Genalex Gold Lion Bias Adjustment

Greetings,
So I have now been listening to music for about 2 1/2 years with my Latino built VTA ST-120 and so far for the most part things have been good. I started out with the Sovtek KT-88's that I bought with the amp and then tried out Tung Sol KT-120's last October. About a month ago I was looking to try a different tube and after a few emails between myself and Jim McShane I went with his recommendation of Genelex Gold Lions. As soon as I took one out of the box I noticed that it looked a lot nicer than the previous thanks to the printing on the glass tube and base color. I finally decided to try them out today. I installed them and set the bias. Here's where my question comes in. The other two tubes had no problems with biasing to .550 VDC however upon a recommendation bumped that down to .500 VDC to prolong the tube life and keep the transformers cooler though I can't substantiate the tube life issue. When biasing the Gold Lions every time I tried setting the bias for higher than .410 VDC or so my Fluke 85 would alarm out. So I set the bias to .400 VDC and decided to try them out. They sound quite good being brand new. Even though the bias was lower I still turned the attenuator down a few steps and the dynamics are still there. I have my Cary SL-100 preamp set to about the same volume level as before.

Do you think anything is wrong with the tubes? Does only being able to bias them to .400 VDC mean they will have a shorter life than the other tubes?

Thanks!

My mistake. I had the range on the DMM set incorrectly. I set the bias to .500 VDC. works fine.

Have you noticed any difference in sound between the KT88s and the KT120s?

I was really quite impressed with how nice the Genelex Gold Lions sounded. I'd say they sounded as nice as the Tung Sol K-120. But then tragedy struck. The left rear tube started glowing bright red. I powered down quickly. I hope nothing else happen. I just put my original Sovteks in and I'll bias them after I send this email. Bummer.

Dogstar wrote:I was really quite impressed with how nice the Genelex Gold Lions sounded. I'd say they sounded as nice as the Tung Sol K-120. But then tragedy struck. The left rear tube started glowing bright red. I powered down quickly. I hope nothing else happen. I just put my original Sovteks in and I'll bias them after I send this email. Bummer.

Bummer indeed. Check your pin-socket tension, power off, some tubes have thinner pin diameters than others and don't make proper contact, so the bias runs away resulting in the dreaded "red plate" calamity. I have run up against this myself, and got a red-plated tube.
Good luck. But DO tighten your pin-sockets a bit, should do it every time you change tubes. Even the smallest bit of "slop" is too much.

Setting your bias at 0.40VDC for a KT88 will actually extend the life of your tubes.

corndog71 wrote:Setting your bias at 0.40VDC for a KT88 will actually extend the life of your tubes.  

I have heard similar advice on the antique 6550s, that .45VDC is a good starting bias point. I honestly can't hear a difference going up to .5 or .6.

Thanks for the advice about checking the contact pin tension. In particular when I installed the Gold Lions I noticed they were exceptionally snug. Because. If that I figured all was good.
I play the Sovteks for about 4 hours without a hiccup. But you tension tightening adjust is a good habit to get into.

Dogstar wrote:My mistake. I had the range on the DMM set incorrectly. I set the bias to .500 VDC. works fine.

Just to clarify things a bit - I contacted Dogstar as soon as possible once I got home from my trip last week. I'm going to replace the tube that acted up for him.

But please be careful about biasing!! Even if the tube continues to work sometimes a mistake in biasing can damage the tube and cause failures later. If the tubes were running over the current or dissipation max during the time the meter was on the wrong scale it could have damaged them. I only point this out to help others avoid trouble, I'm replacing the tube for him at my expense regardless of the cause.

... about a man named Jim McShane.
(Well, it almost works.)
I bought an eight-pack of Gold Lion KT-88s off him, and quite stupidly, pulled the bottle off one of them.
He fronted me a new tube before I could get to the post office to buy a new tube I had stupidly busted.
I am sure some of us have pulled pranks like that. But Jim made me whole before my cheque was in the mail. Do I go back to him for toobs, and listen to his advice? Bloody right.

