Booster or Attenuator?

[TDR1138]

So, I’ve been considering putting together a small pedalboard, and am a little hung up on one thing. I have an L-2000 and an LB-100; both have very different levels feeding from the instrument. I want to run my L-2000 with the volume wide open, because I mute regularly with the volume and don’t want to keep having to find the right volume when I unmute. That’s fine if I’m running directly into the amp, where I can use the input pad to offset the increased signal from the instrument and use the unpadded input for the LB-100 and get a relatively similar signal into the amp, but what about when I’m running directly into pedals? I’m thinking particularly about pedals that are sensitive to input – compressors, envelope filters, even distortions. (Side note, I’m looking to put something together that would allow me to use DI and/or amp, so using the FX send/return on the amp would not be an option.)

So, the ultimate question is, what would be better at the front of the signal chain – a booster (boost the P bass signal) or an attenuator (lower the L-2000 signal) – and why?

Cheap and/or buildable would be a plus. I think an attenuator would be the easiest for that. So, would there be a clear advantage to a booster or disadvantage to a passive attenuator? I was even thinking of making my own dual input box where one input had a preset attenuation (for the L) and the other just went straight through with no affect. Or, conversely, a dual input box with one pass through (for the L) and the other feeding through a boost, probably derived off the LPB-1 circuit or something. I don’t anticipate the need for switching. Really this is just to not have to adjust settings on the downstream pedals when using a different bass.

Thoughts?

[Ken Baker]

Thoughts? Sure.

I'm gonna move this up to Paul's.

Ken...

[Mr. Mom]

I've got the older version of this. Works great.

[Paul Gagon]

So, I’ve been considering putting together a small pedalboard, and am a little hung up on one thing. I have an L-2000 and an LB-100; both have very different levels feeding from the instrument. I want to run my L-2000 with the volume wide open, because I mute regularly with the volume and don’t want to keep having to find the right volume when I unmute. That’s fine if I’m running directly into the amp, where I can use the input pad to offset the increased signal from the instrument and use the unpadded input for the LB-100 and get a relatively similar signal into the amp, but what about when I’m running directly into pedals? I’m thinking particularly about pedals that are sensitive to input – compressors, envelope filters, even distortions. (Side note, I’m looking to put something together that would allow me to use DI and/or amp, so using the FX send/return on the amp would not be an option.)

So, the ultimate question is, what would be better at the front of the signal chain – a booster (boost the P bass signal) or an attenuator (lower the L-2000 signal) – and why?

Cheap and/or buildable would be a plus. I think an attenuator would be the easiest for that. So, would there be a clear advantage to a booster or disadvantage to a passive attenuator? I was even thinking of making my own dual input box where one input had a preset attenuation (for the L) and the other just went straight through with no affect. Or, conversely, a dual input box with one pass through (for the L) and the other feeding through a boost, probably derived off the LPB-1 circuit or something. I don’t anticipate the need for switching. Really this is just to not have to adjust settings on the downstream pedals when using a different bass.

Thoughts?

This sounds like a great project. Let's see what we can do to help. To answer your question, I think your situation should be addressed at the front of the signal chain with a booster. First off, there are a few way to go here but in my opinion you would want to buffer both basses and have the L-2000 pass through with no gain and LB-100 have an adjustable gain of around 3 to 8dB.......here's why. If you're going to mix the signal of these two basses together, you really need to buffer them so that any passive signal chain does not get excessively loaded down by an active signal chain.

I love that you are thinking of building something. Making a two channel mixer is a great idea. One channel is just a buffer and the other has adjustable gain. You really just need to decide on the level of circuit complexity you want. Do you want a mixer with great signal headroom with no chance of clipping? Or, can this just run on either a 9v batter or a 9v power supply. Do you want to go simple transistor route or you wanna go IC chips? Since you're not talking signal switching and are looking at a straight up mixer I would recommend the IC route.

Can I ask a question? What kind of electronics have you built in the past? Im asking this only to see how much fun, and/or crazy we can do here. This sounds like fun and I would be more than happy to help with ideas.
Paul

[TDR1138]

This sounds like a great project. Let's see what we can do to help. To answer your question, I think your situation should be addressed at the front of the signal chain with a booster. First off, there are a few way to go here but in my opinion you would want to buffer both basses and have the L-2000 pass through with no gain and LB-100 have an adjustable gain of around 3 to 8dB.......here's why. If you're going to mix the signal of these two basses together, you really need to buffer them so that any passive signal chain does not get excessively loaded down by an active signal chain.

I love that you are thinking of building something. Making a two channel mixer is a great idea. One channel is just a buffer and the other has adjustable gain. You really just need to decide on the level of circuit complexity you want. Do you want a mixer with great signal headroom with no chance of clipping? Or, can this just run on either a 9v batter or a 9v power supply. Do you want to go simple transistor route or you wanna go IC chips? Since you're not talking signal switching and are looking at a straight up mixer I would recommend the IC route.

