ta2020 New caps - now I get a buzz in tweeter - diyAudio
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Old 12th January 2010, 01:55 AM   #1
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Default ta2020 New caps - now I get a buzz in tweeter

Yes, I'm a newbie,

I put new caps (audiocap theta 2.0) in my ta2020 project and now I have a mild buzz in the tweeters (very effecient Lascalas with JBL 2404h tweeters so the buzz is accentuated). The buzz is there at all volumes and with or without program material.

I mounted the caps with short leads on the board side but ran the other side straight to the potmeter. Maybe I'm getting interference here? unshielded wires picking up Rf? I don't know.

Also, If I ground one of the unused RCA negative rings on the back (I do have a selector switch) to a true ground (another amp that's plugged in but not turned on and has a three prong plug) the buzz goes away almost completely. My head is telling me I lose just a little detail by doing this though, although maybe I just think I hear this?

I remember the TA2020 being totally silent before I think? Do I have to reset the DC offset with the new caps? I didn't think that I would have to. Maybe I've created a ground loop by not hooking the caps to the board on both sides and using the original input wires (doesnt make sense)?
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Old 12th January 2010, 07:30 AM   #2
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Could be due to the not-so-ideal RF properties of your cap. What happens if you change back to the old one ?

Regards

Charles
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Old 12th January 2010, 07:51 AM   #3
Mooly is offline Mooly  United Kingdom
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I think you might be hearing the harmonics of a PSU wiring problem as you mention grounding and the problem dissapearing. What you hear is 100 (120) hz ripple, but it's very spiky, so you hear the harmonics as a higher frequency buzz...
As mentioned in the post above, try the originals back and see.
A physically large cap may pick up the radiated field from the PSU or amp.
DC offset is not affected.

Last edited by Mooly; 12th January 2010 at 08:01 AM.
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Old 12th January 2010, 02:49 PM   #4
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Thanks guys,

I'll try switching back the caps(red ones) and also mounting the new cap snuggly to the board to avoid all that copper leed (antenna) picking up RF too. Are the Audiocap theta's internally "noisey" when used with some power supplies? I am using a switching 12v 5a PS that was sold on the same sight as the TA2020 (MKIIInot to name names).
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Old 12th January 2010, 03:14 PM   #5
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OK, dummy me!

If you have a t-amp sitting directly, in the middle, on top of an Adcom GFA 535 II amp and that amp is plugged in, you get a tweeter buzz. It you unplug the Adcom, the buzz goes away (if I just slide the T-amp to the side of the plugged in Adcom the buzz goes away too).

I think the suggested power supply that came with this amp is really quite good now as I have to put my ear 1 inch from a 103db tweeter to even register the lightest snow.

The caps probably still needed to break in too, as the buzz was 1/4 as loud as it was two days ago before I unplugged the Adcom and I left the T-amp running on FM radio for two days.
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