Could be as simple as needing some very low noise tubes. Could also be too much gain for your amp/speakers and the 'noise' issues could be solved by using a fixed in-line attenuator. But that turn on 'buzz' and high frequency noise after 24 hours, I don't know. But then I would never leave a tube unit on for 24 hours......The turn on buzz is probably nothing more than the unit stabilizing, something many pre-amps avoid by having a mute circuit which engages on turn on (for up to several minutes).
Tackling the tubes first is a good place to start. Sooner or later you will have to change them out, so even if this is not 'the' problem having the spare set is a good idea anyway. |
The high frequency whine that you mentioned rings true to me. I had the same experience and found the problem to be with the tubes, not the preamp. Not sure what tubes you are using but I have had great luck with Cryoset. They cryogenically treat all of their tubes which, in my experience, has resulted in very quiet tubes that seem to last forever. I buy new production Gold Lions and they have been great.
Good luck!
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after the unit has been on for several hours, like 24+ it will start to
emit a high frequency pitch that also is only audible with no music
playing but it is louder than the inherent noise floor of the pre. That is a form of something called 'microphonics' and is a property of all active devices. Tubes have it more than solid state, and its definitely something that you can get rid of by changing a tube! |
The tubes are stock (as far as I know, I'm a second owner) 12au7 and 12ax7 and this being an inexpensive preamp I'm thinking they are not of any significant quality and should be replaced shortly after purchase which is fine by me. Also as far as voltage gain from the pre, I'm pretty sure that is also the issue, I have never dared to play it louder than maybe 11 o'clock position on the volume potentiometer because it's starting to clip a 300 watt amp so the in line attenuator sounds like might be a good idea although I'm pretty wary about putting another thing in the signal path. With having next to zip knowledge in electronics, is there a way to change this value internally? Jolida states that the max output voltage is 30v and voltage gain is 20db (although they have these two values reversed on their website) |
Rothwell - stock 10db in-line attenuators should work just fine. No real downside unless you have ultra high end stuff and you are anal! :-) You can select other values if you want. Lot cheaper than trying to mod your pre-amp internally. BTW, if you are changing tube brands be aware that you will want to insure that their 'tonal' balance is one that you will want in your system. Do lots of research on this before you leap and beware of salesmen's advise and advise from folks who don't know much more about tubes than you do, they abound! :-) |
Also as far as voltage gain from the pre, I'm pretty sure that is also
the issue, I have never dared to play it louder than maybe 11 o'clock
position on the volume potentiometer because it's starting to clip a 300
watt amp so the in line attenuator sounds like might be a good idea
although I'm pretty wary about putting another thing in the signal path.
@lukaszwk, I would try other tubes before doing anything with an attenuator. Its not that weird for an older used tube to get noisy and microphonic. If you replace the tubes, it might be nice and quiet. |
@atmasphere so the preamp is about one year old and it supposedly has only few (two or three?) hundred hours on it, as far as I know. Seems like that wouldn’t be enough time for the tubes to degrade significantly but I’ve also heard different. I’ve been meaning to try new tubes and my question is; is there anyone in the Chicagoland area, retail wise that has a knowledge and inventory of tubes that might be of interest to me? |
@lukaszwk You might try TubeDepot.com I don't know of anyone selling tubes in Chicago, but I'm sure they are there.
I would not regard the age of the preamp as having anything to do with tube condition! Who knows if the tubes were any good when they were first installed??
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@lukaszwk,
You might get better help if you disclosed what preamp.
Sounds like it might need new tubes. |
@atmasphere Huh... That did not occur to me. I kind thought of the preamp/tube as a single entity especially when new but I see how that could be misleading. |
@jperry the info is actually at the end of my post, it's Jolida fusion preamp |
Make sure tube pins are cleaned and tubes of high quality .vintage Matched pair New old stock are best lowest distortion. If that doesnot lower noise to not be audible unless ear us up to the speaker Then your preamp either have problems needing to be fixed or is of Lesser quality and poorly designed. My tube amp is Trans former based and Very quiet. with tube preamps quality is even more important then with solid state ,but when done correctly the soundstaging and 3 dimension realism aspects it brings no Solid state preamp cannot quite match. |
Upscale Audio for a tube overhaul. Good information on the website. Probably will fix the whole thing. Enjoy.
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Thanks for all the info, this basically confirms what I initially thought. Silly of me to think that actually might be happy with my current setup for any significant length of time... This "hobby" and I put this in quotations because I don't think that's what it is, more of a pursuit of something ethereal and unattainable, is sure getting more and more complicated but the chase is eternally on. |
Also something that I may have misrepresented is that the buzz (not the high frequency pitch) i hear is intermittent and comes on every few minutes until the pre warms up so it's not a constant thing.
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Brent Jessee Recording is a little northwest of Chicago at:
1590 West Algonquin Road #111
Hoffman Estates, IL 60192
He does not do tube repairs but he is a major tube seller and might be willing to give your preamp a listen if you give him a call or he could probably direct you to someone who works on tube gear in your area.
Google his name for his webpage. He could give you some good advice when you get ready to buy new tubes. |
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Also something that I may have misrepresented is that the buzz (not the
high frequency pitch) i hear is intermittent and comes on every few
minutes until the pre warms up so it's not a constant thing. That is consistent with a possible bad tube. |
Purchase tubes from a reputable dealer and always ask if they are tested for noise.
Upscale and Vintage Tube Services do noise testing as well as tube matching. Brent Jessee offers noise testing for a $10 fee. Tubes used in the gain stage should always be tested for noise and microphonics. |
Many of us spend a few more dollars on tubes, ESPECIALLY IN OUR PREAMPS, to get the "lowest microphony" possible. eg. on the Upscale Audio site and other sites you can get the "Platinum grade" tubes, that have already been tested, matched. make sure to buy from a dealer who not only matches your tubes, but writes down the specs of the tests, and put them on the tube box for your use, and to reassure you.
If you can afford i lucas, i would suggest researching tubes a bit (eg upscale site- can call them too), then buying some new tubes ASAP, get them burned in for a week or two, then compare them to your old tubes ... .rather than possibly trying to figure out what is wrong with the current tubes (takes time, patience, research, tests) would encourage you to get some great tubes ASAP.
life is too short for crappy tubes. |
Ok, I appreciate all the advice, informative and relevant as always. I will definitely get some quality tubes as soon as I can.
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