these 120+ dB DACs make sense, you can throw away tons of dynamic range by attenuating digitally but because you are starting from so much dynamic range in the first place it doesn't matter.
Michael
My "feeling" is that having my channels balanced is better than not, and having less noise is better than more. Bizarre, I know.
OK, but what if all the music I listen to is 16 bits? And what if not all my sources are digital? You can't produce dynamic range that don't exist, and while it may be true in most cases, in the end it's still all about gain structure, and the problem is that sensitivities are all over. The most transparent DAC with digital volume control in the world can still present audible hiss if the gain downstream is not adequate for the transducer you are using, in the end everything must be viewed as a system working together. Nothing against digital volume, but again, benefits and compromises.
Why would you need an 8-ch volume control if your sources are all analogue? I don’t know any multichannel analogue nor 16-bit digital source.
Not bizarre, but you did not answer my question: "under which conditions"? and which volume control are you referring too? Your questions was way too vague. If you tell us more we may try to answer which is more transparent?
I don't. But Michael statement was general, not referenced to multi channel volume control, unless I misreaded. But to be specific there is about a thousand use cases where you need multi channel volume control for analog sources. It's called a mixing console.
This is a review thread, my point is that this device is objectively worse in every parameter in comparison to things like Benchmark LA4, Holo Serene, Topping Pre90. It's only feature is that it does 8 channels but obviously the implementation can be much better as shown by aforementioned devices.
These things were everywhere in tv/film post about 15 years ago (back when you typically had a 192 or 888 I/O on your ProTools which had no monitoring control at all) but not really in mix rooms, more in cutting [edit] room type setups. In that context, and at that time, it was "fine". There was a similar 5.1 box from SPL I think that had speaker mutes or solos; can't remember what that was called.
Even then it was kinda expensive, but I don't recall any alternatives of this form factor from that era. No one I knew bought it for the quality, nor did they massively care, as it just did what it did. Obviously things have moved on.
Even then it was kinda expensive, but I don't recall any alternatives of this form factor from that era. No one I knew bought it for the quality, nor did they massively care, as it just did what it did. Obviously things have moved on.
OK, thanks, I get now that it's the point you want to make, quite different than the first one you made "should be the most transparent thing in the chain"
I should have specified what I meant. I want my preamp/attenuator to allow me to optimize my gain structure and be like a wire at unity gain.
wisechoice
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Lots of very good points being made here, and also lots of sparks flying!
In case anyone is wondering about the real world use case for this very device, this is it: I have 3 transparent balanced stereo DACs in a home theatre setup, fed by a BlackMagic SDI to audio 4K converter (digital over TRS to RCA/coaxial). The converter itself is fed by another HDMI to SDI converter, and before that, an HDMI splitter. The SDI to audio converter has digital volume control hidden inside a settings panel of the Blackmagic converter utility, as long as the converter is connected via USB to a computer.
So pretty much the only convenient and elegant way to get volume control for all8 6 channels together is with this device. (At least, that I've found.) This device should also make what is currently a very elaborate and complex setup easily usable by my partner, who is non-technical and also dealing with long COVID.
Channel separation and channel balance aren't perfect, but they should be sufficient for multichannel home theatre purposes. Otherwise, it's transparent enough since nothing else in my chain is adding much noise at all. Is it expensive for this purpose? Yes, it's expensive, even at used prices. But otherwise, I would be replacing all of these DACs with a single 8-channel balanced DAC, which are getting much harder to find these days.
I have another DAC (for 4 total with the other 3) which is being fed by TOSlink [EDIT: along with the others -- on separate inputs, obviously], from an RME Digiface USB, controlled by an RME ARC USB. Both are very good, but to use the Digiface USB in the home theatre setup, I need to route everything through my Mac via a Decklink Mini Recorder 4K. This device will allow me to bypass the Mac mini and the Decklink.
For any mixing & mastering, or for playback from the computer, I will use the Digiface, and if I want the most transparent signal possible, I will take this device out of the chain. Something tells me that it will be just fine in the chain, though. I can leave the Volume8 at the level that I want it for mastering, and channel balance using either the speakers or the Digiface USB.
In case anyone is wondering about the real world use case for this very device, this is it: I have 3 transparent balanced stereo DACs in a home theatre setup, fed by a BlackMagic SDI to audio 4K converter (digital over TRS to RCA/coaxial). The converter itself is fed by another HDMI to SDI converter, and before that, an HDMI splitter. The SDI to audio converter has digital volume control hidden inside a settings panel of the Blackmagic converter utility, as long as the converter is connected via USB to a computer.
