• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Active preamp, no EQ

KingRazor

KingRazor

Supporting Member
Jun 4, 2010
6,747
415
37
Beaverton, Oregon USA
#1
Is there a way I could get an active preamp without an onboard EQ? I like the low impedence, reduced signal loss and higher output that can be provided by having an active preamp, but I don't want to mess around with an onboard EQ.

What do you guys recommend?
 
#4
KingRazor said:
Is there a way I could get an active preamp without an onboard EQ? I like the low impedence, reduced signal loss and higher output that can be provided by having an active preamp, but I don't want to mess around with an onboard EQ.

What do you guys recommend?
Click to expand...

acitve preamp and no eq? Yes please!

DIY. ic (op amp) or discrete -it's easy, its cheap.
if this is the route you would like to go in - pm me, I'ld love to help.
 
  • Like
Reactions: ronny_lie
#8
Something like this should be considered a buffer, not a preamp. I just built one for about $10 using a single JFET, a couple of resistors, a couple of capacitors, and a 9V battery clip. It provides a little gain ~6dB. The only tricky part was choosing the resistors to match my JFET. The tolerances on JFET performance are quite large so it's worth taking the time to either tune for your specific JFET or go the opamp route.

Works great with my Dimarzio passive pups.

I can post the circuit design as it's been circulating around the internet for a while. Lots of opamp-based buffers and equalizers can be found as well.
 
#9
thebisch said:
This is a very nice idea. How about this...for example on something like a passive OLP. Master volume, passive master tone, and variable preamp gain! Keeping an eye on this one.
Click to expand...

possible.
IMO the main purpose of an onboard preamp is to unload the pickups and provide a buffer so that you can get all that the pickups can offer.

that said, my dream bass would have no eq/tone control at all. Just a buffer and blend/balance and volume...maybe not even that.

Not quite sure of the passive master tone...have to give that some thought. AFAIK it really is just a low pass filter. Should be quite easy to implement in an active preamp but I would have to think about it.
 
#10
KingRazor said:
I've looked into the redeemer, but I'd prefer something that also boosts the output level of the pickups.

I don't know anything about soldering or wiring. I want something I can buy and take over to the shop and tell em "Put this in plz kthxbai"
Click to expand...

I have given some thought to our PM communication. the overall ckt is simple enough but I do see an issue with taking a DIY preamp to your friendly neighborhood guitar store tech. sorry, don't have a whole lot of faith in those guys.

taking them something from Bartolini, EMG, etc. is one thing. There is plenty of documentation and directions for them to follow. Not to mention someone they can call.

My feeling is that if you take a ckt on a proto-board they might be uncomfortable and may refuse to do it.
 
#11
The active circuit that lowers the output impedance and provides isolation is called a "buffer". If the signal is boosted, then a buffer was almost always used for that job too, though buffers are not always designed for boost. All active preamps and EQ's include one or more buffers.
Click to expand...

Yep, what I'm asking for is basically just a buffer.

It just needs to have the following:

  • low output impedence
  • pickup isolation
  • transparency (it should color the tone of the pickups as little as possible)
  • no or very little signal loss
  • a moderate boost in gain
As far as controls, I'm going for either a 250k or 500k audio taper volume pot (I don't need a smooth transition between volume levels, most of the time it'll be used as an on/off switch) and a 4-way rotary switch for pickup selection.

Position 1: 100% neck pickup, both pickukps in parallel

Position 2: 100% both pickups, both pickukps in parallel

Position 3: 100% bridge pickup, both pickukps in parallel

Position 4: both pickups in series

No tone pot, no EQ. All EQ will be done at the amp or mixing board level.
 
#12
rumblinbass said:
I have given some thought to our PM communication. the overall ckt is simple enough but I do see an issue with taking a DIY preamp to your friendly neighborhood guitar store tech. sorry, don't have a whole lot of faith in those guys.

taking them something from Bartolini, EMG, etc. is one thing. There is plenty of documentation and directions for them to follow. Not to mention someone they can call.

