Amp design.

[highfihoney]

It seems that you & I are doing things backwards from each other,ive spent all my time with 2 channel home systems & im just now starting to get into real car audio at damm near 50 years old.

I set up the system in my mustang using the know how from 2 channel but i also tried to use the all amps sound alike theory when setting it up,i bought good strong amps for the subs (Rockford Fosgate) & even better & cleaner amps for the mids & highs(Butler audio tubes & PPI solid state),i took care of all grounding issues,made sure the amps had all the power they needed,used over gauge wiring & thought that would be it.

I quickly found out i wasnt happy with the sound,it was loud but thats it,i went back & forth between the PPI & Butler on the mids & highs & i tried running the Jl audio dual coil subs in both 2 ohms & 4 ohms,no matter what configuration i ran it wasnt cutting it.

I finally broke down & bought 2 used mcc301 monoblocks for the subs & the pay off was instant,couldnt stop there so i ordered a new mcc602 for the mids & highs,bingo again,i ended up running an adcom gfs speaker selector to split the power from the amp for the fronts & rears.

Mc does have the best amp technology going ,to have 0.005 thd no matter the load or demand is an awesome thing,im still freaking out over the car audio aspect of their amps & ive been a mac owner forever.

Come spring when all this damm snow clears i gotta rip it all out & take the car in for a custom install so it looks like it belongs in the car instead of the hack job install i did

 

[Yamahaluver]

The point here is being cool under pressure, that means delive high current with a huge transformer and caps, and be distortion less at the same time, thats the attribute of a good amp.

 

[PENG]

Damm thats what i get for being on the audioholics forums while i was in a work meeting and to think everybody in the meeting thought i was banging away pulling up numbers for them

Your right though,i transposed current for voltage in several spots,my post should have said the lower the ohmage the more current needed.

I'll see your edit & raise you an edit.

The dynamic power management circuit is pretty awesome so are the autoformer model amps.

So I guess you had some typo in your previous post. Basically, if you keep the voltage the same, half the impedance will result in double the current as Zumbo pointed out correctly.

Using the forumla: P=V*V/Z or I*IZ, one can see quickly that since Power is proportional to the square of the current, by halving the impedance you double the power. Example: Let's us 16V as the output voltage, 16V into 8 ohms, current=16V/8 ohms=2A, power=2A*2A*8 ohms=32W (or using V^2/Z, power=16V*16V/8 ohms=32W).

The same 16V into 4 ohms, current=16/4=4A, power=4A*4A*4 ohms=64W, or doubling the power. However, in practice, doubling the current will cause more voltage drop (V=IZ) that results in power drop, so it is theorectically very difficult (not impossible) for an amp to double down regardless of the size of transformer and capacitors. It is much easier to underrate the 8 ohm rating a little, then to design and build an amp that truly doubles down. Heat can affect the electrical characteristics of electronics and the load, but it can be easily overcome with appropriate cooling and by using overrated components. One more point, to have high current capability, an amp would need more than a large transformer, any components that have to deal with the current, such as the power transistors will also have to be rated for the higher current.

 

[zumbo]

The point here is being cool under pressure, that means delive high current with a huge transformer and caps, and be distortion less at the same time, thats the attribute of a good amp.

You didn't vote for this design.

 

[highfihoney]

So I guess you had some typo in your previous post. Basically, if you keep the voltage the same, half the impedance will result in double the current as Zumbo pointed out correctly.

Using the forumla: P=V*V/Z or I*IZ, one can see quickly that since Power is proportional to the square of the current, by halving the impedance you double the power. Example: Let's us 16V as the output voltage, 16V into 8 ohms, current=16V/8 ohms=2A, power=2A*2A*8 ohms=32W (or using V^2/Z, power=16V*16V/8 ohms=32W).

The same 16V into 4 ohms, current=16/4=4A, power=4A*4A*4 ohms=64W, or doubling the power. However, in practice, doubling the current will cause more voltage drop (V=IZ) that results in power drop, so it is theorectically very difficult (not impossible) for an amp to double down regardless of the size of transformer and capacitors. It is much easier to underrate the 8 ohm rating a little, then to design and build an amp that truly doubles down. Heat can affect the electrical characteristics of electronics and the load, but it can be easily overcome with appropriate cooling and by using overrated components. One more point, to have high current capability, an amp would need more than a large transformer, any components that have to deal with the current, such as the power transistors will also have to be rated for the higher current.

Good morning peng,a couple of things,i didnt have a typo i errantly wrote voltage instead of current,also i did not say it was "impossible" i said it was "not possible with most amps",i think were splitting hairs here as were both saying the same thing.

