joessportster Posted January 5, 2007 Share Posted January 5, 2007 ok 1 more question, (seems the higher you take your system the more sensative things become, and the harder they are to deal with), gear all hooked up and working nicely except for a low level hum, comes thru the speakers i tried powering off each component 1 at a time first the tt, then the pre-amp, then the amps, (hum remained till the amps were shut off), so i tried cheaters on the amp power cords hum remains, next i tried to a seperate power cord and ran it a new route with 1 of the amps and the hum remains, i am assuming i have either a ground loop problem or the high sensativity of the new pre is causing a hum (however it seems to me it is from the amps) because all the adjusting of signal, volume, gain, etc...on the pre does nothing to affect the hum.........., next step i guess is i will try a new set of innerconnects from pre to amp, any other suggestions (the amps are auto biasing, but have hum pots, problem is the hum pots have to accessed from the bottom with the cover removed and the power on seems like a good way to get a shock) any suggestions????????? Joe Quote Link to comment Share on other sites More sharing options...
Chicago_Pete Posted January 5, 2007 Share Posted January 5, 2007 Cheaters did nothing for me when I had this issue. Kimber innerconnects (on the amps only) replaced my Audioquests and no more hum. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 5, 2007 Share Posted January 5, 2007 Sounds like this is a tube amp since you mention auto bais and hum pots. Few things to try...obtain or make some shorting plugs. You can make them by buying regular rca plugs at radio shack and soldering some 10K resistors across them. Use the shoring plugs by plugging into your amp input. Hum status? Do not use shorted plugs with out resistors, like the type installed on phono imputs. Shorted plugs with out resistors can cause damage to your amp if your amp has capacitor leaks. For the below...make that you unplug and wait a few minutes to ensure the amps caps are drained before removing any of the tubes. Next, with the amp off and unplugged, removed the line driver tubes, turn the amp on and do a hum status check. Next, agin with the amp off and unplugged, remove the pre-driver tubes, turn the amp back on and do a hum status check. Finally, turn off the amp, remove all but the output tubes, turn the amp back on, and do a hum status check. The above process will help determine what stage of you amp is the issue and if the issues is bad input or pre-driver tubes. if the hum remains, down to the last step, you probally need a tech to check your amp out for bad capacitors and/or leaking diodes. I recently had a very mild but audible hum/buzz in my amps if you put your ears right up to the speakers. The amps were 15 years old. The problem was resolved by replacing 6 capacitors. Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 5, 2007 Author Share Posted January 5, 2007 what type of kimber cable did you use and where did you get it pete???????? thanks fritz i will try your test as a last resort as i didnt have any hum b-4 so i think its a slight problem, of course i could be wrong!!!!!! Joe Quote Link to comment Share on other sites More sharing options...
frankphess Posted January 5, 2007 Share Posted January 5, 2007 Try a cheater plug on the pre-amp if your pre-amp is a three prong plug. Quote Link to comment Share on other sites More sharing options...
jackpod Posted January 5, 2007 Share Posted January 5, 2007 Joe, Does the new preamp have just a 2 prong plug? if so flip it over Jack Quote Link to comment Share on other sites More sharing options...
Chicago_Pete Posted January 5, 2007 Share Posted January 5, 2007 Joe, I bought the Kimber PBJ's from Audio Advisor when they were running a sale. I have Audioquest Copperheads on all of my other sources but for some reason they just didnt work well with my amps. Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 5, 2007 Author Share Posted January 5, 2007 well i adjusted the hum pots and it helped, buut i guess its time i thought about some better cables !!!!!!!!!!!!!! joe Quote Link to comment Share on other sites More sharing options...
joshnich Posted January 5, 2007 Share Posted January 5, 2007 Joe Try these www.anticables.com Quote Link to comment Share on other sites More sharing options...
