| Author | Message | ||
| gare
Intermediate Member Username: gare Post Number: 136 Registered: 11-2003 |
I haven't found anything so far in my search..but are the filters in our wonderful basses all the same ? From model to model ? Or are they specific per model ? As an example, are the filters in a Signature and a Series I the same ? I understand the difference of the Q switches/resonance controls. It's a curiosity thing. Gary | ||
| palembic
Senior Member Username: palembic Post Number: 1911 Registered: 9-2002 |
Hi Brother Gary, how are ye?? The filters are the same, the Q-switch-things are different. Please forgive me my lack of memory but we have this very good site researchers like brother Dave who will find the requested thing IMMEDIATELY for you. So You have the 0 db to +6 db two position switch I think there was once a 0 db to +9 db position switch also. You have the 0 db to + 6 db to + 9db three position switch Yo have the 0db to + 9db to + 12 db for the Signature and Series I electronics. ANd you have the 0db to + 15db continuously (CVQ) for the Series II electronics. Of course you have Brother goldfish Bob with the onboard half SF-2 on his custom Rogue which is FAAAAAAR out of my league from filter and Q point of view. But for guitars -except the Bob ..."thing" ...all FILTERS are identical. Of course ...it is only MY memory. Paul the bad one | ||
| bsee
Senior Member Username: bsee Post Number: 743 Registered: 3-2004 |
Actually, you have: 1. The 0 / +8 dB 2-position (standard anywhere there is a Q switch on a non-series instrument) 2. The 0 / +6 dB / +9 dB 3-position (standard on Series I, upgrade on lesser models) 3. The 0 to +15 dB CVQ (Series II only) I discussed some other wild options with Mica most of a year ago, so other combinations are possible, but they will cost in both time and money since they would have to pass Ron's bench. | ||
| byoung
Junior Username: byoung Post Number: 16 Registered: 12-2004 |
I can't understand why the Q switch/dial unit is in dB. Q, as I understand it, specifies the bandwidth, and is simply a ratio. I haven't ever heard discussed the actual slope of the Alembic filters, but maybe that's "secret sauce". Brad | ||
| gare
Intermediate Member Username: gare Post Number: 137 Registered: 11-2003 |
Brother Paul..I'm just fine, hope all's well in your hemisphere. I've found alot of info on Q controls and boost switches, and I have those concepts down from working with modular synths. But I've haven't spotted anything describing the filters. It would make sense to use just one filter/pc board tho. So I just had to ask. Oh..and next time, have a lager for me ! G | ||
| bsee
Senior Member Username: bsee Post Number: 744 Registered: 3-2004 |
Brad, we've had that discussion. The Q switch isn't really a Q switch at all. The filter is a low-pass, and the Q switch controls the amount of boost in a band centered on the filter's cutoff frequency. | ||
| cntrabssn
Junior Username: cntrabssn Post Number: 34 Registered: 6-2002 |
Brad, I sometimes wonder the same thing about how Q is expressed. I THINK Q is the ratio of level (at a particular frequency) to bandwidth, so changing the level or the bandwidth changes the Q. Maybe that's where it comes from. The low pass filter slope is 2nd order, or 12 dB per octave. I believe a club member named Werner posted some really good info about filtering in general. You can search the club for his posts. Perhaps some other helpful club members might even dig them up for you. Hope this helps, - nate. | ||
| gare
Intermediate Member Username: gare Post Number: 138 Registered: 11-2003 |
A 12db filter will be 6db on either side of 0 for a given waveform, like a sine wave. So its actually +/- 6db. Think of the filter as a broadband parametric eq. The filter control sets the center frequency. The Q switch boosts the signal at the center frequency by a set amount, be it 6/8/9 db. Not having a Series II bass to verify, but I believe the Series II has both frequency and bandwidth controls, plus boost switches. A filter is nothing more than a sophisticated/specialized equalizer. | ||
| dfung60
Member Username: dfung60 Post Number: 63 Registered: 5-2002 |
The discussion is pretty close, but not exactly right. A "full parametric" EQ lets you control the center frequency of a tone control, the bandwidth or group of frequencies that the filter effects, and the Q factor or the sharpness of the filter's effect. The type of a filter is also a factor - these parameters define a bandpass filter that lets a range of frequencies through and attenuate anything higher or lower than the passband; shelving filters (a high- or low-pass filter) affect only frequencies below the passband or above. The Alembic filters with Q-switch are semi-parametric. The knobs and switches let you select the center frequency and the Q-factor, but not the bandwidth which was preset at the factory. The filter is also configured as a low-pass filter. The effect of the filter is like there's a resonant peak at a certain