You'd be trading a slightly faster tube burn-out, for slightly greater dynamics.
A question of bias for new tube set
Something seemed a bit off with my system so i checked the temperatures of the EL34 power tubes on my Cary Audio Six pacs with a pyrometer and found all the tubes reading a temperature around 360 deg F +/- but one. The errant tube was reading around 175 deg F. Checked the bias on each mono block and found that the set with the errant tube was way off the recommended bias I usually set which is 220 ma. It read 180 ma. The other mono block was operating in spec. I also noticed that with a music source, the bias readings on both mono blocks seemed to swing 10 or so ma with the music. Didn't know if this was normal or not but figured since i had a bad tube and had no idea of the age of the tube set (bought the Six Pacs used), I figured it was time for a full set replacement.
The existing tubes were Svetlana Winged C EL 34s but after some research, I decided to buy a matched set of Electro-Harmonix EL34s from Kevin Deal of Upscale Audio. According to Kevin the EH tubes were less extended in the bottom end but added some sparkle to the upper range. Since they were about half the price of other competitive tubes (I needed 12), came matched and burned in for 72 hours, I figured I'd give them a try.
Swapped them out and set the bias to the Cary recommended 210-230 ma (I chose 220 ma). Noticed a few things. First, the bias with music was now rock steady at the 220 ma setting on each monoblock. And Kevin was spot on in his description of tube sound. However, each of the tubes came marked with specs including bias which were all within a tenth of 41.6 ma. That would equate to a bias setting of 246+ ma on each Six Pac. So my question is, should I stick with the Cary recommended bias of 210-230 ma or crank it to 245 ma?
Comments appreciated,
J.Chip
The existing tubes were Svetlana Winged C EL 34s but after some research, I decided to buy a matched set of Electro-Harmonix EL34s from Kevin Deal of Upscale Audio. According to Kevin the EH tubes were less extended in the bottom end but added some sparkle to the upper range. Since they were about half the price of other competitive tubes (I needed 12), came matched and burned in for 72 hours, I figured I'd give them a try.
Swapped them out and set the bias to the Cary recommended 210-230 ma (I chose 220 ma). Noticed a few things. First, the bias with music was now rock steady at the 220 ma setting on each monoblock. And Kevin was spot on in his description of tube sound. However, each of the tubes came marked with specs including bias which were all within a tenth of 41.6 ma. That would equate to a bias setting of 246+ ma on each Six Pac. So my question is, should I stick with the Cary recommended bias of 210-230 ma or crank it to 245 ma?
Comments appreciated,
J.Chip
12 responses Add your response
I own the last run of AES Six Pacs. The choke is moved from the center to the side, and a pair of small smoothing caps are added to the power supply. After that the Hexfreds, Jupiter Copper foil caps,and silver wire (take your pick). I run them at 210-220, if I'm pushing the amps. I go to 240-50 for late night listening, and low volume, kind of a winter time setting. But when I blast (hard with Six Pacs) 210-20 mA EH valves are close to Ruby in SQ, and a LOT more dynamic, than a Golden Lyon, by far. Because I don't use valve amps for bass duty, I prefer a better Mid Bass, Dynamic (almost bloated) mids and silky smooth highs. EH GREENs are a great valve. Still not quite as freakishly GREAT as Ruby Valves and Cary products. I don't know why.. But for some reason they outperform all of the EL34 stuff. In their, V12s V12i and V12R, ALL just sound better with, Ruby, or EH, valves. Really not the most expensive valves out there. PSVANE That's next on the list of try outs and power valves, $$$$ though. Sure make a good signal valve, 12AX7, 12AU7. Regards |
These sound way better than any EL34 IMO Genalex Gold Lion KT77 Power Tubes They are worth the money and are a sub for EL34 but BETTER !! Explanation at the link below https://www.tubesforamps.com/el34-6ca7-kt77-differences Where to buy Quad Matched https://www.sweetwater.com/store/detail/GENKT77QM--genalex-gold-lion-kt77-power-tubes-matched-quarte... |
