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Benchmark ABH2. This is the new test equipment on the bench.

tomchr

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Ideas about what is going on with the wavy looking left side of the plot?
That's most likely the SSID broadcast of your WiFi getting into the measurement.

Tom
 
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DualTriode

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Hello Tom,

That is a good insight.

I suspected the ARRIS dual band WiFi thing sitting here but I would never have given the name SSID.

Things did clean-up with the addition of the new NEUTRIK SpeakON's and change to Canare Quad Star test leads.

Tom thanks

DT

Tom,

Just for fun I have one of your HP22 amplifiers and power supply sitting her to try an assortment of cords and loads to see how low I can get the THD+N.

DT
 

pma

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That's most likely the SSID broadcast of your WiFi getting into the measurement.

Tom

I measured the same shape when testing opamps, with some BJT opamps. Why only with BJT and not with JFET input opamps, measured simultaneously? I accept it might be the SSID broadcast, however rather resulting in input RFI rectification/demodulation than "getting into measurements". As we both know, BJT input opamps are about 1000x more prone to this.

from ADI "Hardware and Housekeeping Techniques"

1629531921697.png
 

tomchr

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That's why I use EMI/RFI filters on the inputs of my products.

Tom
 
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DualTriode

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Hello All,

Thinking out loud about measurements:

I believe that the speaker conductors should be the best quality. The measurements should be taken at the connection point between the speaker conductors and the speaker. The speaker conductors are an extension of the amplifier output.


Now that I have test load resistors that measure better than -140dB’s for 2nd, 3rd and higher Harmonic Distortions at 8R and 5 Watts, I am going to take a close look at several sets of speaker conductors. Yes it is a sure bet that the amplifier manufactures would rather take measurements at the amplifier and leave the cords out of the measurements. It is my view that there will always be conductors between the amplifier and the speakers on the other side of the listening room and should be included in the measurements. Please, comments from @JohnYang and @tomchr.

I am not looking for magic conductors, just constructed well and with minimal impedance. There will be 5 different types of speaker conductors in my hands is a week or so;

  • 2 conductor #12 AWG SJOOW cord.
  • StarQuad Canare 4 #14 AWG cords wired as StarQuad. The equivalent of #11 AWG 2 conductor cords. (Some claim a shielding effect.)
  • 4 conductor #14 AWG SJOOW cords wired the same as Canare StarQuad. The equivalent of #11 AWG 2 conductor cords.
  • CAT 5 internet cable. (Just because there is a 1000 Foot roll sitting here. Some say that they like it.)
  • 2 conductor #14 AWG zip/speaker wire. (Who knows, the cheapest may be the best or as good as the rest.)
Thanks DT
 
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DualTriode

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Hello All,

Same test conditions;

8 Ohm Vishay RH50 4, 17 Ohm RH50 wire wound resistors in parallel.

Except the speaker wire is 2 conductor 12AWG SJOOW rubber cord. My wife says that the cord smells like a tire store.

The performance is unchanged from the 14 AWG SJOOW 4 conductor cord.

Thanks DT

Screenshot (7).png
12 AWG FFT Spectrum.png
 
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DonH56

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Passive Intermodulation (PIM) is a big concern with things like test loads (among many, many other components). Years ago I had to go to ridiculous lengths to build a suitable 50-ohm test load for a precision DAC (16 bits, then) so it was not the limitation of my measurements.
 
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DualTriode

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Hello,

Today while I was hooking things up and warming things up I did notice that this test load setup had 6 to 8dB's lower distortion, both 2nd HD and 3rd HD were well into the instrument noise floor.

EDIT: As things warmed up the 6 to 8dB's lower distortion improvement disappeared.

I also noticed that the 4, 50 watt RH-50 resistors with 1.25Watts dissipated by each of the 4 were sort of warm to touch in the palm of my hand.

I suppose the load resistor(s) will be better at staying cool if they are attached to a largish heat sink.

There are possibly still improvements to make with this load resistor.

Still at better than -140dB's this load resistor(s) is off the chart good.

Thanks DT
 
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tomchr

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faraday cage lol
Yeah. Faraday cage and feed-through capacitors. Any wire entering the cage is an entry point for RF. Both from the hole necessary to get the wire through and from the wire itself. Recall antennae are just as good at picking up signals as they are at radiating them. :)

Tom
 
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DualTriode

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Hello All,

Yesterday I received a roll of 4S6 Canare QuadStar 4 conductor 20AWG speaker wire. While waiting for 4-pin XLR connectors to test with the A30Pro (handful, of pure watts) reference headphone amplifier I hooked up a SpeakON on the end of a 6 foot length of the 20AWG speaker cable.

On the other end was the usual 8Ohm speaker test load. At 5 watts output with this 20AWG speaker;

There was a drop in 2nd HD

There was a slight increase in 3rd HD

There was a few parts of a dB increase in SINAD

There was a few hundredths of a volt increase in voltage drop across the 6 foot length of the 20AWG speaker cable.


There are a handful of 4-pin NEUTRIK XLR connectors on their way from Mouser next week to test this speaker cable with the Topping A30Pro headphone amplifier.



Thanks DT
 
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DualTriode

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Hello All,

Still waiting on the Canare 4S11 speaker cable.

Meanwhile I have soldered some Neutrik XLR plugs on a length of Mogami Neglex 2534 microphone cable.

It does take some time to prep the cable ends and solder on the XLR’s. I have found that you can purchase the very same already assembled Mogami cable with the very same Neutrik XLR’s at Amazon under the brand name Worlds Best cables. The Amazon shipping is free.



The Worlds Best Cables are cheaper than purchasing the parts.



