So it can be done with the Felix.. and I like the "sound" of the 20 Meg-setting with my Ehrlund...always provided that no too long and good cable is used
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Double Bass How important is input impedance to you? Poll
- Thread starter Hasty
- Start date
I'm young at double bass and still have a lot to learn, but at this time in my experience, where I'm using a dual-channel pickup feeding into a dual channel blending pre-amp, I can only see worrying about impedance once, that being when you're selecting your pickup system to match your pre-amp or your amp.
After that impedance match is appropriately made, I can't imagine a need for multiple impedance selections unless a person is once again trying out other pickups and/or pre-amps/amps. I've been lucky enough to find a pickup/pre-amp combination that I like and I don't really feel a need to switch around.
Maybe I'm missing some important details??? If so, please educate me about it.
After that impedance match is appropriately made, I can't imagine a need for multiple impedance selections unless a person is once again trying out other pickups and/or pre-amps/amps. I've been lucky enough to find a pickup/pre-amp combination that I like and I don't really feel a need to switch around.
Maybe I'm missing some important details??? If so, please educate me about it.
I don't think you are! Once you've matched the impedance from you pre-amp to your pick-up you are good to go. The variable/ multi option thing is only nice so one pre-amp (or whatever) can work with many pick-ups.
I don't think you're missing anything. The only reason I created this poll was to see just how important it might be to people since it's an easy addition to a project I'm working on. There was another thread where many people were discussing preferred input impedance options so I thought it was interesting enough to elicit opinions, and I've seen some great comments come out of this thread.
In my mind, once you know what impedance you need for your pickup it's a one-and-done type situation.
That said... I know lots of guys might have multiple basses with multiple pickups and could be interested in different impedance options. I also know a few guys who travel and rent basses that might have a different pickup for gigs. I could see that being an interesting use case. Of course that's assuming you're traveling with the preamp as a fly rig.
Input impedance has been used in Double Bass amps since the Ampeg B-15N was designed in the early 1960’s. Channel 1 has two inputs. Input 1, 4.6 Megohms Input 2, 1Meg Ohm, Channel 2 2 Megohms. That definitely contributed to the B-15’s success for @17 years. Most modern bass amps that have been widely accepted by DB players are 1 Meg Ohm or higher. The Gallien Krueger Micro bass series 1 Meg Ohm, Walter Woods 1 Meg Ohm. EA Doubler, and Acoustic Image Claris4+. These days a vast majority of bass amps are 1 Meg Ohm or higher. Just my take. 
Passinwind
I know nothing.
- Dec 3, 2003
- 23,054
- 45,943
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- Designer/Toaster Tech @ Passinwind Electronics
Just as soon as I get the last few details posted on my Github repository for my latest OS preamp pedal project, I will be posting a standalone version of the HPF module. I've been using this design for several years in my DIY amps and it's well vetted for both AUB and EUB duty. If it suits your needs you are welcome to it. Github seems to be down right now, but there are links to my long TB thread and my Github pages here: https://www.talkbass.com/wiki/pw3b-lpf-open-source-musical-instrument-preamp/
I'm looking forward to seeing what you've come up with, bonne chance!
That's awesome. Thanks so much!
I've looked at so many different HPF schematics, Sallen-Key designs, and filters in general that my head just spins. Especially difficult for me since I'm trying to make something simple, tiny that doesn't involve SMD, and accessible for someone who doesn't have much DIY soldering experience. Someone earlier mentioned the idea of a fixed value HPF and that's not a terrible idea for a project like this one. Keeps the project smaller and potentially fewer moving parts.
I've got 4 or 5 different possibilities I'm working through because my project is fairly modular. It's fairly simple to port parts of the circuit to different style/sized PCBs to fit a few different needs. I've got a couple of designs that are opamp based and a couple that use FET buffers. My smallest project is 35mm x 70mm and the plan was to use it as a tailpiece mounted preamp with two channels that have individual-level controls. It's essentially a souped-up pair of high input impedance buffers and a mixer. If I could add an HPF to anything... that would be the one I'd want to add it to. I'm waiting for the prototype boards to arrive for this one now, should be next week.
Passinwind
I know nothing.