These sound way better than any EL34 IMO Genalex Gold Lion KT77 Power Tubes They are worth the money and are a sub for EL34 but BETTER !! <<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>> It’s obvious you don’t own Cary/AES Six Pac, Cary V12, V12Rs, Marantz 5,7,or 9s, I DO! The Six Pacs I own came with two brand new sets of matched GL KT-77 Sixtets. They did a super hot rodded AES 6 Pac, NO JUSTICE, they just sounded BAD. Swapped over to a set of Rubys, brighten right up. I tried them in a V12R, for a couple of days, friggin’ valve failed. Started losing the health light on the V12R. I pulled all 6 on one side and put Rubys in, LOL THAT was an eye opener.. Night and Day difference, left and right speaker, GL vs Ruby, no contest.. That valve in ANY of the above amps won’t hold a candle to either EH or Ruby plane and simple. This is from an owner, not a guy trying to sell valves, or reading articles, someone else published. Hands on, OWNER. The only valves that are as good or maybe a tad better is old stock Mullard,Volvo, or Tellies. American made 6CA7, sylvies, are a MUCH better valve if you can find 6 that match at a time. KT77 GL new stock is russian made, 10% tolerance and have a high failure rate. They are dark, they do not represent what a good EL34 is all about. GL is a better bass valve but poor, at what an EL34 is. An El34 has Poor bass, good mid bass, slightly bloated mids, and silky BUT dynamic highs. If you want to build around a GL KT77, there is still a LOT better valve Bottom to Top than a GL, especially for the money, PSVANE is another GREAT valve, but it represents an EL34 sound, but can fetch 2-800.00 for some of their "special" valves, LOL special price. WAY to much.. BTW, 220 mA on the 6 Pac if your cranking it, Late night listening, 240-50, just don't crank it, better low volume listening. Regards |
@oldhvmec1 You are correct i do not own the Cary V12, and I never said that I did. I said they were better than any EL34 that I have heard . Of course I have not heard High Dollar NOS 1950's or 1960's EL34 Who can fiknd or AFFORD those . Your observation is with the amp that he owns , i suppose . I am sure there is a lot better , but ,it was my observation that for the money I thought they were damn good. Of course the GEC KT-77 was probably the best ones , but finding those is like trying to use humming bird hearts for fishing bait, or pulling hen's teeth. I tend to agree with this link.. Sorry for having an opinion ! https://www.tubesforamps.com/el34-6ca7-kt77-differences |
How do you know the original tube with the low bias current was actually defective or aged really? Did you check the bias voltage on the grid of that tube? It could be a problem upstream, affecting grid voltage. In which case a new tube inserted in that socket would display an analogous difference in bias current compared to other new tubes in the other sockets. |
Lewm8 i only surmised that the original tube was bad because it was running at about half temperature than all the others. On the Six Pacs, you can’t check or set individual tube bias. Bias is set for the block of six tubes. When I put the new set in, I was able to set bias to spec which held rock steady and the tubes all displayed the same operating temperature. SQ also returned so it had to be the tube I suspected was bad. j.chip |
@jchiappinelli learned something from you in this thread getting a pyrometer is a good idea to monitor power tube health, at a minimum it let's you read tube running temps in a multi-tube amp most amps do an average bias across at least 2 sometimes 4 tubes, this is a good way to check if one of them is way off the other before more serious issues occur with the tubes glad you found the bad tube was the culprit, and your SQ is back to normal - makes all the sense in the world in these days with chinese and russian tubes as the only new ones available, we really need to verify proper operation, not just trust the factory/vendor |
39.00 usd Handheld automotive/HD thermal gun. -50 to 600 degrees Fahrenheit. It will also tell you when it's Filter cap time. Cary, Mac, VTL, and Marantz, the transformers ALL run extremely HOT when the filter caps start to take a dump. A pyrometer is good, it TOUCH the object that's being tested, they (when calibrated) have a much higher and lower reading. The accuracy is greater than a handheld thermal scanner also, (hardwired to the pickup sensor) It (hand held) will pick up the difference in heat, in a wall outlet though, loose connections, or failing switches, nice tool for the ol pouch, for sure. A new Maxi Tube tester was just finnish and shipped. My 533, and 539 are getting OLD, still great for small valves, but to get a good read on pairs or quads, of power valves. The Maxi is suppose to be the cats meow.. We'll see. He has one for signal valves but is behind on receiving logic boards. Out of Washington area, also has a burn in grid, 16 valves at a time. MAXI is the company.. Can buy in bulk valves out of Turkey, and the Russian region. Not so much with Chinese valves. They (Chinese valves) seem to be bought by the Turks and Others and they sell the bulk Chinese valves, to silly westen suckers, like ME... Can't get a break.. :-) 1-5 per valve in bulk. BUT you have to check them, 3% have issues, after that 24 hours they usually give great service life, 72 hour burn in is VERY rare, BUT the valves is just bullet proof until the grave... Regards |
