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Using Pads and Attenuators? Does it ruin the signal? Dynamics Processors (HW)
Old 29th March 2009
  #1
Gear Maniac
 

Using Pads and Attenuators? Does it ruin the signal?

Theres the Shure A15AS - In-Line Pad for your microphones to pre-amp padding. Can you use the A-Design ATTY just the same way? I know you can use it after the preamp.

I have read of people complaining that the ATTY is a little inaccurate regarding the balance and the mute button causes a bit of problems. I was thinking of getting one for volume control use from my DA to my amp.

Also noise, I was reading on another forum that adding a pad before a pre increases s/n and adds phasing?

How good is the ATTY? Are people finding great use for it or is it just a waste of money?
Old 29th March 2009
  #2
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nosebleedaudio's Avatar
 

A pad reduces your S/N ratio, I prefer the least amount required...Phase? Should have NO affect on sound...
Old 29th March 2009
  #3
The pad barrell just has 3 positions.. It lacks infinate adjustibility...
Old 30th March 2009
  #4
Gear Head
 

Some of the early ATTY units did indeed have a problem with level tracking between the two channels. I had one of these at first, and A-Designs provided great customer service to me in replacing the defective unit. This was a known issue with those early units. AFAIK, that problem has long since been resolved.

Mark W
Old 30th March 2009
  #5
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jjblair's Avatar
A pad will not affect the phase. Your S/N ratio will change because you are decreasing the level of S. The only reason to use a pad is if the signal is too hot and you are distorting the mic pre. S/N generally isn't an issue on signals that hot. Besides, I'd rather have lower S/N ratio than a distorted pre.

I see no reason to use the ATTY for attenuation before the pre. A -15db pad is usually plenty to deal with distortion. The sure uses a "U" pad, I think. There are sonic penalties for padding, but they may or not be noticeable. Also, those penalties are preferable to mic pre distortion, which is a sound I hate.

Does anybody know how the ATTY changes the impedance? This could be an issue with transformer input pres. I'm also cuirious about the reduction of Phantom. Most mics don't require a full 48V, so you can get away with using a -10dB pad or slightly more, but I can see some prosumer cranking down the gain on his ATTY and lowering the voltage on his phantom power too far for the mic to function optimally.
Old 30th March 2009
  #6
Gear Maniac
 

Quote:
Originally Posted by mwurfl View Post
Some of the early ATTY units did indeed have a problem with level tracking between the two channels. I had one of these at first, and A-Designs provided great customer service to me in replacing the defective unit. This was a known issue with those early units. AFAIK, that problem has long since been resolved.

Mark W
I just bought mine second hand. What serial number were the early ones? How long ago are we talking about here?
Old 30th March 2009
  #7
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by jjblair View Post
A pad will not affect the phase. Your S/N ratio will change because you are decreasing the level of S. The only reason to use a pad is if the signal is too hot and you are distorting the mic pre. S/N generally isn't an issue on signals that hot. Besides, I'd rather have lower S/N ratio than a distorted pre.

I see no reason to use the ATTY for attenuation before the pre. A -15db pad is usually plenty to deal with distortion. The sure uses a "U" pad, I think. There are sonic penalties for padding, but they may or not be noticeable. Also, those penalties are preferable to mic pre distortion, which is a sound I hate.

Does anybody know how the ATTY changes the impedance? This could be an issue with transformer input pres. I'm also cuirious about the reduction of Phantom. Most mics don't require a full 48V, so you can get away with using a -10dB pad or slightly more, but I can see some prosumer cranking down the gain on his ATTY and lowering the voltage on his phantom power too far for the mic to function optimally.
Depending on the values it can/will affect the phantom voltage that reaches the mic, this is where a built in pad is better, it has NO affect on the phantom...

Checking it would be easy if you have a VOM. Or just ask the company...
Old 30th March 2009
  #8
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One of my favourite pre's is still the API512c, but to get the best out of them you need to be just hitting the red on the meter. At this input level the output of the 512s will clip most A/Ds and I use the Shure A15AS on the back of my APIs with no adverse affects.
Love it!
Old 30th March 2009
  #9
Quote:
Originally Posted by Recman View Post
I have read of people complaining that the ATTY is a little inaccurate regarding the balance and the mute button causes a bit of problems. I was thinking of getting one for volume control use from my DA to my amp.
For monitoring, it would be advisable to handle that with the proper tool for the job. I would recommend the Coleman M3PH MK2, as its been a LIFESAVER in my project studio. The Attenuator in this unit is very high quality. See below for other ridiculously high quality monitor controllers.









For Attenuating other signals; like a Hot +30 output of an API preamp on Drums;

I would recommend the Little Labs 8 Channel Red Cloud, becasue it has a 5K impedance, and does not mess with the signal one bit. Since this bad boy is 8 Channels with linkable Stereo per pair, you can cover your preamps going to tape, a Monitor Cue, AND a Musician Cue!!

