Amplifier Advice (Emotiva or Parasound) - Page 5 - AVS Forum
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post #121 of 144 Old 05-06-2014, 03:56 PM
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Originally Posted by BVLDARI View Post

So I presume for those of you who believe in no audible difference between amplifiers you own the cheapest ones available on the market?

I use the ones that are included in my receivers. I do have an integrated amp in my two channel system. I believe it cost $150.
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post #122 of 144 Old 05-06-2014, 05:23 PM
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Wow, nice choices so far!
While Emotiva is good value for money and friendly folks over in Emotivaland, if I had the choice, I'd go with the Parasound option, especially for efficient speakers like those Paradigms.
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post #123 of 144 Old 05-07-2014, 06:43 AM
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This is an interesting thread to me as I am somewhere near the same point as the OP.
I have a question to everyone since I haven't seen it addressed in the thread.
Everyone is talking about watts and headroom, but what about capacitance headroom (Amps?)
Doesn't a a device with which amps delivery have some advantage where all other items are the same?

Example:
300w at 8 ohms 35 amps
300w at 8 ohms 60amps

I'm trying to understand how these ratings affect the amp purchasing decision.
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post #124 of 144 Old 05-07-2014, 06:49 AM
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Originally Posted by theblackangus View Post

This is an interesting thread to me as I am somewhere near the same point as the OP.
I have a question to everyone since I haven't seen it addressed in the thread.
Everyone is talking about watts and headroom, but what about capacitance headroom (Amps?)
Doesn't a a device with which amps delivery have some advantage where all other items are the same?

Example:
300w at 8 ohms 35 amps
300w at 8 ohms 60amps

I'm trying to understand how these ratings affect the amp purchasing decision.

Useful if you have speakers with low impedance. My speakers drop down to 2ohm. btw the 100W amps I use have 40A supply..

Krell Evolution 900e x 7

Bose Jewel speakers.

 

Jealous of my speakers?

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post #125 of 144 Old 05-07-2014, 08:50 AM
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Originally Posted by fatbottom View Post

Useful if you have speakers with low impedance. My speakers drop down to 2ohm. btw the 100W amps I use have 40A supply..

And that is meaningful depending on which frequencies are at 2 ohms and how much of the total output of the speakers is at those frequencies. This broad brush statement doesn't mean anything by itself. More important is the nominal impedance rating which provides more guidance to the user than the low point in the impedance curve. The answer to your question, OP, is that the higher current rating means that the amplifier can deliver more current, if needed, than the lower rated model.
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post #126 of 144 Old 05-07-2014, 04:53 PM
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Originally Posted by fatbottom View Post

Useful if you have speakers with low impedance. My speakers drop down to 2ohm. btw the 100W amps I use have 40A supply..

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Originally Posted by FMW View Post

And that is meaningful depending on which frequencies are at 2 ohms and how much of the total output of the speakers is at those frequencies. This broad brush statement doesn't mean anything by itself. More important is the nominal impedance rating which provides more guidance to the user than the low point in the impedance curve. The answer to your question, OP, is that the higher current rating means that the amplifier can deliver more current, if needed, than the lower rated model.

You are both seeming to indicate that amperage is useful to allow for more "Headroom" with lower efficiency speakers for particular frequencies?

So if my speakers efficiency were 84db I would likely want to have a higher amperage amp to help maintain some headroom (as I like to sometimes listen a good volume).
(I understand this headroom may equate to a minimal sound difference or possibly only a difference with certain music/sounds, but that's a slightly different discussion)
Or am I missing the mark here?

If so what happens when you run out of amps - does the amp clip? - does the sound just roll off?

Thanks for the explanations guys!
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post #127 of 144 Old 05-07-2014, 06:43 PM
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Originally Posted by chev265 View Post

A couple of days ago I ordered 2x XPA-1 and 1x XPA-5 Emotive amps
Did they arrive, yet? How did it work out?

Have you conducted proper blind testing, yet?
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post #128 of 144 Old 05-07-2014, 07:19 PM - Thread Starter
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Originally Posted by rcohen View Post


Did they arrive, yet? How did it work out?

Have you conducted proper blind testing, yet?

