Powersoft K3, K20, M50Q (Part II)

Jan 13, 2011
222
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Pensacola
#1
Summary:

The processed Powersoft amps are among the finest products of their type in the world. Lab Gruppen's processed amps share that distinction. Crown's upgrade of the ITech's with the HD series put them in the running as well. Nobody else is home. I'm confident that these companies have accounting departments that tell them to stop the insanity and aim lower. I for one wouldn't be in this business if the passion for excellence that created these products wasn't allowed to the market.

What began primarily as a review of the Powersoft K3 and K20 with DSP and the M50Q amplifiers turned into something much more involved that required a great deal of learning. In regard to these Powersoft amps, my hat is off to you guys. These are amazing products. May 2012 prove to be a successful year for both Powersoft's and Italy's finances. Your country is responsible for many of the very best things our industry enjoys (not to mention AC Milan!).

Subjective comparisons of the sonic character of the amps under test including Powersoft's damping control and unique take on limiting are still ongoing.

Background:

When it comes to the very largest and very smallest amplifiers, it appears that switch mode is here to stay. These tests include some of the best examples in the world and while they sound very good, it is my opinion that some of the less efficient linear types, such as the Camco Vortex series, are still unrivaled sonically. The Camco's in particular can throw a three dimensional sound field between a pair of high end loudspeakers like nothing else I've ever heard from a touring amp. Even if my opinion on this is true, does it even matter for sound reinforcement? For me it does, but I'm a foolish person. My goal is to make every piece of the chain between the source and listener as good as I can possibly make it. And not go broke.

I do not like switch mode amps. The way they work offends the way I think. But their rate of progress sonically has been amazing and gives me hope. I think we may be at a mid-60's like point where folks like me were complaining about those new fangled solid state amps that sounded like a cat fight at HF's compared to a routine tube amp. Or again in 1982 when Sony released the $900 CDP-101 CD player (yeah, I bought the first one in Boone, NC) and folks like me held our ears and cried out for vinyl's revival - maybe via lasers reading the grooves to improve tracking and avoid wear. It never happened and now transistor playback of digital audio can outperform anything the older mediums could have ever achieved. Much of it is still truly terrible while enjoying great success in the marketplace - what's new?

What Powersoft and Lab Gruppen have done by tightly(1) integrating state of the art processing into the best amp designs in this category has resulted in sonics that are approaching my beloved Lake processors into linear amps.(2)

As a warning - I went through a phase in the late 80's with Mark Levinson solid state and Manley tube amplifiers, Martin Logan electrostatic and B&W 801 dynamic loudspeakers, illegal connections of large transformers to the service entrance of my house to provide split 60V "balanced power", mostly stupid cables, etc. I removed passive crossovers, terminated the sections with resistors, measured crosstalk issues with Doug Rife's MLSSA, physically separated the crossover sections, redesigned them with Peter Schuck's XOPT, turned adjacent inductors 90˚, drove smaller drivers with tube amps, bigger ones with solid state, etc. I have stories, many hugely embarrassing. It is now my goal to offer a semi-educated version of this madness to larger audiences.

Overview:

Anyone familiar with the Lake and Crown DSP control software will immediately recognize some of the beauty of the former and the operational simplicity of the latter in the Powersoft software. To be fair to the Lake, it's ability to control multiple processors simultaneously with a single software interface that allows unified personalities of subsets of those processors, including subsets within individual processors, is unparalleled to my knowledge. With the Lake, processing is carried out in "modules" and these modules can be used anywhere in a networked system to do anything Lake processing is capable of. You'll notice this modular schema in the leading installation processors now, which highlights how far ahead of the curve Lake has been. That kind of flexibility necessary requires software that can make use of it, thus for some it can appear a bit complex at first. Anyone dealing with this level of product should have no complaints IMO.

