eth2 Posted June 3, 2014 Share Posted June 3, 2014 (edited) I posted a few days ago that I had just received my tube amp back from the manufacturer. One channel had a hum and the other had static/crackle. Beeker recommended swapping the driver tubes from one channel to the other. Turns out Beeker was right on, and the crackle followed the channel switch, hence a bad tube or three (there are three CA4003 driver tubes per channel). This advice was later offered by the manufacturer.Now for the one channel hum. The manufacturer suggests playing with the biasing and if that does not work, try swapping out all of the KT88 power tubes (2 per channel). So all tubes were tested prior to the expensive upgrade, but now I have to replace all the power, and 1/2 of the driver tubes to see if the unit must be returned (again). Learnings - 1. If you have noise in one channel that sounds like a crackle or static, you may have a faulty driver tube. 2. If you have a one channel hum, you may have a faulty power tube. 3. SS amps have no tubes. Edited June 3, 2014 by eth2 Quote Link to comment Share on other sites More sharing options...
beeker Posted June 3, 2014 Share Posted June 3, 2014 my head hurts for you earl! the other day i had to relax and neary had to take a migrane shot...luckily i could relax my head enough for the pain that vac has caused you to go away...i really dont know what to say man...this amp is getting a little out of hand...id call the guy that sold it to you and possibly file a suit...all depending on what you bought it for and its bluebook value 1 Quote Link to comment Share on other sites More sharing options...
joessportster Posted June 3, 2014 Share Posted June 3, 2014 (edited) 4. buy a better tube amp from someone you can trust to stand behind there product. VAC are very expensive but apparently could care less about the customer once the amps leave warranty example, I owned a pair of thor audio tpa 30 amps, during shipping one of the transformers loosened up and 1 call to Ted Linblad, shipped to him He repaired free of charge and he paid return shipping BTW Ted did not build my tpa30 he bought the rights to the name after the original owner decided to sell out, He simply cares about the name and customer care as well as seems to care more about sound than the business end Edited June 3, 2014 by joessportster 1 Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 3, 2014 Author Share Posted June 3, 2014 Joe and Beeker: You both have very good points. I will likely never buy amps/electronics from anyone unknown to me in the future. I was burned on both VAC amps I bought on AudiogoN. I am going to buy a new set of driver tubes (I have more KT88's). The only positive is that the PA80/80 (now a PA 100/100 after the mod) sound exquisite with the Khorns. Also, when moving into a new hobby, time and patience is very important. I jumped too quickly at tube amps without knowing what I was doing. I should have spent much more time on the Forum before pushing forward. When I first started working, a man close to retirement who came to the US as an immigrant after WWII, and who had been a shift supervisor for MANY years in a power plant I was sent to in order to learn about the business said to me, "You kids (I was 22)...Too late, smart!" Apparently, that wisdom applies to the same kids when they get older. 1 Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 3, 2014 Author Share Posted June 3, 2014 thor audio tpa 30 amps Joe, You have had some GREAT equipment! Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted June 3, 2014 Share Posted June 3, 2014 Jeez Earl, you're luck parallels mine. 1 Quote Link to comment Share on other sites More sharing options...
Sancho Panza Posted June 3, 2014 Share Posted June 3, 2014 Note to self: do NOT get into Tube Amps until Lee & Jackson are paid off; they are like boats & houses (money pits). 1 Quote Link to comment Share on other sites More sharing options...
joessportster Posted June 3, 2014 Share Posted June 3, 2014 Earl it is a long list of gear to be sure. but it did more than afford me the pleasure of hearing stuff. It let me find my preferences in the sound that appealed to me IE...I know I prefer SET / SEP (single end amps), I prefer analog over digital, I prefer Horns over direct radiators except when it comes to impact and on and on and on.................................. The knowledge allows me to drastically shrink a list of potential pieces of gear. 1 Quote Link to comment Share on other sites More sharing options...
joessportster Posted June 3, 2014 Share Posted June 3, 2014 Note to self: do NOT get into Tube Amps until Lee & Jackson are paid off; they are like boats & houses (money pits). If you get the right amp tubes can actually cost less while sounding tons better..........................there are some ?? / answers one needs to know about music preferences and then make an informed decision about which amp suits your needs best.............then realize that NO amp or speaker or any piece of gear is perfect and all have there strengths and weaknesses and it really is not that hard to get a sound you can live with................ Quote Link to comment Share on other sites More sharing options...
