I was looking though the manual for an Elextrix Repeater and toward the
end it has a diagram for building a 12dB attenuation cable for plugging
it into a guitar amp. It's three resistors arranged like this:


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.
My math's not very good though. Could someone just confirm that I'm
wrong so I can go back and look for my mistake(s)?

Thanks

Need to know source and load nominal impedances to work it out.
Is the r/h 2k2 supposed to be to the right of the 3k9 resistor? In OE6 it
does not look right.

"apa" wrote in message
oups.com...
I was looking though the manual for an Elextrix Repeater and toward the
end it has a diagram for building a 12dB attenuation cable for plugging
it into a guitar amp. It's three resistors arranged like this:


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.
My math's not very good though. Could someone just confirm that I'm
wrong so I can go back and look for my mistake(s)?

Thanks

I don't know. I get the same answer. What's the input impedance of the
device it's padding, though? If it's a regular guitar amp, you'd think
the input impedance would be high enough to not matter. Or what if the
output impedance of the Elextrix Repeater is low enough to cause an
additional loss of 3.1 dB with this 8.9 dB attenuator? If my math is
correct, a 700 ohm output impedance would do the trick....very close to
your traditional 600 ohm output impedance for devices back in the day.

Cheers,
Trevor de Clercq

apa wrote:
I was looking though the manual for an Elextrix Repeater and toward the
end it has a diagram for building a 12dB attenuation cable for plugging
it into a guitar amp. It's three resistors arranged like this:


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.
My math's not very good though. Could someone just confirm that I'm
wrong so I can go back and look for my mistake(s)?

Thanks

It all depends on the source and load impedances. Coming from a 100k
plate load resistor it could well attenuate a LOT more than 12dB. IOW,
it's designed for a specific application.

On 2 Apr 2005 14:05:35 -0800, "apa" wrote:

I was looking though the manual for an Elextrix Repeater and toward the
end it has a diagram for building a 12dB attenuation cable for plugging
it into a guitar amp. It's three resistors arranged like this:


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.
My math's not very good though. Could someone just confirm that I'm
wrong so I can go back and look for my mistake(s)?

Thanks

Tony (remove the "_" to reply by email)

Sorry about that. It's PI shaped. The 3.9k is in series tip to tip.
One 2.k to ground before it and one 2.2k to ground after it.

I ran it for 1M ohm and 10M ohm input impedance and got the same
answer, but I didn't figure in the output impedance. The output
impedance is 1K ohm. The way I was looking at it, the output impedance
didn't seem to matter as far as the amount of attenuation. Guess I need
to look again.

Jim Gregory wrote:
Need to know source and load nominal impedances to work it out.
Is the r/h 2k2 supposed to be to the right of the 3k9 resistor? In
OE6 it
does not look right.

"apa" wrote in message
oups.com...
I was looking though the manual for an Elextrix Repeater and toward
the
end it has a diagram for building a 12dB attenuation cable for
plugging
it into a guitar amp. It's three resistors arranged like this:


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.
My math's not very good though. Could someone just confirm that I'm
wrong so I can go back and look for my mistake(s)?

Thanks

It's supposed to be regular guitar amp, so I figured for 10M ohm and 1M
ohm - got the same answer each time in terms of attenuation.

The manual list the output impedance of the Repeater as 1K ohm.

"apa"


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.



** If you put the two 2.2 kohms in parallel at the output end, that creates
13 dB of attenuation with 5 kohms input impedance.




........... Phil

This should help.

http://www.uneeda-audio.com/pads/

In article .com writes:

I was looking though the manual for an Elextrix Repeater and toward the
end it has a diagram for building a 12dB attenuation cable for plugging
it into a guitar amp. It's three resistors arranged like this:


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.

Your math is fine as far as the voltage divider between the 3.9K and
the 2.2K resistor on the ouptut (right) side. The couple of megohms
input impedance of the guitar amplifier in parallel with the 2.2K on
the output won't make a measurable difference.

