Double Bass How important is input impedance to you? Poll

[Hasty]

I'm interested to know more about input impedance opinions, especially those using a dual piezo-type setup.

I'm working on a free, open-source, preamp project centered around the Yamahiko, some of you might have seen prototype pics I've posted before with various configurations. I'm hoping to get things finalized (final PCB, build guide, Github page with resources and Gerber files for free download) in the next few months and turn the project loose on the internet for those who like to tinker.

As I was reading through the most recent comments in the Yamahiko thread and the discussion was turning towards impedance. As I'm working through this project I figured this could be something pretty simple to have as an option for those that would want it.

So let me know your thoughts on something like a simple switch that would allow you to select between two different impedance settings.

Also, since my focus is centered around the Yamahiko with the possibility of dual inputs there could be an option of impedance selection for each channel.

To clarify, the actual impedance values for the project aren't important. Those would be selected by the person actually building out the preamp. So if you like 1M and 20M, cool. Want 3.5M and 10M, have at it! You're only limited by your imagination and stock on hand.

 

[Jefenator]

I wouldn't be opposed to auditioning 1M vs 10M.
Any DIY builder who already knows their preferred impedance could just omit the switch.

 

[Hasty]

I wouldn't be opposed to auditioning 1M vs 10M.
Any DIY builder who already knows their preferred impedance could just omit the switch.

Yeah I thought that too, but as I was reading I found it interesting just how varied the opinions were on input impedance with certain basses and pickups. If you're playing different pickups on different basses it might be important to some people.

For me, I'm pretty much a 10M guy with most preamps and I haven't been disappointed yet. The grass might be greener at 20M or 3M... but I haven't really felt the need to pursue that.

 

[Wasnex]

If I am using an unbuffered piezo pickup, I usually check the input impedance of my amp. But it's not something I am super critical about, unless the sound is bad. I did care enough to buy a Radial PZDI (just in case), but I haven't actually used it.

I consider the minimum for unbuffered piezo to be 1Meg. It has been widely claimed that 10Meg is the gold standard, but from what I understand it varies by pickup design, and optimum is usually somewhere between 2 and 5Meg.

The Radial PZDI is switchable between 220K, 1Meg and 10Meg. Most DIs wire the Thru in parallel to the input...this includes the CountryMan Type-85, which has 10Meg input impedance. So if you run the Thru to an amp, the pickup sees the input impedance of the DI and amp in parallel: 1Meg + 10Meg in parallel is about 910K. The PZDI Thru can be toggled between parallel and buffered, so the pickup only sees the input impedance of the DI.

The Radial StageBug SB-4 is also designed for piezos. Input impedance is fixed at 5Meg and the Thru is always buffered.

The last pickup I used professionally was the original Gage Realist. My understanding is this pickup was designed to be less sensitive to input impedance than the typical piezo. My last touring rig used an Ashley MX508 rack mixer, so I could switch between three basses. The MX508 has mic and line level inputs. I used a Shure A95U line matching transformers to plug straight into the XLR mic inputs. Mic inputs tend to have a pretty low input impedance. The A95U does step the impedance up some, but I am pretty sure it's still less than 1 Meg. Did not seem to matter all that much with the Realist.

There was a thread where someone had a custom input impedance selector added to a nice high-end preamp/buffer. I believe this is it: Sarno Black Box As far as I remember, input impedance can be adjusted at least to 20 Meg, and I believe some felt their pickup sounded best at >10 Meg.

 

[TroyK]

I think if there was a pre-amp that had:

a) variable or optional input impedance

And

b) a sweepable high pass filter

it would be standard for all of us. Those are the two things that seem to matter most and aren't usually on our amp heads.

I have an FDeck and a Tech21 Paradriver. With the Realist Lifeline, I carried the FDeck in case I had an issue in the room, but didn't use it most of the time. I never used the Paradriver with DB unless I needed a DI.

Either of them makes the Yamahiko perform much better and to my surprise the Paradriver sounds better. I think that's the 4.7 impedance input. I've been wondering if it was possible to modify my FDeck.

The Paradriver has a fixed HPF, which is clearly not as good of option as the variable one on the FDeck, but it's been good enough this year.

What else would we need in a pre-amp?

