Christopher

Radio Shack Volume Attenuator

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Originally written by forum user [and owner of Reactive Sounds] Reactive.

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The radio shack volume attenuator

Hi recording enthusiasts,

There have been a few posts discussing a way to reduce the output of your mic's before they hit (and overload) the pre-amp in your minidisc recorder. I should mention now, that some of the Sony recorders out there have very little headroom on the pre-amp section, and cannot handle the input of the Electret microphones that are commonly used for recording. One such solution has been the radio shack volume attenuator.

I have not seen this item, however given it's low cost and availability thru radio shack http://www.radioshack.com/product.asp?cata...t%5Fid=42-2559i do have a few concerns:

An adjustable stereo potentiometer in the range of 10K would provide all the reduction you could ever need. These items range in price from extremly low cost (pennies for the radio shack) and a few bucks for higher quality versions.

I am not knocking this method, as it's very innovative, and it does solve the problem in most cases. Where I do see it being a hinderance is for quiet recordings. Everything you place in line with your microphones will add noise to your recording. Everything! To achieve the highest quality recording with the lowest amount of equipment noise you have to remove the noise making culprits or replace them with better quality parts.

In the case of the Radio shack volume attenuator, I would recommend only to use it when you absolutely need to. After all we have high quality Microphones that are small and portable, and even higher quality Minidisc recorders laying digital tracks while we are on the move. Don't add hiss, crackle and noise to your quieter recordings by introducing low quality equipment.

Why is a stereo Potentiometer noisy? It works as a variable resistor, a carbon track is swiped by an arm with a conductor on it's end. The carbon track can be very dirty, unsealed from environmental dust and moisture, and can wear out in less than a hundred turns. All these issues can be addressed by using a much higher quality Potentiometer.

It should be an easy thing to make for those of you that have a soldering iron and a few minutes. If i get some time this weekend, i'll whip one up and post the DIY instructions and where to find that parts to this forum.

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Why is a stereo Potentiometer noisy? It works as a variable resistor, a carbon track is swiped by an arm with a conductor on it's end. The carbon track can be very dirty, unsealed from environmental dust and moisture, and can wear out in less than a hundred turns. All these issues can be addressed by using a much higher quality Potentiometer.

That's not the main reason for increased noise, basically you lower the signal from the microphone while the noise of the preamplifier stays the same -> lower Signal to Noise Ratio. Even if you have perfect contacts, the SNR will decrease.

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This is very elegant theoretically, gents.

There's no reason to use an attenuator when the source is unlikely to overload the preamp, as in a quiet recording, where you'd also hear the distortion.

But practically speaking, when you want to record an amplified concert with any significant bass whatsoever, and carry a minimum of gear--just the MD, the mics and the attenuator--then as Reactive said, it does solve the problem in most cases. I use it all the time, and you can hear how good it sounds in my Gallery album.

I don't love the Radio Shack attenuator. It's a cheap flimsy gizmo that makes noise when you turn the volume knob and breaks down after some use. (The volume knob is useful, however, for people with older NetMD recorders, like the MZN707 or MZR900, that don't have volume adjustment on the fly.) I wish someone would manufacture a sturdier, non-adjustable version. But until then: it works.

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Here's the "professional" solution, although I wouldn't spend 35$+shipping for two resistors, two plugs and a cable...

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How much difference is there between this and the Radio Shack job, A440?

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A excerpt from the site:

Keep in mind that attenuator cables can't be used between a set of microphones and a recorder if your microphones are powered from the recorder's mic input -- what's sometimes called: "Plug-In Power."

Hmm...

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That excerpt, and the $35, have been holding me back. But Core Sound has a good return policy, and after having yet another Radio Shack fritz out on me at a pretty crucial concert, I think I'm going to give the Core Sound a try. It's the only way to find out if the caveat is just for the electronics purists.

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Be sure to let us know how the Core-Sound version works, A440. I have used a Radio Shack version for three different shows now and am very impressed ... However, I'm a bit uneasy that I may succumb to your fate at a future show and the RS version will crap out on me.

Of course, I always use the attenuator with my battery box anyway, as the bb increases my mics' dynamic range and help to limit the bass even more than the attenuator does. So, I guess that warning doesn't apply to me anyway. Still, Core Sounds is a great company. I'd just like to have someone who has used their product tell me everything works okay before I shell out the $35.

:-)

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I always use the attenuator with my battery box anyway, as the bb increases my mics' dynamic range and help to limit the bass even more than the attenuator does.

If you're using the battery box, are you going through line-in? Then the attenuator might be overkill, or give you overly quiet recordings. The two gizmos are likely also to be working against each other, as the Core Sound warning suggests: the battery box sending power, the attenuator resisting it.

I'll report back on the Core Sound version.

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I've just found the Sony stereo 3.5mm to 2 x RCA attenuated lead I bought many years ago, designed for connecting a line-level source to a mic socket - a fixed 150 ohms resistance per channel. I have in mind to use it for testing what the quality implications would be in such a scenario with my NH900, in an effort to avoid the auto track marking problem. I can't see these listed via Google - maybe Sony has stopped producing them.

