magtech amps?

[CDMC]

Yes I’d like to integrate the rythmik F12G subs. I measured my room without the subs here:

https://sound.stackexchange.com/que...-two-sources-as-a-function-of-dis/48677#48677


You can see from my naive question there that I didnt even know I was detecting comb filtering. I also did some waterfall plots that highlight the need for bass traps in the corners, Frequencies below 50hz seem to last significantly longer than all others. However, the Freya. + preamp does not have a dedicated pair of sub outputs. Although that doesn’t really matter from the subs point of view (it has a built in crossover to exclude frequencies above 120 hz) Rather, I would like to spare having to drive the salon2s at the low frequencies.

Just my thoughts, looking at your room in the link you provided; there are others that know far more than I do that may chime in:

1) As you found, run your measurements on one speaker at a time. Your measurements don't show the bass range or the waterfall which helps a lot.
2) Don't expect in a domestic environment to get great decay times in the bass. It takes a huge number of large bass traps and/or targeted frequency absorption (i.e. Helmholtz absorbers, tuned membrane traps) to have a meaningful effect below 100hz. Not to worry however, as using a distributed bass array and DSP can address 95+% of bass decay and resonate issues.

3) Your room appears well proportioned to spread the bass modes out. It is much longer than wide and the sloped ceiling spreads out the floor ceiling modes.

If it were my room, this is what I would do:

1) Do not add more room treatment. The drapes and carpet you have may already be overly absorbing the high frequencies.
2) Try moving your subs. For two subs, the best starting position is generally with them opposing each other in the middle of the sidewalls or front rear. Quarter wall placement may work well also. Take a look at this article. https://www.audioholics.com/subwoofer-setup/multiple-subwoofer-setup-calibration-1
3) Depending on your listening levels, you may want to consider two more F12Gs which will 1) help further smooth room modes, and 2) keep up with the Revel's at louder levels if you crank them up.
4) No matter what you do, you are going to have an issue when the subs are further from you than the main speakers that they will always be behind the mains by one or more cycles. This is not a huge issue, but can only be corrected if you use DSP.
5) Get a crossover and relieve those Revels from the distortion creating bass. If you are using XLR connections, the DBX223xs works great. If you are using RCA, HSU sells an excellent 24db octave crossover.
6) If you really want to step it up, as I mentioned above, get the Anthem or Mini DSP, and replace your current USB/Coax adapter/DAC/Preamp with a single unit. You will then have full control in the digital domain with crossovers and equalization, as well as adjusting the timing between your speakers and the subwoofers.
7) Buying the subs, MiniDSP SHD, and a pair of NC1200 amps will set you back $6,000 before you sell your old components. This is far less than the mono Magtechs and will net you a huge step forward in sound quality. If you want the really nice unit, spend another $2,000 and get the Anthem instead of the MiniDSP SHD. You are still spending far less for a greater improvement.
8) After you do all the above, get it dialed in, open your favorite beverage and enjoy an absolutely top notch full range system.

 

[Soundstage]

But does the miniDSP SHD have or will have Dirac Live Bass Management?
I believe it does not, and therefore it is not the best option for sub integration or is it?

 

[CDMC]

But does the miniDSP SHD have or will have Dirac Live Bass Management?
I believe it does not, and therefore it is not the best option for sub integration or is it?

Has: https://www.minidsp.com/products/streaming-hd-series

 

[anmpr1]

5) Get a crossover and relieve those Revels from the distortion creating bass. If you are using XLR connections, the DBX223xs works great.

My experience with the 223xs was not happy. I ordered direct from Harman. The 40Hz high pass filter switch on both channels was broken. It took me several weeks, emails, and four phone calls (with a threat to cancel my credit card purchase) before Harman would send me a return shipping label. Their after sales customer support was not very supportive.

That said, the actual crossover is simple, easy to use, ergonomic and flexible for what it is. Doesn't cost much.

FWIW, my advice based on experience is NOT to buy direct from Harman, but go to your local guitar store for the purchase. That way you can be assured of an easy money-back return if you get a 'bad' one, or if it does not fit your needs.

 

[CDMC]

My experience with the 223xs was not happy. I ordered direct from Harman. The 40Hz high pass filter switch on both channels was broken. It took me several weeks, emails, and four phone calls (with a threat to cancel my credit card purchase) before Harman would send me a return shipping label. Their after sales customer support was not very supportive.

