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Old 25th April 2012, 03:06 AM   #1
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Default Is this amp OK to buy, or is this a problem?

I'm considering a Jolida 302B. Having seen reports of humming trannies, I asked the seller about it. His response is below. I don't know if this is a problem or normal. Even if slightly wrong, I'd rather not buy. What do you think?

"With the speakers connected to the 302B, I can hear a very faint hum from the speakers, but you have to put your ear right against the speaker grill to hear the hum. Turning the volume knob on the 302B has no effect on the amount of hum - the sound level remains constant regardless of the volume setting. Again, I must stress that the volume of hum is so slight, I doubt if anyone in a silent room will notice it, even when standing close to it. You really have to put your ear against the speaker to hear the very faint hum. I believe this kind of hum is generated by all amplifiers - try listening to your current amp. When listening to music, I doubt if one can hear the effects of it even in quiet passages.

Now, with a CD player hooked up to the Jolida, the hum level increases as you increase the volume on 302B. When the volume dial is turned down to minimum, the level of hum is very faint (same level as if cd player was not connected). When the volume is turned to MAXIMUM, the hum becomes noticeable as you approach the speaker (about 3 feet away). In addition, when the CD player is on, and the input selector on the 302B is set to other than CD (such as AUX), turning the volume knob has no bearing on the hum level - it stays constant at the barely audible level. I believe what this indicates is that by itself, the 302B is very quiet (just a barely audible hum), and when you hook up a CD player or phono stage, the inherent noise (hum) from those external sources are magnified as you increase the volume. "

Thanks....
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Old 25th April 2012, 03:15 AM   #2
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Default by the description the amp sounds fine.

I'm no expert, but it sounds like the amp has a typical amount of hum, and the seller has a ground loop problem with his CD player.

Ask the seller to plug the CD player into the aux input and see if the hum follows the player, and plug whatever was in the aux input into the CD input.
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Old 25th April 2012, 12:20 PM   #3
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Hi, the seller tried that, and the hum follows the CD player. Does this mean the amp is OK and it's the CD player that has the problem?

Thanks.
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Old 25th April 2012, 02:23 PM   #4
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It most likely means that the amp-CD combo has a ground loop issue. Based on what you are describing, it sounds like the amp is fine. If another source other than the CD player is connected, the hum is barely audible, correct?

All of my amps have a small amount hum if I stick my ear next to the speaker, which is fairly typical. My speeks are 95db sensitivity, so even a small amount of hum can be audible inches from the speaker.
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