FAQ

Why is my gain structure so messed up?

  • This is the most common question I get. My reply was, and still is, the same: “Understand gain structure and you won’t have that problem.”
  • This can be a confusing discussion for those with a limited technical background. There are many facets to this gain management issue, including the “missing link” loading, or impedance matching (or mis matching!).
  • So perhaps I can clear up the muddy waters a bit, and promote a fuller understanding of gain management re: noise, distortion and impedance matching… aka “loading”, and elaborate on the benefit of using a mixer b/w the KB and the SS3.
  • First off, many users unknowingly degrade their S/N ratios, and fail to maximize their “tone.” When using a mixer the LAST Volume to be raised (to need) should be the SS3 Level.
  • Think of the gain management of any signal path as “bigger in front, and lower in rear”. So you would always want to maximize the signal level (short of distorting it) at every stage or decision point. So this allows you to keep the last stage of the gain chain (SS3 level) as LOW as possible as you reach the desired playing (or recording) volume. This a “true rule” for any mixing situation.
  • So, firstly, drive your KB level well up, saving a bit of headroom for those solos as you may want to do occasionally to rightly show off after a guitar solo. So then set your mixer channel 1st trim for input “gain” so that it’s Red LED Clip light is just below it’s “peak” (when you’re cranking out that show off solo).
  • The next “gain” stage is the mixer’s individual channel volume, which should also be set well up. Usually mixers will have a “00” Unity gain setting about two thirds up the channel fader (or rotary) pot and show “+1db” above that point, and “-1db” below it.
  • Now if all signals being mixed were 1st set to the same “clip” point, then had their channel levels set to unity… then in theory they would all have the same volume. But of course, this mix balance may change a bit if you need one channel lower or higher than the others (usually the band member who brings the PA and/or mixes will sound the loudest).
  • But in this way you are using your pre fader “gain control” to balance you various instruments (and vocals) so they all should have about the same “volume” when their channels are set for “00” unity… and you can “mix to taste” from there.
  • Next; raise the “Master” output level of your mixer. If you have a VU meter or a more modern LED metering system, you’d want to get that well up there too, perhaps just below “clipping” when your various sources are really “cooking” (or near their max playing levels).
  • Now at least know your KB and then your mixer is not distorting, while delivering the most amount of signal and the lowest signal to noise ratio possible to the SS3 inputs.
  • OK, so now the LAST thing you do in your “gain chain” is set the Master Level on the SS3 amp. My guess is this will usually be around 12 o’clock, not 3 o’ clock… unless you need ALL of the 107dB the SS3 can deliver (which happens… I fully understand about Marshall stacks and deaf drummers)!
  • So in this way, if you begin to hear distortion you KNOW it is the SS3 hitting the ceiling of it’s ability. (and every amp has it’s limits… the SS3 is no exception). But it can get VERY loud and stay clean if you follow the above “true rules” of gain management.
  • But there is another, often misunderstood, benefit of using a mixer b/w your KB and SS3; impedance management. Matching the “impedance” of your source to the next gain stage is key to getting good clean tone from any instrument and amp combination.
  • Many toss around that word “impedance”, explaining that is a measurement in “Ohms” (true enough), and yet do not have practical or full understanding of it’s possible negative impact (if mismatched), and how important it is to signal processing and keeping a good sound as you manage your “gain” chain.
  • I like to use a layman’s approach of explaining impedance with a simple anaolgy of a water pump and a garden hose. You guys who are more technical, please forgive my over simplification that follows… bite your tongue please.