That said, the actual crossover is simple, easy to use, ergonomic and flexible for what it is. Doesn't cost much.

FWIW, my advice based on experience is NOT to buy direct from Harman, but go to your local guitar store for the purchase. That way you can be assured of an easy money-back return if you get a 'bad' one, or if it does not fit your needs.

Yikes. I purchased mine through BH Photo, which is really good with returns. Fortunately, mine worked perfectly out of the box.

 

[skypickle]

Do you put it between dac and preamp or between preamp and amp?

 

[anmpr1]

Yikes. I purchased mine through BH Photo, which is really good with returns. Fortunately, mine worked perfectly out of the box.

Any store or mail order that is 'local' and actually has a staff you can work with is a better bet. Harman (dbx) uses a call center from who knows where for support. They seem to have a lack of coordination--something as simple as a return mailing label was too much for them. BH, Crutchfield, Sweetwater would no doubt be better for the individual retail consumer.

 

[CDMC]

Do you put it between dac and preamp or between preamp and amp?

I always suggest between the preamp and sub/mains amp. If you put a crossover before the preamp, you wouldn't be controlling the volume with the preamp. I know some people like loud bass at all times, but that might be a bit extreme.

 

[AudioJester]

Ok, so no measurements of this magtech amp available?

 

[skypickle]

Ok, so no measurements of this magtech amp available?

None that I can find. I guess someone smart could call roger sanders. I don’t know enough to recognize amplifier bs.

 

[AudioJester]

So how is this different to other "high end" audio sellers who claim big things with no data to share/prove??
Is it just a bunch of owners saying it sounds great??

 

[anmpr1]

Do you put it between dac and preamp or between preamp and amp?

Here's a 'mind game' for external crossover fans: Let's say you own one of the essentially distortionless DAC/preamps and your amplification is SOA with vanishing SINAD. Then you stick an average spec crossover in the chain. You've essentially 'polluted' your high purity signal.

Now, you can always say, 'Yes, it 'degrades' the signal with noise--at least on paper, but it's not audible'. OK. But in that case, why go to the trouble to buy the low noise gear in the first place?

When I placed a 223xs between my DAC3 HGC and AHB I can't honestly say I heard any sonic degradation. But that was the question I asked myself. In any case I sent the 223xs back due to a malfunction, and decided to use one of the DAC3 analog outs into the subs dedicated crossover. FWIW, my speakers roll off pretty fast below 50 to 60 Hz so I didn't actually notice that the stand alone crossover was beneficial. YMMV

 

[CDMC]

If you a

Here's a 'mind game' for external crossover fans: Let's say you own one of the essentially distortionless DAC/preamps and your amplification is SOA with vanishing SINAD. Then you stick an average spec crossover in the chain. You've essentially 'polluted' your high purity signal.

Now, you can always say, 'Yes, it 'degrades' the signal with noise--at least on paper, but it's not audible'. OK. But in that case, why go to the trouble to buy the low noise gear in the first place?

When I placed a 223xs between my DAC3 HGC and AHB I can't honestly say I heard any sonic degradation. But that was the question I asked myself. In any case I sent the 223xs back due to a malfunction, and decided to use one of the DAC3 analog outs into the subs dedicated crossover. FWIW, my speakers roll off pretty fast below 50 to 60 Hz so I didn't actually notice that the stand alone crossover was beneficial. YMMV

You have a bit of a special situation. Most preamps and amps have sn ratios in the 90db and below range, so the 94db sn and 106db dynamic range of the DBX are theoretically and practically not the weak link.

 

[kevinh]

Well this assertion of his isn't correct

A magnetic speaker presents a mostly resistive load to an amplifier, while an ESL appears mostly as a capacitor.

Since when have normal speakers been mostly resistive? Equally not all esl are just capacitors. Large phase angles can cause problems for amps wether the speaker is an esl or normal magnetic.

Im certainly not criticising the amps BTW, it's a good trait to be able to cope with reactive loads and have loads of current and power available. Important for normal and esl speakers. However I think some of the commentary just plays into the mythology that surrounds esl speakers and what is required to drive them.

I cannot speak to all ESL speakers, but I have owned Sound Lab ESLs, spoke with Roger West about the load they present to an amp (~1990) he stated that the A1's had an impedance of 50ohms around 100hz and 16 ohms @ 1khz dropping to 1-2 ohms @ 20khz, he said that the speakers looked a lot like a cap to the amp. That is who many SL owners prefer Atma Sphere OTL amps since they love the load they present to an OTL.

