Mackie Big Knob vs. SPL Volume 2/8

[valis]

Passive units are essentially adjustable resistors. Resistance is one side of the coin for Impedance, the other side being Reactance (like a capacitor).

You're reading marketing kerfluffle again imo, although it's not baseless. Seems to me that they're trying to say is that there are tradeoffs even for passive control, and they've chosen a different set of tradeoffs which they imagine counterpoint some of the drawbacks of a passive volume control when used with an active load on the other side (the output of your soundcard etc). Then they state that when you can power a gain control, that gives you amplification as well as attenuation (passive controls can only attenuate).

As to the first part, my understanding of the electrical theory of Impedance, is that a pure theoretical 'resistor' would NOT impart any phase shift. Since real-world components are not theoretical, even with a passive controller the quality of your choice of components are going to affect to what degree the signal is altered, even with just resistance. Hence ChampionSound's statement in the first post that he had heard that the M-Patch 2 showed some phase shift at very low levels, and further comments about the device below that.

Note that adding capacitors, I think while they are not actually "active" they will change the phase response of the signal, and still allow the marketing of a product as 'passive' since it's 'unpowered' (lacking transformers and the requirement for self-power).

So I imagine that one side of this discussion (the passive volume maker) will say that using only a variable resistor (or a stepped series of resistors) insures the least amount of components in the path, and thus the purest signal. SPL's side of the discussion here is that they think they've balanced the additional components (active components such as transformers) with a design again to minimize the distorting effects of the circuitry (using distortion in its technical sense of any change at all, not in the 'musical' sense of clipping). They list the added benefits that not only can you now not only have positive gain again, but also have a circuit that gives a more even load to the source that's feeding it across input voltages.

In my opinion--whether or not a unit is passive or active--a designer that balances careful selection of components / use of high quality part specifications with attention to overall design (and imo a MUSICAL EAR) and manufacture, will determine the quality of the unit to the buyer. Comparing the Mackie Big Knob to this SPL unit, one might imagine they're using less of a 'cookie cutter' approach to assembly (where parts are binned together by wider tolerances) and a design that focuses as much on musicality (if not more) as it does ease of assembly/cost. Of course if one uses cost and marketing alone to determine the quality of a unit, one might wind up buying very expensive wooden knobs & "shakti stones".

As usual I typed a ton of caffeine fueled text, I hope my answer was intelligible in that block of text?

[firubbi]

thanks valis. what im looking for a good passive volume control which has at least 2 sets of speaker out and 1 headphone out.
do you recommend presonus Monitor Station? is spl 2Control is safe?
thanks

** or anything that dont color the sound.

[valis]

I haven't any experience with any of the units personally. SPL usually seems to make high quality stuff, I would guess if you can afford it it's probably better than the Big Knob (my guess is reflected in my last paragraph above). I generally hear good things about the Presonus stuff too, but there is one particularly vocal fellow who had one break on him. Of course his replacement is the Dangerous D-Box, which may be a bit more than you're looking to spend...

Personally, I think it's a rather relative question. I know several guitar players that wouldn't ever know the difference between their "Peavey Summing Mixer Amp" and an audiophile quality monitoring controller. I don't think their choice of equipment makes any difference to their fans either, but it's been about 2 decades since I was interested in the 'raw expressiveness' they enjoy. If you're coming from using a DJ mixer (a noisy vestax at that) then even the M-Patch 2 is an audible improvement. If you're using an M-patch 2, perhaps the Presonus is a decent upgrade to allow more inputs, but do note Chris's take on the build quality first.

Since there are basically options from the M-patch 2 all the way up to several grand, the first thing I would probably do is consider my intended budget. Then look at what my options are in that range and make a good decision from what information I could come by.

[firubbi]

after a long thought i went for presonus Monitor Station. im not so happy but it has talkback,headphone,2in/3out.(i'll need 2 i/o) wish spl has that options.

[bassdude]

..... SPL's side of the discussion here is that they think they've balanced the additional components (active components such as transformers) .....

Are you talking about audio transformers? An audio transformer is a passive device.

[valis]

Are you talking about audio transformers? An audio transformer is a passive device.

Thanks for pointing out my mistake. You're right I meant amplifier in each case where I said transformer (I know a transformer is an inductive device that merely connects two circuits...). A side effect of trying to type a long response while waiting on a file upload elsewhere (using forums while working, gasp!).

And truth be told I haven't a clue what design SPL used in that device, I was just commenting on their marketing speak as it's all I've read about the device so far (on their site and on the press release posted up a while back on

[Shroomz~>]

I've been doing a bit of digging around on the DIY side of volume/level controllers & there's some really interesting projects & kits kicking around if you go looking. If anyone else is like me & interested in building their own UBER high quality Passive Level Control that is just a simple big knob for attenuating the level of your active monitors, you should check out the Goldpoint Mini-V Quad stepped attenuator (see picture below). For $249 there may be no better choice.



If you're not into building your own, but want a really high quality Passive Level Control that is just a simple big knob for attenuating the level of your active monitors, you should check out the Goldpoint SA1X Passive Level Control (see picture below). It costs $442, but if you've got really expensive monitor speakers it's probably worth every penny.




~Mark

[Shroomz~>]

Also check out this project page at diyfactory.com if you plan to build your own (this is where I first got the heads up on the Goldpoint products).

[Shroomz~>]

DACT Type 23-Stepped Attenuator 100K - 4 section (quad) type for balanced stereo use - $50

Also available in 50k & 10k versions.