Fjd Posted June 4, 2014 Share Posted June 4, 2014 (edited) Joe and Beeker: You both have very good points. I will likely never buy amps/electronics from anyone unknown to me in the future. I was burned on both VAC amps I bought on AudiogoN. I am going to buy a new set of driver tubes (I have more KT88's). The only positive is that the PA80/80 (now a PA 100/100 after the mod) sound exquisite with the Khorns. Also, when moving into a new hobby, time and patience is very important. I jumped too quickly at tube amps without knowing what I was doing. I should have spent much more time on the Forum before pushing forward. When I first started working, a man close to retirement who came to the US as an immigrant after WWII, and who had been a shift supervisor for MANY years in a power plant I was sent to in order to learn about the business said to me, "You kids (I was 22)...Too late, smart!" Apparently, that wisdom applies to the same kids when they get older. I'm surprised you didn't get more advice from the forum on the amp choice. Here is my stereo VRD amplifier and can be purchased as mono blocks too. No affiliation and I hope you enjoy the levity somewhat. Edited June 4, 2014 by Fjd 1 Quote Link to comment Share on other sites More sharing options...
wvu80 Posted June 4, 2014 Share Posted June 4, 2014 (edited) Earl, maybe have some more patience, before you you get disgusted and sell your rig to me for a hundred bucks? I think Beeker said on your other similar thread that sometimes break-in on tubes can be 50 hours. I know it's hard to listen to otherwise great sounding equipment with some character flaws, but maybe with a little time on the amp this problem will resolve itself. If not, I have a 1995 Pioneer receiver with about 100 watts per channel I'll trade you, straight up. It's solid state. You pay shipping. Edited June 4, 2014 by wvu80 Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 4, 2014 Author Share Posted June 4, 2014 Earl, Do these amps have a "bias computer" "bias lights" or other dead-accurate means of setting bias? It is absolutely true that uneven bias will create hum. Having a "bias computer" (set of comparators and internal references) can also function to give you a go-nogo test on output tubes. How will you bias these? Four idiot lights. Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 4, 2014 Author Share Posted June 4, 2014 Earl, maybe have some more patience, before you you get disgusted and sell your rig to me for a hundred bucks? I think Beeker said on your other similar thread that sometimes break-in on tubes can be 50 hours. I know it's hard to listen to otherwise great sounding equipment with some character flaws, but maybe with a little time on the amp this problem will resolve itself. If not, I have a 1995 Pioneer receiver with about 100 watts per channel I'll trade you, straight up. It's solid state. You pay shipping. Given some of the things I've done recently, this may be one of my better deals. Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 4, 2014 Author Share Posted June 4, 2014 I have adjusted the bias and the hum is almost gone. I was just told to adjust the bias for the tube next to the one that seems to be the problem. Am I adjusting the KT88' power tubes or the cv4003 drivers? Quote Link to comment Share on other sites More sharing options...
USNRET Posted June 4, 2014 Share Posted June 4, 2014 (edited) I have adjusted the bias and the hum is almost gone. I was just told to adjust the bias for the tube next to the one that seems to be the problem. Am I adjusting the KT88' power tubes or the cv4003 drivers? I am fairly sure that would be the -88s, is on my VRD bias. Edited June 4, 2014 by USNRET Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 4, 2014 Author Share Posted June 4, 2014 Thanks Quote Link to comment Share on other sites More sharing options...
minermark Posted June 4, 2014 Share Posted June 4, 2014 My man in Kowloon is standing by, and I must admit, I stand by his products. After a month of running my wifes mono blocks, one of the KT88s was just not glowing like it should and the sound output was down a bit. Emailed Primeamp, and he sent a set of of new 88s no charge. http://www.ebay.com/itm/Music-Angel-XDSE-YC-808MK-KT88B-Vacuum-Tube-Hi-end-Tube-Integrated-Amplifier-PUS-/261018868145?pt=US_Home_Audio_Amplifiers_Preamps&hash=item3cc5efd9b1 Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 4, 2014 Author Share Posted June 4, 2014 Prices are reasonable, but shipping is a killer Quote Link to comment Share on other sites More sharing options...
joessportster Posted June 4, 2014 Share Posted June 4, 2014 (edited) Earl do any of your pre amps have 2 variable outputs ? Edited June 4, 2014 by joessportster Quote Link to comment Share on other sites More sharing options...
eth2 Posted June 4, 2014 Author Share Posted June 4, 2014 Yes Quote Link to comment Share on other sites More sharing options...
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