Testing amp fit dc

[farflungstar]

Ok so I'm an idiot I admit it, but can I check if there's any DC output coming from an amp by connecting a multimeter to the outputs?

[struth]

Yup, you could put a meter across it should be very little dc normally.mv,s i would think. Often it gives hum if youve got any.. unlikely to be both channels tho.

[farflungstar]

I just received the hiraga from Jake, and I'm 100% confident it was OK when he sent it but just want to check it after it's long journey before connecting it to my ANe's.

[struth]

Try a spare set of speakers if youve got any. Unlikely to have developed a speaker destroying fault in transit tho. Wouldnt run a tube amp with no load, certainly not for long ..wouldnt be likely good for the transformer or tubes unless it has protection.

[fatmarley]

It's good practice to measure DC offset when you receive a new amp.

Here's a good guide: LINK (http://audiokarma.org/forums/index.php?threads/amplifier-distortion-dc-offset-and-you.5634/)

My Onix oa21 has 5mv on one channel a 10mv on the other. It was higher but I matched the transistors.

[farflungstar]

Thanks for that link.... Will whip out the multimeter....

Adey

[dantheman91]

Hi Guys

This thread has inspired me so i bought a multi meter - which setting does it need to be on to check for DC current?

Novice here sorry...:scratch:

I want to check my Cambridge P40...

I Read the instructions :lol: - DC current selector? - the probs on RED to RED - Black to Black? Please advice if not and will need a guide if possible?

[walpurgis]

http://www.sciencebuddies.org/science-fair-projects/how-to-use-a-multimeter.shtml

Your meter should have come with an instruction leaflet though. Or, there may be a manufacturer's one online for that model.

[farflungstar]

It's good practice to measure DC offset when you receive a new amp.

Here's a good guide: LINK (http://audiokarma.org/forums/index.php?threads/amplifier-distortion-dc-offset-and-you.5634/)

My Onix oa21 has 5mv on one channel a 10mv on the other. It was higher but I matched the transistors.
This link gives a good overview of how to approach it.

[struth]

Hi Guys

This thread has inspired me so i bought a multi meter - which setting does it need to be on to check for DC current?

Novice here sorry...:scratch:

I want to check my Cambridge P40...

I Read the instructions :lol: - DC current selector? - the probs on RED to RED - Black to Black? Please advice if not and will need a guide if possible?

What you wanting to check for Dan?

[dantheman91]

What you wanting to check for Dan?

Hi Grant

A friend of mine has a P40 but he says its got DC on one channel just wanted to check mine - but its working fine....

Bit stupid really...:eyebrows:

[struth]

Well you want to test for dc volts, not current. Just put amp on and wait a bit for it to warm up. Speakers connected preferably in my opinion. No input and vol down. Put meter across speaker terminals colour coded. Initially use in this case use a bigger dc range than expected. You can always drop it to lower range if it doesnt register much. I wouldnt expect much, say 100mv tops . Check each channel. That will tell you what dc offset youve got approximately. If it were much more than 100mv you would start to hear it. A lot more and your speakers will fry. SS amps generally dont need speakers connected. Valve amps do need a load of some sort. Whether it be speakers or a big wirewound resister

[dantheman91]

Well you want to test for dc volts, not current. Just put amp on and wait a bit for it to warm up. Speakers connected preferably in my opinion. No input and vol down. Put meter across speaker terminals colour coded. Initially use in this case use a bigger dc range than expected. You can always drop it to lower range if it doesnt register much. I wouldnt expect much, say 100mv tops . Check each channel. That will tell you what dc offset youve got approximately. If it were much more than 100mv you would start to hear it. A lot more and your speakers will fry. SS amps generally dont need speakers connected. Valve amps do need a load of some sort. Whether it be speakers or a big wirewound resister

Thanks Grant - I'm still learning i find this quite interesting subject....:)

[struth]

Plenty info on youtube too Dan. Current testing is a bit different to volts and ohms, and meter has to be in the circuit as opposed to over it. But using ohms law you can tell lots by using these three tests in conjunction. Just be careful if near anything that is using higher volts or drawing a lot of current. Even speakers can draw a fair bit of current so don'tshort anything out