 

They haven't arrived yet unfortunately.  Emotiva sent them out pretty quickly but they took a few days to get to the NZ border, and then a few days to go through customs and get cleared.  UPS tracking says from yesterday they are now In Transit locally so I hope to see them today or tomorrow all going well...

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post #129 of 144 Old 05-07-2014, 09:08 PM
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Originally Posted by theblackangus View Post


You are both seeming to indicate that amperage is useful to allow for more "Headroom" with lower efficiency speakers for particular frequencies?

So if my speakers efficiency were 84db I would likely want to have a higher amperage amp to help maintain some headroom (as I like to sometimes listen a good volume).
(I understand this headroom may equate to a minimal sound difference or possibly only a difference with certain music/sounds, but that's a slightly different discussion)
Or am I missing the mark here?

If so what happens when you run out of amps - does the amp clip? - does the sound just roll off?

Thanks for the explanations guys!

That is not what these guys are saying to you. They are saying if your speakers have unusually low impedance (ohms) then a high current capable amp is advisable.

Given that your speakers are very low sensitivity you may want a high wattage amp if you listen at high volumes. It would take four times (4x) the power for your 84dB speakers to output the same amount as a 90dB speaker in the same system/room.
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post #130 of 144 Old 05-08-2014, 05:54 AM
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Originally Posted by Avgass View Post

That is not what these guys are saying to you. They are saying if your speakers have unusually low impedance (ohms) then a high current capable amp is advisable.

Given that your speakers are very low sensitivity you may want a high wattage amp if you listen at high volumes. It would take four times (4x) the power for your 84dB speakers to output the same amount as a 90dB speaker in the same system/room.

So is it improper to equate low efficiency with low impedance? From looking the "low efficiency" speakers I have seen have a 4 ohm impedance - so can you explain why you say that my summary is wrong? The scenario given seems to classify as low efficiency and low impedance as I haven't seen a speaker yet that had an efficiency of higher than 94db with lower than 8 ohm impedance, and any speaker that had less than 94db efficiency had 4 or 6 ohm rating which would appear to classify as low impedance.

Sounds like there is some hair splitting going on I don't understand.

Thanks for the math on the power differential needed, that's a big difference when you come to bigger volumes.
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post #131 of 144 Old 05-08-2014, 06:06 AM
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Efficieny is the dB rating for 1W.
Impedance is Ohm ie 4, 8 ohm

The former is dB output for wattage, latter is how robust the power supply is, in amperes

Krell Evolution 900e x 7

Bose Jewel speakers.

 

Jealous of my speakers?

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post #132 of 144 Old 05-08-2014, 07:17 AM
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Thanks Fatbottom! I do get that, and have more questions but shouldn't drag this thread off topic further.
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post #133 of 144 Old 05-08-2014, 08:04 AM
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Originally Posted by theblackangus View Post

Thanks Fatbottom! I do get that, and have more questions but shouldn't drag this thread off topic further.

 

I didn’t understand fatbottom's comment about impedance (ohms). The nominal impedance of your speakers doesn't correlate to "how robust the power supply is, in amps". Not sure what that means.

 

To understand the way this works, imagine a garden hose connected up to a fawcett. Turn the water on and it will flow out of the end of the hose. This flow of water can be likened to the flow of electrical current in a circuit (which is measured in amps as fatbottom said).  If you put your finger over the end of the hose, you will impede the flow of water (current) through it. You will also feel the pressure of the water behind your thumb. This pressure can be likened to the voltage in an electrical circuit. If you have completely shut off the flow of water with your thumb, the pressure is still there but no water is flowing now. This is like a mains outlet with nothing connected to it - the voltage (pressure) is still there but there is no flow of current (water). Now, move your thumb and let some water squirt out the end of the hose. IOW, impede the flow of the water. By moving your thumb around you can change the amount of water that will flow. In your AV system, the thing that impedes the flow of current is the speaker (the load on the circuit).

 

So in this analogy, water = current, thumb = impedance and pressure - voltage. You can see that they will all be interdependent on each other: if you slightly shut off the fawcett, then the pressure will drop and the flow of water will be reduced. If you open the fawcett more, then the flow of water will be increased, and so on. Ohm devised a formula to represent this, known as Ohm's Law. It is voltage = current times resistance, or V =IR (current is I, go figure). So to calculate resistance the formula would be R = V/I.

