[falkon72]

Ok got the skeleton of the CMOY to work. I'm testing them on a low imped (16) headphone because my 770s haven't come yet. I'm using it on maximum setting because i haven't put in a volume switch yet. I'm getting some background noise when the source is not turned on. Is this just the amp at work, or some error due to my part?

 

[Dreamslacker]

Quote:

Originally posted by falkon72 Ok got the skeleton of the CMOY to work. I'm testing them on a low imped (16) headphone because my 770s haven't come yet. I'm using it on maximum setting because i haven't put in a volume switch yet. I'm getting some background noise when the source is not turned on. Is this just the amp at work, or some error due to my part?

What kind of background noise?
Light hissing?
Occasional clicking/ buzzing?

If it's light hissing, you need to place the output resistor as stated in the article. (Inside or outside of the loop is up to you.

If it's buzzing or clicking, you just have some inteference in the area.

 

[falkon72]

yeah its light hissing but this is on maximum volume on low imped headphones.

 

[falkon72]

i think i probably should wait until the 770 gets here to see if there's still hissing

 

[Dreamslacker]

Quote:

Originally posted by falkon72 yeah its light hissing but this is on maximum volume on low imped headphones.

You're using a pair of low impedance headphones so you could get rid of the hum by using load resistor R5. Whether it is inside or outside of the feedback loop is your choice.

I quote:
Quote:

Nevertheless, there have been a few reports of problems with noise. The first step in troubleshooting noise is to make sure it is coming from the amplifier itself, and not from the audio source. Disconnect the audio source and listen to the pocket amp for any background hiss, static, RF (radio frequency) or EM (electromagnetic) interference. If the headphones are low impedance types (such as the 32 ohm Grados), the amp will function better with the load resistor R5 installed (see figure 1). The load resistor can be added either inside or outside the opamp feedback loop (figure A1). Inside the feedback loop is the preferred method because it keeps the output impedace of the amplifier very low, but some DIYers have reported better performance with the resistor outside the loop.

However, you can leave it as it is and wait for your DT770's. They won't have this problem since they're higher impedance headphones.