There's another voltage divider that we don't know about, though, and
that's the one formed by the source impedance of the Repeater and the
2.2K resistor on the input (left) side. If the intent is to drop the
output of the Repeater by 12 dB, that divider would need to have an
attenuation of about 3 dB. That would make the source impedance about
900 ohms, higher than I would have expected but not unreasonable,
considering the application.

Or maybe they just assumed the output impedance of the Repeater was
1K, used easily obtainable resistor values, and hoped that some
smartass kid wouldn't try to check their math or even measure the
actual attenuation.



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Mike,
That clears things up.
Thanks, Andy

Mike Rivers wrote:
In article .com
writes:

I was looking though the manual for an Elextrix Repeater and toward
the
end it has a diagram for building a 12dB attenuation cable for
plugging
it into a guitar amp. It's three resistors arranged like this:


tip-------------3.9k----------tip
| |
2.2k 2.2k
| |
sleeve------------------------sleeve


From my math, this gives about -8.9dB, not -12dB.

Your math is fine as far as the voltage divider between the 3.9K and
the 2.2K resistor on the ouptut (right) side. The couple of megohms
input impedance of the guitar amplifier in parallel with the 2.2K on
the output won't make a measurable difference.

There's another voltage divider that we don't know about, though, and
that's the one formed by the source impedance of the Repeater and the
2.2K resistor on the input (left) side. If the intent is to drop the
output of the Repeater by 12 dB, that divider would need to have an
attenuation of about 3 dB. That would make the source impedance about
900 ohms, higher than I would have expected but not unreasonable,
considering the application.

Or maybe they just assumed the output impedance of the Repeater was
1K, used easily obtainable resistor values, and hoped that some
smartass kid wouldn't try to check their math or even measure the
actual attenuation.



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

** If you put the two 2.2 kohms in parallel at the output end, that creates
13 dB of attenuation with 5 kohms input impedance.

Yeah, and if you put ice cream under it, and chocolate sauce and
whipped cream on top, that creates a chocolate sundae. The schematic
doesn't show the two 2.2K resistors in parallel at the output end.

Reading is FUNdamental. Apparently so is making irrelevant
observations.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

"Mike Rivers"
Phil Allison

** If you put the two 2.2 kohms in parallel at the output end, that
creates
13 dB of attenuation with 5 kohms input impedance.

Yeah, and if you put ice cream under it, and chocolate sauce and
whipped cream on top, that creates a chocolate sundae.

** Yum.


The schematic
doesn't show the two 2.2K resistors in parallel at the output end.


** The schematic posed by the OP makes no sense at all.


Reading is FUNdamental.


** Taking everything you see utterly literally is *AUTISTIC* !!!


Apparently so is making irrelevant observations.



** Nothing irrelevant about some lateral thinking that produces the right
answer.





............. Phil

Mike Rivers wrote:

The schematic doesn't show the two 2.2K resistors in parallel at the
output end.


Correct. I think Phil is losing it.

On 2 Apr 2005 15:32:20 -0800, "apa" wrote:

It's supposed to be regular guitar amp, so I figured for 10M ohm and 1M
ohm - got the same answer each time in terms of attenuation.

The manual list the output impedance of the Repeater as 1K ohm.

Put that 1k between the left Tip connection and the left 2.2k, and
calculate the attentuation from that. Note that to get the
attentuation ratio at the left 2.2k, you have a 1k in series with the
parallel combination of 2.2k and 3.9k+2.2k. I suspect the result will
be very close to the claimed 12dB.

-----
http://mindspring.com/~benbradley

On 2 Apr 2005 20:00:15 -0800, "apa" wrote:

Mike,
That clears things up.

I suppose I really should read the whole thread before posting...

Thanks, Andy

-----
http://mindspring.com/~benbradley

"Joe Sensor" wrote in message

Mike Rivers wrote:

The schematic doesn't show the two 2.2K resistors in parallel at
the
output end.


Correct. I think Phil is losing it.

*it* was lost by Phil, long ago. ;-)

In article writes:

The schematic
doesn't show the two 2.2K resistors in parallel at the output end.


