Sean.Robinson Posted August 16, 2008 Share Posted August 16, 2008 Hi, not something ive really thought about correcting until now as im sure its normal, but my amp hums/hisses a little when nothing is plugged in and it is just turned on though nothing is plugged in or been played. Ive heard it on all amps so im sure its normal, but is there any way to reduce or even get rid of it all together, such as using balanced cables, or by some mods to the amp head? Quote Link to comment Share on other sites More sharing options...
Platypus Posted August 16, 2008 Share Posted August 16, 2008 Does the amp hum wherever its placed ? - the hum can be caused by electrical interference such as low voltage lights. Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted August 17, 2008 Share Posted August 17, 2008 [quote name='Sean.Robinson' post='263790' date='Aug 16 2008, 06:15 PM']Hi, not something ive really thought about correcting until now as im sure its normal, but my amp hums/hisses a little when nothing is plugged in and it is just turned on though nothing is plugged in or been played. Ive heard it on all amps so im sure its normal, but is there any way to reduce or even get rid of it all together, such as using balanced cables, or by some mods to the amp head?[/quote] Cables can't very well be the issue if the amp behaves badly when none are plugged into it. All amps make noise, how much is a matter of how well engineered they are, or are not, as the case may be. Reducing noise is possible, but not easy, a usual prerequisite to doing so being a EE degree. Quote Link to comment Share on other sites More sharing options...
BassBod Posted August 17, 2008 Share Posted August 17, 2008 What BF said. Virtually all background noise usually gets buried in a performance situation - but some amps are hummers, some are hissers. I find the hummers worse to live with. If the hum level changes (gets noticably worse, with nothing plugged in) then you should get it checked. BB Quote Link to comment Share on other sites More sharing options...
Sean.Robinson Posted August 17, 2008 Author Share Posted August 17, 2008 o, thanks, its in my opinion only a normal level that ive experienced on all other amps but i just wondered if using a balanced cable between the head and cab would reduce interference and reduce it a tiny amount Quote Link to comment Share on other sites More sharing options...
Stewart Posted August 17, 2008 Share Posted August 17, 2008 Balanced cables stop you picking up noise from the environment on very long runs, with very low level signals. Your cab lead is a very short run, with a very high level signal... What make & model is the amp? Quote Link to comment Share on other sites More sharing options...
Stewart Posted August 17, 2008 Share Posted August 17, 2008 Well, a quick search led me to a forum on Eden's site - here's an extract: [i]The previous owner told me that the amp produces a noticable hum through the speaker cabinet even with the volume controls on zero.[/i] ...so perhaps that amp is known for the issue (there do seem to be a number of hits searching for "eden vt40" and "hum"). It looks quite old - has a traditional 'big square lump' power transformer rather than the 'doughnut' toroidal types you usually get nowadays (which reduce hum considerably). Might be worth getting it serviced if you want to keep it and can't put up with the noise, but I'm guessing it will never be near-silent... Quote Link to comment Share on other sites More sharing options...
Sean.Robinson Posted August 17, 2008 Author Share Posted August 17, 2008 Ok, well the hum is certainly not an issue when playing, but other than the reduce in hum what impact does a donut power transformer have on the sound of the amp? and how much would you guess it would be to have on fitted? Thanks Sean [quote name='Stewart' post='263891' date='Aug 17 2008, 11:54 AM']Well, a quick search led me to a forum on Eden's site - here's an extract: [i]The previous owner told me that the amp produces a noticable hum through the speaker cabinet even with the volume controls on zero.[/i] ...so perhaps that amp is known for the issue (there do seem to be a number of hits searching for "eden vt40" and "hum"). It looks quite old - has a traditional 'big square lump' power transformer rather than the 'doughnut' toroidal types you usually get nowadays (which reduce hum considerably). Might be worth getting it serviced if you want to keep it and can't put up with the noise, but I'm guessing it will never be near-silent...[/quote] Quote Link to comment Share on other sites More sharing options...
Stewart Posted August 17, 2008 Share Posted August 17, 2008 I doubt it's worth attempting any major surgery such as replacing transformers (there's no audible change to using a toroidal, they just keep their electromagnetic fields to themselves better) but if some components were starting to break down (such as power supply capacitors) then that might be responsible for a lot of the noise. Whether or not it's worthwhile spending much money on (rather than saving for a replacement perhaps) is a tricky one - mainly dependant upon how much you like it and whether you know (or can find) a good amp technician to take it to... Quote Link to comment Share on other sites More sharing options...
