[Zin_Ramu]

I've recently started listening to some music with greater dynamic range than the rock and alternative stuff that is my main staple. With this music I noticed a nagging problem I've had with the Corda HA-1 since I purchased it - noise from interference, so I ran some basic “tests” to get some info.

When I turn my source off and put the volume of my Corda at 0 (6:15 o’clock), I can hear some static noise. Its loud and legible enough to determine it was a radio channel, and with some effort I was able to make out the DJ voices and even determine which station it was.

At max volume (5:45 o’clock), I again hear the same static, but now it’s a different radio station.

At middle volume (12 o’clock), I can hear some minor noise. It is no longer discernable as voices and instead is more like a minor electronic hum.

Lastly I was going to try removing the ICs to see if the noise persisted. Immediately I noticed when I touched the gold at the end of the Cardas IC the interference was gone. Removing the ICs completely the interference resumed. When I put my finger over both RCA contectors on the Corda, again the interference was gone.

I have absolutely no electrical knowledge so I have no clue what’s going on. But I wanted to see if other people have similar issues or if my unit has some issues.

Zin

 

[HappymaN]

Hopefully Jan can chime in here, because I have the same problem. I believe it is something to do with adjusting the bandwidth of the amplifier.

Also, as soon as I find the right Allen key and a soldering iron, I need to open up my Corda and ground the pot. It hums everytime I touch it.

 

[Magic Robert]

I have an HA-1 that is dead quiet.

I also had the same kind of problem that you are describing when I moved into this house 10 years ago. The problem turned out to be a floating ground in the house wiring. I finally fixed it (and some other stuff that you don't care about) by going to the electrical box and tying it to a NEW ground rod (8 ft of copper coated steel that I drove into the ground.)

I don't think that "my fix" is "your fix", but you both are able to affect the performance by touching that something that <should> be at or near "earth ground."

In both cases your touching something makes a difference. You ARE at "earth ground". (OK, before someone corrects me, they are both big-ass capacitors, too, but the grounding thing is close enough to the truth.)

Make sure your source and the HA-1 are grounded well first. Take'em for a visit to soemoene else's place if you have to.

If that fails, Herr Doktor Meier could have made an error.

But if he shipped your HA-1 like he shipped mine, you had to supply your own power cord (and power....)

Hope that helps.

 

[Zin_Ramu]

I will investigate the grounding issue further. Although I'm not really sure what grounding means. I believe my Corda has the correct power cord, an IEC connection on one end and three prong termination on the other, properly inserted directly into a wall socket.

Additional things to note are:

1) I just checked that the noise occurs even when I remove the ICs and detach the power cord of the source, so the source in no way is causing the interference.

2) I experience no interference on my main stereo system.

3) In the past when other headphone amps were used in my house they displayed no interference.

All this leads me to believe the issue may be with the Corda, but as I said I will do some more reading on grounding and try to figure it out what it means and if it may be the root of the problem.

Zin

Edit: Just found a SurgeMaster and plugged it in and the LED came on showing it was grounded. Pluging the Corda into the surge protector did not reduce the interfence. So it looks like everyhting is grounded okay unless there is something strange going on with the power in my house, like a "floating ground".

 

[Sovkiller]

Did any of you try to reach Dr. Maier by PM or email? Maybe he has an answer for the problem, if there are two similar problems maybe is a known issue, but I think is somethig related to the ground, it looks like RF interference, just my 2 cents!!!

 

[Magic Robert]

I agree with SovKiller. If you have unhooked the Corda from the source, have it plugged in and powered on from the same power that doe not cause a problem elsewhere, and can still hear this through the phones, it looks like you may need Doktor Jan.

The RF you are hearing may be because the "bad" ground is making your Corda into an antenna in addition to an amp. A single bad solder connection could be the culprit.

I would bet Jan would know off the top of his head. I would PM or email him post-haste. He's a good guy (I ain't the only one who thinks so.)

 

[KurtW]

RF interference with the HA1 has been addressed in these forums before. The original HA1 has an extremely wide bandwidth, and this leads to picking up radio stations. Jan has since changed the cap across the pot from 220pF to 680pF and people have said that this fixes the problem. Others have gone to better shielded cables and that also fixed the problem. I've never had the problem because I live in a rural area...my problem is trying to pick up radio stations with a tuner, let alone an amplifier.

 

[Magic Robert]

I am running one of Jan's most recent models with the cap change and (stupidly?) assumed that the units in question wer new, too. You may have solved the mystery.

I am also using a DiMarzio M-Path cable that I just bought from someone who was giving up his headphone addiction. It is WAY shielded (I think that's the correct technical term.) I live in Houston and I am waiting for the fridge to pick up FM.