my amp has a preamp, do I still need one?

topper · #1 08-21-2009, 02:16 PM

Full disclosure, I'm an electric bass player trying my hand at DB (go easy on me). I can't afford two separate rigs and will likely be switching from EB to DB during gigs for a long long time to come. So while I realize running a DB through an electric rig is probably not ideal, it's the situation I'm stuck with for the time being.

I'm still picking out my DB pickup. Don't have a lot of money, so I'm looking to do this on the cheap. You can assume it'll be a basic piezo sort of pup.

My bass amp for my EB is a Genz Benz Neo Pak 3.5. It has a "preamp" on it. Anybody know if I can I plug a piezo pup into this without running through another preamp first?

Would I be better off just micing the DB and running through the PA?

Thanks!

HogieWan · #2 08-21-2009, 02:19 PM

Quote:

Originally Posted by topper

My bass amp for my EB is a Genz Benz Neo Pak 3.5. It has a "preamp" on it. Anybody know if I can I plug a piezo pup into this without running through another preamp first?

Magnetic pickups are a high impedance source and bass amps are designed for that. however, piezos are SUPER high impedance sources and need at least a buffer preamp to match the impedance. A buffer is a simple circuit for anyone with a little experience (or none if you're willing to try it) and can be made very cheaply

Bijoux · #3 08-21-2009, 02:29 PM

there are some UB pick ups that don't need preamp. the Realist, Revolution Solo II, Underwood, are a few that come to mind.
look on the DB side and find a thread "every pick up you'll ever need" or "every pick up you need"... don't remember...
What I do is I normally blend the pick up signal with an attached mic to get a more realistic acoustic sound. but that might be a little more down the road for you.
Another thing that helped me a lot is that I am using the Micro amp by Euphonic Audio. It puts out 550 watts and it has two independent channels for my electric and my upright, they are reasonably priced. check it out, www.eaapms.com
good luck!

peterpalmieri · #4 08-21-2009, 02:43 PM

Looking on the Genz website they do not list the input impedence on their amps. Usually anything with a 1 mega ohm input impedence will work well with a DB pick up. If it is significantly lower then that Fdeck's buffer preamp seems to be a low cost solution that allot of the guys are using with success.

Ric Vice · #5 08-21-2009, 03:04 PM

Quote:

Originally Posted by topper

Full disclosure, I'm an electric bass player trying my hand at DB (go easy on me). I can't afford two separate rigs and will likely be switching from EB to DB during gigs for a long long time to come. So while I realize running a DB through an electric rig is probably not ideal, it's the situation I'm stuck with for the time being.

Topper, there are a lot of players out there who use the same rig on both instruments, for various different reasons.

Quote:

Originally Posted by topper

I'm still picking out my DB pickup. Don't have a lot of money, so I'm looking to do this on the cheap. You can assume it'll be a basic piezo sort of pup.

Quote:

Originally Posted by topper

My bass amp for my EB is a Genz Benz Neo Pak 3.5. It has a "preamp" on it. Anybody know if I can I plug a piezo pup into this without running through another preamp first?

I recently played through a Genz Benz Shuttle 3.0 at the Webster College Summer Jazz Camp.I just plugged my Realist directly into the input without any buffer pre amp. It sounded great. So if you use a Realist, Fishman Full Circle or the Revolution Solo Pickup you may not actually need anything at all. Personally, I wouldn't include the Underwood because it screams for a buffer preamp with my rig. However, getting a HPF buffer preamp from FDeck will definitely improve the sound and the unit is very affordable.

Quote:

Originally Posted by topper

Would I be better off just micing the DB and running through the PA?

Thanks!

Unless you are used to using a microphone with a acoustic bass then I'd go with the pickup. Double Bassists who use a mic through the house and listen through monitors have gone through a "learning process curve" so their ears are used to listening back to their own sound and getting comfortable with that setup. IMHO it's not where you would start

Ric

topper · #6 08-21-2009, 03:28 PM

Quote:

Originally Posted by peterpalmieri

Looking on the Genz website they do not list the input impedence on their amps. Usually anything with a 1 mega ohm input impedence will work well with a DB pick up. If it is significantly lower then that Fdeck's buffer preamp seems to be a low cost solution that allot of the guys are using with success.

My owners manual says:
"The input impedance is 500k ohms."

From what you're saying, it sounds like I need a buffer preamp.

topper · #7 08-21-2009, 03:33 PM

Is this the Fdeck buffer preamp you're talking about?
http://personalpages.tds.net/~fdeck/bass/hpfpre.htm

Runs about $50. So, an inexpensive piezo is going to run me about $50 + the preamp...

Even a "cheap" solution is $100.