Fundamentally it is difficult to make powerful DSP systems user friendly and Powersoft has done one of the best jobs I've seen. The only thing that was difficult for me to figure out was how to do the simple stuff - import or export one or more presets to/from the amplifier. The manual didn't provide much help in this area. This is fascinating because the software control of the sophisticated portions of the amp were extremely straight forward. Another complaint is that there is no way I'm aware of to view which preset is currently running on the face of the amp. The information that is readily available there is the best I've ever seen: voltage and current output, temperature, supply voltage, etc., all kinds of things. It is quite slow uploading presets from a computer to the amp, but all the control functions within the software proper whether you're connected to the amp or not respond very quickly. Other things I'd like to see improved is the addition of a 2 second ramp up to full volume when the amp is turned on, the elimination of the HF click when turning the amp off, and a 2 second ramp down then up when switching presets live. At present, if you switch a preset with audio running, it'll mute, let a brief moment of audio through, mute again, then switch audio on under the new preset. Not pretty. No doubt Powersoft doesn't expect such silliness from its end users, but in the heat of combat audio anything can happen.

The Powersoft DSP reasonably takes a bit more of an amp-centric approach to processing that fits my needs perfectly. Each channel of the amp has a huge number of input parametric filters that can have independently adjustable skirts similar in concept to the Lake's Mesa filters, and 16 output parametrics that can take on all kinds of personalities, such as 2nd order all-pass filters. The output adds high/low pass filters that can be standard IIR or linear phase FIR types. A key reason I wanted to demo the Powersoft DSP amps in the first place was the ability to import FIR coefficients that allow you to roll your own filter universe. This is the magic that EAW and Fulcrum Acoustic does with different specifics toward a similar objective: to reduce that stuff coming out of the loudspeaker in the acoustic domain that wasn't part of the source in the electrical domain. Hopefully direct import of FIR coefficients will eventually become possible with the Lake processors.

Testing Notes:

All DSP is entirely bypassed (in the case of Powersoft), or with all functions off in the case of the IT8000. Although I'm not sure why anyone would want to bypass the amazing DSP in the Powersoft amps, the ability to route the input directly to the amp and completely eliminate the DSP latency is one of those simple-brilliant ideas I've never seen before. All maximum output tests were conducted with 4Ω resistive loads on both channels (only channels 1 and 2 on the 4 channel M50Q).



Due to a fixed input voltage design, the M50Q and PL380 amps were powered with 120v. The K3, K20, IT8000 and FP14000 were powered with 240v. Everything about running large amps at 208v and especially 240v makes more sense than 120v. My power source was a 75' run of 10 AWG 4-wire cable connected directly to the single phase service entrance of my shop. This is a reasonable simulation of a best case power distribution rig and was quite stiff. Very little voltage drop even with the IT8000, which seemed to dim the lights the most under stress. Powersoft's execution of power factor correction seemed to dim the lights the least and the non-PFC FP14000 was in the middle. Real measurements of amplifier efficiency are not hard to make with the right equipment, but I'm not motivated to do that yet. Powersoft released an interesting PFC white paper that includes comparative measurements between the K10 and FP13000(3).



All clip limiters are engaged to simulate probable use and because it isn't possible to disable the clip limiters on all amps. Even when it is possible, it's still nearly impossible to get any of these amps to flat top a sine wave due the other protection mechanisms the user has no control over. The days where you can turn a sine wave into a square wave with a large amp seem to be over, which is a good thing but makes testing a bit tricky. Looking for the 1% THD threshold to determine max output won't always work either because some amps won't even let you go there. Therefore you have to keep an eye on both THD and the compression of the output signal. Compression of 1dB ends the show per the suggestion of Bruce Hofer of Audio Precision.(4) I stopped increasing level at the 1dB compression threshold or when the next 0.1dB stimulus increase saw a spike in distortion in either the THD or magnitude traces.