- Dec 3, 2003
- 23,054
- 45,943
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
Cool! My current pedal project is an attempt to get DIY'ers more comfortable with hand soldering SMDs. So I've used the largest common 1/4 watt resistor size, 1206, and SOIC-8 opamps, and then all the caps on the DIY boards are through-hole:
The board on the left is the standalone HPF, with mounting holes allowing easy installation in a 1590A enclosure. For the V4 pedal there's a smaller version without the mounting holes, identical in plan form to the other two, at ~30mm x 40mm. Porting the resistors and opamps to TH format would be pretty easy, the board size might even be able to stay the same. But for battery powered applications pretty much all the cool new low current opamps are SMD-only, IME. So the usual tradeoffs are in play, same as it ever was.
Nice!Cool! My current pedal project is an attempt to get DIY'ers more comfortable with hand soldering SMDs. So I've used the largest common 1/4 watt resistor size, 1206, and SOIC-8 opamps, and then all the caps on the DIY boards are through-hole:
View attachment 5225285
The board on the left is the standalone HPF, with mounting holes allowing easy installation in a 1590A enclosure. For the V4 pedal there's a smaller version without the mounting holes, identical in plan form to the other two, at ~30mm x 40mm. Porting the resistors and opamps to TH format would be pretty easy, the board size might even be able to stay the same. But for battery powered applications pretty much all the cool new low current opamps are SMD-only, IME. So the usual tradeoffs are in play, same as it ever was.
I was looking at your PCB's on OSHPark and really liked the layout of that HPF. I also appreciated the size, considering OSHPark can be cost prohibitive for bigger projects. I also loved your little utility boards in your shared file section for potentiometers. I can't believe I've never thought of doing that... I have so many PCB pin based pots that I seldom use because of the risk associated with the poor mechanical connection.
I'll definitely be ordering that board when I do my next OSHPark order and see how it fits in with the project.
Passinwind
I know nothing.
- Dec 3, 2003
- 23,054
- 45,943
- Disclosures
- Designer/Toaster Tech @ Passinwind Electronics
If you just build the HPF to the V4 spec it should be plenty close enough for test purposes. You may need to add the omitted 1uF 50V cap at the output to the Mouser BOM, and maybe the output shunt resistor, for which 330K works well if a bypass switch is going to be used. That depends on what comes next in the preamp signal chain, if anything. One twist of my design is that it doesn't need a two section pot for the frequency sweep, which makes parts procurement considerably easier. The repsonse curves are kind of in between the Broughton and fdeck ones, FWIW.
Those pot and switch breakout boards save a lot of heartache, for sure! Some of them also have resistors and/or caps onboard to allow fine tuning mods without having to dive into the main boards, which tends to require more refined technical chops. I do a lot of other little utility boards too: mixer/blenders, buffers, gain stages, etc. Again, you're welcome to any of them if they might work for you.
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I’ve tried a few different pickups and preamps. Generally the higher impedance the better. Usually 10M is where I end up.
Hey Oren!
I also use a Full Circle into a MB CMD121p. My original Italian-made amp has a 500k input (I’m reasonably sure). Is yours a newer model?
Hi, Jason - mine is also a older Italian version. I know I pulled that figure off of some Markbass webpage, but I can’t find it now, nor any reference to the input impedance on that amp. I hope I’m not guilty of spreading misinformation! I’ll keep rooting around.
This page details the newer IV version as having a 1 Mohm input impedance, but I don’t see input impedance on any of the spec pages for earlier versions. MINI CMD 121P IV – Markbass
Mine is the combo head II … I was going off this owners manual online.
I can say that the full circle directly into the cmd is totally fine for most background & small club dates. I use a boss EQ with 1M for louder gigs and the venerable fdeck1 for boomy rooms.
I'll also add that input impedance is not the only factor! I have the FDECK II, FDECK III and Fishman Plat Pro. They are all 10M OHM and all sound very different. My fav is probably the FDECK II. It has a tiny volume bump that just adds a hint of boost and sweetness to the tone. Even when eq'd similarly, the Fishman seems to lack that same warmth
And I'll also add, that input impedance isn't only important for (piezo) pick-ups, but also for microphones... Since I own a Roger Schult preamplifier with adjustable input impedance, I can easily understand how changing the impedance also changes the sound... an additional "tone control"