Thanks DT
 
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DualTriode

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Hello All,

Yesterday the Canare 4S11 speaker cable arrived.

I will attach the SpeakON plugs today and give the new speaker cables a test drive later.

Thanks DT
 
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DualTriode

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Hello All,

I have tested several types and brands of speaker cable.

So far my preferred cable is 2 conductor SJOOW rubber with Neutrik SpeakON plugs. The SJOOW cord is soft and flexible, plus it is waterproof if I want to test speakers out on the damp deck out in the trees in the backyard.

In terms of performance I like the 11 and 12 AWG cords equally well. I do not see any standout differences in the THD+N or SINAD measurements. See the attached plots for the Canare 4S11 10 foot long speaker cable. The test resistor is the same 4, 33R Vishay Dale RH-50 50 watt wire wound in parallel for 8 Ohms total.

Thanks DT

ABH2 5 watts 8R 4S11 canare speaker cable FFT.png
Screenshot (14).png
 
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hwest

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View attachment 146215
Hello All,

I have been eyeing this Benchmark ABH2 power amplifier for several months. This last week I went over the edge. The big brown truck delivered it yesterday. The APx1701 test amplifier is not going away just sliding over to make room.

The AHB2 is cooled without a fan which is a huge plus. The goal is to get rid of the instrument cooling fans that may be adding noise to my speaker measurements.

The plan is to share the literal ins and outs of all the connections, microphone placements and the like. There is an assortment of load resistors and heat sinks coming next week. Also still to be purchased are “sense” resistors to measure voltage drop and calculate driver impedance phase and Thiele Small Parameters (included in the APx500 software)

I have some accessory Speakon cables that need to be fabricated.

First off will be testing of the Benchmark ABH2 with load resistors, the idea here is to test the amplifier with an assortment of different types of load resistors. Perhaps there is a difference among the load resistors?

There are a couple of 500 Watt cheap elevator braking resistors of unknown thermal coefficient (ppm/degree C) that need to be tested with the amplifier. I am thinking that at 5 watts, the standard test around here to test the THD+N and SINAD, that I do not expect to see much heat caused distortion caused by the cheap 500 nominal Watt resistors. Any guesses about THD+N and SINAD?

Thanks DT
For someone new to test equipment where would we recommend starting to get professional results for testing audio equipment so we can see evidence of good sound vs an ear on good sound? How much am I willing to spend, well that's TBD.
 

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For someone new to test equipment where would we recommend starting to get professional results for testing audio equipment so we can see evidence of good sound vs an ear on good sound? How much am I willing to spend, well that's TBD.
Evidence of "good sound" is still subject to debate because the other side of this is the "audibility" of measured signals. Personally, I don't believe external electronic equipment (other than DSP driven room correction and crossover/driver optimization) above a certain grade makes a huge difference, other than offering tone controls. If everything within the electronic chain between source and speaker does its job, which is passing the signal to the speaker, the the sound "should" sound similar, but it does not. You have purposefully designed distortion from tubes which is arguably preferable to many listeners - so what's "good sound" now?
 

hwest

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Evidence of "good sound" is still subject to debate because the other side of this is the "audibility" of measured signals. Personally, I don't believe external electronic equipment (other than DSP driven room correction and crossover/driver optimization) above a certain grade makes a huge difference, other than offering tone controls. If everything within the electronic chain between source and speaker does its job, which is passing the signal to the speaker, the the sound "should" sound similar, but it does not. You have purposefully designed distortion from tubes which is arguably preferable to many listeners - so what's "good sound" now?
It's so hard to train your ear to know and understand what qualifies as great sound, there definitely is arguments these days that the old school sounds with noise are good. However, I like to do my comparisons against what you would actually hear in real life and the more detail, clarity, separation and range you hear should tell you something for those that understand. When you go to hear someone with a powerful, exception voice or playing an instrument that is what you should be listening for in your system. It's soo hard to train your ears for this but when you are extremely anal about sound you start to understand all of these concepts between what is good and bad without the debates in the middle regarding measurements. Of course we can't ignore measurements to a certain degree, they do matter to a certain extent.

I don't think there has ever been a scenario where I have stood beside a person that understands audio while listening to a great sounding system vs something not quite as good and disagreed as we seem to always come to the same conclusion when you know what to look for. We hear the term the sound feels alive, yes that's because it's reproducing as if it were alive, too often these days I hear the big box claims but they simply don't cut it. Denon, Marantz, Pioneer, Arcam, Yamaha, Anthem, Lexicon, and now Onkyo has fallen into that same category but I'm hoping they can produce another winner like the PRSC-5530 with updated features. I'm just not feeling it guys, it's not there no matter how much we convince ourselves otherwise. I seem to be lucky to have found a great combination of components that sound as good as the heavy hitters and now that have just enough test equipment to validate some things, I'll stay there until I hear something better.
 
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hwest

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Evidence of "good sound" is still subject to debate because the other side of this is the "audibility" of measured signals. Personally, I don't believe external electronic equipment (other than DSP driven room correction and crossover/driver optimization) above a certain grade makes a huge difference, other than offering tone controls. If everything within the electronic chain between source and speaker does its job, which is passing the signal to the speaker, the the sound "should" sound similar, but it does not. You have purposefully designed distortion from tubes which is arguably preferable to many listeners - so what's "good sound" now?
There is also a heathy debate on OLED/MiniLED/QLED, IPS vs VA panels, etc. :) As you have been saying on Youtube :) The white screen test shows a ton on this subject, not to get off topic but the MiniLED's from LG do have issues with inconsistencies clouding, etc. I have tested just about every model. I can't bring myself to go with a Samsung as they pretty much act as large heating elements in your house (VA Panel drawbacks). :)
 
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