 

[PENG]

In order for the amp to maintain its same output regardless of load, even more rating tricks would have to be performed.

This is interesting. Let's consider a 2 channel amp that is rated for 100W for an 8 ohm load:

To maintain the same 100W output at 4 ohms, the amp can drop the voltage by a factor of 0.707 (1/sqrt2). That's not hard to do, but in order to maintain the same output when driving a 16 ohm load, the voltage would have to double! How do you do it with the same amp, unless you get another one of the same, and bridge both 2 Channel amps to yield two monoblocks of 100W each. So I guess you are right about "even more rating tricks would have to be performed".

 

[PENG]

Good morning peng,a couple of things,i didnt have a typo i errantly wrote voltage instead of current,also i did not say it was "impossible" i said it was "not possible with most amps",i think were splitting hairs here as were both saying the same thing.

Sorry hifi, that's not my intention, just minor misunderstanding.

 

[MDS]

Exactly Peng. But I think it was highfihoney that said certain amps do something to adjust the impedance so that it is constant. I don't know how that could be done but it is kind of out of my league so I just accept that maybe it could be done.

An amp can only deliver a certain voltage and no more (the 'rail voltage') so unless it limits the voltage (and by implication, the current) I don't see how any amp could deliver the same power regardless of load unless it purposely limits the voltage/current for lower impedance loads to make the lower ohm rating equal to the higher impedance rating.

 

[zumbo]

This is interesting. Let's consider a 2 channel amp that is rated for 100W for an 8 ohm load:

To maintain the same 100W output at 4 ohms, the amp can drop the voltage by a factor of 0.707 (1/sqrt2). That's not hard to do, but in order to maintain the same output when driving a 16 ohm load, the voltage would have to double! How do you do it with the same amp, unless you get another one of the same, and bridge both 2 Channel amps to yield two monoblocks of 100W each. So I guess you are right about "even more rating tricks would have to be performed".

Not talking about 16ohm. I will find some links, and you tell me. The first will be the amp I have decided on. Many other McIntosh share this feature.

http://www.mcintoshlabs.com/mcprod/shopdisplayproducts.asp?hid=1&id=14&cat=Power+Amplifiers&prodid=1151&product=MC205

Mobile audio.
http://xtant.com/html/products/xtant1.1i.cfm

Mobile audio for McIntosh as well.
http://www.mcintoshlabs.com/mcprod/shopdisplayproducts.asp?hid=2&id=22&cat=Power+Amplifiers&prodid=1063&product=MCC602TM

 

[highfihoney]

Sorry hifi, that's not my intention, just minor misunderstanding.

Nor mine,i should have wrtten my responses better,i should have said we were both trying to say the same thing only your post was worded better with a better description.

 

[highfihoney]

Peng & mds,ive been using examples of amplifiers that incorpotate "autoformers" & "dynamic power management" circuits within thier design to control a vast number of things including the load that the amplifier see's from the speaker,from how i understand how they work they interact before the speaker load is seen by the amplifier making it a constant ohmage.

Here is a very brief explaination of the origional autoformer that mcintosh uses in their entire 2 channel amp line & is what i have in my amplifiers,buku info is available on different applications of these.

http://www.mcintoshlabs.com/autoformer.aspx

Here is another much smaller copy cat version made for use between speaker & amp.

http://www.enjoythemusic.com/magazine/equipment/0603/midmonth/zeroautoformer.htm

 

[zumbo]

One thing I have noticed.

Krell doubles. Most I have read about. Sell used at a fraction(of some sort) of the original retail.

Parasound doubles. Most I have read about. Sell at a lower fraction of the original retail.

McIntosh. Used sell right at retail. Some, certainly sell for more than the original purchase price. Deals can be found, and in many cases, you can use the amp for many years, and get your full purchase price back. Or more. Something to that. Certainly everyone hasn't lost their minds.

Same goes for car audio. Amps that resist ohm loads command a preimium price. I have four Linear Power that are not for sale. They do try to double, but are not affected by the load. No matter what load.

 

[PENG]

Not talking about 16ohm. I will find some links, and you tell me. The first will be the amp I have decided on. Many other McIntosh share this feature.

http://www.mcintoshlabs.com/mcprod/shopdisplayproducts.asp?hid=1&id=14&cat=Power+Amplifiers&prodid=1151&product=MC205

Mobile audio.
http://xtant.com/html/products/xtant1.1i.cfm

Mobile audio for McIntosh as well.
http://www.mcintoshlabs.com/mcprod/shopdisplayproducts.asp?hid=2&id=22&cat=Power+Amplifiers&prodid=1063&product=MCC602TM

zumbo, I do frequent the McIntosh website. That's why I said in my last post that it was not hard to do to maintain the same power by simply droping (or varying) the voltage for load impedance between 8 and 4 ohms. So we are not disgreeing at all as long as we are talking about impedance between 8 and 4 ohms or lower. I cited the 16 ohm example just to echo what MDS was alluding to, i.e. the question: how can the same output be maintained regardless of the load impedance.

