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Crown XLI1500 a modern day staple?


jwc
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So I recently purchased a used McIntosh MC-150 amp and my initial plan when I purchased it was to run it off my Yamaha avr pre outs. But my thoughts are changing. This Mac is so clean, so full bodied, so effortless. Absolutely NO noise feeding it straight from my DAP. And the Mac has yet to work hard, I can't seem to get it to heat up feeling overhead. 15 watt peaks is loud!

So I'm thinking a 2 amp/one pair of speakers switcher. AVR for movies and multi channel, Mac for straight 2 channel. The Mac with a really good recording like Diana Krall Love Scenes.....you close your eyes and it sounds like the instruments and Diana are in the room performing for you. It's magical.

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24 minutes ago, polizzio said:

Its all about that first couple watts, the amplifier/avr noise floor. So I recently purchased a used McIntosh MC-150 amp and my initial plan when I purchased it was to run it off my Yamaha avr pre outs. But my thoughts are changing. This Mac is so clean, so full bodied, so effortless. Absolutely NO noise feeding it straight from my DAP. And the Mac has yet to work hard, I can't seem to get it to heat up feeling overhead. 15 watt peaks is loud!

So I'm thinking a 2 amp/one pair of speakers switcher. AVR for movies and multi channel, Mac for straight 2 channel. The Mac with a really good recording like Diana Krall Love Scenes.....you close your eyes and it sounds like the instruments and Diana are in the room performing for you. It's magical.

 

Nothing worse than to sit down with a system that someone  wants you to hear, they hit the power and you're immediately put off from an idle hiss while they're picking out some content to play.   Its like a hair in your soup, its just doesn't go away. And right when things are running along nicely you get this really black rest in the track and there it is again.   No one knows how much silence makes a difference, you add a truly treated room to the equation and suddenly you're hearing parts of a track you never knew were there for past decades.

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19 minutes ago, Max2 said:

 

Nothing worse than to sit down with a system that someone  wants you to hear, they hit the power and you're immediately put off from an idle hiss while they're picking out some content to play.   Its like a hair in your soup, its just doesn't go away. And right when things are running along nicely you get this really black rest in the track and there it is again.   No one knows how much silence makes a difference, you add a truly treated room to the equation and suddenly you're hearing parts of a track you never knew were there for past decades.

 

Even if there is zero hiss at low volume, some low cost amps emit (audible noise level) @ higher gain levels. I had a Crown xls 1002, ran it bridged 4 ohm for a sub, claimed 1100 watts bridged @ 4 ohm load. But if you pause the input and crank up the amp gain, you could hear the hiss, from about 70-80 gain to max. But it worked well for the sub and just bear in mind to keep the gain < 80%. For the price of admission, it is good. This Mac, pause the input crank up the volume and nothing. Its rated @ .005% @ its rated output, not 10 watts or 50. There is a reason why an amp rated @ 150 wpc 2 channel weighs 60 lbs. Well designed/executed class AB amp.

 

I was also thinking about a Peachtree Amp500. 500 wpc @ 1% thd right from their specs. Sure if you operate it < 200 wpc it should be very clean. Most of the Crown xls series are rated @ .5% thd @ rated max output. Some amplifier manufacturers play games with their published output/distortion data. I've seen some publish their noise #s at maybe 10 watts output. Read super low#s, but not @ rated output. Might fool a few. Bottom line is your ears at the end of the day.

 

I remember reading info and reviews about First Watt amps. Excerpt from their web page “The first watt is the most important watt.” There is a lot to be said for 5 or 10 very clean watt output, especially with very efficient speakers.

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1 hour ago, Max2 said:

 

Nothing worse than to sit down with a system that someone  wants you to hear, they hit the power and you're immediately put off from an idle hiss while they're picking out some content to play.   Its like a hair in your soup, its just doesn't go away. And right when things are running along nicely you get this really black rest in the track and there it is again.   No one knows how much silence makes a difference, you add a truly treated room to the equation and suddenly you're hearing parts of a track you never knew were there for past decades.

Amen. I learned about hiss 35 years ago when I bought a new Carver M400. IIRC, it was a new product at the time. 

 

Got it home and hooked it to my LaScalas..."What the hell is this hissing sound?" 🥵.

 

After conferring with the dealer, I ended up taking it back and exchanging it for the Power Line One. Worked great for 35 years. Hope the XLi1500 lasts that long too. 😁

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5 hours ago, babadono said:

Part of the reason is as well as a power input transformer it has 2 output transformers.

 

Perhaps those are the "autotransformers" Mac refers to? 