  • So imagine the pump is your amp (or signal source, in Randelph case his KB)) and this pump is designed to delivering 100 pounds of water pressure into an 1″ garden hose. So, in this case study, the “pipe size” (or impedance”) for the “flow” is like 1 Ohm of impedance. As long as you flow stays in that 1″ pipe, 100 pounds of water pressure (signal) is delivered to the next input stage (IE; the input impedance..AKA “Load”… of your amp or mixer input stage). Matching the pipe size b/w source and input stage keeps the water (signal) flowing easily… and nothing is “lost” in transmission. Life is good.
  • However what of if the next stage has a larger pipe size “input”, or “load impedance? Lets say it’s got an opening of 2” pipe… or otherwise a higher impedance… well, then you’d have a reduction water pressure (gain), cut down by 1/2… now you’d have 50 pounds of water pressure. So then, the next pump stage has to “make up” that loss (amplify more) to get your water pressure back up to 100 pounds. And there’s the 1st problem; in so doing it MUST contribute some artifacts (IE: adds NOISE), and also might degrade some character of the flow as it “adds gain” (loss of frequencies). Not good.
  • The next stage (IE: your mixer, or SS3 amplifiers) can make up that pressure (gain) loss… but it can not make up loss of the source’s sonics and/or get back your noise floor (FYI, each gain stage adds noise… so this “noise floor” accumulates when ever you add amplification!).
  • On the other hand, what if the next stage has a SMALLER pipe size opening (load impedance)? Let’s say it hits a pipe size of just 1/2″. Could you can expect 200 pounds of water pressure out the other end? Or, can you imagine that smaller “load” might cause your water pump to “back up” and work a lot harder. Well, you’d be right about both scenarios… to some extent mismatching these pipe sizes (impedances) can have some negative effect on your “flow”. Also, your pump could possibly “overload” and that could easily cause distortion.. In the common case of a power amp designed to deliver 100 watts into 8 Ohms… loading it down with a bunch of speakers (parallel wiring DIVIDES the load each time you add another cab) down to 2 Ohms can actually cause your “water pump” to blow!
  • Also. imagine in this scenario your pump, even if it doesn’t “blow”, your “source” is having to push harder because it is not well matched to the next stage… and this can degrade signal… even cause distortion.
  • OK, now let me bring this all home, and get back to our “design challenges” when designing the SS3’s input sensitivity and loading impedance.
  • Well, we understood our SS3 could be “looking at” signals from either a (relatively) high impedance (relatively) low gain -10dB Keyboard signal OR a (relatively) low impedance (relatively) high gain +4db mixer signal. So we had to set out SS3 “input sensitivity” somewhere in the middle to accommodate either. And also so either “source” could drive the SS3 to maximum SPL Levels… and stay fairly clean in the process… not easy!
  • Now a typical mono combo KB amp would have a input sensitivity set to optimize a typical -10dB (or slightly higher) KB signal, while a typical mono powered PA speaker has an input sensitivity optimized for a +4db Low Z mixer signal (although some do offer a switch to -10db).
  • But for the SS3 we had to find a “happy middle” ground. That said, using a mixer and turning the SS3 down will usually give you a slight improvement in sonics, and also a slightly lower S/N ratio too.
  • So while the SS3 can deliver excellent sonics and low noise while reaching 107dB + with just a KB plugged directly in (and does for many on this forum), a mixer can possibly improve your results in some situations. And of course, those extra channels and possible builtin stereo FX can really expand your performance options and also provide more flexibility for gain management and better impedance matching.
  • In some situations, adding a mixer b/w a KB and the SS3 did “the trick” when a user complained about noise, distortion, or a thinning of tone. A mixer can optimize both the gain and loading b/w a KB and the SS3 input stage… which is a almost always a good thing.
  • Wow, how can I record that!”

