Klipsher20 Posted November 20, 2009 Share Posted November 20, 2009 Hi all, I recently acquired the Dynaco ST-70 set, which was serviced, power plugs replaced to new, capacitors renewed in preamp. Amp showed suberb graph on spectrum analizer. There are original Western Germany made tubes. (Didn't looks at what exact model number yet). When I connected it to old speakers Sansui x6700 it worked perfectly (Sensitivity about 94-96). After connecting amp with Klipsch KLF-20 with sensitivity 100, there started constant 'zzzzzzzzzzz' sound. Like ground sound or I felt it was like sound from tubes buzzing. Overal sounds amazing, but hum sound is pretty big. Wondering what it might be and how to fix it. Do you have any ideas or advices? Thanks, K Quote Link to comment Share on other sites More sharing options...
db101 Posted November 24, 2009 Share Posted November 24, 2009 Could be a few different things. First thing I would look into would be a ground issue. If the power cable was replaced with a three prong grounded cable try a three prong to two prong adapter at the wall power outlet, this should help if you have a ground loop going on. Do you know what the extent of the amp serviceing consisted of? If the filter supply caps were not replaced there is a good chance that is were the noise is coming from and these would need to be replaced. Good Luck Quote Link to comment Share on other sites More sharing options...
mark1101 Posted November 24, 2009 Share Posted November 24, 2009 I would go over to audio asylum and click on Dynaco Doctor. Those guys will troubleshoot quickly. Look for Curcio and Thomas. Quote Link to comment Share on other sites More sharing options...
Klipsher20 Posted December 1, 2009 Author Share Posted December 1, 2009 Thanks to all with advises. it was a ground loop and buzz can be lowered greatly. I'd like ask if any of you had used such equipment or can recommend which is better for producing clean sound:http://accessories.musiciansfriend.com/product/Furman-S5500-Sequencing-Power-Conditioner?sku=180269http://accessories.musiciansfriend.com/product/Monster-Power-MP-PRO-2500-Rack-Power-Center?sku=182650http://accessories.musiciansfriend.com/product/Monster-Power-Pro-2000-Floor-Standing-Power-Supply?sku=182654http://accessories.musiciansfriend.com/product/Monster-Power-PRO-1000-with-Clean-Power-Stage-2-Power-Outlets?sku=18 Thanks, K Quote Link to comment Share on other sites More sharing options...
db101 Posted December 1, 2009 Share Posted December 1, 2009 No way to know if any of the conditioners you listed will work for you or not without actually trying them in your system. You need to figure out which item is causing the ground loop and then take care of it at the source, lots of times it will be cable T.V. (dissconnect the cable and see if the hum goes away) could also be your CD player, turntable, etc. If you end up having to use a Ground Isolator Transformer make sure you buy a good one, the cheaper ones will lower frequency response resulting in poor sound. Here's good article on ground loop problems: http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz Quote Link to comment Share on other sites More sharing options...
Marvel Posted December 1, 2009 Share Posted December 1, 2009 It might not be a ground loop, but emi/rfi... If you describe it more as a buzz and not a hum, it sounds like 120Hz, the harmonic of your 60Hz line freq. This could be easily be caused by a light dimmer, or other appliance. Fluorescent lights are another possiblity. A line conditioner may help, nonetheless. Quote Link to comment Share on other sites More sharing options...
o0O Bill O0o Posted December 2, 2009 Share Posted December 2, 2009 Hi, I have the same AMP and since It started buzzing I top shelved it, just like a broken "Woody" w/ a torn arm. Since then I have yet to find a repair service or educate myself to take on the role of EEE. Are there recommended business that refurb/refreshes tube amps? I'd ship but the Northeast is the area I live in.. Thanks -Bill Quote Link to comment Share on other sites More sharing options...
gartenman Posted December 4, 2009 Share Posted December 4, 2009 NOSValves.com Quote Link to comment Share on other sites More sharing options...
o0O Bill O0o Posted December 4, 2009 Share Posted December 4, 2009 Wow, thanks for the recommendation. I'll be in contact with them when I get back to my family. _Bill Quote Link to comment Share on other sites More sharing options...
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