Double Bass Full Circle: hot amp killer?

[MingusAmongUs]

I have an NS Cleveland equipped with a Fishman Full Circle pup, which I think is 4 or 5 years old now. Until recently, I almost never used the pickup. But I recently acquired an AI Coda combo amp, which is great, but sometimes horrible sounds come out of it. Basically, if I play at my normal style (which is admittedly aggressive -- I tend to dig in a bit), I hear popping and crackling from the amp on certain notes, particularly on the D string.

If I play through a microphone, I get the same thing, although it's more on the A string.

This happens regardless of where the levels are set on the Coda. AND, even though it's only a month old or so, it's already been back to Rick for repair (it wouldn't power up at all on about the third time I used it). I explained the popping issues as well as the no power. They said it was a bad circuit board causing both, replaced the board, tested it hard, and everything was great. Powers up, no popping. They said. But although it powers up, it still pops at me.

I've tried several different cables, with no change. I've also tried plugging in the Fender P bass, and that's very clean -- although I *can* get it to fuzz out if if really pull on the strings.

So I guess I'm looking for any thoughts here. Does anyone have experience with this issue, with this pickup? Is it a known thing? Is the pickup crapping out? Am I just playing too hard? Been doing it for 22 years or something, so changing my whole right hand technique at this point would be an ordeal. Or should I send the Coda back for another look?

 

[Ric Vice]

... Basically, if I play at my normal style (which is admittedly aggressive -- I tend to dig in a bit), I hear popping and crackling from the amp on certain notes, particularly on the D string.
If I play through a microphone, I get the same thing, although it's more on the A string.

I think the questions, should be, what happens through a different amp using the Full Circle? Do you get the same sound? With a different pickup, will the same thing happen?

........... it's already been back to Rick for repair (it wouldn't power up at all on about the third time I used it). I explained the popping issues as well as the no power. They said it was a bad circuit board causing both, replaced the board, tested it hard, and everything was great. Powers up, no popping. They said. But although it powers up, it still pops at me.

The question here would be to use someones DB with a piezo pickup, and play into the amp to see if the popping continues?

I've tried several different cables, with no change. I've also tried plugging in the Fender P bass, and that's very clean -- although I *can* get it to fuzz out if if really pull on the strings.

Magnetic pickups are a different beast, so it's possible that the issue, is what happens with a piezo, Double Bass, and the amp.

So I guess I'm looking for any thoughts here. Does anyone have experience with this issue, with this pickup? Is it a known thing? Is the pickup crapping out? Am I just playing too hard? Been doing it for 22 years or something, so changing my whole right hand technique at this point would be an ordeal. Or should I send the Coda back for another look?

First, I'd trouble shoot all the possibilities and then if it's still there after you've ruled out everything, what remains must be the problem. Good Luck. Troubleshooting can be a real PITA.

Ric

 

[MingusAmongUs]

Good points Ric, thanks. I do have another amp as well as a second DB w/ a Realist I can try, and that should narrow things down for me...

But I guess if I narrow it down to the pickup, is it worth replacing, or will a new one do the same thing? Hmm...

 

[Ric Vice]

Good points Ric, thanks. I do have another amp as well as a second DB w/ a Realist I can try, and that should narrow things down for me...

But I guess if I narrow it down to the pickup, is it worth replacing, or will a new one do the same thing? Hmm...

Mingus,
Well, I guess that depends on how much you like the Full Circle. I know that others were able to have them repaired by Fishman, depending on the way it was damaged. I've never heard of a Full Circle doing that, but don't actually own one. Once you get it sorted out, you can either call Acoustic Image for an amp repair, or Fishman for a Full Circle repair, or replacement, depending on their warranty policy. I really don't think your technique is the problem!

Ric

 

[iiipopes]

Have you tried it through a separate preamp/buffer, like an fdeck so you can adjust the level before it gets to the amp?

 

[Pat Harris]

Is it a Series 4 Coda?

I experienced a similar issue with my EUB which has a very hot output signal. Rick at AI said that they had modified the gain staging in the series 4 amps and you can overdrive the preamp if the input is too hot. It doesn't matter if your "gain" is super low on the amp, if you dig in, you'll still hear the distortion. This wasn't an issue in the series 3 amp I had. There is the 10dB pad on the series 4 amps, but that only works if you're using an XLR cable.

I'd try another amplifier, and if it is indeed the AI, you can always run a preamp in front of the amp to attenuate the signal spikes.

