Preamp Impedance Question

jimclark68 · #1 09-26-2006, 05:49 PM

I still consider myself very much at the front end of the learning curve in terms of electronics and live sound, so I wanted to throw this question out before I start trying/buying more gear.

I have a Series III Clarus and a Wizzy cab, and I use a K&K Bassmax pickup. The thread about the Ohio Belchfest discusses the midrange hump that the Wizzy has, and I certainly experience the same effect. The louder the setting, the less of an issue it is, but at relatively quieter volumes it makes my teeth itch a little. I do not use a preamp and run my EQ flat on the Clarus.

My question is: the input impedance of the Clarus is 1M Ohm. Would a preamp with an even higher impedance, such as a Fishman Platinum or Baggs (each of which have inputs at 10M ohms), tame this honk any, or is it just a characteristic of the speaker that I must live with?

fish slapper · #2 09-26-2006, 07:19 PM

might suggest looking at the pick-up. Just went down the road you are started on. I have a Clarus into a Schro Mini 12+ and was pondering adding a pre. I ended up getting a Fishman Full Circle and did major improvement on the "mid honk".

I borrowed a Fishman Plantimum from a friend and it improved the sound a little better but not $190 better (with the FC). Might look into one of the cheaper pre's and see how that works.

But the pick-up move was major mo betta.

robgrow · #3 09-26-2006, 10:13 PM

At the belchfest in May, the upper mids on the Wizzy seemed more pronounced to me than the EA VL208 that we had been listening to for an extended period. I think it should be pointed out that The VL208 is a 3-way design with high and mid frequency level controls, and those levels were set to the owner's preferences. Since the Wizzy uses a single full-range driver, it doesn't have any adjustments -- the mids are full on so to speak. If we had been using the Wizzy as our reference and had set the EQ on the amp accordingly, the VL208 may very well have sounded subdued by comparison. It's all relative.

Having said all that, I agree with Fish Slapper: don't blame the cab. I've used the K&K Bass Max, and I don't like its sound. The Revolution Solo II would be a much better sounding alternative IMO. The RSII is also not particullarly fussy about input impedance, and 1 meg should be fine. My personal preference is use a pickup, amp and speaker I'm happy with and not to have to try fix anything with a preamp.

There are a lot of good things about the Wizzy, and I think you would appreciate it a lot more with the right pickup. You also may decide that you don't need a preamp afterall.

(BTW I have a Wizzy and a VL208, and, to me, they sound more alike than different. The Wizzy is certainly a lot easier to move, not to mention that a new one costs around half what a used VL208 goes for, is exceptionally efficient and sounds pretty darn good.)

bribass · #4 09-26-2006, 10:43 PM

Quote:

Originally Posted by robgrow

At the belchfest in May, the upper mids on the Wizzy seemed more pronounced to me than the EA VL208 that we had been listening to for an extended period. I think it should be pointed out that The VL208 is a 3-way design with high and mid frequency level controls, and those levels were set to the owner's preferences. Since the Wizzy uses a single full-range driver, it doesn't have any adjustments -- the mids are full on so to speak. If we had been using the Wizzy as our reference and had set the EQ on the amp accordingly, the VL208 may very well have sounded subdued by comparison. It's all relative.

Having said all that, I agree with Fish Slapper: don't blame the cab. I've used the K&K Bass Max, and I don't like its sound. The Revolution Solo II would be a much better sounding alternative IMO. The RSII is also not particullarly fussy about input impedance, and 1 meg should be fine. My personal preference is use a pickup, amp and speaker I'm happy with and not to have to try fix anything with a preamp.

There are a lot of good things about the Wizzy, and I think you would appreciate it a lot more with the right pickup. You also may decide that you don't need a preamp afterall.

(BTW I have a Wizzy and a VL208, and, to me, they sound more alike than different. The Wizzy is certainly a lot easier to move, not to mention that a new one costs around half what a used VL208 goes for, is exceptionally efficient and sounds pretty darn good.)

A warmer sounding pick up like he Realist or Fishman Full Circle I'm sure would do wonders to tame the "honk". The Realist also does really well into my Focus 2R III without any preamp although the EQ flexibility of the LR Baggs Paracoustic DI does wonders for my sound in problem rooms or when using my combo amps.

jimclark68 · #5 09-27-2006, 05:25 AM

Thanks for the input, everyone. I've been happy with the Bassmax for several years now, and haven't really had the honk issues with other cabs. I've been very happy with the Wizzy otherwise, and it's really a pretty minor issue. I've just never spent a lot of time thinking about input impedance and was curious if it would affect this issue with the cab.

**Chris Fitzgerald** · #6 09-27-2006, 07:19 AM

Quote:

Originally Posted by robgrow

At the belchfest in May, the upper mids on the Wizzy seemed more pronounced to me than the EA VL208 that we had been listening to for an extended period. I think it should be pointed out that The VL208 is a 3-way design with high and mid frequency level controls, and those levels were set to the owner's preferences. Since the Wizzy uses a single full-range driver, it doesn't have any adjustments -- the mids are full on so to speak. If we had been using the Wizzy as our reference and had set the EQ on the amp accordingly, the VL208 may very well have sounded subdued by comparison. It's all relative.