 

Why does any of this matter?  Well you can see from the above explanation that if you lower the resistance (impedance) of the load, then you will cause more current to flow, assuming the voltage remains the same. In practice this means that a low impedance load, like a 4 ohm speaker as opposed to an 8 ohm speaker, will make bigger demands on the amplifier - it will require a theoretical doubling of current to deliver the same output. So if you connect 4 ohm speakers to your amplifier, then you have to be sure that it can deliver. Not all amps, which are commonly rated for 8 ohm loads, can do this and you will overdrive them if you try, potentially causing damage to the amp, but more likely causing it to go into overload protection and shut down. If the amp you are considering is suitable for 4 ohm loads, it will be stated in its spec, or it will show a power rating in watts when used with 4 ohm speakers. This will be higher than when used with 8 ohm speakers, but the amp has been designed to cope with the extra demand. TBH any decent modern SS amp should be able to drive a 4 ohm speaker without any problems arising - if the amp can't deliver more output into a 4 ohm load than it can into an 8 ohm load, then it has an under-specified output stage and/or a poor power supply (which is maybe what fatbottom was getting at?) - done to save money. Both Emotiva and Parasound amps are perfectly happy with 4 ohm loads so you don't need to factor that into a decision about which to buy.

 

The impedance of a speaker has no bearing on its quality wrt to sound. Speaker designers use 4 ohm drivers for a variety of reasons. They are often more sensitive (called 'efficiency' sometimes but strictly that is a different thing) and a more sensitive speaker will, as shown above, cause a good amp to deliver more output than it would into an 8 ohm load. This extra output can be 3-5dB and more output can mean less distortion, more headroom and the ability to play louder of course. Sometimes a lower impedance driver will make it easier to design the speaker enclosure enabling the designer to have higher sensitivity, greater bass extension or a smaller cabinet, or a combination of all three. You will often see 4 ohm speakers at the 'higher end' of the market and rarely at the cheap end, and this perhaps shows that more thought and care has gone into the design of the better speakers and also that the designer is expecting his product to be partnered with a reasonably good amp.

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post #134 of 144 Old 05-08-2014, 08:39 AM
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Speakers with higher impedance will require more current from your speakers. Also if you weren't aware when your speaker load drops from 8 to 4 ohm, with a good amplifier the power (watts) should double, so my 60W amplifiers are actually closer to 90W into 4ohm

Krell Evolution 900e x 7

Bose Jewel speakers.

 

Jealous of my speakers?

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post #135 of 144 Old 05-08-2014, 09:27 AM
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at any given voltage (volume control setting, at least in analog days - - now if you recalibrate for different speakers, the same volume control setting will yield different voltage) more current flows into the lower impedance device, not the higher impedance device.

If you change nothing but the speaker m going to a four ohm unit, current will double (depending somewhat on the frequency content of the sound being reproduced. Power will double, too because power is volts times amps, Power would double for the four ohm speaker all the way until you reach the limits of the amp's output capability. Amps that are specified to double their max output power as impedance is cut in half are usually specified with a lower 8 ohm rating, for example, than they technically could achieve if the exact same THD limits were imposed in both the 8 ohm and 4 ohm case. Lots of ways to fool with amp specs.

How loud the sound will be, whether its 1 watt versus two watts, or 5 watts versus 10 watts, or 0 watts versus 100 watts, depends on how loud the speaker gets with that level of input. That's the speaker's sensitivity.

So an 8 ohm speaker that has a 90 dB sensitivity (1 watt at 1 meter) will be four dB louder than another 8 ohm speaker that has an 86 dB (one watt at one meter) sensitivity. This will be true at one watt, at half a watt, at ten watts and at 50 watts. At some point each speaker starts to compress (not getting as much louder s incoming signal dictates) and you can't count on the 4 dB difference remaining consistent after that.

there is no particular reason for a ohm speaker to have higher sensitivity than an 8 ohm speaker. My Magnepans had a lower rating than my current Paradigms. IIRC, the Maggies were specified at 86 dB and the Paradigms are also rated at 86 dB anechoic, BUT the Maggies were rated at the voltage that yields one watt at 8 ohms, even though they are 4 ohm speakers. That means they're 86 dB at 2 watts, or 83 dB at one watt . . . .