** The schematic posed by the OP makes no sense at all.

Sure it does. Didn't you read my explanation?

** Taking everything you see utterly literally is *AUTISTIC* !!!

You mean like reading a schematic provided by the equipment
manufacturer is autistic? It's simple enough so that it's unlikely
that the original poster made an error copying it. And it has a
perfectly reasonable explanation.

** Nothing irrelevant about some lateral thinking that produces the right
answer.

We call that "thinking inside the box."



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

The schematic doesn't show the two 2.2K resistors in parallel at the
output end.

Correct. I think Phil is losing it.

No, he's just up to his usual trick of dismissing the stated facts
without considering that they could be correct, then changing the
question to one he can answer.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Mike Rivers wrote:

No, he's just up to his usual trick of dismissing the stated facts
without considering that they could be correct, then changing the
question to one he can answer.


Wow! Sounds like Phil went to the same school as my wife. eek

In article , Phil Allison
wrote:

** Taking everything you see utterly literally is *AUTISTIC* !!!



Naa. Autism is considerably more interesting than that.





David Correia
Celebration Sound
Warren, Rhode Island


www.CelebrationSound.com

"Mike Rivers"
Phil Allison

The schematic
doesn't show the two 2.2K resistors in parallel at the output end.


** The schematic posed by the OP makes no sense at all.

Sure it does. Didn't you read my explanation?


** You explained nothing.



** Restoring the original context line the Parrott snipped.

Reading is FUNdamental.


** Taking everything you see utterly literally is *AUTISTIC* !!!

You mean like reading a schematic provided by the equipment
manufacturer is autistic?


** The Parrott is an incorrigible context shifter !!!!!

Plus he has a bad memory.


** Nothing irrelevant about some lateral thinking that produces the right
answer.

We call that "thinking inside the box."


** From a Parrott does all his "thinking" inside a smelly cage - that
is funny.





............. Phil

"Chel van Gennip"
Phil Allison wrote:


** The schematic posed by the OP makes no sense at all.


It is not the schematic I would use in this case, but OP had it from the
manual: http://www.electrixpro.com/files/pdf...repeater_E.pdf


** So ??



Reading is FUNdamental.

** Taking everything you see utterly literally is *AUTISTIC* !!!


If you are answering a question, not reading the question does not help a
lot.


** And you have not read my original post in this thread.



** Nothing irrelevant about some lateral thinking that produces the
right answer.

Your answer might be right, but the question was wrong?


** Supplied information can always contain errors.

Technical mistakes, printing errors and missing data are the cause of many
posted queries on NGs.



If you take in account the 1k output impedance of the device a 12 dB
attentuation might be correct. For an asymetric attentuation 2 resistors
would be enough.
As the OP wants to connect this 1kohm +8dB output to a -20 dB input, I
would use a 24dB attentuation using one 3k9 resistor and one 330ohm
resistor, together with the 1k output impedance this would give about
24dB attentuation.



** So who is ignoring the supplied info now ??



............... Phil

"david"
Phil Allison


** Taking everything you see utterly literally is *AUTISTIC* !!!


Naa. Autism is considerably more interesting than that.



** LOL !!

David just took what I wrote utterly literally !!!




............... Phil

"Joe Sensor"
Mike Rivers wrote:

The schematic doesn't show the two 2.2K resistors in parallel at the
output end.


Correct. I think Phil is losing it.



Quote:

" ** If you put the two 2.2 kohms in parallel at the output end, that
creates
13 dB of attenuation with 5 kohms input impedance. "




........... Phil

"Mike Rivers"

No, he's just up to his usual trick of dismissing the stated facts
without considering that they could be correct,


** Autistic Parrots like Mike Rivers are incapable of imagining other's have
thoughts.



............. Phil

In article writes:

** Autistic Parrots like Mike Rivers are incapable of imagining other's have
thoughts.

Intelligent posters read the question that's asked and don't reply
with someting that doesn't answer the question. Had the original
poster asked how he could make a 12 dB attenuator, your suggestion
(with a diagram or text explanation of how to connect resistors as a
voltage divider) would have been a (not necessarily the only) correct
solution.

