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Double Bass NEW Euphonic Audio iAMP Doubler

#41
I'd like to know exactly what the "variable phase" thing does. I've messed with a device that offered variable impedance and found it interesting. But variable phase? Never heard sucha thing.

So if Dr. Rob, Nurse Les, and others of various titles wanted to weigh in on this, I'd be all ears. How can variable phase help you dial in a good clean sound? While we're at it, how closely can the notch filter gizmo on this thing approximate the effect of a HP filter?

Last, do these filters apply to both channels, or only channel 1? I can't tell from looking - but remember, I'm from Kentucky.
 
#42
drurb said:
So considering all of this, if you have two amplifiers that are otherwise identical and one has a rating of 300 watts and the other has a rating of 550 watts, what does that mean to a "non-EE" double-bassist? Your ears and brain care about ratios-- decibels. The 2.6 dB you'll get by going from 300 to 550 watts is meager. It will be just a kiss louder in the end.
Click to expand...

Yeah, but will it be a kiss by Phil Maneri, or a kiss by Juliette Binoche? There's a difference. :)
 
#44
Chris Fitzgerald said:
I'd like to know exactly what the "variable phase" thing does. I've messed with a device that offered variable impedance and found it interesting. But variable phase? Never heard sucha thing.

So if Dr. Rob, Nurse Les, and others of various titles wanted to weigh in on this, I'd be all ears. How can variable phase help you dial in a good clean sound?
Click to expand...

Ok, here goes. Most of us are familiar with the advantages of phase-reversal switches to cut feedback. As has been discussed here before, given that the DB is an acoustic instrument, the amplified output can actually cause the bass to resonate causing greater output at the amp, causing the bass to resonate more and BOOM-- feedback! If the output of the amp just happened to add in-phase with the vibration of the bass, feedback would get out of control quickly. If the two were to cancel, then the vibration of the bass would actually be inhibited.

In truth, nothing like this ideal situation occurs in the real world. Rather, there may be a particular frequency that is nearly in-phase with the bass and causing some feedback so, if you're lucky, inverting (flipping upside-down) the waveform coming from the amp can calm the problem. The phase relation between the output of the amp and the bass will vary as a function of frequency anyway so inverting the phase can be hit or miss. Sometimes moving the bass a foot or two will do the trick especially when you consider the wavelengths of the frequencies at issue.

If flipping the phase can be hit or miss (you have a choice of 0 or 180 degrees), you might be all that much better off of you could pick any phase between 0 and 180 degrees. What will this do for you? Well, suppose there is one nasty frequency causing the problem. You could "tune" the phase of the output of the amp to minimize the interaction with the bass. You could also move the bass a few inches! In addition, you could cause interactions with other frequencies by such "tuning." For example, adjusting the phase by 30 degrees to get rid of the nasty one may cause another one to be a problem!

So, this phase adjustment isn't about improving the sound at the output of the amp in isolation. Rather, it's about preventing interactions with the instrument, which, after all, ends up improving the sound.


Chris Fitzgerald said:
While we're at it, how closely can the notch filter gizmo on this thing approximate the effect of a HP filter?
Click to expand...

Not closely at all-- unless you dial the "notch frequency" to zero (if it even goes there). The Invalid Link Removed is, once again, a feature that helps you reduce feedback. Let's get back to that nasty frequency causing feedback. One effective way to solve the problem is to zap a very narrow range of frequencies containing the trouble-maker. The notch filter cuts out or puts a hole in the frequency response right at that point. If the notch is narrow enough, your sound shouldn't be adversely affected.

A high-pass filter (HPF), on the other hand, passes all frequencies above a certain frequency. Think of it as the upper half of a notch filter. The usual purpose of a HPF is to get rid of infrasonics and other unwanted very low frequencies. Some use a HPF to intentionally reduce some of the "boom" of the lower end in troublesome venues.

I hope this helps.

Nurse Les :)
 
#45
I find the notch/hpf selectable on the Focus very useful as I more often use the hpf to sculpt tone by pulling out the bottom end. Not that the notch is useless it is useful but if I had a choice between the two I'd want the HPF...

Doc not sure I understand the magic phase knob. Are you saying that as you turn the knob the waves kind of rotate around the speaker until they are upside down?
 
#46
peterpalmieri said:
Doc not sure I understand the magic phase knob. Are you saying that as you turn the knob the waves kind of rotate around the speaker until they are upside down?
Click to expand...