frequency. Everything below the resonant frequency passes through to the output. As you turn the tone knob, this resonant frequency is moving around. When the Q-switch is set at 0db, the circuit acts pretty much like a passive tone control When you flip the Q-switch to the +9db position, there's a bump introduced into the frequency response of the bass - lower frequencies are unchanged, notes at the center frequency are boosted by 9db (a lot, that's 8x the voltage!), and notes higher than the passband are filtered out. There's no knob to tweak the bandwidth, but the Q switch is making a peak of 0, +9, +15, or whatever db in this range. This radically effects the way you hear the sound. This is also why the effect of the Q-switch is expressed in dB - it's the ratio of output levels in the affected area, and that's what dB are for. If you flip the Q-switch to the high Q position and turn the tone knob you'll hear a sweep like a wah-wah pedal. That's the resonant peak sweeping through the frequency spectrum of the instrument. There's other more obscure effects as well - for instance, active tone controls can cause a phase shift that depends on the frequency. Even beyond the parametric characteristics, this is one of those things that you can easily hear but probably can't describe in any meaningful terms. David Fung Obviously you can build a full parametric EQ. On the instrument it probably didn't make sense to do that - it's hard enough to grok the effects of the controls that are there, much less add additional ones that widen the tonal effects. If there had been Q- and bandwidth-switches, it would likely have caused a lot of confusion among users. | ||
| dfung60
Member Username: dfung60 Post Number: 64 Registered: 5-2002 |
The discussion is pretty close, but not exactly right. A "full parametric" EQ lets you control the center frequency of a tone control, the bandwidth or group of frequencies that the filter effects, and the Q factor or the sharpness of the filter's effect. The type of a filter is also a factor - these parameters define a bandpass filter that lets a range of frequencies through and attenuate anything higher or lower than the passband; shelving filters (a high- or low-pass filter) affect only frequencies below the passband or above. The Alembic filters with Q-switch are semi-parametric. The knobs and switches let you select the center frequency and the Q-factor, but not the bandwidth which was preset at the factory. The filter is also configured as a low-pass filter. The effect of the filter is like there's a resonant peak at a certain frequency. Everything below the resonant frequency passes through to the output. As you turn the tone knob, this resonant frequency is moving around. When the Q-switch is set at 0db, the circuit acts pretty much like a passive tone control When you flip the Q-switch to the +9db position, there's a bump introduced into the frequency response of the bass - lower frequencies are unchanged, notes at the center frequency are boosted by 9db (a lot, that's 8x the voltage!), and notes higher than the passband are filtered out. There's no knob to tweak the bandwidth, but the Q switch is making a peak of 0, +9, +15, or whatever db in this range. This radically effects the way you hear the sound. This is also why the effect of the Q-switch is expressed in dB - it's the ratio of output levels in the affected area, and that's what dB are for. If you flip the Q-switch to the high Q position and turn the tone knob you'll hear a sweep like a wah-wah pedal. That's the resonant peak sweeping through the frequency spectrum of the instrument. Obviously you can build a full parametric EQ. On the instrument it probably didn't make sense to do that - it's hard enough to grok the effects of the controls that are there, much less add additional ones that widen the tonal effects. If there had been Q- and bandwidth-switches, it would likely have caused a lot of confusion among users. The circuit also is only set up to have a resonant peak. It could easily have a notch instead, sucking out the sound in the passband, but again, it's getting really complex and not very user friendly. There's other more obscure effects as well - for instance, active tone controls can cause a phase shift that depends on the frequency. Even beyond the parametric characteristics, this is one of those things that most people can easily hear but probably can't describe in any meaningful terms. David Fung | ||
| dfung60
Member Username: dfung60 Post Number: 65 Registered: 5-2002 |
Sorry about the nearly identical double posts. I seem to be having a "patience" problem when posting the last couple of days. I realized that I had gotten that last response out of sequence and dived for the "stop" button expecting to terminate the first posting. Obviously, I wasn't quite quick enough! David Fung | ||
| gare
Intermediate Member Username: gare Post Number: 139 Registered: 11-2003 |
Thanks Dave..I'm not always the most articulate when trying to explain somethings. G | ||