This brings up a point that the great John Roberts has mentioned frequently in these forums - the subjective differences you hear between amps at or near full tilt is more due to the limiting methods employed rather than the heavily advertised aspects of class typology, etc. Lab Gruppen wrote a wonderful little amp testing article that included the following warning concerning listening tests: "The purpose of clip limiters is to prevent serious clipping in the power amplifier. Clip limiters always reduce the peak power of the amplifier. The problem with clip limiters is that even at low listening levels there can be transients which trigger the clip limiter. Yet the user is unaware because the indicator is to slow to indicate it. For this reason and for the reasoning that all clip indicators per manufacture will light at different rates it is important to set all amplifiers with or without clip limiters engaged. To run one amplifier with and one without, will only compare the sound of the clip limiter itself and not the amp."(5)

Switch mode amps to one extent or another output a small component of their 200kHz+ switching frequencies regardless of input. You obviously can't hear this and your drivers and passive crossover components can't reproduce it. The problem is that in order to make high quality low noise measurement gear at the audio frequencies, the input electronics are necessarily limited such that these very high switching frequencies cause all kinds of trouble, mainly slew based distortion. It's a physics thing, so you can't thrown money at it with high slew rate input electronics that are magically low enough in noise. The only way to deal with it is to filter out these above-audio frequencies before they reach the test equipment. The AES covered this in regard to measuring D/A converters in its AES17 standard. Same issue, different application. I read everything I could find on the subject and never saw any "before and after" measurements illustrating this effect, so I did my own. I found articles describing that it was a distortion issue, and why, and an instructive and embarrassing manufacturer slapdown of a clueless reviewer.(6)

I couldn't have understood some of the most important aspects of Audio Precision's excellent discussion of the issues surrounding switch mode amp measurement without the help of the Syn-Aud-Con list participants. It was their input that opened the door wide enough for me to see what was going on. I was absolutely baffled at some of the early results I saw and Ray Rayburn, Pat Brown and Bill Whitlock among others turned the light on. Thank you. :)

The bottom line is that even the best passive high voltage low pass filters made for this kind of testing necessarily (physics again) impart phase error to the test that should not be reported as an amplifier artifact. The best low pass filters (there are only two(7)) have no material affect on the audio frequency region and thus allow accurate magnitude and distortion measurements. Happily, accurate reporting of a switching amplifier's small signal magnitude, phase and noise can be made without the low pass filter, so we are able to measure everything.

It took me 30+ hours of error masquerading as measurement to learn that.

BTW:

I thoroughly expect to have made some errors myself in method and/or interpretation, though probably not in data. I'd greatly appreciate slapdown, correction or instruction in any regard. :)

Footnotes:
  1. By "tightly", I mean that they are able to monitor current, voltage and heat of the amplifier and use that information to do things that are wonderful and effectively impossible when using external processors.
  2. I love the high power and efficiency afforded by switch mode amps with everything under the midrange.
  3. PFC - Power Factor Correction, Powersoft S.r.l., circa 2005.
  4. Measuring Switch-mode Power Amplifiers, White Paper, Audio Precision, Bruce Hofer, 2003.
  5. Lab Gruppen, Testing Procedure, circa 2005.
  6. Limitations in Making Audio Bandwidth Measurements in the Presence of Significant Out-Of-Band Noise, Audio Precision, Bruce Hofer, 2005.
  7. Audio Precision's AUX-0025 and Chris Strahm's LinearX LF280 that I use.

(End Part 2a)
 
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Jan 13, 2011
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Pensacola
#2
Re: Powersoft Digam K3, K20, M50Q (Part 2b)

Switching Noise on the Output:

It seemed reasonable to have a look at the ultrasonic switching noise emitted by these amplifiers that gave me such fits during my initial measurements with and without 4Ω resistive loads. These high frequencies (typically >/= 10x the audio passband) are responsible for the measurement error in test gear designed for the lower audio frequencies as mentioned earlier. In contrast, the scope(1) is down 3dB at 60MHz and laughs at the slew rate required to measure 1/4MHz switching frequencies. The scope was connected at the end of a 12' 14 AWG cable connected to the amp. This cable is either inserted into a 4Ω load resistor or not. The amps that show a marked reduction in switching voltage with the 4Ω load attached have a relatively high source impedance at those frequencies, which is a good thing. These amps may be able to use a loudspeaker load to effectively finish the job of squelching the noise.(2)

The time scale (X axis) is constant for all amplifiers. The voltage scale (Y axis) is 200mV per division for all but the M50Q which apparently uses less filtering on its output. More noise does not necessarily indicate a poor design from an audio point of view, but many introduce EMI approaching the AM radio band. It may be best in terms of raw efficiency for the manufacturer not to add any filtering on a switch mode amp's output, in other ways the ideal is to allow absolutely nothing on the output other than a larger version of what is seen on its input. Engineering draws a line somewhere between these two points to satisfy competing goals, most of which are beyond my knowledge to comment on.

