How do I match impedance without using a preamp?

[Bassist4Life]

I love the sound of my full-circle pickup going directly into my SWR combo.

The output volume is very low without a preamp, so I borrowed a Fishman Platinum Bass preamp. I don't hate the sound, but I love how my bass sounds without the preamp.

I assume the volume issue I'm having is due to the mismatched impedance.

Is there an easy way to match impedance between my Full-Circle and the input of my SWR combo without using a preamp?

Joe

[drurb]

Originally Posted by Bassist4Life

I love the sound of my full-circle pickup going directly into my SWR combo.

The output volume is very low without a preamp, so I borrowed a Fishman Platinum Bass preamp. I don't hate the sound, but I love how my bass sounds without the preamp.

I assume the volume issue I'm having is due to the mismatched impedance.

Is there an easy way to match impedance between my Full-Circle and the input of my SWR combo without using a preamp?

Joe

It would help to know which combo you have and what is its input impedance. It's a little puzzling that the level is very low without a pre-amp. Impedance matching for transducers like the FC is not just about level. The input impedance affects the frequency response. In any case, if you like the sound the way the the SWR loads the FC rather than the way the Fishman pre loads the FC (which is also puzzling), then it seems that you prefer what the SWR does to the frequency response. Even if you could easily change the input impedance of the SWR, you probably would not like the sound. Again, if you'll post which SWR you have, perhaps you can get a more definitive answer.

[Bassist4Life]

Originally Posted by drurb

It would help to know which combo you have and what is its input impedance. It's a little puzzling that the level is very low without a pre-amp. Impedance matching for transducers like the FC is not just about level. The input impedance affects the frequency response. In any case, if you like the sound the way the the SWR loads the FC rather than the way the Fishman pre loads the FC (which is also puzzling), then it seems that you prefer what the SWR does to the frequency response. Even if you could easily change the input impedance of the SWR, you probably would not like the sound. Again, if you'll post which SWR you have, perhaps you can get a more definitive answer.

I have an SWR LA12. I know that it's not a high-end piece of gear, but it works very well for me. I play in a jazz trio. I rarely turn the volume up more than one-quarter of the way (with electric bass). In the praise band I play with, I don't have to turn the volume up more than half way (with PA support). It's a great little amp that I've been using for years.

That being said, I don't know what the input impedance is. I'm guessing that it's not well-suited for my Full-Circle pickup, but I like how my upright sounds through the amp. I need to crank up the volume most of the way when I play my upright through it.

Any thoughts?

[drurb]

Originally Posted by Bassist4Life

I have an SWR LA12. I know that it's not a high-end piece of gear, but it works very well for me. I play in a jazz trio. I rarely turn the volume up more than one-quarter of the way (with electric bass). In the praise band I play with, I don't have to turn the volume up more than half way (with PA support). It's a great little amp that I've been using for years.

That being said, I don't know what the input impedance is. I'm guessing that it's not well-suited for my Full-Circle pickup, but I like how my upright sounds through the amp. I need to crank up the volume most of the way when I play my upright through it.

Any thoughts?

The on-line manual for the LA 12 actually does not list the impedance of the main input.

[Bassist4Life]

Originally Posted by drurb

The on-line manual for the LA 12 actually does not list the impedance of the main input.

Right.

[robgrow]

The input impedance of your amp would have to be exceptionally low for it to seriously effect the output level of the Full Circle. Other members of this forum have reported successfully using the Full Circle with Markbass amps such as the Little Mark II, which has an input impedance of 500K ohms, just to give one example. I think it's more likely that you have a gain structure problem (the output of the FC is too low to drive your amp), which means you need a preamp to give you a little more gain.

[Bassist4Life]

Originally Posted by robgrow

which means you need a preamp to give you a little more gain.

I think that you're right. However, I was wondering if there is a way to change the input impedance without purchasing a preamp. Is there a simple adapter that would do the trick? I dunno... maybe something I could grab off the shelf at my local Radio Shack?