| rover
Junior Username: rover Post Number: 13 Registered: 2-2003 |
And now for the questions from someone who doesn't speak the languages of electrical or audio engineering... Is there a point at which settings on an SF2 could "counterbalance" Q settings on your bass? And as long as I'm rambling about SF2's (just got mine; amazing), what is the impact of the A channel controls when playing in mono? All of the manual diagrams show the A channel set to consistent levels, but I'm not sure why since tweaking them in mono introduces new tones. To those who've never experienced an SF2, it's like having a small box with a few hundred different basses inside. Worth every cent. Any information/edification would be much appreciated. Rob | ||
| lbpesq
Advanced Member Username: lbpesq Post Number: 310 Registered: 7-2004 |
Rob: Been there, done that. The manual was basically a mistake. The settings that change on one side can be set on the other just as effectively. They never meant for one side to always be the same. Both channels work in either mono or stereo modes. Bill, tgo | ||
| byoung
Junior Username: byoung Post Number: 17 Registered: 12-2004 |
Bob, I have read through many (maybe all) of the discussions on Q switches/dials, and I can't remember having seen a discussion of the classical definition of Q as it relates to the specific Alembic implementation(s) (specifically the fact that Q isn't measured in dB). My apologies if this is duplicate or redundant material; I was still confused after having read previous discussions and other (rather heavy) material on filters. Brad | ||
| bsee
Senior Member Username: bsee Post Number: 745 Registered: 3-2004 |
Hi Brad- I didn't mean it that way at all. I just know that we've had this discussion at least once in the past 6-9 months, and was prefacing my comments as representative of info from that collaboration. My recollection of that discussion was an admission that the Q switch really doesn't control the Q. Rather than thinking of it in classical terms, though, the description of the impact of the switch is pretty clear. The switch controls the amount of boost centered at the elbow frequency of the low-pass filter. One thing that I don't think was mentioned in this thread is that a bass that has a filter and no Q switch is hard wired for a +8 dB boost. Does the content of this thread answer your questions, or are there still things left unsaid? -Bob | ||
| cntrabssn
Junior Username: cntrabssn Post Number: 35 Registered: 6-2002 |
OK, I guess I had the Q equation wrong. However, I have seen some stuff that relates Q factor in low pass filters to the peak filter gain, which is expressed in dB, e.g. Q = 1 equals 0 dB resonant peak, while Q = 4 equals a 12 dB resonant peak. I wish I was better at math. I guess I've got some more reading to do  Anyway, the post I mentioned earlier from the other club member is here: http://alembic.com/club/messages/393/3449.html#POST5376 - nate. (Message edited by cntrabssn on February 04, 2005) | ||
| adriaan
Senior Member Username: adriaan Post Number: 481 Registered: 6-2002 |
From what I recall from the discussion, Q is short for quality, and it is an expression for the ratio between the peak level (measured in dB; instead of a peak you could also have a dip) and the distance between the 0 dB points at either side of the resonance (aka bandwidth). So the Q switch really does control the Q, but backhandedly - it actually sets the level of the resonance peak. | ||
| dfung60
Member Username: dfung60 Post Number: 66 Registered: 5-2002 |
adriaan is right on with regard to the classical discussion of "Q" and it does stand for quality. A bandpass filter is selectively favoring part of the full frequency spectrum that is presented to it. If you drew a frequency response graph, it would be a hump. The Q of this filter reflects how steeply the sides of the hump rise, expressed as a ratio in dB. The bandpass of this filter is the width of the top of the hump (the plateau of the mesa!). If you had a really wide bandpass, then you might not notice that a filter had very high Q. If you have a narrow bandpass, then you'll perceive the steep sides and narrow top as a resonance peak. These filter concepts are really important for things like TV sets or radios. Traditionally, the program material is impressed (modulated)upon a carrier frequency and there are many carrier frequencies carrying information in parallel. A bandpass filter very similar in concept to your tone controls is singling out a single station from the jumble. The frequencies and bandwidth are carefully defined by the government, and the Q of your receiver affects your ability to receive stations clearly. A radio tuning circuit is more sophisticated than the tone control in your Alembic, but the mere fact that I just said that will probably cause Ron to develop the first superhetrodyne tone controls for some future Series III bass! :-) Of course, the digital age starts rendering a lot of this analog stuff one step closer to antiquity. Creating filters that would be impossible with physical components is just a matter of software with modern DSPs. I guess that will be Series IV(!), although I doubt that anybody other than Alembic would invest the effort to make a digital filter that is musically beautiful rather than "not too bad". Maybe it's just me - I have an HDTV and find that the digital artifacts from the conversion to progressive scan much more annoying than the interlaced video that it's trying to "correct". David Fung | ||