 

[pjug]

Are the Magtech monos using thermal trak transisitors? I am seeing stories of problems with these in magtech amps (also reading that Roger Sanders provided swift attention and service in such cases). Motorola discontinued the thernml trak, correct? I wonder if magtech is using something else now.
@restorer-john do you have experience with or thoughts on reliability of thermal trak?

 

[DonH56]

ESL loads: Different ESLs present widely variant loads to the amp. Of the current crop, Sound Labs are one of the most benign, Quads in the middle (until they go into protection!), and Martin Logan one of the hardest in the HF due to their very low (often <1 ohm) impedance. Martin Logans are all but one hybrids now, so the bass is actually an easy load for the powered models. In the past, if you look at Beveridge, Acoustat, Dayton Wright, ServoStatik (Infinity), KSL, Janzen, etc. they are all over the map with some very challenging and others not so bad.

SNR/SINAD: A noise floor or distortion component about 10 dB down in power (20 dBV) adds about 1% to the total if it is uncorrelated. How far down "other" signals need to be so that you don't care I could not say. 1% additional noise or distortion on a 100+ dB noise/distortion floor probably does not matter much in the real world. But if you have a 100 dB noise floor and add a component with 60 dB noise floor, then yes it will typically be dominated by the 60 dB source. To do a valid comparison you need to refer the noise to the same point in the signal chain, however, typically the input (input-referred noise) or output (usually of power amplifiers, more rarely of the speakers). A little noise at the input of a phono preamp, which may have 60+ dB gain to the speakers, is going to matter more than the same amount of noise at the output of the power amp where it is applied directly to the speakers. So there are some rules of thumb but you have to work it out for each system. And note the type and frequency of noise and distortion matters -- a bit of low-level noise at 20 Hz is much less likely to be heard than the same noise level at 1 kHz.

FWIWFM - Don

 

[Sir Sanders Zingmore]

There are a couple of photos of THD+N in one of the white papers: In the section where they discuss the use of spectrum analyser to measure their amps

to demonstrate, I have attached two photos of my spectrum analyzer showing the performance of one of my Magtech amplifiers.

The first one shows the distortion when there is insufficient bias to completely eliminate crossover distortion. You see the first 20 harmonics and their levels in small boxes above each harmonic (although it is hard to read the values in the pictures). The large blue box at the top of the screen shows the THD, which in this case is about a half of one percent.

The second photo shows the same amplifier with the bias adjusted to eliminate crossover distortion. You can see that all of the harmonic spikes above the 4th harmonic have disappeared into the noise floor -- they simply don't exist. The second harmonic is the highest, and even it is 99.6 dB below the reference tone. The 3rd harmonic is -102.4 dB, the 4th harmonic is -110 dB and the remainder are unmeasurable. The THD is incredibly low at around one thousandth of one percent.

The amp is being tested under the worst condition, which is at just 1 watt. This is tough because crossover distortion is a greater percentage of the total distortion at low power levels than at high power levels.

Also, the S/N will be much lower at high power levels as the noise floor is fixed and greater output will tremendously increase the magnitude of the difference between the noise and the signal. But even at this very low power level you see that the noise floor is about 118 dB below the reference signal. This is a very quiet amplifier.

 

[restorer-john]

@restorer-john do you have experience with or thoughts on reliability of thermal trak?

Not enough experience with them from a repair perspective. Very few commercial products I have seen with them in a failed state. In my opinion, once you stray away from standard pinouts (5 pins with TT trs- internal diode) and hybrid/semi hybrid devices, you end up with problems down the track when they are discontinued.

The Sanken darlingtons in a TO3P package seem to have stood the test of time however and have been adopted in mid range gear.

 

[pjug]

Not enough experience with them from a repair perspective. Very few commercial products I have seen with them in a failed state. In my opinion, once you stray away from standard pinouts (5 pins with TT trs- internal diode) and hybrid/semi hybrid devices, you end up with problems down the track when they are discontinued.

The Sanken darlingtons in a TO3P package seem to have stood the test of time however and have been adopted in mid range gear.

Thanks. The cases the owners have shared on the Magtech are amps idling hotter than they should be. The thermal tracking seems like a good idea, but I take it not as straightforward as on the face of it.

 

[AudioJester]

Thanks @Sir Sanders Zingmore

Someone needs to send one to Amir, so we can compare to other amps. It looks like it will measure well.