I'm still learning about this amplifier, and its technologies. Below is an excerpt from its owner's manual:

 

"The use of 6 complimentary connected output transistors per channel, allows not only full
power output into normal loads, but extra high current output to drive uneven speaker loads.
Some speaker designs have impedance characteristics that may dip to as low as 1 or 2
ohms at certain frequencies. It is possible for the MC150 to deliver as much as 50 amperes
peak current into these lower impedance loads.
The MC150 provides this extra current output with complete reliability due to the use of
Mclntosh Sentry Monitor protection circuits. Some power amplifier manufacturers have
claimed that their products do not use protection circuits since they compromise performance.
The real genius of Mclntosh engineering design has recognized these potential
problems and completely eliminated them. Properly designed protection circuits assure you
an amplifier that will operate under all types of user conditions with maximum reliability and
freedom from possible speaker or amplifier damage. The benefits of these designs mean you
own an amplifier that will continue to operate safely for many years.
The MC150 output is so distortion free, it is difficult to measure with conventional instruments.
The performance limit is 0.005% maximum distortion, yet it is typical for an amplifier
to measure less than 0.002% at mid frequencies."

 

50 amperes of peak current....I'm guessing very briefly, but that is a massive release of stored energy. And its performance data does not change be it a 2, 4, or 8 ohm speaker.

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It does have different "taps" for the 2 or 4 or 8 ohm speaker, correct? That means it is going through an output transformer (autotransformer). Whatever you call it, its a chunk of iron and has significant weight. That was my point.

Love Mac equipment. I had an MC2105 paired with my LaScalas back in the day. Unfortunately it got stolen (bastards). Then life happened and I have not been able to afford their gear since.

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41 minutes ago, babadono said:

It does have different "taps" for the 2 or 4 or 8 ohm speaker, correct?

 

Yes sir, gold plated spade terminals. Broke out some spades instead of bananas :) 

 

I ordered a spade to female banana plug adapter from amazon to make it quick and easy to disconnect my existing speaker wires but its gold plated spade is way too large (.520" width) for the Mac terminal. In retrospect I'm thinking it was made for speakers with no banana plug receptacles from the factory. 

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43 minutes ago, babadono said:

I had an MC2105 paired with my LaScalas back in the day. Unfortunately it got stolen (bastards). 

 

That is just so wrong. They should be apprehended and lashed in the public square. This is my first Mac piece.

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On 1/31/2020 at 12:36 PM, BobRiff said:

Sweet!  Please let us know what you think of them.

 

The amps arrived in one day after ordering from Sweetwater. Seems like a nice small company, customer service contacted me to make sure all was good and to answer any questions.

The amps are heavy and seem solid. Using these in my HT, one to drive Quarter Pie bass bins, the other to drive the rear pair of speakers. They both are doing a great job and are nice and quiet.

Happy I followed this thread for sure!

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2 hours ago, tromprof said:

 

The amps arrived in one day after ordering from Sweetwater. Seems like a nice small company, customer service contacted me to make sure all was good and to answer any questions.

The amps are heavy and seem solid. Using these in my HT, one to drive Quarter Pie bass bins, the other to drive the rear pair of speakers. They both are doing a great job and are nice and quiet.

Happy I followed this thread for sure!

 

Sweetwater's service is about the best I've seen.

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On 1/31/2020 at 11:23 AM, polizzio said:

 

I remember reading info and reviews about First Watt amps. Excerpt from their web page “The first watt is the most important watt.” There is a lot to be said for 5 or 10 very clean watt output, especially with very efficient speakers

I have to laugh when I read this. When I bought a Radio Shack Peak Power LED meter for my Khorns, there was a -20 db attenuation switch on it. The peak value could be 200 W or 2 Watts. I used 2 watts most of the time and PEAK values of 10 Watts on the LED meter, was Too Damn Loud! So basically, you will never reach the full peak of this amplifier at any normal listening level for RECORDED music. Even on symphonies, the "crest factor" is only 17 db, so when you start with about 50 milliwatts (typical average on a Khorn, Jube, MWM, Quarter Pie, etc. bass sections) for nomal listening, this represents a Minus 7 DB WATTS, with ZERO DB Watts being 1 Watt output. Add another 10X that 1 watt, and you can see you will never need more than 10 Watt peaks for live sounding symphonies.

 

PWK used to frown on high powered amplifiers, but when I went to his house, he had a BGW 100 Watt/ch. amp as his main, and Half of a Crown D60 or D75 for the center Belle. Why di he go against his prior recommendations of 10 W tube amps?????

 

Because of the lower Intermodulation Distortion in them, as discovered by Dr. Matti Otala of Finland. PWK was a fan of his work and put his money there.

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  • 4 months later...
On 2/2/2020 at 1:40 PM, ClaudeJ1 said:

Even on symphonies, the "crest factor" is only 17 db, so when you start with about 50 milliwatts (typical average on a Khorn, Jub, MWM, Quarter Pie, etc. bass sections) for normal listening, this represents a Minus 7 DB WATTS, with ZERO DB Watts being 1 Watt output. Add another 10X that 1 watt, and you can see you will never need more than 10 Watt peaks for live sounding symphonies.

 

A visual on the "dB watts" scale that I plotted ("dB watts" on the vertical axis, amplifier rated watts output on the horizontal axis).  Once you get to 80-100 watts/channel, the dB watts scale really flattens out.  Increasing the amount of power beyond this point reaches the point of diminishing returns very quickly.  This is one reason why loudspeaker efficiency is a big deal.  Inefficient loudspeakers simply can't accurately reproduce wide dynamics in recorded music due to this logarithmic effect of how we hear...

