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Double Bass EA iAmp Micro300

#41
drurb said:
The p/u will "see" the input impedance of whatever device into which it is plugged. The input impedance of the amplifier, per se, would not be altered. It seems like Tom is describing an outboard circuit that is essentially the same as that which I currently use, save for the phase-reversal. That's simple to incorporate. Because Tom mentioned that it is also a buffer, it seems like a device that will sit in front of the input.
Click to expand...

That is correct. It will function in this regard much the same as a buffering preamp.

Tom.
 
#42
The question I was trying to ask was whether this device preserves the impedance match between the PU and the amp.: i.e. if you have a piezzo PU connected to a high impedance input (> 1MOhm) on an amplifier, do you create a mismatch between the pickup and the device or the device and the amplifier with the insertion of the device?
 
#43
I didn't realize the demand for an low cut (high pass) filter. Designing a low cut filter is easy... designing an adjustable low cut filter is a bit trickier.

The problem with an adjustable filter is that the steeper the slope, the more parts have to change at the same time. An adjustable -12dB/octave filter is fairly easy since only two parts need to change. You can use a dual (stereo) pot. Any more than -12dB/octave and you need specialized parts.

But if we take the -12dB/octave adjustable filter and put a fixed 20Hz -12dB/octave filter in front of it, we can now get a -24dB/octave cut at 20Hz. The drawback is that as you go up in frequency, the slope lessens. But it will never be worse than -12dB/octave.

Another idea is to have a fixed set of filters, say 30/40/60/80, that can be selected with a switch. The advantage to this solution is that you do not have to compromise in the filter design. An adjustable filter has to make some compromises.
 
#44
jsbarber said:
The question I was trying to ask was whether this device preserves the impedance match between the PU and the amp.: i.e. if you have a piezzo PU connected to a high impedance input (> 1MOhm) on an amplifier, do you create a mismatch between the pickup and the device or the device and the amplifier with the insertion of the device?
Click to expand...

Let's take these one at a time. We'll call the amplifier Tom was discussing "the device." Assuming there is nothing goofy about the design (a given, if Tom is involved), there will be no mismatch between the device and the amp. Using your example, we would have an active transistor or op-amp device "looking" into the high (>1 M ohm) impedance input of the amp. That is rather ideal.

Now, the piezo pickup will "see" the input impedance of the device. That is, the input impedance of the device will determine the matching. I am assuming that the input impedance of the device Tom discussed is at least 1M ohm. The pickup will not "see" the amplifier input at all. Rather, the active device will act to isolate or "buffer" the pickup from the amplifier. Think of the device as saying to the pickup, "You talk to me and I will talk to the amplifier."

Logically speaking, one could design a device like Tom described so that it had a low input impedance, say 10k ohms. That would be a poor choice if one intended it to be used with piezo pickups. If one did that, there would, indeed, be a "mismatch" between the pickup and the device and the frequency response would suffer. This is because the pickup would "see" the 10k ohm input impedance of the device while being buffered from the 1M ohm input impedance of the amplifier.

On the other hand, a device like Tom is discussing, that has a high input impedance (>= 1M ohm), can be used to solve a "mismatch" problem. Here's how. Suppose you are using a piezo pickup with an amp that has a 10K ohm input impedance. That's no good for a piezo. If you place a buffer amp with a high impedance in front of the amp and plug the pickup into that, your problem is solved. The piezo will "see" the high impedance and the buffer amp will "see" the 10k ohm impedance of the amp and it will not be bothered by that.

I hope this helps.
 
#45
seanm said:
I didn't realize the demand for an low cut (high pass) filter. Designing a low cut filter is easy... designing an adjustable low cut filter is a bit trickier.

The problem with an adjustable filter is that the steeper the slope, the more parts have to change at the same time. An adjustable -12dB/octave filter is fairly easy since only two parts need to change. You can use a dual (stereo) pot. Any more than -12dB/octave and you need specialized parts.