In short, yes. Think of your sound as being composed of a series of sine waves closely spaced in frequency and added up to create the specific waveform that comes out of your speaker (Fourier's theorum). Each of those sine waves has a particular amplitude and a particular phase. Now, if you flip a phase inversion switch, you turn the entire waveform upside down. That's mathematically equivalent to rotating all of the phases of all of the sine waves by 180 degrees.

Now, back to all those sine waves that make up your sound. One can build a circuit that rotates the phases of all of them by some specified amount, e.g., 30, 55, 263 degrees whatever you want. It's easy to do this with digital signal-processing but not so easy with an analog circuit. Most analog circuits sort of approximate doing this. I only know of one laboratory device ever commercially built that did this successfully. It was designed in 1959 and used routinely in labs until the early 70s. Yep, it was all vacuum tubes.
 
#47
The jump to 500 wants gives you more head room. I don't know how relevent the volume increase is. Does it matter though? How does it sound! I am looking forward to checking one of these out. I have always liked the way that iAMPs sound with both Double Bass and Electric. One of the better sounding doubling amps out there, and now they actually HAVE a doubling amp!
 
#48
Adrian Juras said:
The jump to 500 wants gives you more head room. I don't know how relevent the volume increase is. Does it matter though? How does it sound! I am looking forward to checking one of these out. I have always liked the way that iAMPs sound with both Double Bass and Electric. One of the better sounding doubling amps out there, and now they actually HAVE a doubling amp!
Click to expand...

Around and around and around we go! :) Check here and here. Assuming the same basic design, the jump from 300 to 550 gives you 2.6 dB more continuous power, 2.6 dB more transient power, 2.6 dB more peak power-- whatever power measure you like. Of course, how it sounds is quite important! It's good to be informed and understand how the numbers work so that you can evaluate how it will likely perform in situations that you may not be able to experience before you plunk down the $$$.

I certainly share your satisfaction with EA amps!
 
#49
As far as the phase switch, the biggest advantage is in combining a pickup and a mic or another piezo. Even using two of the same pickups in different locations there are phase anomalies. More so with a mic or another pickup.
Has anyone ever tried combining two different piezos or a piezo and a mic? Typically, the sound can often be worse than either one separately. This is due to out of phase relationships at different frequencies. But these phase relationships typically do not lie at exactly 180 degrees out of phase. Lets say that on one range of the bass your pickup and mic are out of phase. This will likely mean that at these frequencies the volume of the notes would be more quiet since the out of phase signals cancel eachother. Thses phase relationships occur somewhere between zero and 180 degrees out of phase. The variable switch allows you to dial in the best phase relationships.So now you can combine with a mic or pickup that previously sounded crappy in combination.
 
#50
Mike Arnopol said:
As far as the phase switch, the biggest advantage is in combining a pickup and a mic or another piezo. Even using two of the same pickups in different locations there are phase anomalies. More so with a mic or another pickup.
Has anyone ever tried combining two different piezos or a piezo and a mic? Typically, the sound can often be worse than either one separately. This is due to out of phase relationships at different frequencies. But these phase relationships typically do not lie at exactly 180 degrees out of phase. Lets say that on one range of the bass your pickup and mic are out of phase. This will likely mean that at these frequencies the volume of the notes would be more quiet since the out of phase signals cancel eachother. Thses phase relationships occur somewhere between zero and 180 degrees out of phase. The variable switch allows you to dial in the best phase relationships.So now you can combine with a mic or pickup that previously sounded crappy in combination.
Click to expand...

This is true only if there is individual phase adjustment that affects only one input at a time and you assume that you are feeding each of the devices (e.g., mic, pickup, etc.) to individual inputs. Does the new EA amp allow for that? From what I've seen it does not. If that's the case, then one would not be able to adjust the phase relations between two input devices and the phase control will not likely help much at all with the very real potential problems you cite. It could to the extent that there are substantially different path lengths (distances) between the speaker and each of the devices (mic, pickup, etc.) and you just happen to get really lucky.
 
#51
I have spent a considerable amount of time learning and researching this kind of thing, but there are so many other factors involved that specs(wattage, peak or RMS) don't really mean what they say. I have owned a TON of amps over the past 5-6 years, and there is a such a wide range of variables. Of course having a broader knowlege of technical aspects will help in choosing, but I have seen enough of EA to know that their new amp should respond like other iAMP's! I don't wish to argue, its just in my experience I have found that there are so many underlying variables that it is tough to make a choice based on spec.

On another note... the Phase knob looks to be a GREAT addition. Looking forward to this...
 