 

image.png.c197f597048cbf0e5b833ba1b218536b.png

 

On 2/2/2020 at 1:40 PM, ClaudeJ1 said:

Why did [PWK] go against his prior recommendations of 10 W tube amps?????  Because of the lower [transient] intermodulation distortion [TIM] in them...

In the mid-to-late 1960s up to about 1980, large amounts of negative feedback used in solid state amplifiers was there to compensate and linearize the output of the amplifier--instead of designing an amplifier having more inherently linear output without feedback (NPN transistors were generally not available then to match the PNP transistors that were available then, etc., so circuit workarounds were used to build usable SS amplifiers back then).  This is the root cause of TIM at that time in SS amplifiers. 

 

Since then, the design of SS amplifiers and devices (FETs and bipolar transistors, etc.) has progressed to the point that much less negative feedback is needed in order to linearize the voltage input-to-output gain curve of the amplifier.  So the problem of TIM in SS amplifiers is really an issue with those early SS amplifiers, which did sound harsh and opaque back then. 

 

Chris

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2 hours ago, Chris A said:

Since then, the design of SS amplifiers and devices (FETs and bipolar transistors, etc.) has progressed to the point that much less negative feedback is needed in order to linearize the voltage input-to-output gain curve of the amplifier.  So the problem of TIM in SS amplifiers is really an issue with those early SS amplifiers, which did sound harsh and opaque back then. 

The biggest offenders were the "quasi complementary" designs. I built a pair of Southwest Technical Products monoblocs when I was 20 years old. I had a Scott Tube Integrated amplifier (pre amp and power amp together) which sounded sweet and I noticed right away that 250 W  SWTP amp did NOT sound as good. But I needed the power for my DJ Gigs. As soon as I could afford Dynaco Kits, I built those and they sounded much better. When I got Khorns, after selling off my Big Bass Reflex Altec/EV monsters for Khorns, I also sold the 200 WPC amps and built some 75 WPC kits...........................followed by Hafler DH-220 kits after I got LaScalas for my DJ Gig Setup, which were operated by my 2 brothers without a single failure for several years until I sold them. I still have the smaller Dynaco and it still works over 40 years later.

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ChrisA,

 

The curve you posted is a perfect visual to my points. I have always hoped that the Audio INDUSTRY would rate their amplifiers in DB Watts, but I think the Marketing Folks will never allow it.

 

This reminds me of my film photography days, where Kodak made an ad showing a model sitting at a table and lit by a Single Candle!! Grainy Picture, but everyone who didn't understand went "wow." In reality, a photographer could have done the same shot with Kodachrome 25, an f/1.4 lens, and a tripod. The difference between ISO 100 and ISO 1,000 is only 3 1/3 stops, very similar to DB watts where you are using Logarithmic numbers that look less impressive. Same applies to Watts vs. DB Watts.

 

This is why I used to laugh when reading specifications concerning AVR's. Where each successively more expensive models touted more Watts!! As if the difference between 75 or 90 Watts made much difference. Especially to horn guys. It was the FEATURES that sold me years ago, not the stupid watts. Now that I have a small living room instead of a loft inside of a huge space for Stereo and HT, I'm optimizing my power amps to have about 10 DB Watts less than before in the big loft.

 

Now I use Pre Pro's so I can buy FEWER watts for my 100 db/Watt (and higher) speakers. Even Klipsch owners don't fully realize this, and still insist on buying way more watts than they need just because they are cheap and available. Either way, pretty much all amplifiers sound good today, and watts don't make that much difference except for LIVE Sound!!

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  • 1 year later...
On 4/29/2017 at 4:22 PM, John Warren said:

 

The idea was to develop an active bandpass filter for any bass horn (say a Klipschorn) that's otherwise impractical to realize using passive components.  The XLi is low cost, has excellent %THD below 1kHz, is class AB and lends itself to the mod.   The actual filter is text book Sallen-Key, very easy to implement in the small signal section of the amplifier.  In the schematic, the filter is outlined in red.  I've placed it between the input op-amp (U2) and front panel pot comprised of R35, R44 (pot is at full CW).  The schematic shows just the small signal processing of the XLi.  U1 is the gain amp, U3 is the error amp. 

 

The response plots shown are small signal simulations that are possible using cascaded Sallen-Key filters.  The PC board for the filter is installed vertically sharing a couple of the mounting screws used to mount the amplifier board to the chassis.   By implementing a 4th order bandpass in the small signal domain the amp drives the Klipschorn to work within its horn loaded range.  The horn loaded range is where it makes the best sound.  

 

 

 

XLi1500_band_pass_HF_response.jpg

XLi1500_band_pass_LF_response.thumb.jpg.294109ab25986d68478e11e7983fb2e2.jpg

XLi1500_band_pass.jpg

Good day John Warren. i have been following this thread over crown xli amplifiers. I have an xli 3500 i am working but am having challenges. Can you please share a full picture of the bottom image so i can do further troubleshooting.

 

thanks in advance

Edited by elsaint1990@gmail.com
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