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zord
6
Jan 5, 2019
My La Figaro amp has a humming even when no RCA cable is connected to it. I moved it to a different location and it still hums. I tried several different HP, with either dynamic drivers or planar magnetic. No difference if connected directly to a power outlet , power strip, or Panamax 5510. It plays music just fine. Trying another amp, "Little Dot MK III" tube amp, it doesn't do that at all when connected to the same power outlet or digital music player. I checked to make sure the power outlet is grounded. I took the amp far from any electronics but the hum is persistent. The hum increases as volume is turned higher. I wonder if I'm missing something.
Horseknight
179
Jan 5, 2019
zordHi! The problem may be the tubes. Some tubes are sensitive and generate humming sound, some are just quiet. 339 is a great machine and it deserves to get matched with the right tubes you find appropriate. I would try different tubes. The smaller tubes can be easily replaced by 6AC7 tubes (or many others) which are priced very reasonable. The larger tubes can be easily replaced as well with such as 6080, 5998, or 6AS7. Some of my tubes have constant humming, some hum only the first few hours during burning-in, some are just perfect & quiet. I hope this is helpful.
(Edited)
zord
6
Jan 5, 2019
HorseknightI appreciate the info. Thank you. And yes, the tubes have less then one hour of use. They give out some smell, just like you mentioned. If I may, is there a significant difference between the larger tubes? How would I know which one to get first? Is the number an indication of quality, as usually is the case with models of the same brand: the higher the number, the better? Also, is there a best place to shop for them? I've just switched to tube amps, and I have no experience with humming tubs. I looks like lottery then. Paying $600 for a new machine is not a guarantee of perfect performance. Having to invest more $ in new tubes that may have similar humming is a bit frustrating.
Horseknight
179
Jan 5, 2019
zordHi! Good morning here. Yes, the small tubes came with 339 always smell strong when heated. It is a strong bad chemical smell. Switching to different tubes are essential to enjoy this wonderful 339. Both small tubes & large tubes have effects on sound. Although there are expensive tubes out there, I recommend trying some commonly found tubes with reasonable prices first. There are many 6AC7 (each cost around $6 or less) and 6080/6AS7 (can be found around $15 each or less) out there. I think spending around $50 on 4 tubes can dramatically improve 339's performance. I order most of mine via Ebay. There are many reliable sellers on Ebay for tubes. I tried "Tubedepot" before but was very upset & disappointed with their customer service and return policy on damaged shipped tubes. I received SEVERAL damaged/broken tubes from Tubedepot and have to ship them back on my own money. They also charged me both-way shipping even though they shipped me broken tubes. I lost quite some money dealing with them. I do not purchase from tubedepot anymore after my last upsetting chaos dealing with their damaged and broken tubes.
(Edited)
Horseknight
179
Jan 5, 2019
zordAlso, 6AC7 are to replace the small tubes. 6080 or 6AS7 are to replace the large tubes. 6080, 6as7, 6ac7...are the tube TYPE names. There are different manufactures producing these tubes. I do not think the numbers are related to quality.
zord
6
Jan 5, 2019
HorseknightI have to say all this information is helping a lot and I'm greatfull for it. For some reason I believed the larger tubes would be more expensive. Or they are and I just don't realize it? Could be. Again, your advice is greatly appreciated. Thank you.
Horseknight
179
Jan 5, 2019
zordYou are very welcome. Enjoy your 339 with new tubes. I was on my 339 for 2 hours this afternoon. Here is my today's set up: Large Tubes: GE 6AS7. Small Tubes: RCA 6ac7.
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scottlu
346
Mar 4, 2021
Horseknightdoes GE sound good?
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