However, he didn't ask how to make a 12 dB attenuator, he posted a
diagram of a circuit taken from the product's manual, which they
recommended for dropping the output level for the purpose of
connecting it to a guitar amplifier. Since the manual states that this
circuit provided 12 dB of attenuation, and being a curious person
wanting to reinforce his understanding of voltage dividers and dB
calculations, tried to verifiy the attenuation and recognized that he
didn't know how to account for all the components and get 12 dB.

I explained that. I answered his question. Hopefully he learned
something that he didn't know, and might be able to apply this
knowledge to something else.

You told him that if he chose to ignore the manufacturer's recommended
circuit and used yours, he could make something that would work in
this instance. You didn't answer his question, you answered a question
that you made up without stating it: "How do I make a 12 dB
attenuator?"

As I said, reading is FUNdamental. Read the question first. If you
choose to answer a different question, you at least own the poster the
explanation of why you're suggesting a different approach rather than
one that (barring publication errors) has apparently been tested by
the manufacturer.

But then, since you're a jerk, details are optional.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

On Mon, 4 Apr 2005 12:29:54 +1000, "Phil Allison"
wrote:

** Autistic Parrots like Mike Rivers are incapable of imagining other's have
thoughts

Other's what?

"Mike Rivers"
Phil Allison

** Autistic Parrots like Mike Rivers are incapable of imagining other's
have
thoughts.

Intelligent posters read the question that's asked and don't reply
with someting that doesn't answer the question.


** Others had already supplied such answers - so I chose to supply
another and BETTER way to configure the same resistors.

" If you put the two 2.2 kohms in parallel at the output end, that creates
13 dB of attenuation with 5 kohms input impedance. "

Even Mike should know it is better to use a 5 kohms load than 2 kohms as
there may be a low value cap on that line output.



Had the original
poster asked how he could make a 12 dB attenuator, your suggestion
(with a diagram or text explanation of how to connect resistors as a
voltage divider) would have been a (not necessarily the only) correct
solution.


** The OP likely needs *much* more than 12 dB of attenuation - only he
has no idea most guitar amps have input sensitivities in the -40 dBm range.

But I will wait for him to try his 12 dB one and then come back here for
that.


However, he didn't ask how to make a 12 dB attenuator, he posted a
diagram of a circuit taken from the product's manual, which they
recommended for dropping the output level for the purpose of
connecting it to a guitar amplifier.


** A circuit that makes no sense - so is likely an error.



You told him that if he chose to ignore the manufacturer's recommended
circuit and used yours, he could make something that would work in
this instance.


** I chose to supply another and BETTER way to configure the same
resistors.

" If you put the two 2.2 kohms in parallel at the output end, that creates
13 dB of attenuation with 5 kohms input impedance. "

It is better to use a 5 kohms load than 2 kohms as there may be a low value
cap on that line output.


You didn't answer his question,


** Others had already supplied such answers.

I supplied another option - something for him to consider.



As I said, reading is FUNdamental. Read the question first. If you
choose to answer a different question, you at least own the poster the
explanation of why you're suggesting a different approach rather than
one that (barring publication errors) has apparently been tested by
the manufacturer.


** But Mike Rivers has no ****ing idea what attenuator configuration will
work and what will not.

He is not a 35 year experienced audio tech or circuit designer like I am.

Mike Rivers is just a puffed up, pedantic, autistic, ****ing Parrot.


But then, since you're a jerk, details are optional.


** That Parrott cage Mike lives in really blocking his view.

Has someone left the cover on it ???




............. Phil

In article , Phil Allison
wrote:

** Taking everything you see utterly literally is *AUTISTIC* !!!


Naa. Autism is considerably more interesting than that.



** LOL !!

David just took what I wrote utterly literally !!!



I'm a bit utterly touchy on that subject. And I would appreciate it if
you found another adjective to poop on people with in this forum.




David Correia
Celebration Sound
Warren, Rhode Island


www.CelebrationSound.com