AIUI, the trend toward lower impedance speakers may have at least part of its origins in simple salesmanship. In analog days, if I changed from an 8 ohm speaker to a 4 ohm speaker without touching the volume control, the power doubled into the 4 ohm speaker. Depending of course upon the two speakers' relative sensitivities, the power boost to the 4 ohm speaker might be enough to yield a small difference in overall output. There's a lot of evidence that louder sounds qualitatively better, even when we don't notice that it's louder. Makes sense, based both on the Fletcher-Munson curves and the fact that as you get louder, details that might be masked or go unnoticed reveal themselves. SO the louder speaker seems more detailed and may seem to have more bass. While the volume difference isn't all about noise floor, it's really easy to perceive when you play music in your car. A level that might seem loud, and certainly is getting you most of the important detail, sitting in your driveway with the motor off, isn't loud enough for driving through the neighborhood at 20 miles an hour, which isn't loud enough for driving down the highway. As noise floor goes up, more and more sounds are masked by the noise and suddenly all you can barely hear are the vocals, while the bass, drums, guitars and/or keyboards may be partially or totally swamped by the sound of the road.

Of course at home, you'd set the volume control at the sound level you want, and the qualitative differences between the speakers might turn out to be a bit different if they were auditioned at the same actual SPL (or played at the same SPL in one's home).
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post #136 of 144 Old 05-08-2014, 10:16 AM
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AIUI, the trend toward lower impedance speakers may have at least part of its origins in simple salesmanship.

 

There is some truth in that of course. But one generally finds lower impedance speakers in the higher quality designs. Agreed there is no particular reason why 4 ohm drivers should be more sensitive, but it seems they usually are, and not by an insignificant amount. I can’t recall where I read an interview with Paul Scarpelli of Triad who explained it in some detail. Might have been the Triad thread here that I am thinking of - I was considering Triads once.

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post #137 of 144 Old 05-08-2014, 10:16 AM
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Originally Posted by fatbottom View Post

Speakers with higher impedance will require more current from your speakers. Also if you weren't aware when your speaker load drops from 8 to 4 ohm, with a good amplifier the power (watts) should double, so my 60W amplifiers are actually closer to 90W into 4ohm

 

Other way around.

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post #138 of 144 Old 05-08-2014, 03:58 PM
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Originally Posted by kbarnes701 View Post

I didn’t understand fatbottom's comment about impedance (ohms). The nominal impedance of your speakers doesn't correlate to "how robust the power supply is, in amps". Not sure what that means.

I was more talking about understanding this bit:
Efficieny is the dB rating for 1W.
Impedance is Ohm ie 4, 8 ohm

The outstanding questions I have were around the last statement =)
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post #139 of 144 Old 05-08-2014, 03:59 PM
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I think subsequent responses from the others have clarified things somewhat but to put my spin on it...

Sensitivity (dB/watt) and impedance (electrical resistance) are not significantly correlated for any reason associated with the physics of speaker design (different coil weights can affect things in a minor way). Low impedance high sensitivity speakers are not rare. There are many professional PA speakers with sensitivities well excess of 94dB which have a 4ohm nominal resistance. A few examples of HT speakers with high sensitivity and 4ohm nominal impedance - JTR Noesis 212HT, Klipsch P-39F, Legacy Audio Focus SE, Danley SH50.

When the impedance of a speaker halves it tries to draw twice as much current from the amplifier (which would result in double the power). There is no perfect amplifier, and so when tested, no amplifier on the planet exactly doubles it's output, but some do come close. Manufacturer's specs sometimes indicate a doubling of output as this is seen as the sign of a good amp by some audiophiles, although this 'specmanship' is normally achieved by underrating the output at 8ohms.

