Test Your Audio Amplifier With a Multimeter and a Smartphone

[@jungtarcph]

In the process of building the Akitika Z4 amp, thanks for the info! Greetings from Copenhagen!

[@ColtonFaulk-n1i]

I’m not going to lie. I laughed so many times during this video. I know nothing about electricity. But I do know that you are a very intelligent person, and I am trying to fix my system in my truck and although I don’t think I got what I needed from this video, I enjoyed it so much. I just sent it to my wife.

[@peterbulanyi1708]

Terrific instructional video. Thanks.

[@DruNicholsMD]

Please do create a video talking about gain in preamps vs amplifiers!

[@Neurochrome2010]

The measurement is the same, actually. Preamps just tend to have a wider range of gains. Could be anywhere from slight attenuation to 20-30 dB.

[@marekwaczynski3894]

Very easy to understand Thanks. So bridging input to ground is a must to measure DC offset. No excuses, right ?

[@Neurochrome2010]

Yep. The input must be shorted for a true DC offset measurement.

[@POLMAZURKA]

is the50 ohm for the genmerator in parallel,then with the load?

[@Neurochrome2010]

A feed-through terminator like the HP 10100C that I'm using in the video has the 50 Ω in parallel with the load. The load of the amplifier is 47 kΩ, so the 50 Ω terminator makes the generator 'see' 50 Ω.

[@ronchinoy]

Hi from India. I follow all your posts on diyaudio. And your web site. Where I have been stuck for the past 6 months is how to measure thd using rew or arta I have a dac I have a noisy China function generator and I have my phone with many apps to put out single or multiple tones I also have a datsv3 My real problem is my dac has an input but that input does not show up in windows datsv3 input does show up How about a video on this It would help if you mentioned what is an acceptable dc offset as well as how to tune it if ots off

[@Neurochrome2010]

I am planning a video on how to do distortion measurements on the cheap. So stay tuned.

[@mobilered2776]

Hi nice video. I need Ur suggestions to select digital multimeter use for servicing repair work for Amplifier , LCD DLP projectors , power supply....etc AVG or TRMS meter ?

[@Neurochrome2010]

Definitely a true RMS meter. The Fluke 70- and 80-series are really tough to beat and available calibrated for not much money on the used market.

[@ronchinoy]

Is it safe to short your input wire on all amps ?

[@BertKrus]

Thats what I really wonder too

[@Neurochrome2010]

Yep. Any amp can handle 0 V on the input and that's what a short-circuit provides. Often I'll use a 50 Ω terminator instead of a short, but either works.

[@jikim0916]

@neurochrome Awesome contents. Thank you so much for sharing. I just followed instruction and tested with my first DIY amp and DC offset is 0.9mV DC. However, Gain is something not right. when I play 400Hz wavetone RCA Male jack measures 1.15v and gain from speaker out is 0.003v which equates -50db gain (negative figure) based on the equation. How gain figure can be negative? (scratch my head)

[@Neurochrome2010]

Hmmm... Is the amp turned on? Sorry I couldn't resist. I would verify that you do indeed have 1.15 V out of the sig gen once it's loaded by the amp input. If the amp doesn't provide a higher voltage that its input, I'd make sure that the right input is selected and start debugging the amp.

[@daviddawkins1]

Thank you. This has really helped me. Much appreciated.

[@rogerwalter2500]

Can you please make a video on how to check oscillations in diy amps?

[@Neurochrome2010]

Great suggestion. Thank you. Which tools should I assume the builder has access to for the oscillation video?

[@rogerwalter2500]

@@Neurochrome2010 From what I have learnt, DSO is a must. I tried to check chipamp oscillations on a DSO(not mine) but couldn't understand what to look for

[@Neurochrome2010]

I'll see if I can get something together. Thanks for the suggestion.

[@anandshah71]

I have a Hypex MP252 amp that had gone defective. My friend whom is technical had mentioned use it onky for bass duty not midrange or highs How to test actually what’s the right way

[@Neurochrome2010]

You can test it following the procedure in the video. You can choose a lower frequency (say 60 Hz) if you'd like.

[@janetyer7147]

Liked and subscribed.

[@James-dt7ky]

I have that exact same Fluke meter sitting in front of me. :)

[@OneDamNote]

Play Fatboy Slim Funk Soul Brother in another tab and on this video here keep pressing 5, 6, or 3. Almost perfect match.

[@Eric48359]

You never showed how to do it with a phone and multimeter.

[@Neurochrome2010]

I explained how.

[@blueturtle7942]

My fluke went up to 20kHz.

[@Neurochrome2010]

Cool! Many of the cheaper DMMs won't go much past 440 Hz.