Old 30th March 2009
  #10
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paterno's Avatar
 

Quote:
Originally Posted by jjblair View Post
Does anybody know how the ATTY changes the impedance? This could be an issue with transformer input pres. I'm also cuirious about the reduction of Phantom. Most mics don't require a full 48V, so you can get away with using a -10dB pad or slightly more, but I can see some prosumer cranking down the gain on his ATTY and lowering the voltage on his phantom power too far for the mic to function optimally.
I don't think this is correct -- A properly designed microphone pad will not lower the phantom power voltage.


JP
Old 30th March 2009
  #11
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by paterno View Post
I don't think this is correct -- A properly designed microphone pad will not lower the phantom power voltage.


JP
If you read what I posted above it depends on "Where" the pad is, is it before or after the phantom, it depends on the values used, you can have very different values for the same dB attenuation...

So the best are for either output pad, or input pad...IMHO...and the least amount as well...
The pad in my JM-130 pre is about one dB within clipping of BOTH the pre out and the typical AD input (+24dB). Which works out to be a 12dB pad...
Old 30th March 2009
  #12
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paterno's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
If you read what I posted above it depends on "Where" the pad is, is it before or after the phantom, it depends on the values used, you can have very different values for the same dB attenuation...

So the best are for either output pad, or input pad...IMHO...and the least amount as well...
The pad in my JM-130 pre is about one dB within clipping of BOTH the pre out and the typical AD input (+24dB). Which works out to be a 12dB pad...
Hey Mike --

I had not seen your previous post. Before I made my reply, I did indeed check this with a VOM against some -10 and -20 dB pads that I had made at some point, and the phantom power voltage is the same with or without the pad. I plug these in between the output of the mic [which has no pad] and the mic pre in. The mics I use them on are all phantom powered.

And yes, I agree that there definitely is math involved, along with precision components and someone who really understands the trade-offs of the design, the impedance, and the attenuation.

Cheers,
John
Old 30th March 2009
  #13
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by paterno View Post
Hey Mike --

I had not seen your previous post. Before I made my reply, I did indeed check this with a VOM against some -10 and -20 dB pads that I had made at some point, and the phantom power voltage is the same with or without the pad. I plug these in between the output of the mic [which has no pad] and the mic pre in. The mics I use them on are all phantom powered.

And yes, I agree that there definitely is math involved, along with precision components and someone who really understands the trade-offs of the design, the impedance, and the attenuation.

Cheers,
John
Are you checking the voltage WITH the mic in line?
If not the voltage should be the same, NO load...
If you look at a schematic my other post will make more sense.
I would check it with the VOM on Ohms from pin 2 in to pin 2 out and see what the resistance is, this is what will be in series with the 6.8K phantom resistors..
Old 30th March 2009
  #14
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paterno's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
Are you checking the voltage WITH the mic in line?
If not the voltage should be the same, NO load...
If you look at a schematic my other post will make more sense.
I would check it with the VOM on Ohms from pin 2 in to pin 2 out and see what the resistance is, this is what will be in series with the 6.8K phantom resistors..
I'll check it out when I get a few minutes...
Old 31st March 2009
  #15
Gear Head
 

Just checked my ATTY, and I can't find any serial number on it -- I don't think they have them. I believe mine is about four years old by now or so (and I bought it new).

JJ - I called A-designs and asked what value pot is in the ATTY before I bought it, and they told me 10K. I had/have somewhat similar concerns as you do. I decided that if it didn't behave like I expected, and/or I couldn't stand my own curiosity anymore, I would just take the thing apart and see how things are connected inside. But, it works and sounds great for me (as a monitor level control for my S3As), so I've never bothered with it any further. Maybe if you called up Peter he would send you a schematic?

MW
Old 31st March 2009
  #16
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jjblair's Avatar
Inline pads are made using resistors. If you run current through a resistor, the voltage drops. That's how a resistor works.

I'm assuming that the ATTY uses a potentiometer, which is a variable resistor.
Old 31st March 2009
  #17
Gear Addict
 
MicSlut666's Avatar
 

I can recommend the following page:

Uneeda Audio - Build your own attenuator pads

I built the 10dB and 20dB version and use them with my API 3124+ to hit the meters in the red without clipping the AD. Works awesome and is very cheap compared to the Shure A15AS.
Old 31st March 2009
  #18
Led
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Led's Avatar
+1 for building your own. It's so easy it's laughable and costs heaps less.
Old 31st March 2009
  #19
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by Led View Post
+1 for building your own. It's so easy it's laughable and costs heaps less.
Right, all you need is 3 resistors and a barrel connector..
Old 8th April 2009
  #20
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Will the shure works with a line level source? (to be conected to a mic pre (Chandler TG2) or does the ATTY is better suited?
thanks
Old 8th April 2009
  #21
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mikymike's Avatar
 

Quote:
Originally Posted by jjblair View Post
A pad will not affect the phase. Your S/N ratio will change because you are decreasing the level of S. The only reason to use a pad is if the signal is too hot and you are distorting the mic pre. S/N generally isn't an issue on signals that hot. Besides, I'd rather have lower S/N ratio than a distorted pre.

I see no reason to use the ATTY for attenuation before the pre. A -15db pad is usually plenty to deal with distortion. The sure uses a "U" pad, I think. There are sonic penalties for padding, but they may or not be noticeable. Also, those penalties are preferable to mic pre distortion, which is a sound I hate.