A final observation is that many switch mode amps employ a gating feature that eliminates the switching noise when no signal is present after a short period of time. The reason for this apparently is to meet some RF friendly specification when the amp isn't doing anything. These measurements were made without the gating engaged. BTW, it's wise to keep your RF racks away from racks with Class D amps.

K20, K3, M50Q:



FP14000, IT8000, PL380:



Transfer Functions:

These were made at 8Ω (blue trace), 4Ω (red trace) and 2Ω (pink trace). Note that for convenience I used a single pair of a 12' 14 AWG quad cable from the amps to the junction of the load resistor. That formed a slight voltage divider with the 12' amp cable to load resistor. When I combined all four wires of the quad cable to drop its effective wire gauge to 11, you can see a 0.1dB improvement. Another slight improvement could be made by measuring directly at the amps' output terminals, but that would be a pain and wouldn't highlight the point that loudspeaker cabling forms a passive attenuator on the output of your amp, particularly into low impedance loads. More on this later.

14 AWG vs. 11 AWG Amp Cabling:



K20 Transfer Functions:



K3 Transfer Functions:



M50Q Transfer Functions:



FP14000 Transfer Functions:



IT8000 Transfer Functions:



PL380 Transfer Functions:



Footnotes:
  • Fluke 192C ScopeMeter.
  • Then again, maybe not. Most loudspeaker systems do not have a 4Ω impedance into the MHz region, but probably something more on the order of 600Ω or so.
 
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Jan 13, 2011
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Pensacola
#3
Re: Powersoft Digam K3, K20, M50Q (Part 2c)

Long Term Tests:

Last time I posted an amp review Ivan "old school" Beaver fussed at me about not socking the poor things with continuous sines. I thought I'd do that in addition to improving a short term test that better indicates what the amp can do in its intended application. This was going to be a quick no-brainer: 20Hz, 100Hz, 1kHz, 10kHz, 20kHz at clip then done. That was the plan. Nothing doing, it turns out that amp manufacturers have figured out that a continuous sine wave is more likely to be an error at the input than anything related to music and takes appropriate action - limiting, protect, tripped breakers, shrieking fans. The first second or so of the sine near the amp's maximum voltage will get through and then it'll be forced downward a few dB or more. So what to report? The initial let-through or the limited output or something in-between? The first would effectively be another short term test, the second simply reports the limiter's behavior, and the third is too subjective. I'd given up on Ivan if it weren't for ARTA's STEPS module that allowed me to develop a test that is reasonably long term (3.7 sec on / 2.3 sec off) and removes the subjectivity from the measurement. It also allowed me to simply recreate a longer version of the CLIO based gated sine bursts that make sense to me given the intended application of an audio amplifier (music as opposed to welding). I call this long term test the i^2Test (pronounced "Ivan's-square-test") contrasted by the cool Apple-like lettering. :)

You'll notice that I chose four frequency intervals that simulate the sub, low, mid and high passbands. This is more interesting than a straight 20Hz - 20kHz max output test in that it reveals where the amp's strengths and weaknesses are such that it may help in selection for your application. These frequency intervals were used for both long term and short term tests.

In my last amp review I mention that I'm done with watts. The Y-axis of the max output tests are in dBu RMS voltage units regardless of what it says. I used reference calibration in the measurement software to achieve this. Since the stimuli used in all measurements were sine waves, the RMS nature of the measurements mean that the amp was actually delivering 3dB more than that in peak voltage. Another way of stating this is that sine waves have a 3.01dB crest factor. Voltage makes SPL. Watts makes heat. If you have an amp that can produce 2dB more voltage than another amp, that will result in 2dB more SPL. This assumes the loudspeaker can handle the additional voltage and do so without material increases in voicecoil resistance through heating.