  • This is the most common question I get when first demonstrating CPS in my APR studio, which was where CPS was born and developed. My reply was, and still is, the same; why, in MS of course!
  • While there are many methods of stereo recording, my personal favorite is MS (or Mid/Side) because MS has that “being there” center channel (but still stereo) image. It’s not “Hard Left and Right” . much like most things we hear in real life, so IMHO it has a more natural stereo sound. MS is also the method we have used to record all of our on line videos.
  • It also is one quick way I can explain another most common question asked upon hearing CPS for the first time; “How does it work?” , that is IF I am speaking to a fellow audio engineer. Most musicians today have a studio or extensive recording experience, too… so I usually start with those 3 little words: “It’s MS backwards”, which usually followed by big smiles and slapped foreheads. FYI, “reversing MS” was the original spark of inspiration for CPS by my dear departed friend and CPS partner Drew Daniels, who was also an excellent audio engineer… and a big advocate for MS recording.
  • How does Center Point Stereo work?

  • CPS special electronics inhales stereo Left and Right signals and exhales Front and Side signals for reproduction by the special (spacial?) CPS speaker configuration of a Front facing and Side facing speaker.
  • The Front speaker contains and reproduces ONLY those signals that are the “same” in the L&R signals (or mono).
  • The Side speaker contains and reproduces ONLY those signals that are unique in the L&R… or the Left and Right “stereo” parts of the two signals.
  • Because the special (spatial?) Front and Side speakers are positioned at a right angle to each other – or technically “out of phase” – they do not combine as do conventional stereo signals; instead, they repel each other and do not mix, enhancing their dispersion (CPS dispersion is 300 degrees – nearly a full circle – unlike most stereo speakers, which have a 30×90 degree dispersion pattern.
  • Furthermore, because they emanate from a “center” point, they travel and arrive at the exact same time at your ear, your band mates ears, or your audience’s ears where they are reassembled to provide a unique, realistic and almost 3D stereo image, unlike a conventional stereo image
  • What kind of stereo signals can be used for the SS v.3?

  • The input sensitivity of the v.3 will accommodate both instrument and line level unbalanced stereo signals. It can also accommodate audio files, such as MP3 music files from an iPad, a CD player or a smart phone.
  • What is the warranty period on my Spacestation amp, and
    why is there no way to register my purchase on your website?

  • The laws on warranty today are quite clear; a manufacture’s warranty is in force from DOP (Date of Purchase), so you are “covered” regardless of any registration.
  • You have one year “parts and labor” on your Aspen Pittman Designs product, which is established by your DOP.
  • There are only 2 places I sell APD products; Sweetwater Sound and my Aspen and Associates website. So both you and I will always have good records of this date.
  • The corporate habit of “collecting names” by your registration for building an internal email list for “future promotions” (or to sell it to those who do that) is just not interesting to me. I do not care to add “special offer” messages to your inbox spam folders. Frankly, this archaic practice offends me.
  • So don’t worry, be happy… and enjoy your Center Point Stereo amplifier! And, be sure to let me know if anything disrupts your enjoyment. In the very rare case anything should go wrong, I will personally see that you are satisfied. Customer service after the sale is my personal commitment to you… you are family now! – Aspen
  • What is the nature of the signal coming from the SUB output, and how can I best use it?

  • The SUB output is an unfiltered full frequency range signal that is a combination of both the Left and Right signals (or the mono mix).
  • It is a line level signal suitable for driving a powered sub woofer, sending as a “mono” signal to the FOH mixer, another to drive an additional stage monitor (e.g. to the far side of a stage).
  • Subwoofer signal path Behringer B1200D

  • I just picked up a Behringer B1200D-Pro subwoofer for use with the Spacestation v3. Im guessing the best setup with the subwoofer is to run into the sub and out from the sub to the Spacestation. Would you foresee any issues with using a balanced XLR to 1/4 cable for the sub outs to Spacestation inputs? Yes, it would be the obvious path to run KB-B1200-SS3, and make use of the hi pass filter… and there should be no problem for the 1/4-XLR cables… short ones like 3′ are perfect and the TRS works as well as a TS on the 1/4″ side.
  • However, I noticed that this path seems to suck about 6-10dB of gain from the KB to the SS3, which can be compensated by increasing the level of the SS3… there is enough makeup gain but the signal-to-noise ratio suffers, albeit not noticeably. So in my studio and on a few gigs I have used the B1200 run out of the SS3 sub output with just one cable – KB -> (mixer-optional)>SS3 -> B1200. For extremely loud gigs, the opposite way may prove the better way but for medium SPL gigs I do not think the SS3 suffers from getting a full range signal. Also I think too much sub can be a bad thing… so be careful to keep it (the hi pass filter) under 125Hz tops, even better may be 80-100Hz and also not too much level (just enough to feel it). When I run the sub after the SS3 it’s easy to plug and unplug the sub and judge the difference. Basically, it’s just the under 100Hz LF that needs support. But if you have a bass player in the band you may find yourself leaving the sub home for those smaller gigs. Although, I prefer bringing the sub and just keeping it “low”, it just sounds better to me. This also allows me to elevate the SS3 which can be a good thing, but be careful not to listen to it “on axis” or you will probably be mixing the Width too high… listen to it off axis is possible. Some users are even putting it on an amp stand sideways so the side speaker bounces off the floor. This gives some nice bloom in close quarters.
  • Can I use 2 Spacestations on the same stage? What happens to the CPS effect if I do?