In the end I guess that's not that bad. Still more than I've got at the moment.

Wallyphonic · #8 08-21-2009, 05:16 PM

I think your best "budget" solution is to get the K&K BassMax (assuming you are playing mostly pizz). It generally sounds pretty good without a buffer preamp and costs $96. I haven't heard of a pickup cheaper than that that sounds worth a darn. Later when you get some extra scratch you can add the fdek pre and get a little better sound.

sirero · #9 08-21-2009, 05:27 PM

On my upright I run a bp-100 through an mxr 10-band eq into the rig I am using which varies from gig to gig. At my own stuff I use a Fender Blues deville guitar amp with an extension cab, and I play in a town orchestra that supplies me with a fender rumble, and I have no problems whatsoever with either setup. after killing most of the overtones it magnifies the soudn of the bass beautifully.

Oh and every working combo amp and bass rig has a preamp. for a working amplifier you need a preamp and a power amp.

bassist1962 · #10 08-21-2009, 07:20 PM

As an electric player, do you have a sansamp? if so, that should work.

HogieWan · #11 08-21-2009, 09:03 PM

Quote:

Originally Posted by bassist1962

As an electric player, do you have a sansamp? if so, that should work.

that would have the same input impedance as the amp. For most piezos, I would suggest closer to a 10Mohm input

agedhorse · #12 08-22-2009, 10:17 AM

500k is a good compromise for piezo pickups (except for the very small crystals, series wired crystals, and some Kynar film types) because as the input impedance goes up, other factors come into play, including the tribo-electric effect of the cabling and the potential for RFI intrusion in high RF areas. There are enough amp products that exhibit sensitivity to RFI that it is a very real concern IMO.

The NeoPak 3.5 input impedance works quite well with most piezos, you should definately try it before assuming it will not perform satisfactorily. I spent about 10 years in an earlier life designing piezo pickups, there are some misconceptions that have made it into urban myth... one of them being that the higher the input impedance the better. If fact, input inpedance is one of the tools an amp manufacturer can use to voice a SYSTEM response for piezo applications.

topper · #13 08-22-2009, 03:07 PM

Thanks for all the help. I don't have a sans amp, but I do have a multi effects pedal with a higher input impedence. My pedal manual says its a 1 megohm input. I guess I'll try and give it a go without a buffer.

Jefenator · #14 08-22-2009, 03:28 PM

Spec's definitely aren't everything - good idea to try out whatever you got and see if something works. (I once got good results with an Ibanez Tube Screamer in bypass mode.)

FWIW I found the Realist and Full Circle were both noticeably better w/ some kind of buffer before my amps (G/K & Markbass, both 500K).

HogieWan · #15 08-24-2009, 02:23 PM

Quote:

Originally Posted by agedhorse

500k is a good compromise for piezo pickups

whoa - you really need to do a side by side. I don't think you know what a piezo should sound like if you are using 500K inputs. try at least 2M and you'll hear a big difference. Obviously different sized crystals will have a different impedence, but I haven't seen one that sounds it's best with less than 1M

agedhorse · #16 08-26-2009, 09:29 AM

Quote:

Originally Posted by HogieWan

whoa - you really need to do a side by side. I don't think you know what a piezo should sound like if you are using 500K inputs. try at least 2M and you'll hear a big difference. Obviously different sized crystals will have a different impedence, but I haven't seen one that sounds it's best with less than 1M

Do you really think I haven't done side by side tests? 10 years of designing piezo pickups AND 25 years of amps puts me in a bit more of the "bigger picture" perspective on this topic.

There are tradeoffs in EVERYTHING, and IMO, I have found that as the input impedance varies there is a point at which the knee and the interactions become generally objectionable but for many of the currently used pickup products 500k is a good choice. That's why many amp manufacturers have settled around this number. (I think I settled on about 650k when all low frequency variables are included.)

The benefits to the lower input impedance is much lower tribo-electric noise due to movement of the center conductor relative to the shield, and vastly improved RFI rejection even at lower RF frequencies. This is especially true in a live performance situation where RFI can be a big problem with no solution one you realize you have a problem. This is not much of an issue though if there is a preamp (or buffer) on-board the bass. The problem is that we must accomodate both situations with our amps. Many passive DB pickups are out there.

Something else to consider... even though a published spec might indicate a "NOMINAL" 1 meg input impedance, I would also suggest that many are not actually 1 meg but are significantly lower and most vary over the 20-20kHz audio range too.

Again, I suggest that you try the pickups you are planning on using to see how it sounds for your application. You may find that it works just fine and achieves your target tone without messing with additional outboard gear. Maybe not, but to automatically make the assumption is probably not a great approach IMO.

Hope this helps.