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Double Bass EA iAmp Micro300

#21
Randy Ward said:
...I think Bob Gollihur is saying the micro won't reproduce the sub frequencies that require a high pass at higher volumes with an amplified double bass. Therefore the lack of one would make it unnecessary.
Click to expand...

Indeed, that is the case but the devil is in the details. If you search these threads you will find the story of my EA iamp200 and how I brought to EA's attention the problem of infrasonics that is created by using an amp with a high-pass cutoff around 5 Hz for amplification of a DB fitted with a piezo pickup.

The designer of the iamp, Gary Gibilisco, graciously modified my iamp200 so that it would have a higher high-pass cutoff. While an improvement, I found that the modification wasn't sufficient to rid me of the problem entirely so I now use a dedicated, adjustable HPF.

It would be important to know what is the HP cutoff of the EA Micro. Keep in mind that 1) a four-string DB does not produce acoustically any frequencies below about 40 Hz (the fundamental of the E string); 2) many cabinet designs that fall under the broad class of "ported" have resonant peaks near or below about 40 Hz; 3) piezo pickups can transduce undesirable infrasonics that can drive the speaker cone crazy and rob you of precious amplifier power.

This all adds up to the fact that it is often desirable to employ a steep (at least 12 dB/oct) roll-off below about 30-40 Hz when using such a setup. If such a roll-off were built into an amp, then many five-string and BG players might find it quite undesirable. That's why the best of all worlds is to have an amp with an adjustable HPF. Again, it would be interesting to learn where EA has placed their built-in HP cutoff for the Micro.
 
#22
drurb said:
Indeed, that is the case but the devil is in the details. If you search these threads you will find the story of my EA iamp200 and how I brought to EA's attention the problem of infrasonics that is created by using an amp with a high-pass cutoff around 5 Hz for amplification of a DB fitted with a piezo pickup.

The designer of the iamp, Gary Gibilisco, graciously modified my iamp200 so that it would have a higher high-pass cutoff. While an improvement, I found that the modification wasn't sufficient to rid me of the problem entirely so I now use a dedicated, adjustable HPF.

It would be important to know what is the HP cutoff of the EA Micro. Keep in mind that 1) a four-string DB does not produce acoustically any frequencies below about 40 Hz (the fundamental of the E string); 2) many cabinet designs that fall under the broad class of "ported" have resonant peaks near or below about 40 Hz; 3) piezo pickups can transduce undesirable infrasonics that can drive the speaker cone crazy and rob you of precious amplifier power.

This all adds up to the fact that it is often desirable to employ a steep (at least 12 dB/oct) roll-off below about 30-40 Hz when using such a setup. If such a roll-off were built into an amp, then many five-string and BG players might find it quite undesirable. That's why the best of all worlds is to have an amp with an adjustable HPF. Again, it would be interesting to learn where EA has placed their built-in HP cutoff for the Micro.
Click to expand...
I own a Focus 2 III and in all the time I've played the bass thru an amp I have never come across a single feature more useful then the variable HP filter. I use it on nearly every gig. For amping uprights (thru different cabs...unlike a GK) it seems essential...
 
#24
flatback said:
I own a Focus 2 III and in all the time I've played the bass thru an amp I have never come across a single feature more useful then the variable HP filter. I use it on nearly every gig. For amping uprights (thru different cabs...unlike a GK) it seems essential...
Click to expand...

Agreed. I even upgraded from the Focus 2 II to a series III just to get the HP filter on both channels. I set them anywhere from 50 to 80 hz depending on the sound of the room. They make all the difference in the world. A phase switch would also be nice, but the Focus has enough buttons on it as it is. The EA Micro would be tempting with a HP filter on both channels.
 
#25
thanks drurb etc!
This is interesting. I've never thought of this. And I've used a lot of different basses, pu:s and amps. The only thing I've been concerned about is that some pu:s need a high imp. connection (solved by using an external pre-amp). Looks like I should get a pre-amp with HPF. Are there any suggestions from you folks?

BTW Are there any facts about which pu:s that are more prone to produce undesirable infrasonics?
 
#26
The only preamp I'm aware of that has an HPF (besides the one in the Acoustic Image amps) is the Fishman Platinum Pro EQ Bass (the depth control). It would be great if someone sold a little inline HP filter that could be just connected between cables/inputs with a rotary adjuster on it. There are inline attenuators and transformers but as far as I can see, no inline HP filter let alone one in a separate box.

From my point of view, it seems like my AI Focus II is still the best choice for the smallest dual channel setup. For a single single channel setup I have thought about a Fishman preamp with a Flying Mole amp. It's a pity the series III AI heads got bigger and heavier.

The Micro 300 is close but just doesn't quite get there for me due to the lack of features in the preamp. Pity they don't just offer the power amp by itself.
 
#31
In this discussion about HPF and phase reversal switch features, Adrian Cho pointed out that the Fishman Pro EQ Platinum Bass has both those features, although they call the high-pass filter a low-cut filter (same difference) and name it "Depth" on the device. I've been using one for the last two years and have been pleased with it. His idea of just a micro power amp might allow more flexibility for matching and mixing equipment using an outboard preamp, eliminate preamp redundancy, and allow the saved cash to be used for other features/equipment.