#52
Adrian Juras said:
I have spent a considerable amount of time learning and researching this kind of thing, but there are so many other factors involved that specs(wattage, peak or RMS) don't really mean what they say. I have owned a TON of amps over the past 5-6 years, and there is a such a wide range of variables. Of course having a broader knowlege of technical aspects will help in choosing, but I have seen enough of EA to know that their new amp should respond like other iAMP's! I don't wish to argue, its just in my experience I have found that there are so many underlying variables that it is tough to make a choice based on spec.
Click to expand...


Agreed!
 
#54
Mike Arnopol said:
As far as the phase switch, the biggest advantage is in combining a pickup and a mic or another piezo. Even using two of the same pickups in different locations there are phase anomalies. More so with a mic or another pickup.
Has anyone ever tried combining two different piezos or a piezo and a mic? Typically, the sound can often be worse than either one separately. This is due to out of phase relationships at different frequencies. But these phase relationships typically do not lie at exactly 180 degrees out of phase. Lets say that on one range of the bass your pickup and mic are out of phase. This will likely mean that at these frequencies the volume of the notes would be more quiet since the out of phase signals cancel eachother. Thses phase relationships occur somewhere between zero and 180 degrees out of phase. The variable switch allows you to dial in the best phase relationships.So now you can combine with a mic or pickup that previously sounded crappy in combination.
Click to expand...
drurb said:
This is true only if there is individual phase adjustment that affects only one input at a time and you assume that you are feeding each of the devices (e.g., mic, pickup, etc.) to individual inputs. Does the new EA amp allow for that? From what I've seen it does not. If that's the case, then one would not be able to adjust the phase relations between two input devices and the phase control will not likely help much at all with the very real potential problems you cite. It could to the extent that there are substantially different path lengths (distances) between the speaker and each of the devices (mic, pickup, etc.) and you just happen to get really lucky.
Click to expand...
Interesting stuff. Suppose you did have the abillity to adjust the phase of each input channel independently. And suppose you did make an adjustment that corrected an out of phase condition in one part of your instrument's range. Isn't it possible that you would then introduce an out of phase condition in another part of the instrument's range?

Not being critical. Just trying to understand. I blend a mic and a p/u thru my amp all the time, run them both in phase, and am very pleased with the results for the most part.
 
#55
bolo said:
Interesting stuff. Suppose you did have the abillity to adjust the phase of each input channel independently. And suppose you did make an adjustment that corrected an out of phase condition in one part of your instrument's range. Isn't it possible that you would then introduce an out of phase condition in another part of the instrument's range?

Not being critical. Just trying to understand. I blend a mic and a p/u thru my amp all the time, run them both in phase, and am very pleased with the results for the most part.
Click to expand...

Right you are! The phase between two such devices is likely to vary as a function of frequency. If you look back at my post #44 in reply to Chris, I mention how reducing the effects of an interaction between speaker and DB in one frequency region can create problems in another. Yes, the principle is the same with regard to two transducers. I'm not convinced at all that a variable phase control is all that useful.
 
#58
Mike D. should chime in, but from what I told the EA guys, the phase switch should affect only the second channel.( or first, but not both simultaneously) To be honest it doesn't matter too much which channel it's affecting. Otherwise it's pretty useless. The idea (at least from my end ) was the ability to combine two sources ( mic and piezo or piezo and piezo) and correct any phase problems. It never occured to me that it would affect both channels together.
Mike?
 
#59
Hey from EB land! Happy Holidays to the DB side.

Since my name came up in this thread, just a few comments for the heck of it.

1) A 550 watt iAmpMicro sounds very cool. I liked the tone of the original unit, even for EB, but just not enough ooomph. I'm with Peter on his more working man's definition of headroom... i.e., not having to turn the amp up to its absolute max to get through a gig. I think the iAmpMicro550 or whatever should put EA in a nice position in the ever expanding micro amp category. Nice!

2) Master Volume. I've actually grown to really like the audio taper (if I have that term correct) master volume controls that EA, TecAmp and Glock use. Yes, it takes a while to get over the fact that the master volume has to be turned up past the noon setting to really start cranking, but once you get over the psychology of the visual look of that control turned up to 3 o'clock, most will appreciate the smooth, even, and subtle way that those type of pot tapers can be used through their entire range.

3) Doubler... cool. That brings to mind the original Walter Woods designs, which had input impedance and EQ center points optimized for DB or EB in the two channels.

Nice stuff.... things sure do keep moving forward in the class D/SMPS amplification world.
 

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