Actually, the results of the i^2Test were interesting - it's always interesting to see how amps handle abuse far beyond the nature of their intended application. It doesn't really give a proper feel of "dynamic headroom" when compared to the short term tests because it's just too harsh compared to anything approaching the RMS nature of music. On a positive note, it made the 32 gallon SuperBucket™ containing a triatomic thermal inertia compounding agent so hot that it steamed. I have discovered that ARTA, the K20 and the SuperBucket™ make the most expensive clam cooker in the world. Given that the total cost of ARTA and the bucket are less than $200, that's sort of like saying the combined assets of Bill Gates and myself are enormous. I suppose cooking temperature could be regulated by modifying the tone burst sequences.

The SuperBucket™:



Triatomic Agent:



The following measurements were made with the STEPS module in ARTA at 1/6 octave intervals with approx. 3.7sec ON, 2.3sec OFF.

K20 Max LT Output:



K3 Max LT Output:



M50Q Max LT Output:



FP14000 Max LT Output:



IT8000 Max LT Output:



PL380 Max LT Output:



(End Part 2c)
 
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Jan 13, 2011
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#4
Re: Powersoft Digam K3, K20, M50Q (Part 2d)

Short Term Tests:

I used CLIO's "slow" gate sine burst module measure the amps' short term maximum output capability. "Slow" in this case means the longest stimulus period available (green trace). The period used varies between about 12ms and 14ms down to about 250Hz and then transitions to 4 wavelengths under about 160Hz. Audiomatica calls these periods the "meter on time". When you see small zig-zags in the THD traces, it's generally due to these small transitions in the stimulus burst period, not artifacts within the DUT.

CLIO Stimulus Burst Period or Meter On Time:



I have found this a magnificent tool for finding the peak output capability of loudspeakers in all passbands and it coincides perfectly in the subwoofer region with what I consider the reference standard: Don Keele's 6.5 cycle tone bursts. This module also changed the world for me in finding the ideal limiter settings for any given amplifier/loudspeaker combination.

K20 Max ST Output:



K3 Max ST Output:



M50Q Max ST Output:



FP14000 Max ST Output:



IT8000 Max ST Output:



PL380 Max ST Output:



(End Part 2d)
 
Jan 13, 2011
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Pensacola
#5
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Powersoft Damping Control:

This is so unusual that I've devoted a special section to it. Wouldn't it be lovely if you could, say, drive a subwoofer array with a net nominal impedance of 2Ω with a 100' 14 AWG cable and have it sound the same as if it were at the end of a 10' 4 AWG cable? That was what went through my mind the first moment I heard of this feature, the next moment brought: So… What's the Catch?

Crown released a cool amp called the "Delta Omega 2000" in 1983 with "active control for the speaker voice coil". Otherwise known as an adjustable feedback loop from the amplifier's output to input to simulate a negative resistor. This is done in an attempt to offset the loudspeaker cable resistance, voice coil resistance and heating, or maybe just for fun to do the opposite and turn your tight, low distortion horn loaded subs into sloppy sounding direct radiators for a DJ! Infinite damping factor or none. Simple huh? How many amps do YOU know on the market that have this feature? Like dude, if this makes my subs sound better, I'll just turn that little knob more and more and it'll sound better and better AND smoke. Runaway oscillation. This is one of those simple concepts that obviously is not so simple to execute.

Powersoft's damping control works by sensing output current and returning a calculated voltage back to the DSP's input. It's basic I*R = E from Ohm's Law that uses the resistor value you select (range +/-2 Ohms) to multiply by the actual current the amp delivers to its load. Very clever. When you engage the damping control feature you'll notice that a 400Hz low pass filter is inserted regardless of resistor size selected. The longer wavelengths probably make the unavoidable latency (this is DSP) of the feedback loop much less of an issue and reduce the potential for oscillation. Only the LF passbands really benefit from this sort of thing anyway.