EQ is nice, but every amp head has EQ. The sweepable mid on the paradriver is useful as is the blend, but I could live without them. I've actually be considering replacing it with a Q Strip, so that I could have a 2nd sweepable mid band and just bypass my amp's altogether, though my iAmp has 4 semi-parametric bands, so I'd be wasting that excellent preamp by putting an eq in front of it. My micro-head has 3 fixed bands and while that is "good enough", when I want to carry something lighter, it would benefit from a more robust eq.

Some people need to blend 2 signals and want to be able to reverse phase. As noted, some pickups are more sensitive than others, but for anyone who felt like they needed a preamp, including Yamahiko users, a & b above cover all of the standard needs in a way that I don't think anything on the market below the price at which I'm willing to look more closely at it don't.

 

[brianrost]

Impedance only matters to me when it’s too low.

All my stage amps have high impedance inputs. My two A.M.P. heads are 4.7 Mohm, the AI combos are 1 Mohm. Not sure about the Walter Woods spec but it sounds fine with piezos.

I see no need to be able to switch impedances.

 

[flatback]

I have Sarno's variable impedance preamps: one sweeps up to 10M and the other sweeps up to 20M. About 9 oclock is 1M. Just below that the bass (on most piezos) drops off to nothing pretty quick. Just above that piezos rapidly sound much better depending on the pickup. Some pickups (Yamahiko) to me sound better with 10M-20M and the bass cut back with a sweep able HPF. I really like the dual pickup into the Felix (one on 20M and one on 10M) IT is hard to beat that for versatility and simplicity.

 

[Hasty]

I really like the dual pickup into the Felix (one on 20M and one on 10M) IT is hard to beat that for versatility and simplicity.

That comment on the Yamahiko thread you made is part of what planted this whole idea into my head.

 

[Hasty]

I think if there was a pre-amp that had:

a) variable or optional input impedance

And

b) a sweepable high pass filter

it would be standard for all of us.

That, and phase inversion is a big part of why I started down the preamp path. I've been reading up on the variable impedance part and it's really interesting.

I've sort of put the sweepable HPF on the backburner because a few others do that so well and I was focused on just trying to make a nice preamp that could feed into other things. I might tackle that option in V2.

My biggest issue is I keep thinking of things I like and want to add and it really detracts from my original mission of a small, battery powered preamp that can go anywhere, or be a reasonable backup that someone can build themselves.

There are so many really smart people here with such great input that it's hard to not include everything I read on this website.

 

[oren]

I use a Full Circle and run it into a Markbass CMD-121P unbuffered. The amp has a 1 Mohm input impedance and it sounds good. When I used to use an Underwood into a Genz Benz Shuttle with 500 kohm input impedance it sounded much better with a Fdeck buffering the signal.

 

[Ric Vice]

In the late 70's Walter Woods purchased a pickup from Underwood and set the input impedance of the MI-100-8 to 1 Meg Ohm. As newer pickups have come on the market, the Realists seem fine at 1 Meg-5 Meg. Full Circles and Yamahiko's need 10 Meg.
Markbass Amps other than the Nanomark II, are set at 500 K Ohms. Fishman sets their own preamps at 10 Meg. Just my take of course. I checked the manuals to confirm what I remembered.

 

[TroyK]

That, and phase inversion is a big part of why I started down the preamp path. I've been reading up on the variable impedance part and it's really interesting.

I've sort of put the sweepable HPF on the backburner because a few others do that so well and I was focused on just trying to make a nice preamp that could feed into other things. I might tackle that option in V2.

My biggest issue is I keep thinking of things I like and want to add and it really detracts from my original mission of a small, battery powered preamp that can go anywhere, or be a reasonable backup that someone can build themselves.

There are so many really smart people here with such great input that it's hard to not include everything I read on this website.

Yeah, but most DBists don't have or want a pedal board. I'm confident saying that we would ALL rather just plug straight into whatever amp was available and with some pickups, like The Realist, you can do that.

HPF is almost always essential and only Acoustic Image (to my knowledge) actually puts one on the amp.

 

[Ric Vice]

Yeah, but most DBists don't have or want a pedal board. I'm confident saying that we would ALL rather just plug straight into whatever amp was available and with some pickups, like The Realist, you can do that.

HPF is almost always essential and only Acoustic Image (to my knowledge) actually puts one on the amp.

