Double Bass Not getting enough VOLUME from my amp!

Riley Z

Riley Z

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Nov 27, 2015
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#1
Hello all!

I'm still a bit of a novice when it comes to gear so please work with me here!

I'm a double bassist that is frustrated with how little sound he is getting from his amp. I'm playing a plywood with a Fishman Full Circle, plugging into a Carvin BX1500 amp head through a SWR Goliath III 4x10 cab. The cab can handle 700w (at 8 ohms I think), but the head has "dual mono block" or something so I run half of it (750w at 2 ohms) into the cab. It can also do 300w at 8ohms and 450w at 4ohms, and the bridge output lets me do 900w at 8 ohms and 1500w at 4 ohms. Honestly I don't really know how to switch between all of these, I just know that the amp CAN do all of that. That's my setup!

So I'm not getting enough volume from my Fishman Full Circle, and I tried to solve this myself but quickly went down a confusing rabbit hole, this is a petition for help! I noticed a few potential solutions but I'm not sure which to pursue.

Do I need to adjust my amp? I heard something about impedances and making sure they are matched, I really don't know much past what I typed out in my setup (my cab being able to handle 700w at 8 ohms, and my amp having its capabilities). I'm learning slowly, but I'm learning!

Do I need a preamp? I heard something about piezo pickups like the Fishman Full Circle needing a preamp to boost the signal. I've never used a preamp before in my setup, and I don't exactly want to spend $300 on a Platinum Pro if I can avoid it. Will this solve my volume crisis?

Should I get another pickup (or clip-on mic) and blend them? I've heard some phenomenal sounds from people who blend a combination of pickups and mics to get a big sound, should I be looking into this?

THAT'S A LOT, I KNOW. SORRY. AND THANK YOU SO MUCH!
 
#4
Your amp's input impedance is spec'd as >200KΩ (200KOhms), which is low for a piezo pickup. You need 1MegΩ or higher; without it, the bass will sound thin. A preamp with at least 1MegΩ will take care of that part of the problem. However, before you do that read the next paragraph.

Regarding the Full Circle, the face of the pickup wheel that contacts the bridge (the nonthreaded side) must lie perfectly flush with the bridge surface to work properly. If all four of the pickup elements aren't under pressure, you won't get the full output from the pickup. Have your luthier take a look at it.

When you shop for a preamp, you don't need much: input impedance at least 1MegΩ and a high-pass filter (HPF) that will let you roll off very low frequencies. It must be the first thing in the signal chain after the bass (not in the effects loop of the amp). The simplest and most recommended one around here is the HPF-Pre: hpftechllc

Hope this helps.
 
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#5
Above response basically says it. Before even buying anything, do the part where you check the actual contact of your pickup to the bridge. Chances are it's not fully seated or whatever, and my guess is that your volume will double if you address this first.
 
#6
It's important to know the resistance of your speaker cabinet for sure (should be clearly marked on the back panel). If it's 8 ohms, you might well notice more "oomph" running the power section bridged to get 900 watts instead of just 300. (That exceeds the cab rating slightly but you should be OK if you're careful - a 4x10 approaching capacity is going to be pretty freaking loud...)
If it's 4 ohms, bridging would probably not be a good idea - it would be harder on the amp and you'd be driving the speaker cab with roughly double the rated power. (Though, honestly, even if you're currently only getting 300 watts, that really ought to be more than enough for most upright bass applications.)
 
#7
IME the Full Circle actually puts out a pretty hot signal so if it's the output signal that seems weak, double-checking the installation might be a good idea. (With my plywood bass w/ Full Circle, I usually have to turn way down to about 9 o'clock to avoid overloading the amp input.)
I usually find the Full Circle sounds better with a preamp of some sort (not always but usually). I like the fDeck HPF-Pre preamps - IME they provide everything I need and nothing I don't. (High pass filter and phase switch can be very handy for combatting boominess and/or feedback. The most basic model has no volume control but I would recommend getting the next model up that does.) They are inexpensive enough, IMHO it's worth getting one just to have handy. (Even if your current amp winds up sounding better without, odds are pretty good you will eventually encounter another amp that does benefit from it.)
HTH
 
#9
I'm presupposing a lot, but a 4x10, IME is a tough cab to monitor with. By the time the volume starts to feel right in relation to where you're standing (estimating a few feet in front or to the side of the cab) you are murdering people 20 feet in front of you.

You could also try going with a totally flat EQ, then roll off the lows, and boost the overall volume on the amp. Being "heard" and being "felt" are two different things.
 
#11
You can try to turn the wheel with the pickup a bit, up to a quarter turn, that changes sound but can also change volume. I only use the lower volume because of the better sound.