So pretty much the only convenient and elegant way to get volume control for all
Channel separation and channel balance aren't perfect, but they should be sufficient for multichannel home theatre purposes. Otherwise, it's transparent enough since nothing else in my chain is adding much noise at all. Is it expensive for this purpose? Yes, it's expensive, even at used prices. But otherwise, I would be replacing all of these DACs with a single 8-channel balanced DAC, which are getting much harder to find these days.
I have another DAC (for 4 total with the other 3) which is being fed by TOSlink [EDIT: along with the others -- on separate inputs, obviously], from an RME Digiface USB, controlled by an RME ARC USB. Both are very good, but to use the Digiface USB in the home theatre setup, I need to route everything through my Mac via a Decklink Mini Recorder 4K. This device will allow me to bypass the Mac mini and the Decklink.
For any mixing & mastering, or for playback from the computer, I will use the Digiface, and if I want the most transparent signal possible, I will take this device out of the chain. Something tells me that it will be just fine in the chain, though. I can leave the Volume8 at the level that I want it for mastering, and channel balance using either the speakers or the Digiface USB.
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wisechoice
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I think the only thing that matters is the total performance of the chain. Who cares what an individual component measures if the chain as a whole is still audibly transparent? If none of your other components are adding much noise, and the volume control is the weakest link, does it matter whether it measures better or worse than a DAC with 21 bits of dynamic range? Most things do measure worse, and nobody can hear something that measures better!
It would probably be accurate to say that the original [EDIT: digital master file] should be the most transparent thing in the chain. And then you could also say that any problems introduced downstream of it "defeat the purpose" of digital audio. But audio isn't digital, bits are, and we can't hear them. At some point, you need a DAC and transducer, and if you can't have, or don't, want software [EDIT: or digital] volume control, you need a device like this one.
I'm also not sure that +/-1dB of channel imbalance is going to break a device like this for monitoring purposes. Based on my reading of the measurements shared by @pos, which I linked above, that is about what you're facing above 50% volume. A lot of studio monitors probably have more than that amount of variance between units. If needed for reference listening/monitoring, you would typically leave the volume control in one position anyway, and then measure and balance the speakers separately.
Also, the channel imbalance is relatively consistent between channels here. So if you have compensated for channel imbalance before or after the speakers at your chosen monitoring level, deviations from that will still not be as great as the differences if you hadn't done that. Not sure that I can hear that difference, personally.
As for the crosstalk, I'm pretty sure that there's much more crosstalk happening in a well-treated room than there is in this device. I'm not an expert though, so others can feel free to correct me on any or all of this.
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wisechoice
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It could all just be rationalization for my weird and piecemeal way of building a combination home theatre/research/creation setup, all while also trying to save money (I know it doesn't look like it!) and hold onto the possibility of multichannel DSD.
EDIT: In any case, I'm very grateful to Amir for having measured this unit. I can't manufacture something else myself at the moment, nor afford something better. So this will have to do—and knowing its limitations, such as they are, makes it much easier to properly integrate into my existing setup.
EDIT: In any case, I'm very grateful to Amir for having measured this unit. I can't manufacture something else myself at the moment, nor afford something better. So this will have to do—and knowing its limitations, such as they are, makes it much easier to properly integrate into my existing setup.
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Almost certainly for controlling surround sound signals going to monitors. These multichannel volume controls are almost always for people who are distrustful of digital volume attenuation since they believe it will introduce noise.
Setting up monitoring for 5?1 or 7.1 sound is expensive business unfortunately. I think you need a special version of protocols for example.
Some speaker diy people also use devices like this to control all 8 channels of an active 4 way speaker like a linkwitz lx521. You send a digital signal to a minidsp, which then outputs 8 channels of digital audio to 4 different stereo dacs. You then attenuate the dac with this device before sending to 8 power amps. All because nobody wants to control volume using bits.
It's the SPL SMC 2489. I used to have it in my tv/film video editing with 5.1 audio setup at work. I think this It is an extremely well made device, but like any mechanical device, it is sensitive to its environment. It was disposed of because channels would randomly drop after years of use. Dirt started to enter the push buttons and possibly the volume potentiometer itself.
Instead of replacing it with a brand new one, we bought a Denon AVR-x3700h and I did a network based volume controller with an arduino. We probably lost a few dBs of SINAD, but no more scratchy pots! I think that IC based attenuators are the way to go for surround systems.
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