Anyway, like MDS, my vote goes to amps that double down even though I strongly suspect they all do it by under rating their 8 ohm outputs to certain extent (expectedly less so in high end products such as Krell). To me, a Krell amp that can do 250W 8 ohms, 500W 4 ohms is better than a McIntosh that does 300W 8, 4, or 2 ohms because the Krell will assure me that when my speaker's impedance dips low, the amp is able to maintain the voltage to deliver the needed current whereas the McIntosh will lower the voltage automatically (or artificially)to limit the current draw during the impedance dips. Hence the Krell will perform better in terms of dynamic punches whether I need them or not. IMHO, both schemes are fine for most applications that call for steady to high transient outputs, but the Krell will do better for applications that frequently call for very high transient power output.

 

[zumbo]

zumbo, I do frequent the McIntosh website. That's why I said in my last post that it was not hard to do to maintain the same power by simply droping (or varying) the voltage for load impedance between 8 and 4 ohms. So we are not disgreeing at all as long as we are talking about impedance between 8 and 4 ohms or lower. I cited the 16 ohm example just to echo what MDS was alluding to, i.e. the question: how can the same output be maintained regardless of the load impedance.

Anyway, like MDS, my vote goes to amps that double down even though I strongly suspect they all do it by under rating their 8 ohm outputs to certain extent (expectedly less so in high end products such as Krell). To me, a Krell amp that can do 250W 8 ohms, 500W 4 ohms is better than a McIntosh that does 300W 8, 4, or 2 ohms because the Krell will assure me that when my speaker's impedance dips low, the amp is able to maintain the voltage to deliver the needed current whereas the McIntosh will lower the voltage automatically (or artificially)to limit the current draw during the impedance dips. Hence the Krell will perform better in terms of dynamic punches whether I need them or not. IMHO, both schemes are fine for most applications that call for steady to high transient outputs, but the Krell will do better for applications that frequently call for very high transient power output.

Very interesting. And, thank you PENG, highfihoney, MDS, and others for your contribution and views to this forum.

So, how is it that Mcintosh retains their value, while others lose value?

 

[PENG]

Peng & mds,ive been using examples of amplifiers that incorpotate "autoformers" & "dynamic power management" circuits within thier design to control a vast number of things including the load that the amplifier see's from the speaker,from how i understand how they work they interact before the speaker load is seen by the amplifier making it a constant ohmage.

Here is a very brief explaination of the origional autoformer that mcintosh uses in their entire 2 channel amp line & is what i have in my amplifiers,buku info is available on different applications of these.

http://www.mcintoshlabs.com/autoformer.aspx

Here is another much smaller copy cat version made for use between speaker & amp.

http://www.enjoythemusic.com/magazine/equipment/0603/midmonth/zeroautoformer.htm

We are definitely saying basically the same thing!
By varying the voltage, like mcintosh does, one can achieve the goal of maintain the same output whether the load impedance is 8 or 4 ohms. My 16 ohm example is only cited to show one of the scheme's potential limitations.

It is the double down thing that I, and apparently MDS too, find hard to achieve (edited...) for reasons mentioned in previous posts. Larger transformers and capacitors alone won't do it.

 

[Seth=L]

It is the double down thing that I, and apparently MDS too, find hard to achieve without resorting to innovative/tricky ways to specify the output ratings. Larger transformers and capacitors alone won't do it.

Of course, everything has to be beefed up. Caps, power supply, all the parts of the output stage. Upgrading the power supply and caps would be like putting a massive engine and a turbo charger in a Geo and not upgrading the transmission and computer.

 

[zumbo]

It is the double down thing that I, and apparently MDS too, find hard to achieve without resorting to innovative/tricky ways to specify the output ratings. Larger transformers and capacitors alone won't do it.

So. Krell, Parasound, and others are FOS?

Look at it from my POV. I have 4ohm speakers with a peak input of 180W. I could purchase a Krell, Bryston, or Parasound 125W amp and kick butt. However, any of these amps will also double their distortion.

Now, I can get a McIntosh 200W amp that maintains it's power @ 4 ohm. And, not only does it deliver a true 200W, it does it at it's rated spec of .005 distortion. I tell you, this is what SQ is made of. And, why they command a premium resale value, along with mobile amps in my past.

 

[highfihoney]

Very interesting. And, thank you PENG, highfihoney, MDS, and others for your contribution and views to this forum.