But if we take the -12dB/octave adjustable filter and put a fixed 20Hz -12dB/octave filter in front of it, we can now get a -24dB/octave cut at 20Hz. The drawback is that as you go up in frequency, the slope lessens. But it will never be worse than -12dB/octave.

Another idea is to have a fixed set of filters, say 30/40/60/80, that can be selected with a switch. The advantage to this solution is that you do not have to compromise in the filter design. An adjustable filter has to make some compromises.
Click to expand...

I agree with everything you said except for the need to make compromises when using an adjustable filter. One can build an essentially no-compromise -12 dB/oct adjustable high-pass filter. I have one and use it all the time. In addition, I have personally made all kinds of detailed measurements on it and it really is a fine device.

In practice, I see no need for a fixed high-pass filter in front of a -12 dB/oct high-pass filter. Here's why. Assuming you are playing a standard four-string bass, you don't need to transmit any frequencies below about 40 Hz. Indeed, the bass will not produce any acoustically. The frequencies you want to vanquish are the artifactual infrasonics that can be transduced by a piezo pickup. Those frequencies lie below 20 Hz or so. I have found that the real trouble-makers seem to lie in the 5-10 Hz region. With a -12 dB/oct slope with a "corner" at 40 Hz, those frequencies will be attenuated by about 20 dB. Given that they are not of high intensity to begin with, that's plenty. In parctice, it works like a charm!

Now, should one desire to move the corner of the HPF up to, say, 80 Hz (perhaps to tame some cabinet resonances), then the infrasonics would be attenuated to an even greater degree because they would fall even farther from the cutoff.
 
#47
drurb said:
... Logically speaking, one could design a device like Tom described so that it had a low input impedance, say 10k ohms. That would be a poor choice if one intended it to be used with piezo pickups. If one did that, there would, indeed, be a "mismatch" between the pickup and the device and the frequency response would suffer. This is because the pickup would "see" the 10k ohm input impedance of the device while being buffered from the 1M ohm input impedance of the amplifier.
Click to expand...

This was the point I was making with the question.
 
#48
Got my Micro300 yesterday and played through the Wizzy 10 fo a good little while today. Initial impressions are positive. I did an informal comparison with my Focus 2 (sII). The Micro is a little noisier but it could be something in my house. The Focus also has some noise at home which I haven't noticed elsewhere. Really not an issue once you start playing anyway.

At 4 ohms the Focus is providing 600 Watts, but the Micro at 300 (325?) is plenty. With the input at 12:00 and the master at 9-10 it is already as loud as I would want it. It seems pointless to crank up the volume in a small room, it just sounds ugly regardless of the gear. I'll have to wait til I can test it in a large space.

Tonally they are similar. The Focus has more of a smooth quality to it, the Micro a bit of a shine. Both are pleasantly uncolored, but one could argue that the Focus is a duller, more bland sound while the Micro has a little zip to it. The matte vs. semi-gloss thing. This could be in part due to the fact that I have the filter on the Focus set to notch out the highest frequency. Either one could be preferable, depending on your taste or what kind of music the gig calls for. But I should emphasize they are more similar than different. The EQ is subtle on both heads. The Focus has some more flexibilty because of the notch / high pass.

Feature-wise the Micro does have some cool stuff. Having two channels with quarter inch inputs allows me to blend two pickups easliy (the Focus II has one quarter-inch and one xlr). This is how I got the best sound in fact. Also the input switching button allows you to compare the two signals without turning knobs or unpugging anything. You could also switch back and forth between the two channels for one pickup, if for example you wanted one EQ for bowing and another for pizz. Another cool thing is the input indicator light, which flashes at a certain level - useful for evening out the level if one pickup is hotter than the other.

It comes with a nice long power cord and a nice short (2') speakon cable. Of course the most exciting feature of the Micro is its size and weight. If there is anything else this small and light that sounds this good and loud, I would be really suprised. I am looking forward to many easy load-ins and having that little bit of extra energy I can spend on making music that I would have spent on schlepping and kvetching about my sound not being right.