I received the Genalex tube in question back from the purchaser yesterday - I tested it and found it to be completely dead. However I will not be able to ask New Sensor to warranty the tube as it appears to have lost bias and run away - which is not covered under warranty. So I will have to absorb the expense of the replacement tube since I gave my word that I would replace it at no charge.

As well, the purchaser emailed me last night and said that the brand new U77 Genalex I sent him along with the replacement KT-88 tube wasn't working either. Then a short time later after swapping in and out a series of other rectifiers the U77 now works fine. The symptoms his amp displays all point to poor pin to socket contact. This is a tube killer in the case of power tubes, and as I've posted before MOST "bad" power tubes I get returned to me were victims of other amp malfunctions.

So this case is closed at my end, but the purchaser has to tend to his amp to be sure it doesn't act up in the future. If you'd like to get more info look at this FAQ post of mine on the Tube Asylum from a few years ago, it may help answer some of the common questions that arise: http://www.audioasylum.com/audio/tubes/messages/25/253369.html

Jim,
Interesting rant. Thanks for re-posting.
When I'm not blowing the neighbours' windows out with the stereo I do a bit of reloading on the gun bench. A micrometer, a good one, is essential to such hobby. If same tool is applied to tube pins, one quickly learns of their disparate diameters.
Tighten, tighten, tighten, and a bit of de-oxit won't hurt, either. BTW, the 88s and 120s you sold me years ago are still running strong. Thanks.

As I described in my post the KT-120's and Weber rectifier were working fine prior to installing the Gold Lions. On the Fluke 85 DMM if I have the meter set to read mVAC the maximum amount of mVAC it measures is 400. In order to have it measure anything more than 400 mVAC I have to set it to VAC and then measurements are output as .400 VAC or higher when setting the bias. I had set the bias to be .500 VAC for the Genelex Gold Lions. After reading this forum and others I came to understand that setting to bias to .500 VAC as opposed to .550 VAC which s what Bob Latino's instructions specify for a bias setting. Incidentally in the course of setting the bias on tubes prior to powering up the amp I made sure the bias pots were turned down so that when starting the bias adjustment process the meter is reading between 50 and 100 mVAC or .050 and .100 VAC so me not having the range set incorrectly was in no way going to have to bias adjustment way higher than it should have been. As soon as I saw that the Genelex Gold Lion KT-88 wa beginning to red plate I turned the amp off. After letting tubes cool down I pulled them all and installed the Sovtek KT-88's. I set the bias to .500 VAC and the amp worked perfectly OK. After getting the replacement GL KT-88 and a Genelex rectifier I installed only the rectifier since I didn't want to go through the process of biasing KT-88's. The GL rectifier did not power up at all. The amp was on for no more than a minute when I saw that so I powered it down and decided to put the Weber back in. It worked perfectly. I also have a Groove Tube rectifier that I had gotten a long time ago when a Sovtek rectifier failed and the quickest way to get a rectifier was to buy one from Guitar Center. The Groove Tube rectifier also powered up fine. I then put the Gold Lion back in and it worked. I still haven't tried the GL KT-88's but will tonight after I get some more stuff moved into my new house. But as far as I see I don't see where anything I had done as the reason the Gold Lion KT-88 failed. Now i want to believe Jim McShane is a great person to do business with but it sure seems that his rant was blasting me.

You MUST measure DC not AC !
Set your fluke to measure DC and adjust to 0.5V

The .5v is dropped across a 10 ohm resistor, you're not reading current directly!!

Use the DC scale!!

OK.....That's exactly what I was reading...my mistake. I'm not an electronics guy. I'm a mechanical engineer. I got my terminology wrong. But I was still performing everything correctly. My meter has VDC and mVDC on the selector.

Dogstar wrote:OK.....That's exactly what I was reading...my mistake. I'm not an electronics guy. I'm a mechanical engineer. I got my terminology wrong. But I was still performing everything correctly. My meter has VDC and mVDC of the selector.

The better Flukes are pretty amazing; they seem to have a "dope circuit" so when you stick the sucker in the wall outlet with the thing set for MA DC it figures it out. Mine has saved me from electrocution several times

Did the Fluke save you from electrocution, or itself from self-immolation?  