Sean.Robinson Posted August 17, 2008 Author Share Posted August 17, 2008 [quote name='Stewart' post='263908' date='Aug 17 2008, 12:22 PM']I doubt it's worth attempting any major surgery such as replacing transformers (there's no audible change to using a toroidal, they just keep their electromagnetic fields to themselves better) but if some components were starting to break down (such as power supply capacitors) then that might be responsible for a lot of the noise. Whether or not it's worthwhile spending much money on (rather than saving for a replacement perhaps) is a tricky one - mainly dependant upon how much you like it and whether you know (or can find) a good amp technician to take it to...[/quote] Well it is in my opinion worth keeping, a real nice wam tone and you can really hear the tubes come through, like i say its only audible when nothing been played so it no huge problem, if it came through when playing through it it would obviously be a different matter. I went to Pete Hartley and he seampt a good tech, knew what he was talking about and was very quick so id be going back to him, like i say its a matter of price and how significant the reduction in noise would be. He also gave it a clean bill of health when he looked over it so i nothings broke and from what your saying its just from the old style transformer that im getting the nosie, so would you have a vague idea of cost? Thanks Quote Link to comment Share on other sites More sharing options...
Stewart Posted August 17, 2008 Share Posted August 17, 2008 I'd hazard a guess at £30-50 - but that would be for a standard (off-the-shelf) model - the voltages the Eden needs might not be readily available, and having a custom-built transformer would not be cheap. Your best bet would be to post a query on the Eden forum, I'd have thought - and see what other users think/have done. (You'll need detailed info. from Eden regarding the transformer voltages/current rating anyway...) [url="http://www.eden-electronics.com/forum/default.asp"]Eden forum[/url] Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted August 17, 2008 Share Posted August 17, 2008 [quote name='Sean.Robinson' post='263962' date='Aug 17 2008, 09:43 AM']Ok thanks for all your help, i have shifted the topic onto eden as you've advised ([url="http://www.eden-electronics.com/forum/topic.asp?TOPIC_ID=13332"]http://www.eden-electronics.com/forum/topi...?TOPIC_ID=13332[/url])[/quote] Changing to a toroid power transformer alone would have an imperceptable effect on hum level. A complete refurbishing of the power supply, incuding major upgrading of the filter caps, would be required. Basically what you want to do is to take a Ford and bring it up to Mercedes specs. While not impossible to achieve, you'd find it a far simpler matter to sell the Ford and buy a Mercedes. Quote Link to comment Share on other sites More sharing options...
Sean.Robinson Posted August 17, 2008 Author Share Posted August 17, 2008 (edited) having looked through the forums on hiss and hum is there any chance the old tubes (16 years old) could be causing the hum/hiss, i was considering some mullards or telefunks anyhow so will be replacing them at some point but would like this clarified first please Edited August 17, 2008 by Sean.Robinson Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted August 17, 2008 Share Posted August 17, 2008 [quote name='Sean.Robinson' post='264067' date='Aug 17 2008, 01:37 PM']having looked through the forums on hiss and hum is there any chance the old tubes (16 years old) could be causing the hum/hiss, i was considering some mullards or telefunks anyhow so will be replacing them at some point but would like this clarified first please[/quote] Tubes are seldom the source of hiss. In a tube amp it's primarily the resistors, in SS the SS devices themselves, which is why tubes tend to have less hiss than SS. Tubes that aren't biased correctly can contribute to hum. Old Fender designs had what they called a hum control. The only tools required were a screwdriver and your ears, you simply turned the control until the hum was at a minimum. Quote Link to comment Share on other sites More sharing options...
Sean.Robinson Posted August 17, 2008 Author Share Posted August 17, 2008 ok, thanks again, how much would the work you previously stated cost then to have done and can you say in detail what has to be done, i think ill keep the topic here, after five hours the ive received the suggestion to use a electro harmonix hum debugger so that was a little let down from what i was expecting. Thank you for all the advice thus far Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted August 17, 2008 Share Posted August 17, 2008 [quote name='Sean.Robinson' post='264142' date='Aug 17 2008, 03:10 PM']how much would the work you previously stated cost then to have done[/quote]More than the value of the amp. That's why if you aren't happy with the amp's inherent signal to noise performance you're better off to find a better one. BTW, I had a Hartke 3500 that was rated for S/N at 78dB. While about average for a bass amp, that would be considered unusable for PA or hi-fi. In those genres 90dB is considered the minimum acceptable, 100dB being a really good figure. Quote Link to comment Share on other sites More sharing options...
Sean.Robinson Posted August 17, 2008 Author Share Posted August 17, 2008 Ah ok thanks for all your help then, as i say it doesnt seem any worse than what ive heard from other amps its just one of those things if there was a cheap fix i thought why not, yet again thank you Quote Link to comment Share on other sites More sharing options...
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