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Old 30th May 2007, 12:07 PM   #1
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Default n00b phono preamp troubleshooting..

Hi all,

something went wrong with my phono preamp, I'm about to investigate it, but being not that long into tubes I don't really know where to start

The problem is that the stereo image keeps shifting.. Everything's in the center, and a few minutes later I have to turn my head 30 degrees to the left to get the proper image After that it slowly goes back to the center, and this cycle keeps on repeating..

Here's the schematic:

(image removed by moderators)

Any help will be greatly appreciated!
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Old 30th May 2007, 12:44 PM   #2
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I removed the image, which was a copyrighted drawing (Triode Dick "Phono Dude" preamp). For the benefit of others, it's basically two mu followers sandwiching a passive RIAA. The circuit design is unlikely to be the culprit here anyway.

First question: does this image wander happen when you substitute another phono stage?

Second question: Have you swapped tubes between channels? If so, does the image wander still go in the same direction?
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Old 30th May 2007, 01:35 PM   #3
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Quote:
Originally posted by SY
I removed the image, which was a copyrighted drawing (Triode Dick "Phono Dude" preamp).


Oops, sorry, hadn't thought of that

Quote:
For the benefit of others, it's basically two mu followers sandwiching a passive RIAA. The circuit design is unlikely to be the culprit here anyway.

First question: does this image wander happen when you substitute another phono stage?
Haven't tried that yet, cd's are fine though. I will try that.

Quote:
Second question: Have you swapped tubes between channels? If so, does the image wander still go in the same direction?
I swapped tubes between channels ànd tried another set, no difference

I'm diving into it now, I'll keep you posted. Thanks so far
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Old 30th May 2007, 02:14 PM   #4
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SY, you seem to have hit the nail right on the head!

I tried another preamp, and apart from sounding a lot worse the problem is still there..
So it must be the TT then?
This seems more apropriate in the 'analog' section.. What's going on here? I still have no clue. Cartridge alignment? Arm gone bad? The funny thing is the cycles are quite short, every two minutes..

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Old 31st May 2007, 12:19 AM   #5
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Problem solved One of the cartridge clips got bent..
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Old 31st May 2007, 12:51 AM   #6
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Join the club. I recently built a new phono preamp with (on paper) stunningly low noise. And it actually worked out that way- in one channel. The other showed a low level low frequency burble. It was inaudible from more than a foot away from the speaker, but clearly something was wrong. Swapped tubes, no change. Resoldered everything. No dice. Rebuilt large portions of that side. Same same. On a hunch, I swapped the connections at the cartridge. Still the same. Wow, I was stumped.

I had used a DIN plug for the input and built my own cable to feed a balanced signal to the preamp input. And you guessed it, the problem turned out to be the last thing I checked: the cable. Bad solder joint at the right angle plug that connected to the tonearm.
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Old 31st May 2007, 02:16 PM   #7
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