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Old 9th February 2006, 01:31 PM   #1
KT is offline KT  United States
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Default Charlize input cap problem - Help!

Yesterday I replaced the Charlize's stock Cerefina input caps (10uF 50V) with Blackgate N's of the same spec.

Sometimes I take the plastic wrap off my caps, and I did so in this instance. A small problem arose, however, because the diameter of the BG's is wider than the Cerefines. When both BG's were installed on the board, their bare bodies touched each other.

I played the amp for about 10 minutes before I realized I was listening to a mono signal. Apparently, because the aluminum case is attatched to one terminal of the cap, the input signal was being mixed together. I placed a mica spacer between the caps and everything returned to normal at that point.

In the morning, however, I played some music but there was no sound coming from the left channel. I didn't have time to examine it before I went to work, but I wonder if that brief period when the caps touched could have damaged something.

One thing I know about the Blackgates is that one terminal, either the long or short one, I'm not sure which, is connected to the outer foil. The other is connected to the inner foil. I was aware of this and oriented both caps in matching directions. Also, the Blackgate N's are non-polar, so theoretically they can be inserted with either terminal towards the input signal.

Another thing I'm aware of with the Tripath chips is that they have a biasing voltage. Because of this, the original Cerefines were oriented with the "-" terminal facing toward the input signal (the input RCA's), and the "+" terminal facing the rest of the circuit. This is because the bias voltage on the board is at a higher potential than the input signal.

With this in mind, could touching the input caps' bodies together for 10 minutes result in damage to the cap or amp? Everything seemed to work normally after I inserted the mica spacer, and since both caps were insulated from each other, everything was in a "regular" state. Only the left channel was silent in the morning.

Also, I left the amp on overnight after I inserted the spacer.

Any help would be greatly appreciated.

Thanks!
KT
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Old 9th February 2006, 02:20 PM   #2
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I just checked some of my BG N 10/50 caps and the cylinder is not connected to any of the leads.

Although those caps are non-polar, their orientation in a circuit will affect sonics. Personally, for coupling, I prefer short lead (or the side with NonPolar print) directed towards the incoming signal.
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Old 9th February 2006, 02:51 PM   #3
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Hi Peter,

Hmmm.... That's strange.

Playing the Stereophile Test CD 3 ("This is the left channel... left channel..."), the signal was clearly coming from both speakers. After I inserted the mica spacer, the track was coming from hard left, with nothing coming out of the right speaker. Vice versa with the right channel track.

I can't imaging it could be anything else other than the input signal shorting at the cap cases.... but if you found that they're not connected to the leads.... . I wonder what could be going on.

Yes, I took your advice from a previous thread and oriented the Blackgate N's in the way you recommended (actually, I oriented it with the short lead towards the higher potential - normally this woud be the input signal, but since there's a biasing voltage on the board I put the short lead facing the board. Don't know what the difference will be in this case.)

I'll take a look when I get home today. Hopefully it's something stupid I overlooked....but any other suggestions would be helpful.

Thanks,
KT
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Old 9th February 2006, 08:35 PM   #4
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Well, I'm officially confused.

I measured resistance between each input RCA hot and ground in case the left input cap was damaged and creating an open circuit. Both sides measured roughly the same.

I also measured resistance between the aluminum cap housing and both the ground and the input hot. In both cases, the measurements for both channels were roughly the same.

Oddly, it wasn't an "out of range" reading which is what I'd expect if the cap housing were isolated from the leads. Rather, it was a reading which steadily increased. The reading of the hot-to-housing was different than the ground-to-housing reading, but both channels measured approximately the same...all measurements slowly increasing with time. Sorry, I was only looking for indication that one of the caps may have been damaged, so I didn't write down the exact figures.

Since both sides looked about the same, I hooked up the amp with the spacer still separating the caps.

Well, the thing seems to be working fine.

I'm wondering if a connection may have come loose causing one channel to cut out. I made sure the speaker wires were tight and that the RCAs were secure, though, so I don't know.