Can I ask a question? What kind of electronics have you built in the past? Im asking this only to see how much fun, and/or crazy we can do here. This sounds like fun and I would be more than happy to help with ideas.
Paul

I should be a little more clear about my intent. I'm actually not looking for a two channel mixer or switcher. My current playing situation is just with a couple of churches, both of which will feed me through FOH, one without an amp. I'm only bringing one bass at a time and doing no switching around while I'm there. I'm really just thinking of having a couple of "presets" where, depending on whether I bring an L or something else, that I can just plug in and have a consistent signal hitting the first pedal.

Right now, I'm playing with a very simple setup - basically an EQ pedal into a DI box. I've got a tuner pedal sitting around, and I was thinking of investing in a compressor or limiter to smooth things out. So I was thinking of building a small board to make setup easier. I've also got a few distortions/fuzzes that I could work into the board, but I really can't see them fitting in either context, so I would probably leave them off until I felt like I could use them. So, really the thought originated from the idea of how to get a consistent signal into a comp to avoid knob twiddling if I brought the L one day and the LB another.

I have modded several pedals (mostly Boss-type) and built a pedal or preamp on pre-etched boards, but nothing truly from scratch. I want to make that step, though. I'm comfortable with soldering, good at following directions, but not quite at the "design your own" stage yet. If I went the route of the boost, I was thinking of building a clone of an existing circuit, something simple like the EHX LPB-1 and adjusting it to suit (i.e. larger in/out caps to voice to bass). The LPB-1 is a transistor-based circuit with a pretty low component count.

As far as buffering, I was thinking of putting a Boss TU-2 at the start of the chain if I did a switchable buffer/attenuator second. Or I was thinking of putting the TU-2 second if I did a buffer/attenuator with different inputs. I had no real good reason of thinking of separate inputs, other than making it look clean and like the input on an amp. Just plug into the one you'd need, that sort of thing.

But hey, I'm here because I'm open to ideas and input.

[Paul Gagon]

Ohhhhh.......OK. I think your right, making a simple signal booster like an LPB-1 would be great. You would have the unit be either unity gain or switch in a variable gain control for a boost of between 2 and maybe 6dB. You know what? I designed a pedal for BBE called the Boosta Grande that was pretty much what I believe you're talking about. It used an op-amp but it's pretty simple.

Anyway, if the LPB-1 style is what your after, maybe I could scribble down a few ideas and post it here. If you're into trying out a few circuit ideas it might be fun.
Paul

[TDR1138]

So I was doing a little research over the weekend about boosters, and it seems the LPB-1 does have an inherent tendency to overdrive the transistor in the circuit. Not sure if that's a good thing or a bad thing - I think P basses with flats tend to benefit from a little warmth in their signal chain, and while a transistor is never going to replicate a nice tube amp, maybe a little hair on the signal wouldn't be so bad. But at the same time I'm thinking an op-amp based circuit might be a little cleaner, so I'm starting to think along those lines, too. Maybe build a couple and see what works best.

Boosta Grande looks interesting, but and I did find some stripboard layouts that I'll have to study and figure out how to put it all together.

Or, how does something like this look?
http://www.jer00n.nl/2010/07/28/clean-b ... r-or-bass/
Seemed to have a lower part count than a Boosta Grande.

[Paul Gagon]

So I was doing a little research over the weekend about boosters, and it seems the LPB-1 does have an inherent tendency to overdrive the transistor in the circuit. Not sure if that's a good thing or a bad thing - I think P basses with flats tend to benefit from a little warmth in their signal chain, and while a transistor is never going to replicate a nice tube amp, maybe a little hair on the signal wouldn't be so bad. But at the same time I'm thinking an op-amp based circuit might be a little cleaner, so I'm starting to think along those lines, too. Maybe build a couple and see what works best.

Boosta Grande looks interesting, but and I did find some stripboard layouts that I'll have to study and figure out how to put it all together.

Or, how does something like this look?
http://www.jer00n.nl/2010/07/28/clean-b ... r-or-bass/
Seemed to have a lower part count than a Boosta Grande.

You're right, the LPB-1 does overdrive the signal. As designed, the circuit has a fixed gain of around 10 and you only have control of the output level. Another characteristic of the LPB-1 is its low input impedance (around 64K ohms). I have made modified LPB circuits that have adjustable gain and a fixed output but you still have the low input impedance, although it's not too difficult to get it in the 220K zone.

An op-amp based circuit would be better. It's a bit more involved than a single transistor circuit but still pretty simple. The circuit example you posted looks good and should work. It also has a fixed gain and you might get distortion from the L-2000, but worth a try. Anyway, I think it's awesome that you're trying these ideas out. Please keep us all posted on what you try out. Thanks, Paul

[TDR1138]

An op-amp based circuit would be better. It's a bit more involved than a single transistor circuit but still pretty simple. The circuit example you posted looks good and should work. It also has a fixed gain and you might get distortion from the L-2000, but worth a try. Anyway, I think it's awesome that you're trying these ideas out. Please keep us all posted on what you try out. Thanks, Paul

Cool, thanks. I'm probably a month or two out from trying this out - I've got some stuff coming up in February that will keep me busy - but afterward I'll probably start collecting parts and mocking things up. Also on my to-do is to build a M preamp into a pedal, so I need to start taking inventory of what I have and start making a shopping list...