Audio Dummy Load V2 - Making the Dummy Load Smart!

Time for an update of the audio dummy load. Let's see if we can make it smart!

[@davidbishop5736]

Sam Hunter is correct. You will tie those separate circuits back together with your oscilloscope. Even if you use two scopes that are connected to a common grounding system, the chassis connections on those scopes back to ground will defeat your attempts to isolate the circuits.

[@Chrissy4605]

Having been trained to do rework soldering on extremely small solid-state packages like CPU's and other chips I was taught first and foremost use flux as it greatly aids in laying down solder. Second, use your soldering iron ahead of the path! For example, lead the pin you are about to solder. What you had done was follow the pin bringing the solder so much closer toward the last pin soldered. this made it easier to leave too much solder and create a high probability of a solder bridge.

[@Gerrit-Max]

That's actually a very good tip, thank you for that.

[@kardeef33317]

I checked eBay, Amazon and thier local distributor and all cost $60.00 +-$1.00 each for the kits. Figured people might want to know what they go for. Out of my price range but Great Video. Thanks again for another great video!

[@umajunkcollector]

i'l stick with my rad shak analog meters, they look kewl too

[@kgsalvage6306]

Definitely a little pricey! Especially for a kit. I'd pay $30US, but $120 for two is a bit much. I also have a diy with analog meters. Works good enough for now.

[@EdwardLehman]

A little solder paste works great on SMT components

[@bergiebee1]

Parts are on order, cant wait to build mine Thanks Tony

[@EJP286CRSKW]

50mVRMS at 220K OHMS, not Hertz. You should have applied flux before doing all those small adjacent pins. It stops the solder bridges from forming. Clean off afterwards.

[@stevec5000]

The price of the soldering station didn't go up on Banggood, it was always higher from China and cheaper from the US warehouse and when the US supply ran out it only left the more expensive option from China. My guess is the ones in the US were discounted because of having a power cord with an Australian plug and instead of shipping them back or whatever they just cut the price until they were all gone.

[@esnam6557]

This is a very neat upgrade. Thank you very mcuh.

[@Wil_Bloodworth]

So... what are you going to do when you need to test and amplifier that puts out > 50V RMS? Do you just use something different in that case or do you bypass these meters entirely somehow? OR... is this just a moot point since you don't plan on testing anything that puts out more than 78 watts into 8 ohms?

[@CoolDudeClem]

I have one of these pre-assembled in my box of odds and ends, never really knew what it was for though, I just used it as a spectrum analyzer.

[@baghdadiabdellatif1581]

Thank you. At 49:15 with 1 Watt at 2 ohm you should get 1.414 Volt RMS and 5.224 dBu and 30dBm, however on your spectrum analyzer screen it shows 83 dB at the main dB-meter. What is that 83 dB?

[@oneflatlander]

Looks like you'll be getting into optocoupler design to really separate the two channels to the scope(s).

[@sneakysnake109]

The not so dumb load! Lol. Very Nice!

[@pda49184]

Thank you for a really comprehensive tutorial Tony.. When I was messing around with rock band PA systems back in the 80's I wanted to add a spectrum analyser to the system until I realised it would cost me a months salary to buy one ! Just shows how electronics has moved on, and prices plummeted. (My wages never seemed to go up much after the 80's, ha-ha!). I did wonder if connecting a scope up to the system would compromise the isolation of your loads power supplies ? 73 ..G4RYO

[@antraciet]

Perfect solderwork!

[@antimaga856]

You mentioned not having to use a magnifying glass for the SMT capacitors. In your Soundcraftsmen power amp video, I noticed you had one. What model magnifier do you have/recommend? Really enjoy your thoroughness!

[@robertcunningham1542]

Great job but there can be one big potential problem. If the amplifier has a bridged output with plus and minus outputs when you hook up with both scope channels you are shorting them together to ground through the scope and signal generator. Which can cause big problems. I speak from experience on this, we were attempting something similar to this and we burned out several amplifiers and one scope channel before we realized what was happening.

[@xraytonyb]

That is an issue. The only way to avoid grounding both channels through the scope is to only test one channel at a time. Good catch!! Thanks for bringing this up!

[@esnam6557]

Maybe adding a diode to isolate the channels can solve the problem.

