Double Bass Variable input impedance for DB amplification

[Bander]

Revisiting this old crazy thread because of recent experiences with impedance and high pass filtering.

Aside from the Summit TD-100, I'm wondering if a sweepable impedance circuit would be a difficult thing to add to a potential custom preamp box in the future. @shwashwa recently posted a picture of a really great custom preamp by Broughton Audio that basically has all of the controls he wanted baked into it by request, and a lot of people are over the moon about this builder's work. If this is a feature that could be easily built into a custom preamp along with sweepable HP filter and other requests, it might be worth the trouble at some point.

I might be game for this feature, but the TD-100 needs a higher maximum impedance. I've got a sack of DI's for piezo's, my favorite is a Radial. Its selectable, but only two impedance settings. Earlier in the thread someone explained that higher impedance is more universal for all situations, and I agree with that, so that might be why the convention is "higher is better", but that wouldn't apply if you are optimizing for one application, particularly upright bass. As far as I've found, 20M ohms is the highest available, and you have to spend some money for that. I'd like to experiment with the Ehrlund mentioned earlier, and even better a sweepable.

 

[bass12]

It is possible and I've contemplated doing it. I haven't been taking on custom work, but on occasion I'll do a small batch build of a single design where there is interest. A single knob impedance pedal in a 1590A enclosure would be fairly simple to accomplish.

If you were to do a run of such a design I'd be interested.

 

[Azure Skies]

If you were to do a run of such a design I'd be interested.

I'll give it some thought. Maybe I'll combine it with my HPF design in a bigger box. What's a good range of impedance? 1 to 10 meg? 20 meg? You might not notice much change after 10 meg, so half your rotation range would seem to do nothing.

 

[bdowd]

Color me interested, sounds like a great db tool with hpf and variable imp.

 

[shwashwa]

It is possible and I've contemplated doing it. I haven't been taking on custom work, but on occasion I'll do a small batch build of a single design where there is interest. A single knob impedance pedal in a 1590A enclosure would be fairly simple to accomplish.

 

[shwashwa]

View attachment 2964077

By the way this is how you have to place orders with Josh, by meme. Maybe he will build it for you, maybe your dreams will get crushed.

 

[jmlee]

By the way this is how you have to place orders with Josh, by meme. Maybe he will build it for you, maybe your dreams will get crushed.

Or Crushered!

 

[Azure Skies]

You guys are assimilating the DB forum with memery

 

[Ric Vice]

Just my take of course, but I'd prefer a Volume Control, HPF and Variable Input Impedance. As that covers all the "basses".

Ric

 

[Francois Blais]

I'll give it some thought. Maybe I'll combine it with my HPF design in a bigger box. What's a good range of impedance? 1 to 10 meg? 20 meg? You might not notice much change after 10 meg, so half your rotation range would seem to do nothing.

Agree, and above 10Megs one would probably get more (unneeded) noise.

 

[Francois Blais]

Just my take of course, but I'd prefer a Volume Control, HPF and Variable Input Impedance. As that covers all the "basses".

Ric

+1

 

[bass12]

I'll give it some thought. Maybe I'll combine it with my HPF design in a bigger box. What's a good range of impedance? 1 to 10 meg? 20 meg? You might not notice much change after 10 meg, so half your rotation range would seem to do nothing.

As an owner of your HPF + LPF pedal I'd say that would be great place to start.

 

[TwentyHz]

Lurking & learning.

FWIW, as a less-informed guy: I'd pop on what may result. It sounds like a great way to explore the nuances of using an HPF and variable impedance as part of the tone/signal recipe.

I'm doing my best to finger, pickup/mic, pre-amp, EQ, amp, and cab my little country shuffles outta my humble plywood thumper. The proposed solution sounds like the one thing I could be missing. Doesn't it always?

 

[Stumbo]

I'll give it some thought. Maybe I'll combine it with my HPF design in a bigger box. What's a good range of impedance? 1 to 10 meg? 20 meg? You might not notice much change after 10 meg, so half your rotation range would seem to do nothing.

I suggest a phase reverse switch as well.

 

[Ric Vice]

I suggest a phase reverse switch as well.

Perhaps a Variable Phase Reverse. I.E.
the EA Doubler.

And the size of the box and the cost just went up.

 

[Ric Vice]

Agree, and above 10Megs one would probably get more (unneeded) noise.

Sounds good I’ve only know a few players who used the 20 meg setting on the Headway EDB-2.

Ric

 

[Azure Skies]

I've got an idea that I will test. It will have a HPF (25 - 190 Hz), level (off to +20 dB), phase switch, and impedance (1M to 10M). I'll try to figure out a way to make the footswitch function to be selectable as true bypass or mute.

 

[Francois Blais]

Sounds good!

 

[Leo Smith]

I've got an idea that I will test. It will have a HPF (25 - 190 Hz), level (off to +20 dB), phase switch, and impedance (1M to 10M). I'll try to figure out a way to make the footswitch function to be selectable as true bypass or mute.

I'd buy into something like this.

 

[Ric Vice]

I've got an idea that I will test. It will have a HPF (25 - 190 Hz), level (off to +20 dB), phase switch, and impedance (1M to 10M). I'll try to figure out a way to make the footswitch function to be selectable as true bypass or mute.

While were spitballin’ here, if a variable phase dial vs a phase reverse switch is possible it would be nice.