Of greater concern is the possibility that something could have cause the chip's internal protection to kick in. I don't know a lot about the Tripath TA2020, but does the protection mode in a chip shut the whole thing down, or can only one channel shut down? If the whole chip shuts down, then this isn't the culprit as only the left side cut out.

OK, I hope everything works fine from here on out. Thanks for your help, Peter.

KT
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Old 9th February 2006, 08:40 PM   #5
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That's why it's not recommended to remove plastic jackets form caps

But seriously, did you observe much difference (jacket on and off)? I can detect a bit more effortless sound, without jacket, but nothing really major and in most cases I don't even bother to remove them (and I'm talking here about BGs only)
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Old 9th February 2006, 09:14 PM   #6
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Peter,

In all the cases where I did a before and after comparison, I found that the effect was as you described. The sound became more effortless and less "uptight," mostly a subtle but welcomed difference. I haven't had a chance to do a before and after with the Blackgates, however. I usually just skin them if there's no risk of them shorting against anything. Of course in this case I miscalculated the spacing of the holes and had some contact between the exposed caps.

Interstingly the most dramatic improvement that I've experienced removing the skins from caps happened with my Creek 4330. Creek has a belief that using an array of smaller PS filtering caps is sonically superior to using a couple of large ones. Well, on a whim I went in and carefully removed the skins from all the caps in the power supply. Boy, I couldn't believe the difference. The presentation from the amp was so much more effortless and so much less tense, uptight, and constrained. The sense of rhythmic flow improved, and it seemed that the timing of the bass was more natural and tuneful. I was really happy.

Encouraged by this, I went in and skinned all the caps in the Special Edition phono card in the same Creek, over a dozen in all. Well, I couldn't detect the slightest bit of difference after I skinned the phono caps. Nada. Sounded the same. Skinning the PS caps in this amp yielded a huge change, though.

In most other cases, the differences were subtle. I personally will still do it if I'm confident nothing will get damaged, but I can see how this might be one of those "diminishing returns" things. I wonder if the effects can be additive, though.

In one case I came to the conclusion that skinning the caps shifted the sound too far to the "easy and loose" side. The amp lost punch and sounded somewhat amorphous. I don't remember which amp that was off the top of my head, but that experience showed me that everything can be done to a fault.

Best,
KT
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Old 10th February 2006, 12:21 AM   #7
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KT,
I would encourage you to ensure that the caps do not come into contact with each other once the cap's plastic jackey/sleeve is removed.

Using a multi-meter to measure for resistance when it is not connected or 'actively' working will not show anything prominent at all. Always treat the the cap's housing or can as another electrode when it is connected to a power source.

I've not tried measuring what had happened as with your case on the Charlize but experience working with tube-amps most of the time shows that when the reservior caps is supplied with high voltages, there are about 1/3 of the voltage apperas on the cap's aluminium housing. The reading might varies but still a potentially high lethal voltage.

I would suspect that shorting the 2 input caps causes somethong to the baising voltage on the TA2020 that in a way shuts one of the channel down.
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Old 10th February 2006, 12:37 PM   #8
KT is offline KT  United States
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Thanks vt4c,

I'm keeping the mica spacer between the caps, so caps are totally isolated from one another. The bare caps aren't in contact with anything else.

I, too, was wondering if the caps touching might upset the biasing arrangement on the board. Peter found no connection from the case to the leads, but I did observe that a hard-panned signal was getting to both channels when the cap bare cases touched each other, so.... .

In any case, it's obviously safest if the caps were isolated from each other, the way the circuit was designed.

Right now the amp seems to be working fine. The Blackgate N's are nicer sounding than the same value Cerefine in the input position, btw.

Best,
KT
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Old 10th February 2006, 03:02 PM   #9
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KT,
Hope you have good time enjoying her company.
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Old 10th February 2006, 03:22 PM   #10
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I just measured BG N caps in an active PS, and indeed, depends on orientation, they may have the full voltage potential on the cylinder (one cap has short lead to ground the other cap has long lead to ground and only one of them shows DC on the cylinder).
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