[Neutron]

I was reading about the SPL one today (and laughing at the price) it is not passive.
It says it has active (but analog) circuits in it.

sometimes its better to have a buffer in there anyways, otherwise varying (or vintage) equipment may not work well together depending on input and output impedance of the amplifier and source. on the other hand, most things we use these days (converter, active speakers, amps etc) already have a buffer stage on the outputs and inputs, so passive is fine.

the price is ridiculous though. for that much I would expect tubes and dilithium crystals for a simple gain control circuit.
we are getting out of ridiculous studio equipment prices up there with outrageous "audiophile" prices.

[Neutron]

I've been doing a bit of digging around on the DIY side of volume/level controllers & there's some really interesting projects & kits kicking around if you go looking. If anyone else is like me & interested in building their own UBER high quality Passive Level Control that is just a simple big knob for attenuating the level of your active monitors, you should check out the Goldpoint Mini-V Quad stepped attenuator (see picture below). For $249 there may be no better choice.



If you're not into building your own, but want a really high quality Passive Level Control that is just a simple big knob for attenuating the level of your active monitors, you should check out the Goldpoint SA1X Passive Level Control (see picture below). It costs $442, but if you've got really expensive monitor speakers it's probably worth every penny.




~Mark

That looks rather nice. the switch is still a bit much, but at least you know what its doing and not some mystery volume control circuit.

remember if you have balanced stereo out/in then you need the 4 attenuators to do it well.

im looking at this one. http://cgi.ebay.ca/Balance-XLR-23-stepp ... 240%3A1318
its 4 ch balanced switch, easy to set up and $50. but you need some XLR/TRS panel jacks, and case. but im a cheap bastard and will do without the "better sonic qualities" [without any actual graph or numbers to show it lol]

[Shroomz~>]

im looking at this one. http://cgi.ebay.ca/Balance-XLR-23-stepp ... 240%3A1318
its 4 ch balanced switch, easy to set up and $50. but you need some XLR/TRS panel jacks, and case. but im a cheap bastard and will do without the "better sonic qualities" [without any actual graph or numbers to show it lol]

That's the one I linked to up above. It only comes in 10, 50 & 100k resistance values though. So you think 10k would be best? I don't need mutes & A/B switching & a headphone amp & all that stuff, so just the passive volume attenuator is what I want to make. I'm thinking the price could be brought down a lot more by just using a standard 4-gang pot instead of these expensive stepped ones. Then you'd only be looking at a couple of bucks plus the cost of the 4 XLR sockets & a box. What do you reckon?

[Neutron]

Yes 10k is the norm for that type of attenuator. you could test it by lashing up some cheap 10k pots (audio taper) just to be sure.

then just wire it up to XLR (well im going to use TRS, because my a16 and speakers have TRS, and they are cheaper, and the holes are easier to drill, and i have some)

and you can use as nice or as cheap a box as you like. i have some cocobolo blocks, ill route one out and put aluminum rear plate for connectors, and knob ill turn on my lathe. for a change its a project i can make without buying more crap apart from the main part

If you get TRS ones, and want to use a metal mounting box or plate, then dont get ones which are grounded to the mounting hole. there should only be 1 ground connection to the case or you can get a earth loop (hum) but the grounds should continue from in to out cables as if they were a straight cable. as well as the line from the input ground to the switches ground (2 per channel)

[Shroomz~>]

I was thinking I could get away with using something like this (only 2 of the 3 decks for balanced stereo attenuation though) ... I would use deck 1 for the L & R hot signals & deck 2 for the cold signals -



I noticed on that Goldpoint website that their $442 passive volume attenuator box uses a 25k version of that Mini-V stepped pot, but they say they can give you it with anything from 10 - 100k resistance. Also noticing that some of the Alps pots designed for volume attenuation are 100k, so I'm uncertain what to go for. I think some tests are in order.

[Shroomz~>]

I think I've found the perfect pot for the job Neutron. Couple one of these up with some high quality XLR (or in your case TRS) sockets/jacks in a nice box & you've got a passive volume controller that would cost you hundreds of dollars. >> ALPS-Quad-Potentiometer-RK27114-Pot-RK27-10K-o-5K-Audio

[Shroomz~>]

Even better would be THIS high-end 6-gang motorized alps pot that costs less than $20. In theory, you could use 4 gangs for stereo balanced attenuation & the other 2 gangs for stereo unbalanced, giving you a dual purpose box with balanced & unbalanced I/O's that doesn't even need any switching. The same German company that sells that Alps pot also sell compatible remote kits for $90, but that's a bit OTT since it's needless cost & you'd need to power the unit to use the pot's motor & remote the kit.

[Neutron]

in that case, using regular pots then just
http://www.music123.com/SMPro-Audio-Nan ... 0.Music123

as for that motorised alps, thats cool because you could put it behind your gear so the cable run is short, and just run a small wire that only controls the motor (via H-bridge) to control on your desk.

[Shroomz~>]

as for that motorised alps, thats cool because you could put it behind your gear so the cable run is short, and just run a small wire that only controls the motor (via H-bridge) to control on your desk.

There's no reason why you couldn't do just that with a normal high-end alps pot (or whatever) as well, since the cable diameter wouldn't be that much bigger. So you'd only have a very small housing for the pot/knob itself on your desktop & a box or 1U rack panel housing the I/O sockets away from your central monitoring position. Nice idea tbh, as cables should be kept to a minimum in the area that you'd ideally want a volume controller for your monitors.

Btw, the main reason I like the motorized one is that it's half the price with 2 xtra gangs.