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PostPosted: Tue Jun 27, 2017 5:41 am 
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I was reading Roger Sanders whitepaper recently and he's saying that, with little investment we could measure our amplifier frequency responsable and by using a spectrum analysez see second and above harmonic.

I'm trying to figure what's the equipment needed tout complet the task.

Let say that I own a picoscope 2204A usb scope with software.

What do I need next and how do I wire everything?


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PostPosted: Tue Jun 27, 2017 7:22 am 
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It's all done with the picoscope and software.
Best to read the online manual.

Gary

Gonna need a dummy load also.


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PostPosted: Tue Jun 27, 2017 7:35 am 
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sasquatch wrote:
It's all done with the picoscope and software.
Best to read the online manual.

Gary


Maybe IT will appears dumb, but I want to know what kind of probes do I need. How do I feed the frequency on the amplifier? With a usb dac since my amplifier only has RCA connectors. I guess I have to get a load connected instead if speakers.

I guess what I need is à step by step procedure to get everything done.


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PostPosted: Tue Jun 27, 2017 7:41 am 
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For audio frequencies you don't need special probes, but you will need the BNC connector and whatever at the other end (banana jacks?). Any wire will do. You'll also need a cable for the function generator...again, with BNC and RCA for the amp.

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PostPosted: Tue Jun 27, 2017 7:48 am 
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ripblade wrote:
For audio frequencies you don't need special probes, but you will need the BNC connector and whatever at the other end (banana jacks?). Any wire will do. You'll also need a cable for the function generator...again, with BNC and RCA for the amp.


Ok so with a two channel picoscope I'll use channel one bnc's to connect at speakers connectors, let say with banana plugs, to "capture" the frequency response. Then with channel two bnc's to connect to an RCA input I'll feed the signal. Do I understand correctly?

Then un order to prevent any speakers and hear damage, I'll add a dummy load made with a resistor (at least half the amplifier's power at same impedance.


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PostPosted: Tue Jun 27, 2017 8:03 am 
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picoscope has a built-in function generator which with appropriate cable will feed your amp the signal all done with the software.
It's a procedure I don't recommend for a layman so not step by step friendly.
One wrong move with a power amp and you just inherited a door stop.

Gary


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PostPosted: Tue Jun 27, 2017 8:06 am 
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Location: Montreal, QC, CA
Générateur de signal (BNC out) --> (RCA in) l'amplificateur à tester (sortie audio) --> (BNC in) oscilloscope

2 cables requis:
BNC à RCA
Fils dénudés à BNC

1 dummy load


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PostPosted: Tue Jun 27, 2017 8:27 am 
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technicien38 wrote:
Générateur de signal (BNC out) --> (RCA in) l'amplificateur à tester (sortie audio) --> (BNC in) oscilloscope

2 cables requis:
BNC à RCA
Fils dénudés à BNC

1 dummy load


Merci je t'ai envoyé un message en privé.


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PostPosted: Tue Jun 27, 2017 8:28 am 
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patate91 wrote:
ripblade wrote:
For audio frequencies you don't need special probes, but you will need the BNC connector and whatever at the other end (banana jacks?). Any wire will do. You'll also need a cable for the function generator...again, with BNC and RCA for the amp.


Ok so with a two channel picoscope I'll use channel one bnc's to connect at speakers connectors, let say with banana plugs, to "capture" the frequency response. Then with channel two bnc's to connect to an RCA input I'll feed the signal. Do I understand correctly?

Then un order to prevent any speakers and hear damage, I'll add a dummy load made with a resistor (at least half the amplifier's power at same impedance.
The 2nd channel is useful for checking phase relationships with a Lissajous trace but is not needed for spectrum analysis. Follow technicien38 recommendations.

High power dummy loads are expensive. If you test at high power the resistor(s) will get very hot, very quickly. You'd probably get more accurate distortion specs if you used your speakers as load instead, but you'd need to wear headphones as sine tones sound pretty awful. Also, your neighbours will probably complain lol.

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PostPosted: Tue Jun 27, 2017 8:35 am 
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Well, for a newbie I don't recommend testing with speakers on.
A bad/wrong setting with the generator and bye bye the tweeters... and also your ears.


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PostPosted: Tue Jun 27, 2017 8:50 am 
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technicien38 wrote:
Well, for a newbie I don't recommend testing with speakers on.
A bad/wrong setting with the generator and bye bye the tweeters... and also your ears.
All good points....

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PostPosted: Tue Jun 27, 2017 9:00 am 
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I use my amps with a frequency of two or three times a day! :mrgreen:


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PostPosted: Tue Jun 27, 2017 2:34 pm 
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EL34 wrote:
I use my amps with a frequency of two or three times a day! :mrgreen:

Ouch!. :lol:

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PostPosted: Tue Jun 27, 2017 3:26 pm 
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EL34 wrote:
I use my amps with a frequency of two or three times a day! :mrgreen:


I need more informations to accept your numbers!!! What's your protocole and which equipments you used? :lol: :lol:


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PostPosted: Tue Jun 27, 2017 6:28 pm 
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patate91 wrote:
I was reading Roger Sanders whitepaper recently and he's saying that, with little investment we could measure our amplifier frequency responsable and by using a spectrum analysez see second and above harmonic.

I'm trying to figure what's the equipment needed tout complet the task.

Let say that I own a picoscope 2204A usb scope with software.

What do I need next and how do I wire everything?


I don't think that it has enough resolution to see the harmonics.


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