Re: acoustic bass amplification


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Posted by Charles Stephens on July 21, 2000 at 09:09:50:

In Reply to: Re: acoustic bass amplification posted by Bob Gollihur on July 21, 2000 at 06:36:10:

: : I have many problems with current amplification of my upright. The first is that my sound isn't deep enough. It has a lot of tenor and not a lot of bass, no matter what the equilizer settings are. There is also the larger problem of feedback. I have to play in a number of big band gigs, so getting enough sound is important, but too much sound causes some painful feedback. I have only been playing upright for a couple of years, so I am still running it through the same stuff that I use for electric: A GK 800RB head and a 16'' JBL cab. I have the usual Underwood pickup on my bridge. I know that I should run my acoustic through a more acoustic friendly system. My first question is, are there any little things that I can do (i.e. pickup placement) that might give me a better sound? Secondly, what type of amplification system has worked well for you (I'm preferably looking for a combo amp) and how much did it cost you? Thanks!

: A couple things come to mind. First, Underwood pickups and other, similar piezo-based pickups usually require an impedance matching preamp-- piezo pickups have very high impedance levels-- 1 million ohms and up, while the average amplifier's input is looking for 10,000 ohms or so. This can often result in a sort of nasal, quacky, sort of response, with an undesired emphasis on highs and mids. EQ'ing doesn't help, as you have found. Many preamps (and even some stomp boxes, when engaged) designed for acoustic instruments (and therefore, piezo pickups) can due the job-- Fishman, LR Baggs, Sadowsky, as well as the K&K Sound ones I sell. Perhaps you can borrow one from a guitarist or fellow bassist to hear the difference. Key is a 1 megohm input impedance or better.

: Another thing to try-- some Underwood users only use one of the transducers-- they seem to prefer the sound. It's worth a try.

: As far as combos, it has been my experience that speakers smaller than 15" are better for a variety of reasons-- my preference is 10", I have a 2x10 cabinet. Tens seem to be have a better transient response, are clearer and more distinct, and avoid the muddy bottom that 15s often have-- they also seem to be less prone to excite the bass body and cause feedback. Bass Player magazine (www.bassplayer.com) did a test of a bunch of small combos a while back-- it is posted on their web site and is definitely worth a look (look under GEAR).

: OTOH, I highly recommend the Carvin 2x10 cabinet I have, which you could easily drive with your GK - it's a great cabinet (Eminence speakers) for around $300 - (www.carvin.com). Another thought -- some GK users who have outboard preamps, like I mentioned above, bypass the "electric sounding" GK preamp section by plugging directly into the effects loop return jack-- I've not tried it but have heard reports of a more acoustic sounding result-- another action worth a shot.

: I send a page of info on avoiding feedback with every pickup and preamp I sell -- email me off-list and I'll paste the info into an email message- you may find it helpful.

: Enjoy, Bob

I agree with Bob about the preamp, I bought one from him. However I also use a Trace Elliot EQ in front of the preamp to refine the Underwood pickup. The whole signal then goes to my Acoustic Image Contra, which I prefer over my former amp, an SWR Workingman 15. This give a very very good clear Upright Bass sound.


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