So, how is it that Mcintosh retains their value, while others lose value?

There are quite a few reasons mac gear retains its value with the most important reason being lifespan,ive got mac gear in the attic thats over 40 years old that i havent even looked at in a couple years but i know its plug & play when i want to use it.

The lifespan of the product far exceeds any other amp on the market,the same features that make the amp able to hold its ratings also drasticaly add to the lifespan of the amp,you cant overheat or short out a mac amp,you can short out every connection on the amp at once & nothing will happen.

No mac amp to date has become outdated or unservicable,you can get parts for every amp mcintosh has ever made,a owner will never be left hanging with broke down gear,the glass face plates play a large roll in resale,as long as somebody didnt smack the glass hard enough to break a 0.5 inch thick face it will look like new 20 years from now & they do too,the lettering will never rub off .

Another reason is that the style that some people say is outdated,its easy & fairly cheap to add or upgrade your mac gear without dropping a wad on this years model,a mac from 1977 looks like a mac from 2007,some like it some dont but the basic looks stay the same & dont follow trends in audio.

Mcintosh dont play model games like most other big amp manufacturers,take a look at pass labs to see a company out of control,every year they come out with some new & costly upgrade to amps that cost the buyer thousands of dollars only to find out next year the manufacturer (improved)the design,this is not the case mith mac,they make a model & keep it in the line up for years.

Other than the extremely long lifespan the biggest reasons are the sound and performance that stays constant throught different models & new technology,their isnt a bad model mac amp that has garnered bad press from owners,unlike pass,krell,audio research,conrad johnson where people say that one model is good while another model is to be avoided,by keeping the basic design a constant they have avoided all the hype concerning models.

I know that to some i sound like the posterboy for mcintosh but i have owned,bought & sold a flat out ton of mcintosh gear over the years & from owning & talking with a ton of owners & buyers alike they all cite these reasons as to why they buy mac & are willing to pay the price,these are also my reasons.

 

[PENG]

So. Krell, Parasound, and others are FOS?

I am quite confident that Krell and Parasound are true to their specifications, but for them to do 100% (splitting hair) double down I guess the 120V supply voltage would have to be held constant. That being said, if you have a 20A dedicated circuit and the the outlet is not too far from the main panel, then their double down spec shouldn't be far off. I don't know what FOS means but in trying to make a point I went a little too far in saying that people use innovative/trick ratings. If I could edit my post I would.

As for mcIntosh's high resale value, why not, they are well built like a tank, reliable, great looking and sound great. Just because I prefer a Krell that doubles down to a mcIntosh, does not make the mcIntosh a lesser amp. Actually for preamp I prefer the mcIntosh and am still planning on getting one sooner or later.

By the way, do you really think Bryston's (4BSST) slightly higher distortion for 500W into 4 ohms matters that much?

< 0.005% 20Hz to 20kHz at 300 watts into 8 W
< 0.007% 20Hz to 20kHz at 500 watts into 4 W

 

[zumbo]

I am quite confident that Krell and Parasound are true to their specifications but for them to be able to 100% (splitting hair) double down I guess the 120V supply voltage would have to be held constant. That being said, if you have a 20A dedicated circuit and the outlet is near the main panel, than their double down spec won't be far off. I don't know what FOS means but in trying to make a point I went a little too far in saying that people use innovative/trick ratings. If I could edit my post I would.

FOS means full of $#!t. You did say tricks. Looks like fact to me.

As for mcIntosh's high resale value, why not, they are well built like a tank, great looking, reliable, and sound great. Just because I prefer a Krell that doubles down to a mcIntosh does not make the mcIntosh a lesser amp. Actually for preamp I prefer the mcIntosh and am still planning on getting one sooner or later.

If you have the funds to give the power needed at lower distortion, why not? Looks like a good enough reason for the resale value, along with all the other things mentioned.

By the way, do you really think Bryston's (4BSST) slightly higher distortion for 500W into 4 ohms matters that much?

< 0.005% 20Hz to 20kHz at 300 watts into 8 W
< 0.007% 20Hz to 20kHz at 500 watts into 4 W

Looks like the percentage of power achieved equals the percentage of distortion. So I ask, if 500W is what is needed, wouldn't an amp that produces 500W constant be ideal. I mean, it is proven that even an 8ohm speaker dips down. As it does, distortion goes up. But, not with a McIntosh. If the speaker needs 500W, the McIntosh delivers it. Clean. True. Without a doubt. No worries.

Everyone knows, as the volume knob goes up, the music looses it's detail. Why? All things mentioned. But, if the amp maintains it's composure, the detail remains as well. This, I believe, is the reason for the value.