 

[MingusAmongUs]

Haven't tried putting any gadgets in front yet. I was hoping the Coda would eliminate the need, but I guess not. I've got an fdeck that I can use if that's what it takes.

Yes, the coda is a 4. Thanks!

 

[SVT4001]

I experience a somewhat similar problem, and I have narrowed it down to my Full Circle. This is on a Shen SB80, gut strung into a Series 1 Contra.

Sometimes the pickup works fine, other times I get no sound at all. On other occasions, when I pluck a string, the signal is fuzzy and distorted, and there are sounds like the crackling and popping you describe. I have found that if I rotate the pickup/adjuster back and forth a bunch it will usually make the problem go away.

I have read stories about Full Circles dying, and though I like the sound I get when it's working, I'm not sure I want to replace the one I have with another one...thinking about and Ehrlund!

I'm not sure if your trouble is the same as mine or not, but I wish you luck with it!

Joe

 

[MingusAmongUs]

I just realized I have the older hpf/pre, the one without any level/gain control. This would probably not do the trick, would it? Does anyone know if the newer one (with the volume control) allows for attenuation (ie, to lower the amount of signal going out to the amp), or is the knob at zero equal to pickup output?

 

[robgrow]

Are you using the string-mounted jack that comes with your Full Circle? Some people may not know that it is an integral part of the FC pickup. It is a filter and an attenuator. The output of the FC is substantially higher without the jack that comes with the pickup, and can overload the input of some amps.

Also you are dealing with very high impedance and high gain here. Dirty contacts anywhere in the front of your signal chain can cause problems. Try using Caig DeoxIT sprayed on a q-tip to clean contacts on the FC's jack and the amp's input jack. My Walter Woods amp suddenly became unreliable last year until I cleaned the input jacks with DeoxIT. Works perfectly now.

 

[DoubleMIDI]

The volume control on the HPFpre II does attenuate the output signal going to the amp. This is clearly visable from the schematics on FDecks site for those who can read schematics.

 

[MingusAmongUs]

Are you using the string-mounted jack that comes with your Full Circle? Some people may not know that it is an integral part of the FC pickup. It is a filter and an attenuator. The output of the FC is substantially higher without the jack that comes with the pickup, and can overload the input of some amps.

Also you are dealing with very high impedance and high gain here. Dirty contacts anywhere in the front of your signal chain can cause problems. Try using Caig DeoxIT sprayed on a q-tip to clean contacts on the FC's jack and the amp's input jack. My Walter Woods amp suddenly became unreliable last year until I cleaned the input jacks with DeoxIT. Works perfectly now.

I do have the jack mounted. Good suggestion on the contact cleaner. Wouldn't hurt to try.

The volume control on the HPFpre II does attenuate the output signal going to the amp. This is clearly visable from the schematics on FDecks site for those who can read schematics.

Count me as someone who does not fall into that category. I did not see the schematics, but thanks for putting it in layman's terms for me.

 

[MingusAmongUs]

So, different bass, Realist pup, same amp, no fuzz. I don't think. Hard to tell with everything vibrating. But the signal from the Realist was noticeably lower -- had to really push the amp to get the same output level I was getting from the FC.

The Series 1 HPF Pre actually adds a touch of gain, so that's out.

I had an older Presonus Tube Pre kicking around, which solved the problem to a degree, but introduced other problems (assuming impedance mismatch). I kept the tube drive at 0 and the gain not much higher. The Presonus has both a 1/4 inch and XLR IO, and I found that I could *greatly* reduce the gain going into the amp by running a 1/4 inch from the Full Circle into the TubePre, and a balanced XLR out to the amp. But I'm not sure if that's a bad idea (unbal-->bal). The sound is not bad at all, but I think I can hear that thinness that usually comes with plugging a piezo into a low impedance input. Thoughts?

 

[GrowlerBox]

The Series 1 HPF Pre actually adds a touch of gain, so that's out.

You may still derive some benefit from reducing infrasonic (and some audible low frequency) stress on your speaker. This isn't generally described as "popping", but descriptive terminology being what it is, I guess it's hard to rule out.

A series 2 or 3 HPF-Pre would make for a relatively inexpensive experiment ...

 

[MingusAmongUs]

You may still derive some benefit from reducing infrasonic (and some audible low frequency) stress on your speaker. This isn't generally described as "popping", but descriptive terminology being what it is, I guess it's hard to rule out.

A series 2 or 3 HPF-Pre would make for a relatively inexpensive experiment ...

