| TheDriver41 |
I got what looks like a resistor saying "2.7ÙJ 2W" and a small relay looking thing saying "100n CR 63v BC 0423416."
I didn't find them on the parts included on the guide. Any ideas?
Thanks,
Matt |
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| Nuuk |
| Sounds like a Zobel network to me. If it is, then you connect them in series between the two speaker terminals. |
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| Evan Shultz |
You didn't say if it was the LM3875 or LM4780 GC kit. However, Nuuk is right: they are the Zobel network.
2.7ÙJ 2W = 2.7ohm 2W resistor
100n CR 63v BC 0423416 = .1uF cap
There is a spot on the 3875 boards for the Zobel, not sure about the 4780. As an alternative, you can connect the parts in series across the speaker terminals for the same result. Peter and Brian have both suggested to only use the Zoebel if required, and there are many happy GC owners who do not use it. Unless your speakers cables are exceedingly long, or exceptional capacitive, I suggest you leave the Zobel off or at least listen both ways. |
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| metha |
About the order of R C for zebol. I am curious. Typically I connect the zebol R (1 ohm) to the speaker out (signal) and the Cap ( 0.22 or 0.1 UF) connect to the speaker ground.
I found some GC board connect the R C reversely (i.e. the zebol R connect to the speaker ground instead). Any difference between both approarch? |
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| soundNERD |
| quote: | Originally posted by Nuuk
Sounds like a Zobel network to me. If it is, then you connect them in series between the two speaker terminals. |
Nuuk, would it be better to actually connect it on the speaker? or on the amp PCB? both?
sorry if it's a stupid question |
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| Sheldon |
| quote: | Originally posted by metha
About the order of R C for zebol. I am curious. Typically I connect the zebol R (1 ohm) to the speaker out (signal) and the Cap ( 0.22 or 0.1 UF) connect to the speaker ground.
I found some GC board connect the R C reversely (i.e. the zebol R connect to the speaker ground instead). Any difference between both approarch? |
Nope. The output is AC, so no polarity concerns.
Sheldon |
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| Sheldon |
| quote: | Originally posted by soundNERD
Nuuk, would it be better to actually connect it on the speaker? or on the amp PCB? both?
sorry if it's a stupid question |
The normal recommendation is to place it on the board, or near it. That short circuits any high frequency resonances closest to where they would be generated.
Sheldon |
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| Nuuk |
| quote: | | The normal recommendation is to place it on the board, or near it. That short circuits any high frequency resonances closest to where they would be generated. |
Thanks to you guys for taking over while we UK chaps took a nap!
Yes, as Sheldon says, the Zobel needs to go close to the amp, ie on the terminals or even on the PCB if there is room. |
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| richie00boy |
| quote: | Originally posted by Sheldon
The normal recommendation is to place it on the board, or near it. That short circuits any high frequency resonances closest to where they would be generated.
Sheldon |
Actually, it's nothing to do with shunting resonances. You place it close to the board because the further away you place it the higher the inductance of the connection, which limits the zobels usefulness (as it is trying to compensate for the phase angle caused by inductive loads).
| quote: | Originally posted by Evan Schultz
Unless your speakers cables are exceedingly long, or exceptional capacitive, I suggest you leave the Zobel off or at least listen both ways.
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Not quite. If your speakers or leads present a highly capacitive load, you should add an output series inductor. The zobel is for inductive loads. |
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| rnoble |
Hi,
I noticed this thread and headed down the shop to to add a zobel to my Gainclone to see what the fuss was about. I feel that there's been an improvement in sound, particularly there was a little level difference between LR that seems to have gone - but most noticeably the top end seems less forced and less forward, perhaps less bright? It is hard to put a Zobel on and off with a switch so I can't discount a possible placebo effect, however I do feel it has compensated to the audio quality in some small improvement.
Worth a try.
Cheers
Rod |
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| Sheldon |
| quote: | Originally posted by richie00boy
Actually, it's nothing to do with shunting resonances. You place it close to the board because the further away you place it the higher the inductance of the connection, which limits the zobels usefulness (as it is trying to compensate for the phase angle caused by inductive loads).
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Quite right. I guess the term "oscillation" would have been better too. Just curious; as the issue is the phase angle of the feedback eventually going positive, it follows that a zobel would not be needed on an amp with no global feedback?
Sheldon |
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| richie00boy |
| Correct. No loop feedback = no problems with phase shift. |
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| johngalt47 |
| The board does not have a lable for the Zoebel resistor. I assume that it is soldered to the holes parallel to the nfb resistor. |
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