| adriaan
Senior Member Username: adriaan Post Number: 483 Registered: 6-2002 |
David, Couldn't agree with you more about the digital stuff (this coming from one who spends his working day stuck behind a computer). The resonances that an analogue filter produces in electric signals is - well - analogue to the resonances that the body of an instrument produces on the sound waves travelling through the instrument, and that is what makes the audio fingerprint of that particular instrument. With digital sound synthesis you get chopped up resonances - try listening to a digital piano for longer than 1 minute and say your ears don't get tired from the never-ending resonance fits and starts. Try sustaining a single note on that same digital piano and listen how the sound chuckles as it decays. I have been considering getting a digital piano so I could play with headphones, but the drizzle ... | ||
| gare
Intermediate Member Username: gare Post Number: 140 Registered: 11-2003 |
Guess I kinda opened a can of worms huh ? LOL Prehaps Mica or Val will jump in and verify my original question..are the Alembic filters all the same ? Adriaan..checkout General Musics digital pianos, just recently reading up on them, looks interesting..they're at www.Generalmusic.com. I also really like the Kurzweil grand piano sound. and thanks everyone for the responses and info. Gary | ||
| rover
Junior Username: rover Post Number: 14 Registered: 2-2003 |
All, My questions may be overly naïve to some, but I would still appreciate some guidance regarding the possibility of the Q settings on my bass (Anniversary) having an impact on the functionality of the SF2 or vice versa. For example if the Q switch on the bass is activated to give an 8db boost and the filter is nearly “closed” thus blocking passage of the lowest onboard frequencies, is there a contradictory ramification of having the SF2 set in low pass mode which introduces frequencies lower than the instrument electronics allow on their own or does one (instrument v. SF2) simply override the other? Thanks, Rob | ||
| the_mule
Senior Member Username: the_mule Post Number: 419 Registered: 1-2004 |
>>> "Are the Alembic filters all the same?" All filters on Alembic's basses are low-pass filters. Only a few exceptions to this rule, this is one of them: http://alembic.com/club/messages/411/16123.html?1107342100 With Alembic's SF-2 Superfilter rackmounted 'box of wonders' you can also use high-pass and band-pass filtering. This is how I explain the difference to interested friends and relatives. Maybe not 100% accurate, but they seem to understand... low-pass = frequencies below the selected frequency are allowed to 'pass' high-pass = frequencies above the selected frequecy are allowed to 'pass' band-pass = a certain bandwith around the selected frequency is allowed to 'pass' >>> "I would still appreciate some guidance regarding the possibility of the Q settings on my bass (Anniversary) having an impact on the functionality of the SF2 or vice versa." I don't have any technical background, so I can't give an explanation, but hopefully someone else? I can only tell you what my experiences are: I have a EVH 4 carrying custom electronics (2x volume, standby-switch, 2x low-pass filter and 2x 3-position q-switches) and I use it sometimes with, sometimes without a SF-2 Superfilter. I noticed that when both the SF-2's 'direct gain' and 'filter gain' are activated, thus mixing the natural signal of the bass with the signal of the SF-2, it's not hard to find settings which result in a strange (interesting, ugly, out-of-this-world, etc. etc.) interaction between your bass and the SF-2. I can only conclude that it's an interaction, and not a case of one 'overruling' the other... Wilfred | ||
| adriaan
Senior Member Username: adriaan Post Number: 485 Registered: 6-2002 |
Rob, The part of the spectrum that you filter out by tuning the onboard filters to a lower frequency (with or without the Q boost) you simply cannot magically reclaim with an outboard EQ of any kind. I've forgotten the niceties of the one time I played through an SF-2 (it was the second time I held an Alembic bass, and actualy the first time I held my Epic, so my attention was on other matters) but it don't think even the SF-2 can reclaim a missing part of the spectrum. | ||
| rover
Junior Username: rover Post Number: 15 Registered: 2-2003 |
Thanks for the insights. I'm sure I'll have more questions as I learn the basics of the SF2 over the next decade or so. Rob |