A good rule of thumb is that for every additional 3dB output you need twice the power.
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post #140 of 144 Old 05-08-2014, 04:48 PM
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Every amp doubles power at half the impedance until it runs out of steam. No amp puts out full power all the time. Bwatching a movie at reference, dislog mighy average 82 dB. Loud stuff could get as loud as 105 dB in dach speaker. The peak requires 200 times more power than the average dialog. Thre amp may clip trying to play the peak into a 4 ohm load but it will handily double power from half a watt or even 2 watts to one watt or four watts.
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post #141 of 144 Old 05-08-2014, 06:25 PM
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I thought it was self evident we were discussing max output. Wattage ratings for amplifiers are all at some point where the amp is running out of steam.
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post #142 of 144 Old 05-09-2014, 04:35 AM
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Quote:
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Quote:
Originally Posted by kbarnes701 View Post

I didn’t understand fatbottom's comment about impedance (ohms). The nominal impedance of your speakers doesn't correlate to "how robust the power supply is, in amps". Not sure what that means.

I was more talking about understanding this bit:
Efficieny is the dB rating for 1W.
Impedance is Ohm ie 4, 8 ohm

The outstanding questions I have were around the last statement =)

 

I thought that I, and others, had answered that fairly comprehensively.  Speaker sensitivity is the amount of noise the speaker makes when you input 1 watt and measure the noise from a distance of 1 metre. Eg, 89dB/1w/1m.

 

Impedance is exactly what the name implies - it is the resistance to the flow of current which the speaker (load) imposes. Because of Ohm's Law, the lower the impedance, the more current will flow. Just like in my hosepipe example - if you lower the impedance (move your thumb a bit more from the end of the hosepipe), the more water will flow through it.

 

(We shouldn't really use the words 'sensitivity' and 'efficiency' as though they are interchangeable, but this is how they are usually used. Speaker sensitivity is what I describe above. Speaker efficiency refers to how much of the input is converted to sound output, as opposed to being 'lost' (eg converted to heat) in things like crossovers, voice coils etc.)

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post #143 of 144 Old 05-09-2014, 05:00 AM
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Originally Posted by kbarnes701 View Post

I thought that I, and others, had answered that fairly comprehensively.  Speaker sensitivity is the amount of noise the speaker makes when you input 1 watt and measure the noise from a distance of 1 metre. Eg, 89dB/1w/1m.

Yes you did and thank you!
I responded to the 1st part of your statement then my wife grabbed me and I had to leave.! =)
The responses above were great and very helpful.
This leaves me with much more knowledge than when I started reading.

Quote:
Originally Posted by Avgass View Post

I think subsequent responses from the others have clarified things somewhat but to put my spin on it...

Sensitivity (dB/watt) and impedance (electrical resistance) are not significantly correlated for any reason associated with the physics of speaker design (different coil weights can affect things in a minor way). Low impedance high sensitivity speakers are not rare. There are many professional PA speakers with sensitivities well excess of 94dB which have a 4ohm nominal resistance. A few examples of HT speakers with high sensitivity and 4ohm nominal impedance - JTR Noesis 212HT, Klipsch P-39F, Legacy Audio Focus SE, Danley SH50.

When the impedance of a speaker halves it tries to draw twice as much current from the amplifier (which would result in double the power). There is no perfect amplifier, and so when tested, no amplifier on the planet exactly doubles it's output, but some do come close. Manufacturer's specs sometimes indicate a doubling of output as this is seen as the sign of a good amp by some audiophiles, although this 'specmanship' is normally achieved by underrating the output at 8ohms.

A good rule of thumb is that for every additional 3dB output you need twice the power.

Ahh I had not looked into the professional realm of speakers. (I have heard the JTR Noesis tho but didnt know the specs)

Thanks everyone who helped me gain a better understanding with this subject, I'm a bit of a nerd and like to know how things work.
Sorry to derail the original thread.
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post #144 of 144 Old 05-09-2014, 05:03 AM
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Quote:
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I thought that I, and others, had answered that fairly comprehensively.  Speaker sensitivity is the amount of noise the speaker makes when you input 1 watt and measure the noise from a distance of 1 metre. Eg, 89dB/1w/1m.

Yes you did and thank you!
I responded to the 1st part of your statement then my wife grabbed me and I had to leave.! =)
The responses above were great and very helpful.
This leaves me with much more knowledge than when I started reading.

 

You're welcome.

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