dbflash Posted January 5, 2007 Share Posted January 5, 2007 Joe, I don't know if this will help, but it worked for me. What didn't work: Used cheater plugs on all equipment. Swapped out all IC's. Ran a dedicated 20A circuit and a power conditioner. Tried 3 different preamps. What ended up working was: I moved my preamp as far away from my amps as possible. I am using 1 meter IC's so it wasn't a big seperation, but it worked. I had some hum with both my Wright Set amp and my VRD's. I could hear it sitting in the sweet spot with no music playing. Now I have to put my ear up against my khorns and I can hear alittle hum. Old set up: New set up: cdp preamp (there is now 22" between the top amp shelf and the preamp shelf) preamp cdp amp amp amp amp Good Luck Danny Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 6, 2007 Share Posted January 6, 2007 Joe, Take some old junk IC's the kind that come stock with a CD players. cut them about 4" back from the RCA jacks. Strip the outer insulation off and you will find the shield/ground wires move them off to the side and expose the inner insulated conductor, now strip the insultion off the inner conductor. Twist the outer shielding ground wire together with inner conductor and tape it off. Now shut your amps off and lift them from ground. Plug these RCA shorting plugs you just made into the amps. Fire them up. If they are still humming them you have humming amps. If they are quiet start adding one single component until the hum presents itself again and you have cornered the little bugger and can go at the component that is causing the problem. Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 6, 2007 Share Posted January 6, 2007 As you found, adjusting the hum balance pots probably took care of most of the problem. Some AC DHT amps are a little more fussy than others, but the hum null control can get rid of the majority of what you hear. It's kind of awkward that they are on the inside of the amp, though. As you roll output tubes, it's sometimes necessary to readjust those controls. Also: It can be difficult to find the correct position on the potentiometer if the amp is some distance from the speaker -- and you're doing this by ear. you can also make the adjustment with a voltmeter on the outputs. Erik Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 6, 2007 Author Share Posted January 6, 2007 craig you had given me this advice in the past and i tried it early on the amps were dead silent with the shorting plugs, thanks again for you assistance, i always take everything you say seriously because this is afterall your professison and my hobby............. eric i was lucky enough to be 3 feet from the speaker so i could hear the hum and all i did was switch the other amp to the same speaker so i could hear it clearly, i really cant hear humming anymore but i do get a hiss/static sound when the pre is set at a high volume, and the selector is on phono.........dead silence when the selector is on anything else, these tests are being done with the cornwalls and the x-overs are original 1980 so i would assume i can get some noise out of them i will be bringing in the k-horns next week with alk's in them so i will either have the sound amplified by them or helped by them thanks for all the great advice Joe Quote Link to comment Share on other sites More sharing options...
Parrot Posted January 6, 2007 Share Posted January 6, 2007 eric i was lucky enough to be 3 feet from the speaker so i could hear the hum and all i did was switch the other amp to the same speaker so i could hear it clearly, i really cant hear humming anymore but i do get a hiss/static sound when the pre is set at a high volume, and the selector is on phono.........dead silence when the selector is on anything else, these tests are being done with the cornwalls and the x-overs are original 1980 so i would assume i can get some noise out of them i will be bringing in the k-horns next week with alk's in them so i will either have the sound amplified by them or helped by them You've described a totally normal situation of hiss/static with tubes, especially in the phono section, and highly efficient speakers. You'll likely hear it more once you substitute in Khorns. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 7, 2007 Share Posted January 7, 2007 craig you had given me this advice in the past and i tried it early on the amps were dead silent with the shorting plugs, thanks again for you assistance, i always take everything you say seriously because this is afterall your professison and my hobby............. eric i was lucky enough to be 3 feet from the speaker so i could hear the hum and all i did was switch the other amp to the same speaker so i could hear it clearly, i really cant hear humming anymore but i do get a hiss/static sound when the pre is set at a high volume, and the selector is on phono.........dead silence when the selector is on anything else, these tests are being done with the cornwalls and the x-overs are original 1980 so i would assume i can get some noise out of them i will be bringing in the k-horns next week with alk's in them so i will either have the sound amplified by them or helped by them thanks for all the great advice Joe Joe, Okay now here is what you have to do. First adjust these hum pots with the shorting jacks in place and the forget those hum pots completely your done with them. It sounds like they must have little efect since the hum or noise your hearing is not in the amps. The shorting plugs absolutely proved that. The noise your getting is from up stream components. If this noise is hum (HUM COMES DIRECTLY FROM THE WOOFER). It sounds like the lowest notes you as a human can HUM... many people describe noise improperly. Noise out of the tweeter and mid horn is much higher in frequency and would be called buzz or hiss. Now just attach you preamp and insert the shorting plugs in whatever input you choose on the slector switch of your preamp. Turn the system on is this noise present? If it is the preamp is the noisy item or you have a ground loop. If the amps and the preamp have 3 wire power cords the lift two items from ground doesn't matter which two but just have one 3 wire power cord for these three components. Then fire it the system back up. Does it have the noise? If it still has the noise swap out the IC's between the amp and the preamp. Again any change? You keep doing this type of component isolation until you have isolated the noise producer. Separates can be a real pain in this respect. Methodical step by step approach is the only true sensible way to track it down. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 7, 2007 Share Posted January 7, 2007 Oops missed your mention that your noise is just phono section. Harder to isolate since the proper way to test the phono input would be to make a shorting plug with the proper loading character to match the load of the cartridge. But you can go ahead and use the shorting plugs in your pnono input and see what the difference is with the TT out of the equation. Let me know what you hear like that. Craig Quote Link to comment Share on other sites More sharing options...
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