The following measurement is not at all indicative of the effect this damping control feature will have on a real loudspeaker. This measurement is into a flat resistance, nothing like the typical double-humped impedance curve of a direct radiator subwoofer. What this measurement shows is that the voltage adjustment does in fact respond directly to current flow into the load. The general idea is that you add a negative resistance value into the Powersoft amp that equals the positive resistance of the cable. The amp will then output more voltage to regions of the passband in proportion to current flow. Since it follows Ohm's Law, it works. The amp will run out of voltage swing the same as before, but the sonic contribution of the cable will be gone. Technically this is very cool, but I do wonder if the market may have become used to what they hear now and not like the cable-less sound. TBD.

K20 Damping Control Transfer Functions into Fixed Resistances:



Harsh Reality:

You cannot overcome the laws of physics with clever engineering, only politicians are able to do this. This cool feature can allow you to achieve the SONIC characteristics of a short loudspeaker cable run, or no cable run at all, or even of a much longer cable than is being used. Nevertheless, you will still have voltage division going on due to the actual loudspeaker cable resistance in use and you are still throwing away output with that resistance.

Application of Harsh Reality:

Keep the round-trip loudspeaker cable resistance down to about 5% of the voice coil(s) resistance you're driving, which will limit cable losses to less than 1/2dB. Practically speaking, using 12 AWG 2 wire cable will allow a 50 foot run to a 4Ω load, twice that into an 8Ω load and half that into a 2Ω load. With subs use all four wires of the NL4 cable. Paralleling each pair of wires will obviously cut your resistance in half, it also drops the effective AWG by 3. Typical 14 AWG 4 wire cable used in this way is equivalent to an 11 AWG cable. Your amp racks and subs will need to be wired appropriately of course.

FIR Filters:

The quantity and power of the processing available in both the Powersoft and Lake products are a dream come true for the loudspeaker designer and end user. Both offer loads of parametric EQ with independently adjustable skirts. Both allow multiple input filter "pages" that I find useful for separating preset personalities relating to HF absorption compensation, etc. Both have 2nd order all pass filters. There are differences in implementation that are well thought out on both sides, but it would take months of experience with the Powersoft amps for me to comment in depth. My bias is that the Lake is the standard by which all others are judged and the Powersoft processing is a very serious competitor. One significant advantage with the Powersoft processing is that it allows direct FIR coefficient download for manufacturers to implement processing characteristics that are impossible any other way. Powersoft makes both EAW focusing and Fulcrum Acoustic TQ processing available in this way. It is the future and it's about time. :)

Powersoft chose to make its user selectable FIR filters a mid to high transition tool with a fixed latency of about 5ms. The Lake also allows for crossing lows to mids while staying within useable latencies for live sound (generally </= 10ms). Keep in mind that in the following measurements the Powersoft traces are through an amplifier while the Lake is a stand alone line level processor only. An interesting note that some (or many) Lake users may not be aware of is that the control software doesn't always show differences between FIR filter skirts at different latency selections. I've noticed this with the 8th order LR shaped FIR filters at lower frequencies, such as with the 250Hz filter measurements below.

Powersoft 400Hz:



Powersoft 2.5kHz:



Lake 250Hz:



Lake 2.5kHz:



(End Part 2e)
 
Last edited:
Jan 14, 2011
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Tel Aviv - Israel
#6
Re: Powersoft K3, K20, M50Q (Part II)

Thanks Langston,

Amazing test drive. I chimed in just to let you know that it's possible to see the preset name on the amp display. Its done by navigating to the display menu (on the front panel) and setting the "amplifier name" to "on".
 
Jan 13, 2011
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Pensacola
#7
Re: Powersoft K3, K20, M50Q (Part II)

I chimed in just to let you know that it's possible to see the preset name on the amp display. Its done by navigating to the display menu (on the front panel) and setting the "amplifier name" to "on".
Sure enough. :)

Powersoft chose an interesting thing to do with this "amplifier name" thing. When enabled, the preset name will flash on the screen for 1 second and then the ampere histogram will return for 3 seconds, then cycle back to the preset name, etc. That works, but is a little distracting.