My feeling is that if you take a ckt on a proto-board they might be uncomfortable and may refuse to do it.
Click to expand...
I would trust them much more so than myself, but I do have a few friends that know how to work a soldering iron that could probably do it.
 
#15
KingRazor said:
  • low output impedence
  • pickup isolation
  • transparency (it should color the tone of the pickups as little as possible)
  • no or very little signal loss
Click to expand...
KingRazor said:
As far as controls, I'm going for either a 250k or 500k audio taper volume pot (I don't need a smooth transition between volume levels, most of the time it'll be used as an on/off switch) and a 4-way rotary switch for pickup selection.
Click to expand...

a boost in gain is no problem. 250k or 500k is not necessary for volume control in an active preamp/buffer. for passive electronics; yes. when I pot is connected directly to the pickup a higher value pot is less of a load.

KingRazor said:
Position 1: 100% neck pickup, both pickukps in parallel

Position 2: 100% both pickups, both pickukps in parallel

Position 3: 100% bridge pickup, both pickukps in parallel

Position 4: both pickups in series
Click to expand...

just have to find a rotary switch...

KingRazor said:
No tone pot, no EQ. All EQ will be done at the amp or mixing board level.
Click to expand...

+1!
 
#16
KingRazor said:
  • no or very little signal loss
  • a moderate boost in gain
I don't need a smooth transition between volume levels, most of the time it'll be used as an on/off switch
Click to expand...

Since the buffer is an active component, you won't get any signal loss. You will get gain depending on the design of the active circuit. If the gain is less than one, it's the same as signal loss. Since you want modest gain, the concept of signal loss doesn't really make sense. What might make sense is a high input impedance to the buffer/preamp. If you're using magnetic pups (vs piezos) this isn't a big deal as long as you keep it reasonaably high.

You'll likely find some form of volume control at the bass useful unless you are playing the same equipment setup with the same band in the same venue all the time.
 
#17
rumblinbass said:
a boost in gain is no problem. 250k or 500k is not necessary for volume control in an active preamp/buffer. for passive electronics; yes. when I pot is connected directly to the pickup a higher value pot is less of a load.
Click to expand...
So what should I use for volume control in this scenario?
Rob22315 said:
Since the buffer is an active component, you won't get any signal loss. You will get gain depending on the design of the active circuit. If the gain is less than one, it's the same as signal loss. Since you want modest gain, the concept of signal loss doesn't really make sense. What might make sense is a high input impedance to the buffer/preamp. If you're using magnetic pups (vs piezos) this isn't a big deal as long as you keep it reasonaably high.
You'll likely find some form of volume control at the bass useful unless you are playing the same equipment setup with the same band in the same venue all the time.
Click to expand...
I wasn't necessarily implying that there would be a chance that I would have signal loss, I was simply stating that I don't want any.
If I'm playing anywhere but my bedroom I have my volume knob at 10. The only time I go below that is if I'm at home and it's late at night.
 
#18
KingRazor said:
So what should I use for volume control in this scenario?
I wasn't necessarily implying that there would be a chance that I would have signal loss, I was simply stating that I don't want any.
If I'm playing anywhere but my bedroom I have my volume knob at 10. The only time I go below that is if I'm at home and it's late at night.
Click to expand...

250K or 500K should be fine, just don't think that they have to be that high. 100k should be fine.
 
#20
Rob22315 said:
When I installed my buffer, I just left the existing passive controls v/v/t in place. Since they are on the input side of the buffer, do what's simplest.
Click to expand...
That's what I was hoping I could do. Right now I have Volume/Balance/Mid/stacked treble & bass, I'd like to be able to still use the same volume pot (it may be 500k though, I'm not sure). The balance pot works well enough, I'd prefer a rotary switch but the current balance pot does the trick. I'd pull the mid and stacked pots and maybe throw in a series/parallel switch in one of them, the other one could probably be an active/passive switch, although I'd rather just swap the battery real quick than go passive, it might be nice.

Edit: that would be if I put a buffer in my current bass. I'm also planning a custom build and that's the one that would have a rotary switch as opposed to a blend pot.
 

Latest posts

Top Bottom
Back