popping noise when turning on amp/preamp

thanks for the info mezmo. as i stated in a post above, the problem was solved by changing interconnects. however, there may still be a slight grounding problem, as there is a very slight hum in the speakers. i have to put my head right next to the speaker to hear it.

Personally, wouldn't rush to blame your equipment. In my experience, a relatively minor (yet admittedly alarming) pop or such is fairly common on powering down high current gear. Order matters, and that is why you should turn off the equipment closest to the speakers first (and on last) – precisely to combat amplification of power bleeding artifacts to the speakers from gear up the chain. If the amps off, don’t matter what the preamp does when you turn it off, you get the idea. Put differently, it's common enough that it is an accepted rule of thumb. And unless your amp is really dramatic, wouldn't let it concern you. (And by dramatic, you'll know it when you hear it. For example, I know that Bryston amps – and likely all amps – utilize a “muting switch” on power down that engages immediately to break the feed to the speaker taps so that, as power dissipates from wherever it's stored in there, you don't have to listen to it, you might get a “pop,” but it saves you from the worst of it. Well, apparently some time near on 20 years ago, a batch of 4b-st's left the factory with muting switches that were known to fail, and one of said amps ended up in my living room. Sans muting switch, turning the thing off kinda sounded like someone very large and cross was tearing the speakers in half. Successfully, mind you, not just trying, either. No bueno. Bryston, of course being Bryston, fixed it immediately no questions asked – but, just saying, when that type of issue rises to problem levels, it aint subtle).

As for the hum, sounds very much like a classic ground loop. In fact, unless it is only in one channel – in which case I would indeed look to the gear – my bet’s definitely on a ground loop hum. To start, the most common source of a ground loop is a cable feed: you have cable TV plugged into anything vaguely associated with the speakers? If so, that’s it. You could theoretically get the cable company to reground stuff, or you could put a form of filter in there to hack off the hash. Jensen Transformers (google will take you right there) makes a whole variety of options for this. They work like a dream and I use one (the “Cable TV RF Isolator”).

If no cable TV, could still be a ground loop. I’ve found that they can be insidious little beasties, and entirely beyond my comprehension. Changing the slightest thing can cause one to pop up. For example, I have likely over a dozen items interconnected throughout my system and it’s, generally, dead silent. One day, I swapped out the hard drive feeding the music server – replacing a powered 2TB jobbie with a 1TB raid powered entirely off of the firewire. Removing that one plug from the system earned me a ferocious ground loop hum. Why? No f-ing clue, but that’s the sole thing that changed. I tried rewiring everything (things are fed from three different outlets – splitting or moving things is one way that sometimes works). No love. I tried lifting the grounds on single and then various permutations of groups of gear (your “ground” is the third prong on the electrical plug. “Lifting the ground” is disabling this third prong, most easily, by using one of those 3 into 2-prong adapters. In the right spot, this can also lick a ground loop hum – although it’s generally not the best long-term plan, those things are grounded for a reason. But a perfectly viable diagnostic tool.) No love. Then I remembered that I had one of those Jensen jobbies lying around from before we moved, and that did it. But, lesson learned, changing anything can change your grounding pattern and earn you noise. In all events, a real common problem, just search “ground loop” here and you’ll get more info than you bargained for. Not saying that’s your issue, but something I’d definitely consider before racing around trying to fix stuff that might not be broke.

You probably have a bad solder joint (or joints) in one or more of the interconnects. Bring them to a qualified technician (guitar amp repair shop used by professional musicians in your area) and he can check continuity a make the repair in usually less than 5 minutes.

Perhaps shielded vs. unshielded interconnects! Try to route your more expensive (culprit) differently and away from power cables... and see if the buzz goes away.... or stick with the cheapo ones if you hear no difference in sound....

thanks. i thought of trying just what you suggested after i started the thread. using the cambridge as a preamp, i heard no buzz or popping. so i figured it was the bryston preamp.

but then i decided to use the same interconnects i was using on the cambridge on the bryston. that took care of the problem! in other words, the interconnects were the culprit.

interestingly, the interconnects i was originally using on the bryston were more expensive. the interconnects that ended up sounding good were cheapo ones you get with any stereo system.

Just to establish a few points, first, the pre amp should be turned on first and turned off last (your preamp should always be in control of your amplifier). That said, it sounds like you have a problem in one or both of those two components. If you use the "pre-outs" of the cambridge (if you have them, and I believe that you do), you can substitute the Cambridge for your preamp, and if the humming and buzzing persist, you will know that the amplifier is the likely culprit (a qualified tech should then be able to provide a repair without too much angst), assuming that all of your connections are firm (go over all of them just to be sure). I hope this helps, Happy Listening