What I'd prefer is that they allow an option to have the preset name on the bottom line where the legends are for the hardware buttons directly below the screen. Once you press one of the buttons, the legends would reappear instead of the preset name. Then have the legend display timeout after 5 seconds and go back to the preset name.
 
Sep 27, 2011
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New York
vibrantsoundz.net
#8
Re: Powersoft K3, K20, M50Q (Part II)

Just seeing your constant praise for the Camco Vortex 6 amplifiers makes me want to hold on to my own 2 for a while longer which is what I think i will do.. thanks again for the information and the time taken to do the testing..
 
#10
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Crown released a cool amp called the "Delta Omega 2000" in 1983 with "active control for the speaker voice coil". Otherwise known as an adjustable feedback loop from the amplifier's output to input to simulate a negative resistor. This is done in an attempt to offset the loudspeaker cable resistance, voice coil resistance and heating, or maybe just for fun to do the opposite and turn your tight, low distortion horn loaded subs into sloppy sounding direct radiators for a DJ! Infinite damping factor or none. Simple huh?
(End Part 2e)
great writeup langston. very informative. i had to glom onto the discussion of the almighty Delta Omega. what a great amp. the sound company i cut my teeth on used those for all the low end and subs in the shop. tweaking the feedback circuit for each show was just part of the charm. we kept a tweaker screwdriver in the workbox just for that task. good times. good times. 'course they were mono and weighed approximately 457,000 pounds. but big fun. when we finally replaced them with QSC Powerlights a part of me died. although my back was not of the same mind...
 
Jan 13, 2011
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#12
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Hi Brian:

Cool story - thanks. :)

This is a sport of passion for most of us and that's where much of the joy is found. I pity those who have audio as a mere vocation because there are many other ways to barely make a living that involve far less effort.

Ad copy from 1983 that you'll enjoy.
 

Bennett Prescott

Just This Guy, You Know?
Jan 11, 2011
10,840
7
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Wallingford, CT
www.bennettprescott.com
#13
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Hey Langston,

Do you have any subjective listening impressions to report? Especially of the active damping control? I'm kind of curious whether the amp did or did not meet or exceed your expectations for performance and sound quality.
 
Jan 13, 2011
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Pensacola
#14
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Hey Bennett:

I'm short on labor and long on shows lately.

Overnight reindexing of my accounting database lists my worldwide full-time workforce count at 3. One has been out on tour with one of my systems for a few weeks and a second just made a good decision after some back issues to exit the industry in favor of rational behavior. Too bad too - he was wonderful. That leaves me with one guy who is one of the best drummers I've ever heard and a great LD, but I need to be on the shows for the audio.

We have a Tuesday - Thursday out of town event this week, so tomorrow will allow some time for more experimentation with the amps after show prep. Friday should sew it up and allow me to post. I'll also be ready soon to post my review of the Fulcrum FA12, FA15 and FA28's. It's pretty disgusting so far - having a tough time finding something I don't like.
 
#15
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Hey Bennett:

I'm short on labor and long on shows lately.

Overnight reindexing of my accounting database lists my worldwide full-time workforce count at 3. One has been out on tour with one of my systems for a few weeks and a second just made a good decision after some back issues to exit the industry in favor of rational behavior. Too bad too - he was wonderful. That leaves me with one guy who is one of the best drummers I've ever heard and a great LD, but I need to be on the shows for the audio.

We have a Tuesday - Thursday out of town event this week, so tomorrow will allow some time for more experimentation with the amps after show prep. Friday should sew it up and allow me to post. I'll also be ready soon to post my review of the Fulcrum FA12, FA15 and FA28's. It's pretty disgusting so far - having a tough time finding something I don't like.
Hey Langston,

I'm ready to head down to FL whenever you need me!