It might be that the Full Circle has a damaged element which might be a reason for a low output. But first try a high impedance buffer/preamp.

A high impedance buffer/preamp (which only enhances how much the output can be loaded by the next stage input, which is usually your amps preamp stage) with anything between 1 and 10 MegOhms would enhance sound and might give you a stronger output (because the signal doesn't break partially down because of the load).

Also a high pass filter (with a low frequency) can filter out a lot of unwanted lows and gives your amp more power for more valid frequencies. The FDeck HPFpre (version II is the best option for you since version III is mainly for bass guitar) has an impedance buffer and a high pass filter and even gives a very small boost to the signal. It's also the cheapest thing you can order new for your application, worth the money and always good to carry with your bass, even if you use other amps.

Even without a impedance buffer it might be a good idea to turn down the lows. A pickup signal has too strong low frequency components compared to the air radiated sound of the instrument, so by taking back the lows you free the amp from the high energy low frequencies and can use the power for medium to high frequencies to hear yourself better.
 
#12
I use an Fdeck HPF-Pre Series 3, and while it "cleans up" the low end, (while doing so), it does not substantially increase the volume. (I use a WW Electracoustic amp and don't ever even approach maxing out the capability of the WW amp's modest 450watts @ 8ohms.)
The OP's problem sounds like a "pickup" output problem, not an "amp/power" reproduction problem to me.
IME.
TMI/FYI - I have never used the Full Circle pickup and probably never will, based upon the many (un-)reliability and flimsy design issues that appear here on a weekly bassis. (See what I did there?!)
Thanks.
 
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#13
I realize the issue you are having is already addressed. I would like to help you a bit on the Carvin settings. Great amp that can be a bit overwhelming at first! You understand what it can do, so you probably have the manual and have looked through it. If not http://carvinimages.com/documents/bass-amps/BX1500_manual.pdf

Riley Z said:
I'm a double bassist that is frustrated with how little sound he is getting from his amp. I'm playing a plywood with a Fishman Full Circle, plugging into a Carvin BX1500 amp head through a SWR Goliath III 4x10 cab. The cab can handle 700w (at 8 ohms I think), but the head has "dual mono block" or something so I run half of it (750w at 2 ohms) into the cab. It can also do 300w at 8ohms and 450w at 4ohms, and the bridge output lets me do 900w at 8 ohms and 1500w at 4 ohms. Honestly I don't really know how to switch between all of these, I just know that the amp CAN do all of that. That's my setup!
Click to expand...

May or may not relate to your volume issue, but three knobs control the volume, Master, of course, Gain, then the less obvious 1/Lo and/or 2/Hi, depending which channel(s) you plug into.

If you want to bridge, be very careful with the volume! You want to have nothing plugged into the regular channels, the outer two of the three output jacks. The manual doesn't state, but I would mute the amp, turn the master down, then turn it off. Plug the speaker into the bridged output (center, dark green, and you really do want speakon connectors for this), then press the recessed bridge mode button on the back until it clicks. Power on and gradually bring up the volume. I don't have a cab capable of handling bridged with my BX1600, same thing only different.

If you want some tube grind, you get that by diming the gain, setting the Master as low as it will go, just off full CCW, then adjust the the volume with 1/LO and or 2/Hi. You can get more grind by hitting the preamp (instrument) input hard with an active signal from your preamp and leaving the input selection at passive. I realize you might not be after the grind, but you never know, you could wake up tomorrow jonesing for Judas Priest and find yourself shopping for an active bass :D

If you have questions, be sure to post up! There are many of us Carvinites kicking around. I'll see it if you post here, but I wouldn't even call myself a real bassist, much less a musician, so it would be best to start another thread with Carvin BX1500 help in the title, especially if you have questions of dialing in the tone. @BassmanPaul IS a real musician and helped me a great deal in choosing the BX1600 and setting up what I did not understand. He's a good egg too.
 
#20
I've played lots of shows as loud as I ever want to play the DB with a 4x10 cab and a 300 watt amp, so this should be more than loud enough for many situations -- assuming the amp and speaker are both working properly. I suspect it's more likely your problem is at the beginning of the signal chain. As has already been suggested, make sure the Full Circle is installed and adjusted properly, so get that checked out before going any further. The FC has a hot enough output to overdrive many amps when it's working properly. Too much is made of input impedance here. Increasing or decreasing the input load impedance will not necessarily effect the overall level of a piezo pickup, just the perceived tonal balance. Input load impedance is only one of many possible variables. I've heard lots of amps that sounded good with a piezo pickup that did not have the optimum input impedance often recommended here. Good luck!
 
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