4 Strings Posted July 10, 2011 Share Posted July 10, 2011 Hi, hope someone can help my lad. Hartke HA3500, when plugged into a speaker gives out a whistling noise from the speaker, but no sound from a bass if plugged in, just the whistle. Tried different leads, speakers etc, just happens when plugged into a cabinet regardless of anything in the input. (Fortunately there was another amp at his gig but this was a sudden thing, ok in the afternoon, whistling in the evening). I wondered if this was a typical symptom for something? Not the valve as it still whistles without it. It starts after the relay(?) has clicked inside releasing the output. Any ideas anyone? All gratefully received as he hasn't the money to leave it at our local amp man. Cheers Quote Link to comment Share on other sites More sharing options...
Subthumper Posted July 10, 2011 Share Posted July 10, 2011 [quote name='4 Strings' post='1299030' date='Jul 10 2011, 03:34 PM']Hi, hope someone can help my lad. Hartke HA3500, when plugged into a speaker gives out a whistling noise from the speaker, but no sound from a bass if plugged in, just the whistle. Tried different leads, speakers etc, just happens when plugged into a cabinet regardless of anything in the input. (Fortunately there was another amp at his gig but this was a sudden thing, ok in the afternoon, whistling in the evening). I wondered if this was a typical symptom for something? Not the valve as it still whistles without it. It starts after the relay(?) has clicked inside releasing the output. Any ideas anyone? All gratefully received as he hasn't the money to leave it at our local amp man. Cheers[/quote] Hi, it sounds like you definitely have a problem in the amp or the pre amp. You can isolate the two by putting a jack into the fx send. If the noise stops its somewhere in the pre amp. If it doesent its the power amp. Either way it needs looking at by someone who knows how to trace through a circuit and find the individual components or connections that are responsible. I have a copy of the schematic if you know someone who can look it over so PM me and I'll email it. Dont let someone "have a go at it" or the amp tech who finally gets to fix it could end up with a real headache. I've had one of these amps for 13 years and no such problem but worth getting them serviced because the fan sucks in a lot of dust which attracts moisture and causes bad contacts, corrosion, bad sound and crackly pots and sockets. (any amp with a fan). Good luck Cheers Just Quote Link to comment Share on other sites More sharing options...
4 Strings Posted July 11, 2011 Author Share Posted July 11, 2011 Hi, thanks. The whistle is there regardless of anything being plugged in anywhere so I suppose its the power amp. I have a copy of the schematic, thanks, and in the end it will go to the amp tech if this isn't 'typical of ...' and something I can do. Most will say its the valve but I've always found valves to be the most reliable and resilient of components (may still be the valve, but that would mean it's the pre-amp). Problem with the amp tech, however reasonable he is, he'll be about the price of another s/h amp and the lad can afford neither. Quote Link to comment Share on other sites More sharing options...
brensabre79 Posted July 11, 2011 Share Posted July 11, 2011 My Hartke A100 started doing this recently. But it will still make sound. My amp tech has had it for 3 weeks and still not discovered what is wrong with it except that it is getting very very hot in use. Sorry I can't be any help but my guy said that since Samson started making these the quality has gone through the floor. He's already told me it would probably be cheaper to get a new amp. I wouldn't recommend buying a S/H amp to fix the problem though because you might find that has faults of its own. My A100 being case in point. At least with this one you know how its been treated/stored etc. Unfortunately Subthumper is right, you need someone who knows what they are doing to tace the circuit and test every single component in the signal path. You can eliminate some of the work for the amp tech by checking if its the Pre amp or Power amp stage. Try bypassing anything you can. And check to see if any controls affect the whistle. In my case the Comp/limiter modified the whistle so we know its coming from before there in the signal path... Quote Link to comment Share on other sites More sharing options...
Slipperydick Posted July 11, 2011 Share Posted July 11, 2011 If it was a microphonic valve I would expect the noise level to be affected by the master volume control. Its most likely positive feedback from somewhere in a later stage. Dont run the amp trying to find out, or something expensive will fail. Get it sorted by somebody who knows what he's doing. Hartke amps are notorious for dry joints and fans failing/getting noisy. As has been said, worth getting em serviced occasionally Quote Link to comment Share on other sites More sharing options...
4 Strings Posted July 11, 2011 Author Share Posted July 11, 2011 Cheers guys, looks like he'll be relying on the headline band rig for a little while! Its a well used amp, his is a busy band and it was well used before he got it. We'll be keeping an eye for a cheap s/h one while he does some saving. Quote Link to comment Share on other sites More sharing options...
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