I know, I agree, but the AI *has* an HPF built in. And a relatively high impedance input (but not as high as the fdeck gadget). My hope was that I could eliminiate the need to have doodads hanging off the speaker box, vibrating and rattling around and using up batteries. Nuts! I sent fdeck a note to see what he thinks. $70 is certainly not a lot for such a cool device, but it's not so cheap for "experimenting", with a slightly upgraded version of a device I already own. At some point I have to stop throwing good money after bad.

I got an answer for everything, don't I?

 

[GrowlerBox]

I got an answer for everything, don't I?

Almost; did you try the HPF-Pre I, and did it make a difference? What difference does using the on-board HPF make (and is it adjustable on the AI amp?). Other than that, I guess we still don't know whether other combinations of amp and pickup are associated with the same problem. No doubt you'll try these when you get a chance.

Keep us posted.

 

[MingusAmongUs]

Almost; did you try the HPF-Pre I, and did it make a difference? What difference does using the on-board HPF make (and is it adjustable on the AI amp?). Other than that, I guess we still don't know whether other combinations of amp and pickup are associated with the same problem. No doubt you'll try these when you get a chance.

Keep us posted.

I did try the Pre S1 and (I think I mentioned above) it added gain, and therefore made the "popping" worse.

The onboard HPF in the AI works well in general, but it's further down the signal chain and so doesn't help with the hot input.

I tried a different bass/pickup combo with same amp, no popping.

I tried same bass/pickup with different amp, no popping per se, although the amp is a 45 year old tube monster in need of TLC, and makes a lot of unwanted noise anyway, so that wasn't a perfect control.

At this point it appears to be specific to the FC+AI pairing. I would *love* to hear from anybody who has used this combo before....

FYI, I realize words do little to convey a sound, but the popping I'm hearing sounds like the distortion that comes from clipping.

 

[Matthijs]

I did try the Pre S1 and (I think I mentioned above) it added gain, and therefore made the "popping" worse.

The onboard HPF in the AI works well in general, but it's further down the signal chain and so doesn't help with the hot input.

I tried a different bass/pickup combo with same amp, no popping.

I tried same bass/pickup with different amp, no popping per se, although the amp is a 45 year old tube monster in need of TLC, and makes a lot of unwanted noise anyway, so that wasn't a perfect control.

At this point it appears to be specific to the FC+AI pairing. I would *love* to hear from anybody who has used this combo before....

FYI, I realize words do little to convey a sound, but the popping I'm hearing sounds like the distortion that comes from clipping.

This, and what Pat Harris told about that model amp, points in the direction of a signal that's too hot for the AI. I can't see any other way out besides hanging doodas of your speakerbox or bass, at least for testing purposes. You either need a pre that allows for attenuating or a DI that will make you use the padded XLR input. Only other thing I can think of is making a tech install a permanent 10db pad inside the AI.

The Full Circle and the AI Coda should not be a very exotic combination though, You'd think others would have had the same experience. Maybe the combination of a Full circle, the AI and your agressive style is unique?

 

[Chris Fitzgerald]

This, and what Pat Harris told about that model amp, points in the direction of a signal that's too hot for the AI. ... You either need a pre that allows for attenuating or a DI that will make you use the padded XLR input. Only other thing I can think of is making a tech install a permanent 10db pad inside the AI.

The Full Circle and the AI Coda should not be a very exotic combination though, You'd think others would have had the same experience.

I've had a similar experience, although not with a series 4. In my case, it was a combination of a very aggressive playing style on loud/intense passages and a hot FC pickup signal. To solve the problem, I had to leave the input gain down very, *very* low and crank up the master. I have also had this same problem on the Headway EDB-1. The amp I use now has an adjustable input gain where the middle point is unity, and also has a clipping light, so I know the sound MAU is describing well, but because the pre can be adjusted below unity, it's not an issue.

I've heard tell of an attenuating cable from David Gage that some folks use to tame an overly hot new Realist signal into the EDB-1, so maybe that could be a solution? (can't find it on the Gage website, though).

 

[Ric Vice]

I've heard tell of an attenuating cable from David Gage that some folks use to tame an overly hot new Realist signal into the EDB-1, so maybe that could be a solution? (can't find it on the Gage website, though).

Chris,
Yeah, that link is buried way down at the bottom of a page on the David Gage Site. The only way to find it is to look for the Realist logo on their website, under their cables link.

http://www.davidgage.com/store/product_info.php?cPath=53&products_id=491

This link will take you right to it, although there is no picture, just a Realist logo and a $29.00 price.

Ric