I heard at some point they may develop higher powered versions. Now if they would add combination input jacks, high pass / notch in both channels, and put it together in one box with the Wizzy 10, that might be hard to beat! But seriously, I have to applaud EA for their commitment to excellence, and thank them for these products that really address the needs of working Double Bassists!
 
#50
and have spent the last 3-4 hours with it in my home "studio" thru a wizzy 10 and my old kay with a fc, fender jazz bass, and a ns cello bass:

- yep, this thing is startingly small. near the same size as the raven labs preamp i used for years, but feels a bit lighter to me. dunno why... physically it feels very well made and i have no visual or ergonomic isses with anything. this 'lil thing is designed really well.

- thru the wizzy and with all basses i found the sound to be everything i liked about the wizzy combo i once owned. flat but not lifeless and a really flexible eq. on all 3 basses, the 3 band eq was wide and deep enough to take anything to an extreme. the preamp sounded great with all the basses and made the fc on my kay sound better than any rig i've used it with so far. i haven't tried the di yet, but i plan on using it as a preamp for a gig where i just plug into the house pa...

- there is a noticeable buzz coming thru the cab even with nothing plugged in, mute on and gain down. i tried it with a few cabs and it's definitely the micro. i hate to say it, even tho' it's low, it was annoying in my "studio" and i'm afraid it may be noticeable is some of the really quiet singer/songwriter gigs i do. i want to try the di to make sure the buzz isn't also coming out of the di... fwiw, my room is wired well and i do a fair bit of recording for various folk and have yet to have a noise issue...

all in all, this is an astonishing amp.

more soon,

tony
 
#52
Hi Tbal and Tony

Computer monitors, tvs and light dimmer switches are the worst things for making creating a buzz.
Fridges and freezers can sometimes create a buzz in the mains.
You might already have tried this but switch everything in the house off and see if the buzz is still there.
Some power conditioners can get rid of these problems if that's what it is.
Remember to switch the freezer back on or there'll be trouble!

cheers Quee
 
#53
hey quee,

yep, my "studio" was properly wired and grounded for recording, so i'm used to dealing with this. it's actually a small building seperate from my home that was built for recording.

the old gk mb150 and swr cali blonde sitting next to the micro, plugged into the same gang of outlets were quiet as usual...

tony
 
#54
Hi Tony

That's a shame that such an otherwise excellent amp should have a hum.
I would have a word with the people at EA.
I know these things can be really annoying, especially if you mike your cab for recording.

cheers Quee
 
#58
uglybassplayer said:
Hi Bob,

For those like me who have already received ours, is there something that can be done if ours turns out to be one of the affected units?

- Frank.
Click to expand...

Any buyer should contact their seller, but I've spoken with Larry at EA a number of times and he's said a number of times that no owner need worry-- all will be taken care of to their satisfaction... and fewer than 35 Micro 300 amps are in customer hands.

I've spoken with two of my buyers and offered them the option to get an immediate refund, return the amp, or just hold onto it pending the resolution, when we'll probably just swap them for another unit. In both cases they elected to hold on and use the amp in the meantime and wait.

Really, nothing prevents the use of the amp; while it could stall its use for recording, it's just fine for gigging or practice.

You can find dozens, maybe hundreds of testimonies on this board praising Euphonic Audio's attention to customer service.
 
#59
Bottom line is that when you buy a brand new product at the front of the first production run, there are likely to be a few rough edges. I've experienced this with both EA and AI products, and while it was kind of annoying that this great new thing I was waiting for wasn't perfect, I got taken care of by both companies quickly and with no hassles whatsoever. That's part of the reason I hold both companies in such high regard. I doubt that I would get the same level of immediate and personal service from most companies in similar circumstances.
 
#60
Not to hijack the thread or anything, but . . .

I'd really love to hear how the Micro 300 compares to the GK-MB150E combo, as well as the Contra SIII combo.

See, I'm in dire need of a new amp/cab or combo, and until recently I was having trouble deciding between the Contra and the MB150. Just when I thought I had made up my mind, this little guy comes along!

I play a carved bass through an Underwood, although that will soon be replaced or added to with some other pickup like a Realist or a Full Circle.

Any thoughts?
 

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