[@kgsalvage6306]

QUESTION on the grounding. You have the two separate power supplies to keep the channels grounds independent. If you have your scope connected to both channels, will it not ground them together through the scope? Just a thought. Pretty cool unit though. Is it working out good for you?

[@kgsalvage6306]

Sorry, I just noticed others have commented on this. I seen someone mentioned an octocoupler circuit to remedy the situation. If you do, please make a video on doing it. Thanks!

[@keithcoltron3171]

Hi Tony, could you please let me know where you obtained the Velleman VPA20's as I'm in the UK and according to the Velleman site there is no such thing, maybe available in the USA only?

[@tecnisdaimondm.g9321]

Excelente

[@chadhudson2046]

Awesome job!!

[@wesleypowers]

Tony- do you have a schematic available?

[@rusty1187]

Hey, Tony.... Do you have any idea what the refresh rate (sampling) is on these devices?

[@xraytonyb]

I haven't used them in a while, but they seem to work similar to the software RTA that you use on your computer sound card. I checked frequency accuracy and it made a fairly good representation of the signal. I thin they were intended for use in car audio installations.

[@rusty1187]

@@xraytonyb Thanks! I am currently collecting parts for my own build. I also wanted to say that i have been watching your "amps" video series, and you explain it in a way that is MUCH easier to understand than my electronics teacher did 45 years ago!

[@keithcoltron3171]

Hi Tony please ignore that request I've found it, sorry.

[@xraytonyb]

No worries

[@standishgeezer]

Sorry if these are dumb questions....Question 1: am I right in thinking that this unit, in itself, is NOT a dummy load and that you still need connect the device under test to either speakers or dummy load(s)? Question 2: The specs say it measures between 20Hz and 20kHz but the spectrum display only seems to start at 30Hz ...is that right? I initially thought these were too expensive (sellers quoting around £60) but I notice that, in the UK, you can buy direct from Velleman for £29.94 (including tax & shipping) www.velleman.co.uk/contents/en-uk/p335.html so I'm still interested.

[@xraytonyb]

I must apologize, as I may have caused some confusion with this video. This video is actually an upgrade to my existing dummy load (check out my previous video on that). I am still using the existing 8 ohm 300 watt non-inductive resistors as the load. The only thing I did was to upgrade the 10:1 divider network for the scope with one that is adjustable, so that I could get an exact 10:1 ratio. In addition, I added the Velleman audio analyzer modules to allow me to directly monitor the output power and spectrum. I wanted to show the assembly and operation of the modules in case anyone would be interested in building them for their dummy load. The power meter function is supposed to be accurate from 20-20kHz, but the spectrum display only goes down to 30 Hz for some reason. Bummer.... Thanks for watching!!

[@standishgeezer]

Thanks for your reply. I don't there is any need to apologise as I guess most of your viewers understood that is a 'monitoring' solution and that connection to a dummy load is still required. Just good, I think, that you have clarified. Best Wishes

[@esnam6557]

In fact the loads are shown clearly in the manual, section load connection pages 10 and 11, www.velleman.co.uk/manuals/k8098.pdf

[@bergiebee1]

Parts arrived now its scrapped Version 3 Grrr

[@umajunkcollector]

kewl whatmeter

[@adrongarretson6195]

73 back too you

[@Mikexception]

Since speaker is nothing common to resistor and has no predictable impedance it may be only considered fun with jumping harmonics. .

[@Stereosandotherfun]

What are you going to do with your old load hub? Be a shame to toss it out!

[@Stereosandotherfun]

I can dispose of it ....

[@xraytonyb]

I'm still using the resistors from the old load. As for the break-out box, I have a set of 2000 Watt non-inductive load resistors for really high power amps that i am going to use it for. Thanks for watching!

[@coldfinger459sub0]

Definitely what I was looking for I like to build tube headphone amplifiers and small tube or chip based amplifiers low wattage headphone amplifiers are in the mA usually not over 1 W. Small amplifiers by Nelson Pass at pass labs, diyaudio.com or Pete millet, I just finished building his NuHybrid amp using Kong Nutube dual 6p1, pmillett.com I want a way to Measure Millli watts seen improvement in spectrum analyze as I modify and tweak the board with different capacitors and resistors values and voltage. Would Also want to measure the improvement from the power source switching from a switch mode wall wart power source to building my own linear power supply for the headphone amp