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Double Bass "Padded Cable?"

J

James Gibson

Mar 3, 2007
266
4
Brooklyn, NY
www.myspace.com
#1
Hello all,

I recently bought the Headway EDB-1 to mix my Realist and another pickup/mic. The Realist's signal was too strong for Channel 1 on the Headway, and I was getting clipping/light distortion through the speaker. Littler at Headway offered to modify the preamp to offer less gain at Channel 1, but I don't want to modify the preamp incase I want to use a different pickup in the future. I heard David Gage offers a special cable to attenuate the signal from The Realist, so I ordered one. My concern is what to do when/if this cable shorts. The Gage rep I spoke to called it a "padded cable". Has anyone heard of any other distributors/manufacturers offering a similar product?

thanks!
 
#2
They're more commonly known as "attenuator cables." Lots of types depending on the connectors and the dB of attenuation, but they're out there.

Attenuator pedals also exist, I know Electro-Harmonix makes one. Or, if you're at all handy with electronics, you could probably make your own attenuator box and then just use standard instrument cables.
 
#4
For a piezo pickup, I recommend a capacitor in parallel with the pickup as a way to pad the signal. This will provide "flat" padding across the frequency spectrum. The reason is that a piezo acts (approximately) like a voltage source in series with a capacitor. A second capacitor forms a voltage divider with the capacitance in the pickup.

My guess: Try something like 0.01 microfarads. Radio Shack sells a 10 uF film cap. Catalog # 272-1051, for a buck and a half.

This only works for a piezo. It's a rare case where something simple actually works with a double bass.
 
#7
I realize that in theory that adding that resistor to a cable shouldn't change the sound or dynamic feel of the pickup performance. But it does, IMO, and that's a whole 'nother debate. It's kind of silly that Gage is actually selling a "padded cable" to deal with a problem that is inherent with his pickup design.
 
#8
Anonymatt said:
Google shopping results

I've never used one. Don't know how sound quality would vary between products. The "padded" cable is probably alright.

But I would hate to have a mic cable floating around my studio that had a pad built into it!
Click to expand...

This has absolutely nothing to do with attenuating the output of a piezo bass pickup. These things are designed for low impedance mic lines, not super high impedance unbalanced lines.
 
#9
fdeck said:
For a piezo pickup, I recommend a capacitor in parallel with the pickup as a way to pad the signal. This will provide "flat" padding across the frequency spectrum. The reason is that a piezo acts (approximately) like a voltage source in series with a capacitor. A second capacitor forms a voltage divider with the capacitance in the pickup.

My guess: Try something like 0.01 microfarads. Radio Shack sells a 10 uF film cap. Catalog # 272-1051, for a buck and a half.

This only works for a piezo. It's a rare case where something simple actually works with a double bass.
Click to expand...

MR PC said:
I realize that in theory that adding that resistor to a cable shouldn't change the sound or dynamic feel of the pickup performance. But it does, IMO, and that's a whole 'nother debate. It's kind of silly that Gage is actually selling a "padded cable" to deal with a problem that is inherent with his pickup design.
Click to expand...

Now it makes sense. The padded cable just using resistors is the wrong solution here. Unless it happens to use caps like Fdeck clever solution.

If piezo acts like a votage source followed by a cap, then adding a resistor pad is making some kind of high pass filter out of the thing. That's going to change the sound.

I just always use a preamp - even to make it quieter. I should go play with some caps and carry one less battery device.

Somebody should make cables with caps. Double bass means double the price.
 
#10
James Gibson said:
That sounds promising, but frankly, I have no idea what this means. Could you please explain further?
Click to expand...

I'm thinking of a component like this:

pRS1C-2264681w345.jpg


Its two terminals are soldered to the two terminals at one of the plugs on the cable -- either one, doesn't matter. Otherwise, it could also be soldered to the two terminals of the output jack on the pickup, to have a permanently padded pickup that you can use with any cable. Or, installed inside your preamp.

The 10 microfarad value is just a guess, but should be in the ballpark of what you need.
 
#11
This was noted on the BG forum. It's not in production yet. But it's a good guess that this plug contains some capacitors that are selected by the switch. If so, and if the caps are the right values, this would be a "padding plug" for a piezo pickup. When they are available from my favorite supplier (Mouser), I will get one and report on its characteristics.

[Invalid or Expired Link Removed]
 
#14
FWIW I measured the capacitance of a Fishman Full Circle. Coming right out of the pickup at the RCA phono plug, disconnected from the string-mounted output jack, it measures .014 microfarad. The output jack (which has an internal shunt capacitor that provides some attenuation) measures .023 uf across its terminals. A Realist pickup measured .0068 uf.
 
#16
I received the cable from David Gage yesterday. It seems it is along the lines of what fdeck mentioned. Keep in mind, I am very naive to the inner workings of electronics, so I might be completely wrong.

What they sent me looks like a modded planet waves cable. It came in the same box The Realist comes in, but in the upper right corner it says "Padded Cable." Apparently the Realist doesn't play nice with various preamps, so Gage offers this cable? The cable itself looks like the Planet Waves instrument cable we all know, the ones with the molded, bendable sleeves and gold connectors. The only discerning feature is that one of the ends has a teal-ish ring painted right where the connector meets the molded sleeve, along with a decal past the PW emblem that reads "SHIELDED END".

I a/b'd the cable with the ones I usually use. I'm using an EA iAmp 800, so I have the LEDs at the preamp stage to show the amount of gain the pickup is sending. As advertised (or not[?] as I had to order the padded cable by phone, I couldn't find it listed on the Gage website.) the padded cable attenuated the signal. I tried it from The Realist to the Headway EDB-1, and all the clipping I experienced was gone. I did notice a slight change in frequency range, but I was still able to get a good sound. Now, I'll have to experiment with blending pickups and mics with The Realist.
 
#17
It just seems odd to me that any passive piezo pickup would produce a signal intense enough to overload the input on the amp. If there is distortion I would mark it up to impedence mismatch, which would be better dealt with by a transformer or a matched external preamp. Buying a patch cord with a built in shorting resistor or capacitor just seems like a totally back-asswards approach.
 
#18
robobass said:
It just seems odd to me that any passive piezo pickup would produce a signal intense enough to overload the input on the amp. If there is distortion I would mark it up to impedence mismatch, which would be better dealt with by a transformer or a matched external preamp. Buying a patch cord with a built in shorting resistor or capacitor just seems like a totally back-asswards approach.
Click to expand...

It was overloading the input stage on a Headway EDB-1 preamp, not the amp.
 
#20
SteveFreides said:
Wouldn't the Fdeck gadget itself be the perfect solution here? It's designed for a piezo transducer _and_ it has a volume control.

-S-
Click to expand...

The volume control on my gadget is after the rest of the circuit, so an excessively "hot" pickup will still overload it. So far I haven't had reports of problems with distortion, so the headroom or the preamp may be sufficient.
 

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