Agreed. The 208 was mine, and had been part of my setup for years, so I knew exactly how to set the EQ for it. I'm not sure if it mentions this in the belchfest thread or not, but what the Wizzy I tried didn't like was my AMT mic; if memory serves correctly, it liked the Full Circle just fine. I'm sure if the Wizzy had been my main speaker, I would have had the EQ set for it in a way that would make the VL208 sound funny in a 10 minute test. We weren't striving for scientific accuracy, just first impressions. It would have been nice to do some more in depth comparisons with a more limited collection of gear, but we had a whole bunch of stuff to try out. Maybe we'll do it again sometime with a more specific plan...

Quote:

Originally Posted by DAVECLARK5

I have a Series III Clarus and a Wizzy cab, and I use a K&K Bassmax pickup. The thread about the Ohio Belchfest discusses the midrange hump that the Wizzy has, and I certainly experience the same effect. The louder the setting, the less of an issue it is, but at relatively quieter volumes it makes my teeth itch a little. I do not use a preamp and run my EQ flat on the Clarus.

If you've got your EQ set flat and you're hearing a mid hump, I'd try tweaking the EQ long before buying a second preamp. I think the EQ controls on the series III AI amps get a bad rap sometimes - they're actually pretty versatile, just not fancy looking. I used a Bass Max for years on my old Czech bass, and got pretty decent results from it. If I were running it through a series III EQ, I'd use the HP filter set at about 70 or 80 hz (high noon on the knob) and try cutting the highs and mids to taste. Alternately, you could leave the EQ flat and use the notch filter instead of the HP to try and zero in on the frequencies that are annoying your ear. Just by way of comparison, I roll off the mids and highs to taste with the VL208...both usually stay between 9 and 12, but they vary depending on the room and the humidity level at the time of the gig.

PB+J · #7 09-27-2006, 07:21 AM

In my limited experience impedance matters, but not in the dramatic way it used to matter with the first generation of piezos. I ran a rev solo into an ampeg B-15, and avalon U5 (3 meg ohm), a Raven labs PMB-1 (10 meg ohm) and a fishman proplatinum (10 meg ohm). The Avalon sounded the best, but I couldn't really hear a dramatic difference of kind, if that makes sense. The avalon sounded better all around, but there was no clear evidence that impedance was the reason. I recently tried a summit audio preamp with a variable impedance control, using a passive electric bass, and there was a very noticeable but not dramatic change in tone as i moved the control knob--the tone got "mellower" at one extreme, then got louder and vaguely brassy, then smoothed out a little. i didn't have a lot of time to mess with it but it was interested. Not a huge difference, and nothing eq couldn't overcome

jimclark68 · #8 09-27-2006, 08:45 AM

Thanks Chris, I have been experimenting some with the filters, but I've yet to find the magic frequency. I can discriminate between the extremes of the filter range, but when I get into fine-tuning those frequencies around the middle of the range, I have harder time. I'll keep plugging away at it.

drurb · #9 09-27-2006, 09:11 AM

I agree with most of the comments above. At present, there is no evidence that the Wizzy has any mid-range "hump." It is clear that the comparisons in question were relative ones with different EQ settings, etc. I have never noticed such a frequency response anomaly with my Wizzy.

That being said, I certainly have noticed that the K&K BassMax is consistently more "honky" and less "neutral" sounding than is the RS-I or RS-II. I think the best advice you got above was to look into a better pickup.

On the matter of EQ, it is always best to have a setup that requires as little "fixing" as possible. The physical reality of large variations in room acoustics and their profound effects on the propogation of the low ferquencies in which we are interested makes judicious use of EQ a necessity. As I've said before, it's well worth learning to use EQ effectively. I've pointed out before how one can learn to identify frequency regions by ear. IMO, one of the most powerful tools available on amp heads is the parametric EQ on the EA amp heads.

Finally, I'd like to put in a plug for the adjustable high-pass filter that fdeck is developing. When you use a piezo with a ported cabinet, such as the Wizzy, the infrasonic frequencies the pickup produces can cause excessive "cone dance" that not only leads to earlier breakup but which robs power from your amp. I have a prototype of fdeck's design and it has become an integral part of my rig. I set it at 40-Hz and away I go. It also addresses input impedance issues in that it's value is 10 Mohms.

David Santos · #10 10-10-2006, 02:59 PM

Does anyone knows if 500 kohms is too low for the rev solo II? I've been thinking about buying a Markbass ac101 (seems a good choice when you have to think about portability, wattage, frequency response, price, ...) but the input is only 500 kohms. By the way, Markbass seems to have some interesting stuff for th urb though their inputs, except the xlr, are 500 kohms. I know I could buy a pre but that means a higher investment, more to carry/worry for gigs and one more cable. Anyone?