Good point, I believe the Doubler had a HPF trim pot accessible from the top. The Grace Felix has a very good HPF that’s first inline control
On the EQ section.

 

[brianrost]

HPF is almost always essential and only Acoustic Image (to my knowledge) actually puts one on the amp.

That’s why even though all three of my amp heads have high (enough) impedance inputs, the lack of an HPF means I have to use an fdeck with them anyway. Maybe I should experiment with the fdeck in the FX loop?

 

[Brent Nussey]

Hi Hasty! I think that it might be handy to have the option of a couple of different input impedences. As you point out, if someone's going to build one, they can choose which they like, and even change out the resistors if they want to figure out the perfect setup.

For me personally, I have basses with different pickups, and so I might like to be able to switch between, say 1 and 10M. But I don't think it makes sense to go nuts with multiple input impedences, most people will have one they prefer and just stick to that. Maybe you should focus on a preamp that solves the problem of dual element pickups (or just using 2 pickups), with phase switching and a couple impedance options, and then people could use it almost as a part of the pickup, in front of their favorite preamp or amp. I love that other preamp you built, but something that's a simple tool to get the most out of a dual element pickup would be a welcome addition to the bass world too, something that we're not likely to get from any manufacturer.

A built in HPF seems like it would make it a complete front end for a lot of people, but as you say, maybe version 2.

 

[Hasty]

Yeah, but most DBists don't have or want a pedal board. I'm confident saying that we would ALL rather just plug straight into whatever amp was available and with some pickups, like The Realist, you can do that.

HPF is almost always essential and only Acoustic Image (to my knowledge) actually puts one on the amp.

All valid points. I don’t always put a lot of emphasis on HPF because I’m one of those that is either playing through an amp that already has a built in HPF (AI, EA Doubler, Grace Felix) or I’m plugging into FOH.

I’m definitely not against the idea of an HPF and I agree that most bassists would consider that essential. However there aren’t many schematics out there for an HPF that aren’t a direct copy of the FDeck or Josh Broughton’s designs that I could use as an open source project.

I will likely mull over that one for a while, study some circuits, and see what I can come up with in a way that satisfies me musically and ethically.


Thanks for the input! All the feedback has been helpful.

 

[Hasty]

For me personally, I have basses with different pickups, and so I might like to be able to switch between, say 1 and 10M. But I don't think it makes sense to go nuts with multiple input impedences, most people will have one they prefer and just stick to that. Maybe you should focus on a preamp that solves the problem of dual element pickups (or just using 2 pickups), with phase switching and a couple impedance options, and then people could use it almost as a part of the pickup, in front of their favorite preamp or amp. I love that other preamp you built, but something that's a simple tool to get the most out of a dual element pickup would be a welcome addition to the bass world too, something that we're not likely to get from any manufacturer.

.

Hey Brent! Funny you should mention that setup. I’m about 95% done with that version. It’s dead simple. 3 channels with phase options, individual volume controls, and a mute. It is literally a bring your own amplifier solution.

I’m just cleaning up the circuit a little, I need to reroute the opamp power lines to prevent some static crackle when adjusting volume levels. After that I’ll create a build guide and turn it loose. It works really well with the Yamahiko if you’re just looking for something to plug into an amplifier.

 

[Brent Nussey]

Beautiful! Mute is a nice touch too!

 

[crd]

I really like the dual pickup into the Felix (one on 20M and one on 10M) IT is hard to beat that for versatility and simplicity.

That's my sweep spot also.

 

[crd]

All valid points. I don’t always put a lot of emphasis on HPF because I’m one of those that is either playing through an amp that already has a built in HPF (AI, EA Doubler, Grace Felix) or I’m plugging into FOH.

I’m definitely not against the idea of an HPF and I agree that most bassists would consider that essential. However there aren’t many schematics out there for an HPF that aren’t a direct copy of the FDeck or Josh Broughton’s designs that I could use as an open source project.

I will likely mull over that one for a while, study some circuits, and see what I can come up with in a way that satisfies me musically and ethically.


Thanks for the input! All the feedback has been helpful.

A fixed HPF would be great. I never seem to take the hpf on my Felix above 40. The variable aspect of the Fdeck I think was mostly about pushing speakers (like the MAS stuff) to go loud without chaffing. At least that was how I used it.