Jeff
 
#16
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Hi Langston,
Congrats! This a an amazing job and, believe me, I understand how long it takes to run such tests.
It’s fun that the superbucket is something very similar to what we used at the early design stage to run power tests on K20s, it works perfectly until it does not get hot… then getting rid of 100lt’s of boiling water is not so much fan at all.
Regarding the Damping Control, it would be interesting to have your comments on the sound behavior.
Actually, on Kseries Damping Control is proposed as a “cable compensation” but this is coming from another world of processing, that is called IPAL IpalMod | amp-modules | products
In this deeper application, the possibilities of changing the output impedance of the amplifier is merged with the full control of the acoustic domain.
Not only Qes of the driver variations are possible. I guess this would sound interesting to you.
Very very cool job, again

Claudio

Powersoft S.r.l. Italy R&D Chief
 
Apr 8, 2011
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#18
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Great stuff Lang! All your power tests were done at 4 ohms? Both channels driven? So the biggest amp at low frequencies was K20 with 44dBu short term (3763W for us old school guys) and long term 42dBu (2376W)? Of course these powers double if 2 ohm.
 
Jan 13, 2011
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Pensacola
#19
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Hi Brian - I knew you'd be interested in this. :)

All your power tests were done at 4 ohms?
All maximum long term and short term power tests were into 4 ohms.

Both channels driven?
Into 4 ohms, yes.

So the biggest amp at low frequencies was K20 with 44dBu short term (3763W for us old school guys)…
Yes, but:

1. The short term test was 44.2779dBu or 4,021 watts into 4 ohms.

2. The amp's clip limiter was engaged during testing. It would have certainly shown more voltage swing with it off. The amp is rated at 5,200 watts per channel into 4 ohms or about 1dBu more than I measured.

…and long term 42dBu (2376W)?
A little more than 42dBu, but it outperformed every other amp in this testing and did so with an ease (fan speeds less than full) that made it obvious that it would have done very well into 2 ohms. This is the best LF amp I'm aware of.

Of course these powers double if 2 ohm.
Not exactly of course, some voltage drop occurs but not much. The K20 is rated at 9,000 watts per channel into 2 ohms. With the clip limiters off, I wouldn't be surprised if it achieved that. Both the FP14000 and K20 seemed quite comfortable in both the short term and long term max tests into 4 ohms. It was obvious that both had quite a bit more cooling capacity remaining for full tilt 2 ohm operation. In contrast, the M50Q, IT8000 and PL380 fans seemed to be at full throttle during the 4 ohm long term testing.

One observation on the cooling design of the Powersoft vs. Lab Gruppen amps is that to achieve a given thermal transfer rate, the former takes a more active (fan based) solution, whereas the latter uses high quantities of thin copper fins (much higher heat transfer than aluminum) in a more passive approach. Passive cooling has always been the more expensive path but generally allows quieter operation for a given efficiency. Powersoft has wisely chosen squirrel cage type fans that can achieve very high air flow with reduced fan tip speeds (tip speed is proportional to noise output). I noticed that the Powersoft fans are very carefully regulated as well, they immediately adjust for the load involved - very little lag time. I'd guess that it senses the current the amp is delivering, thus anticipating heating instead of simply reacting to it.
 
Apr 17, 2011
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#20
Re: Powersoft Digam K3, K20, M50Q (Part 2e)

Taken from the servic manual...

To keep the amplifier between the correct range of working temperature the KSeries amps has two fans controlled by NTC sensors and microprocessor.The fan working state is: The fan speed rises up when the amplifier internal temperature rises
- About half second full speed run at power up.
- Without input signal with an environmental temperature of 18°-20° the fan does not run
- Low speed run when the amp reaches about 30°C.
- With environmental temperature at about 18-20ç and standard music program the amplifier internal temperature should be about 40°-42° and the fans should run at about 1/3 speed.
If one of the fans does not run (faulty fan or fan blocked from any external object) with environmental temperature of about 18°-20° and standard input signal the amplifier internal, temperature stabilizes at about 55°C.
At about 55°C amplifier internal temperature the fans should run at about half speed, at about 85°C they should run at full speed. If one or both the fans are not working (for a fan fault or fan blocked from any external object) it's possible to have an amplifier over-temperature in few minutes.​
Franz
 
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