  • Of course you can use 2 SS v.3 on the same stage, but it probably is not necessary and may not even work as well as one. One reason the CPS is so impressive is its clarity and 3D like image come from one “center” point. However, using 2 to reproduce the same signals creates two point sources, and that may actually diminish the 3D stereo effect.
  • However, if he two SS v.3 speakers are reproducing separate signals, for examples a band may use one to amplify the vocals, while the other for instruments. This can work amazing, especially if they are stacked, and therefore “time aligned”. This can be a very effective way to provide sound reinforcement for a small combo group performing in a small to medium sized venue because the performers here exactly the same mix, and it is the same mix as the audience will hear.
  • Can this be used in both 120v and 230v countries?

  • Yes, can be used for both 120v and 230 countries. However a conversion is an internal rewiring, and there is also a fuse value change required; T3.1a for 120v slo blo and 100v countries, and T2a slo blo for 230v countries.
  • What is the best way to position the SS v.3 on a stage?

    On the floor, and well behind you if you are performing. Even better if you can place it by a wall or in a corner. The CPS image improves the farther away you are from it, unlike conventional speakers or stereo speaker. It has a gentle and very wide dispersion so it travels all over the stage to the audience no matter where they sit in the venue.
  • CPS works best where it can “reflect” the best – on the floor, near a wall or -even better – in a corner. That’s because the more reflective interaction between the Front and Side speakers, the better they manipulate and disperse each other; and, in so doing, create a more powerful stereo effect.
  • We therefore recommend placing it well behind you and near a back wall or in a corner… don’t worry – you will hear it fine, and so will the rest of the room! If no wall or corner is available, an effective method of enhancing the CPS effect can be achieved by placing a reflective surface behind the speaker, such as a few guitar cases in a “V” configuration; or, you can use a hinged panel forming a “corner” behind the Side speaker and projecting it’s energy forward to manipulate the Front speaker.
  • What instruments can be used with the SS v.3?

  • The SS v.3 is a full range triamped low distortion amplifier well suited for live performance amplification all electronic keyboards, guitars, drums, strings (violin, cello, mandolin, etc.), and vocals. It is the most effective when the instruments or vocals contain some stereo content, such as stereo delay, stereo reverb, stereo chorus or various forms of Doppler stereo image modeling such as a KB Leslie simulation. It can also be a very effective stereo system for backing tracks for the vocal or instrument performer to sing over, or for playing along with in live performance.
  • What’s the recommended procedure for setting the SS v.3 rear level controls?

  • The SS v.3 has 4 Class D amps powering the four speakers; the 8″ Front woofer, the 1″ Front MF horn driver (this is a coaxial speaker – so one driver nested inside the other), the Front HF Tweeter, and the 6.5″ full range Side speaker. The level controls on the rear panel set the balance between these four speakers. The following is how we recommend setting these level controls. Depending on your application, we recommend playing a recording of your keyboards, guitar, your vocal or your whole band with vocals through the SS v.3 while adjusting the controls.
  • We also recommend you stand well away from the speaker, (even off axis) while setting and evaluating the level controls (do NOT stand directly in front of it). With all level controls full off, start by turning up the LEVEL control to a comfortable sound level you can hear from a distance.
  • Next, turn up the MF level to about 12 o’clock. The vocals and instrument fundamentals should now be very pronounced. You can dial in more or less depending on how it sounds to you… some instruments are very strong in this area.
  • Then, turn up the HF to 12 o’clock or higher… but if your signal doesn’t have much HF content you will probably not hear much coming out of this component.
  • Lastly, turn up the Side speaker level to about 12 o’clock… this will reveal the amount of stereo content in your L&R signals. You may wish to exaggerate this by turning it up all the way and then back it off until it sounds just right. In more reflective or acoustically live room you may need less Side level. Conversely, in a dead room you may want a bit more Side level. Once you have the three Side/MF/HF levels set for tonal and stereo “balance”, the Level control can be adjusted up or down without affecting the over all balance of the four speakers.
  • Finally, we should mention here that we have set these 3 Side/MF/HF levels to be acoustically “normal” at about 12 o’clock. So it may be faster and easier to just start there and raise the master Level control to the level you need. Watch this!