Does anybody know how the ATTY changes the impedance? This could be an issue with transformer input pres. I'm also cuirious about the reduction of Phantom. Most mics don't require a full 48V, so you can get away with using a -10dB pad or slightly more, but I can see some prosumer cranking down the gain on his ATTY and lowering the voltage on his phantom power too far for the mic to function optimally.
Unless you hate the sound of mic pre distortion!!!
Old 8th April 2009
  #22
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Martin Kantola's Avatar
 

A pad will always drop the phantom voltage a little, but how much depends on the resistor values and more importantly the current draw of the microphone! Voltage drop is current multiplied by series resistance.

A simple, fixed U or H type pad with only a few resistors (see Uneeda link) is probably the best sounding option, can't see how the fancy boxes would sound better. A switchable resistor configuration is the second best option, but don't see how that would be very useful. Having a -10 and -20dB pad handy should fix most issues. EDIT: You can NOT use the ATTY before a pre.

Especially with a tube microphone with transformer output, the output impedance is not the same over the whole frequency range, so adding a pad in series with the signal will affect the sound somehow. But as JJ hints, hard to predict how.

Finally, having a pre-amp that can be set to 0dB gain (or less!) is a real blessing.

Martin
Old 8th April 2009
  #23
Gear Maniac
 

Which atenuator is better?

If halfway is set on the ATTY and that is equivalent to the Shure attenuator at -20db padding. Out of the two, which would give a better attenuation that will not alter the sonics of the original signal.
Old 8th April 2009
  #24
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by Recman View Post
Which atenuator is better?

If halfway is set on the ATTY and that is equivalent to the Shure attenuator at -20db padding. Out of the two, which would give a better attenuation that will not alter the sonics of the original signal.
The least amount pad...using a 20dB when a 10dB is all that is needed is affecting the signal MORE than you need...
IF you choose to roll your own pad make sure the "Pair" is matched with in 1% or better, this will affect your CMRR..

Also be aware of this; the pad is NOT what affects the sound on most pres, its the fact the input is NO longer hitting the transformer harder, which is what increases the distortion...

I made a mic splitter box a while back for two main uses; one to split the signal to two inputs, second to vary the load on the mic, it has a pot across the splitter enabling a variable load...which in turn reduces the output that feeds the mic pre input...does that make sense???
Old 9th April 2009
  #25
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jjblair's Avatar
Quote:
Originally Posted by mikymike View Post
Unless you hate the sound of mic pre distortion!!!
I think you misunderstood me. I'm saying that if there's a pad, you don't need the ATTY. The pad should take take of saturating the pre.
Old 9th April 2009
  #26
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jjblair's Avatar
Quote:
Originally Posted by Recman View Post
Which atenuator is better?

If halfway is set on the ATTY and that is equivalent to the Shure attenuator at -20db padding. Out of the two, which would give a better attenuation that will not alter the sonics of the original signal.
OK, here's something to think about:

If you are using a U pad for mics, you optimally want make one or use with with values that give you the same impedence of the mic. When you change the impedence that the mic pre's transformer sees, you're going to start getting different coloration.

That being said, since we know nothing about how the ATTY works (somebody from A designs, feel free to chime in), I'd like to know the impedence.

I think a fixed pad is a much more practical way to go, and as I said above, if you have a -15dB pad, that is way more than enough to keep a pre from distorting. There is no need for a ATTY beyond that.

Personally, I'd go to soniccraft.com and order some PRP resistors, and make a -15dB pad with a Switchcraft barrel.
Old 9th April 2009
  #27
Gear Maniac
 

O.K. how about this situation.

I have my DAC-1 that I use to send my vocals out to get processed.
On my DAC-1 I can pad the output internally at
-10 = 1600ohms
-20 - 500 ohms
-30 = 60ohms

I have my La3a which requires 600 ohms I think. I am always finding that my signal is too low and I have to put that gain mod and 50db switch on at the back of the La3a when I pad the DAC-1 internally at -10 or not padded internally at all.

I also have my Api 2500, I don't know what loading that requires.

If I pad the DAC-1 internally at -10 and if I switch the DAC-1 to variable and put the volume knob to max, would that be equivalent to 0db no padding at maximum volume or is that maximum volume at -10 padded?

In this situation where I am plugging my DAC-1 to the La3a. Would I be better off setting my DAC-1 to -20 so that it can match close to the La3a impedence or am I better off not padding internally the DAC-1 and just use -20 DIY H pad cables I made.

Are DIY H pads cables at -20 the same as the internal padding of the DAC-1 at -20?

Also is the DAC-1 in variable and the volume knob at somewhere half way to get the same level reduced at -20 padded be the same as a DIY -20 H pad cable connected or internally pad the DAC-1 at -20?

Do you get different impedence using each approach, -20 internally, -20 DIY H pad cable, -20 Volume knob at variable mode or is it all the same impedence?

If I need to plug the DAC-1 to my 2500, I just switch the DAC-1 to variable and turn the volume knob to maximum? Would I be better off putting the DAC-1 to calibrated at no padding internally?

Which method should I be applying to my rig?
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