It seems that drurb may be using a custom made high-pass (low-cut) filter. From what I've seen, this type of filter is added to a product, like the Fishman pre-amp/EQ or a device like Nady's 31 band EQ, GEQ-131, which has a fixed frequency (40 Hz) low-cut filter. I doubt that there's enough demand for any manufacturer to market a stand-a-lone device yet, at least I haven't found one.

I have a Micro 300 pre-ordered and I still intend to use the Fishman Platinum Bass EQ with it, although I'll test it direct in and see what it sounds like without the outboard preamp/eq/di. I've also been using a Tech21 Sansamp Acoustic DI that I got a few months ago. It has a mix of features different than the Fishman, but it gives me a little different control on the sound and I like what I've been hearing. Perhaps as the demand for micro amps builds (hopefully), there'll be room for more innovation.

Lloyd Howard
 
#32
flatback said:
I own a Focus 2 III and in all the time I've played the bass thru an amp I have never come across a single feature more useful then the variable HP filter. I use it on nearly every gig. For amping uprights (thru different cabs...unlike a GK) it seems essential...
Click to expand...
Adrian Cho said:
I could not be without my HP filter. There is not to my knowledge, any commercially available circuit out there that has an adjustable HP filter in a small package.
Click to expand...
This made me think about the variable input impedance feature of the Summit Audio TD-100 that was opening ears on TB a while back. Almost seems like it had a sonic sculpting effect somewhat similar to a HPF from what I read here. Spin the dial and go from thick to thin. With piezo p/u's that is. I think that maybe some of the Radial DI's have this capability too.

Which begs the question - Who's got a stand-alone unit w/ HPF, phase reversal, and variable input impedance? That might could be interesting.
 
#33
lhoward said:
It seems that drurb may be using a custom made high-pass (low-cut) filter.
Click to expand...

Yes, I am.

lhoward said:
I doubt that there's enough demand for any manufacturer to market a stand-a-lone device yet, at least I haven't found one.
Click to expand...

Well, I disagree. For example, I have an iamp200. I have no need for a full-featured outboard pre-amp. I do, however, have a need for an adjustable HPF. Many other players seem to be in a similar position. Just keep visiting this forum and in the near future you will discover just such a device for sale for a modest price. No, I will not be the one offering it and no, I have no financial interest in it. I was, however, involved in its development.
 
#34
bolo said:
This made me think about the variable input impedance feature of the Summit Audio TD-100 that was opening ears on TB a while back. Almost seems like it had a sonic sculpting effect somewhat similar to a HPF from what I read here. Spin the dial and go from thick to thin. With piezo p/u's that is. I think that maybe some of the Radial DI's have this capability too.

Which begs the question - Who's got a stand-alone unit w/ HPF, phase reversal, and variable input impedance? That might could be interesting.
Click to expand...

It makes sense that variable input impedance could alter radically the sound of a piezo. That, however, would seem to be a poor way to adjust tonal characteristics. For a piezo pickup. While phase-reversal and a HPF are desirable features, I'd have little to no interest in variable impedance. That's gimmickry.
 
#35
drurb said:
Just keep visiting this forum and in the near future you will discover just such a device for sale for a modest price. No, I will not be the one offering it and no, I have no financial interest in it. I was, however, involved in its development.
Click to expand...

Any approximate ETA for this device?

Sadly, the folks at EA don't seem to understand the need for an HP filter nor phase reversal nor phantom power nor XLR inputs. I hate to simplify things but as far as I can see, this is a fundamental difference between EA which is very EBG oriented and AI which better understands the needs of acoustic bassists.
 
#36
Adrian Cho said:
Any approximate ETA for this device?

Sadly, the folks at EA don't seem to understand the need for an HP filter nor phase reversal nor phantom power nor XLR inputs. I hate to simplify things but as far as I can see, this is a fundamental difference between EA which is very EBG oriented and AI which better understands the needs of acoustic bassists.
Click to expand...

The best information I have is within a month or so.
 
#38
Adrian Cho said:
I am so tempted by the Micro 300 but the lack of a high-pass filter is the one thing that is stopping me.
Click to expand...

I have mentioned before that I know of a product which should soon be available (and believe, me, I am bugging the manufacturer!) which would allow for the incorporation of a variable high pass filter, signal buffering, and phase reverse into pretty much any rig, in an easy, simple, and cost effective manner.

FWIW, and all that. :smug: :p
 
#39
Tom:

Do you know if the input impedance of the amplifier would be affected by the presence of this device? i.e. would the PU see the same impedance with and without the device present?

Jim
tombowlus said:
I have mentioned before that I know of a product which should soon be available (and believe, me, I am bugging the manufacturer!) which would allow for the incorporation of a variable high pass filter, signal buffering, and phase reverse into pretty much any rig, in an easy, simple, and cost effective manner.

FWIW, and all that. :smug: :p
Click to expand...
 
#40
jsbarber said:
Tom:

Do you know if the input impedance of the amplifier would be affected by the presence of this device? i.e. would the PU see the same impedance with and without the device present?

Jim
Click to expand...

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.
 

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