I remember reading something in a BP not too long ago where an upright bassist mentioned using a box that he created to match impedance.

Any more thoughts on this?

Joe

[bolo]

Originally Posted by Bassist4Life

I love the sound of my full-circle pickup going directly into my SWR combo.

The output volume is very low without a preamp, so I borrowed a Fishman Platinum Bass preamp. I don't hate the sound, but I love how my bass sounds without the preamp.

I assume the volume issue I'm having is due to the mismatched impedance.

Originally Posted by Bassist4Life

I'm guessing that it's not well-suited for my Full-Circle pickup, but I like how my upright sounds through the amp. I need to crank up the volume most of the way when I play my upright through it.

Any thoughts?

This is puzzling, for a coupla reasons, just like Doc said.

As stated above, impedance matching is one thing to examine if the tone is too thin and nasal sounding. It's more about tone and frequency response than about volume or output level. But you said you liked the tone. If you like the tone, that's good!

When you "crank up the volume" using your upright like you described above, are you getting enough volume to do the gig(s)?

Just because you have to turn up the knobs higher w/ the upright than you do with your EB is not necessarily a problem, IMO. If you are getting a good sound, and enough volume to cut the gig on your upright, don't fret. Just enjoy.

[Bassist4Life]

Originally Posted by bolo

This is puzzling, for a coupla reasons, just like Doc said.

As stated above, impedance matching is one thing to examine if the tone is too thin and nasal sounding. It's more about tone and frequency response than about volume or output level. But you said you liked the tone. If you like the tone, that's good!

When you "crank up the volume" using your upright like you described above, are you getting enough volume to do the gig(s)?

Just because you have to turn up the knobs higher w/ the upright than you do with your EB is not necessarily a problem, IMO. If you are getting a good sound, and enough volume to cut the gig on your upright, don't fret. Just enjoy.

Okay. I'm getting it now. I was under the assumption that matching impedance had to do with volume, not tone. I'm understanding now that it's the other way around. Thanks for clearing that up guys. Thanks for your patience on my misunderstanding.

The volume I get can get me through the gig; however, I might need more volume for other venues. In which case, I'll use the Fishman Platinum Preamp (that I'm borrowing).

Thanks again guys. Sorry for the confusion.

Peace,
Joe

[robgrow]

Originally Posted by Bassist4Life

I think that you're right. However, I was wondering if there is a way to change the input impedance without purchasing a preamp. Is there a simple adapter that would do the trick? I dunno... maybe something I could grab off the shelf at my local Radio Shack?

I remember reading something in a BP not too long ago where an upright bassist mentioned using a box that he created to match impedance.

Any more thoughts on this?

Joe

fdeck's HPF-Pre is well worth the price ($50) just for it's buffering capability which provides a 10 meg ohm input. The sound is also quite good, plus it provides a variable high pass filter and phase reverse capability. Available directly from TB'r fdeck here: http://personalpages.tds.net/~fdeck/bass/hpfpre.htm

[drurb]

Originally Posted by Bassist4Life

Okay. I'm getting it now. I was under the assumption that matching impedance had to do with volume, not tone.

Not to throw a wrench in the works but impedance matching is, in fact, classically about maximum power transfer and that would affect intensity and thus, volume. It just happens that in our applications it turns out to affect the spectrum ("frequency response") of piezo pickups more than anything else.

[Bassist4Life]

Originally Posted by drurb

Not to throw a wrench in the works but impedance matching is, in fact, classically about maximum power transfer and that would affect intensity and thus, volume. It just happens that in our applications it turns out to affect the spectrum ("frequency response") of piezo pickups more than anything else.

Hmmm. Okay. So matching impedance will increase my volume; however, may also change my tone?

[drurb]

Originally Posted by Bassist4Life

Hmmm. Okay. So matching impedance will increase my volume; however, may also change my tone?

I expect that it will have a modest to small effect on volume but potentially a large effect on tonal balance. That is, unless something is highly unusual.