GP49 wrote:Did the Fluke save you from electrocution, or itself from self-immolation?  

Well, put it this way: we both survived. That is a good thing.
I actually knew John Fluke way back when. He was board chairman of the Association of Washington Business, where I was a flunky writer. If he had a sense of humour I was unable to detect it.

Dogstar wrote:As I described in my post the KT-120's and Weber rectifier were working fine prior to installing the Gold Lions. On the Fluke 85 DMM if I have the meter set to read mVAC the maximum amount of mVAC  it measures is 400. In order to have it measure anything more than 400 mVAC I have to set it to VAC and then measurements are output as .400 VAC or higher when setting the bias. I had set the bias to be .500 VAC for the Genelex Gold Lions. After reading this forum and others I came to understand that setting to bias to .500 VAC as opposed to .550 VAC which s what Bob Latino's instructions specify for a bias setting. Incidentally in the course of setting the bias on tubes prior to powering up the amp I made sure the bias pots were turned down so that when starting the bias adjustment process the meter is reading between 50 and 100 mVAC or .050 and .100 VAC so me not having the range set incorrectly was in no way going to have to bias adjustment way higher than it should have been. As soon as I saw that the Genelex Gold Lion KT-88 wa beginning to red plate I turned the amp off. After letting tubes cool down I pulled them all and installed the Sovtek KT-88's. I set the bias to .500 VAC and the amp worked perfectly OK. After getting the replacement GL KT-88 and a Genelex rectifier I installed only the rectifier since I didn't want to go through the process of biasing KT-88's. The GL rectifier did not power up at all. The amp was on for no more than a minute when I saw that so I powered it down and decided to put the Weber back in. It worked perfectly. I also have a Groove Tube rectifier that I had gotten a long time ago when a Sovtek rectifier failed and the quickest way to get a rectifier was to buy one from Guitar Center. The Groove Tube rectifier also powered up fine. I then put the Gold Lion back in and it worked. I still haven't tried the GL KT-88's but will tonight after I get some more stuff moved into my new house. But as far as I see I don't see where anything I had done as the reason the Gold Lion KT-88 failed. Now i want to believe Jim McShane is a great person to do business with but it sure seems that his rant was blasting me.

Rest assured I wasn't blasting you - look at the date of that Asylum post, and note that it was written some time back to become part of the permanent Frequently Asked Questions section. Second, it wasn't a rant deepee99 - it was simply a series of statements answering questions I receive all the time. I get a HUGE number of emails with questions, and often it is the same questions over and over. So I posted what I typically would send as a reply to an email inquiry.

And finally, poor pin to socket contact is the ONLY logical explanation for what occurred with the rectifier - and possibly the KT-88 tube. So I am encouraging a thorough cleaning and retensioning to prevent any possible issues in the future.

Jim, I meant "rant" in a complimentary way, the way Hunter Thompson used the term. I write rants on a weekly basis. If I'd called it a tirade then you could take offense. I thought the article you posted very informative.

Just so everyone knows - the poster with the KT-88 bias issue has accused me of fraud and selling shoddy merchandise ("covering up a bad batch of tubes"). This despite the fact that I promptly replaced the KT-88 tube he found fault with.

He also rejects the idea that poor pin to socket contact could be responsible for his GZ34 issue. He says I'm "scolding" him for passing along the advice I did - to clean and retension the sockets to ensure good contact. Deepee99 offered excellent advice in his post on that subject in this thread as well.

I just wanted everyone to know that I really appreciate the recommendations that Bob Latino gives me, and I take them very seriously. I feel I'm responsible for Bob's good name as well as my own - that's why I try go go above and beyond the call to help members of this forum. And why I take accusations like those leveled at me very seriously.

Thanks for putting up with me!

Count me among Jim's supporters!

I am one of Jim's most athletic supporters.
Seriously, Mr. McShane is one solid dude. Unlike many "tube experts", he has never, to my knowledge, inflated a price, nor given anything less than stellar advice and service.

audiobill wrote:Count me among Jim's supporters!

Moi aussi. Great man to know. Good with advice for dumb questions, and he has never sent me a lame tube.
Salud from this hiker to Jim.