(Trouble is I've had to lend the NH900 to a musician who wanted to listen at once to a concert recording, and of course the HI-MD recording wouldn't play on her older MD - so she's gone off with the machine leaving me an address and phone number... gulp. I shall post results if I get it back!)

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Update - My NH900 has been returned (whew!) and I've now tested the Sony 150 ohm attenuator lead, playing a CD into the mic socket having previously played it into the line socket with a normal lead.

Using the attenuator lead requires an input level setting of 18/30 with 'mic sensitivity' set to high, compared with 16/30 using the line input with a normal lead.

Peak noise level on the mic input is about -62dB, compared with -72dB on the line input, but under real-world conditions room noise would usually be above that noise floor, so it's no disaster.

So I'm faced with the choice of getting lots of unwanted track marks using line input, or having full control of track marks and adding 10dB of noise using mic input.

It would be good if someone came up with a service mode hack to turn off auto track marking on the line input, but that's been said a good few times before!

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It would be good if someone came up with a service mode hack to turn off auto track marking on the line input, but that's been said a good few times before!

I haven't heard results yet (and haven't tested it myself) but there was this trick with setting autotrackmarks to 60min which was supposed to overrule the other (silence-triggered) automarking so you'd only end up with a few tracks in stead of a lot of autotracked-by-silent-moments tracks

I would say, give it a try and post results

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Doesn't work. I've heard comments to the effect that it does for some people, but I've yet to see anyone put their hand up (since I've been here) and categorically state it works for them. (Hey, but thanks for the suggestion).

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I have been lurking on these forums for quite a while now, and I've gotten pretty good at live recording. I have a sony MZ-NF810 recorder, SP-BMC2 mics and I had been using a sound pro battery box....until 2 days ago. I finally decided to test out the Radio Shack attenuator (It was te first time Ive gotten to record a band that I'm not really in to).

Definitly got my best recording ever last night using it. I recorded another show today (Vertical Horizon, 3EB, and the Pat Mcgee band)...The recordings all came out fantastic. Its amazing that a $6 part can do the job better than a $50 one. Needless to say, I have no use for the battery box anymore.

Thanks for all the advice.

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Can't say for sure, but looks promising. I have Shure E3s, and to use them on a plane I plugged in my Radio Shack attenuator, so I suspect this has the same level of resistance.

That big volume control might be a little clunkier than the Radio Shack, but if it's more durable it would be worth it.

Someone's going to have to experiment. Maybe you?

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Note to users in the U.K. :

deadwing has discovered that the Maplins chain has its own Headphone Volume Control that also works as an attenuator.

http://www.maplin.co.uk/Module.aspx?Module...ldID=6&doy=17m4

I've just ordered the Maplin volume control, and will try it out as soon as it arrives. I put on weekly gigs which can be VERY loud. I've recorded them before, and at first I had problems with distortion, cos my mic is very sensitive indeed, even with my MD on low sensitivity settings. I got a battery box, and it solved that problem.

I then had problems with the minidisc skipping, or switching off altogether, on very loud sections, or sections with lots of sub-bass. I've always had this problem with no matter what MD I use (I have 4) at very loud gigs.

I've tried putting the MD on something padded, like a cushion, or a folded up jumper etc, and that definately helps, but doesn't solve the problem completely.

I've just bought an old Sony Professional Walkman 2ndhand believe it or not, and tried that out at another very loud gig tonight, and the bass levels distorted the mic input from my sensitive mic (on loud sections), so I'm actually buying the Maplin Volume control to try with that, but I will end up trying it with my MD recorders too.

I love my old Sony MZR30 and R35 though (more than any MDs I've had or tried since), and would use them if I could stop vibrations from causing them to skip.

Do any of you regularly record LOUD gigs, and have problems with skipping and dropouts?

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Anybody tried to build an attenuator himself? Wouldn't it be possible to buy a stereo cable, cut it in two and solder two resistances between the parts? Anybody know about how much resistance the Radio Shack attenuator adds? (ohm)

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I've had halfway acceptable results with resistors parallel to the microphones, about 3.3 kOhm (or somewhat less, like 2.2 kOhm, for more attenuation) - determined by trial and error, but then i've built a battery box and never looked back...

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I would be interested to have a look inside such a thing, to know its impedance - would anyone equipped with a multimeter and a camera be willing to disassemble it for a moment?

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When my next Radio Shack wears out--usually one channel goes first--I'll mail it to you, GM, and you can do the surgery.

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Very nice - if you think it would be worth the long way - i'll post my observations here then. It's propably easily to be modified to be used with a fixed instead of a variable resistance so that there's no wearout or contact problems at least.

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No, firstly it won't fit into the mic-in jack because of additional connectors for information transfer, secondly a digital volume control with up/down keys would be useless - all it does is to control the volume output of the unit, there's no passive attenuation - there need to be suitable fixed or variable resistors inside in order to do the job.

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