ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Re: Mesa "special requirement" power tubes - long

7/7/2000 4:42 AM
Richie	Re: Mesa "special requirement" power tubes - long Still cracking up here reading this.Almost the same thing happened to me. In a music store looking to see what came out of pawn.. and they had some EL34G sovtek tubes.. I asked the price and he said 28.oo..each!!!! I said, you mean a matched set don't ya.. nope!!! 28.oo ea. and he says.. matched to what ever amp uses EL34 tubes. I have heard one great sounding mesa head. And usually all the mesa's run their preamp tubes way up in voltage. And they don't last long.And some models are a pain to work on. Maybe the robo tube tester needs itself repaired..Or maybe giving an exact reading when it really isn't.. or maybe he tested all day with the same screen on the computer..they all were exacly alike!! Richie{~}==:::

7/7/2000 4:42 AM

Richie

Re: Mesa "special requirement" power tubes - long

Still cracking up here reading this.Almost the same thing happened to me. In a music store looking to see what came out of pawn.. and they had some EL34G sovtek tubes.. I asked the price and he said
28.oo..each!!!! I said, you mean a matched set don't ya.. nope!!! 28.oo ea. and he says.. matched to what ever amp uses EL34 tubes. I have heard one great sounding mesa head. And usually all the mesa's run their preamp tubes way up in voltage. And they don't last long.And some models are a pain to work on. Maybe the robo tube tester needs itself repaired..Or maybe giving an exact reading when it really isn't.. or maybe he tested all day with the same screen on the computer..they all were exacly alike!!
Richie{~}==:::

7/7/2000 4:42 PM
Patrick	"I was curious to see how good the "Robotube" tester hype was anyway." Well, the gal running the Robotube is cute, so it must be true, right?? Hey Randall, I've been there myself. Every now and then I say, well, these folks are selling stuff and have these big $$ ads, so that can't be ALL hype. Sadly, I have found, as have you, more often than not, it is hype. Much like our man Clinton, style over substance, and the American people keep buying into it, not once but twice!! But each time we bite, we get a little smarter.

7/7/2000 4:42 PM

Patrick

"I was curious to see how good the "Robotube" tester hype was anyway."

Well, the gal running the Robotube is cute, so it must be true, right??

Hey Randall, I've been there myself. Every now and then I say, well, these folks are selling stuff and have these big $$ ads, so that can't be ALL hype. Sadly, I have found, as have you, more often than not, it is hype. Much like our man Clinton, style over substance, and the American people keep buying into it, not once but twice!!

But each time we bite, we get a little smarter.

7/9/2000 5:53 PM
andyfuchs	This whole thread reminds me of a bizzarre experience I had while I was managing a service shop that was "Mesa Authorized". A customer brought me a MK-1 for a retube (I asked him when was the last time he brought eggs to a diner and asked him to cook them, but he missed the joke), and he brought in a full set of Mesa "selected" replacement tubes (cause Mesa says there's nothing better for their amps). Well besides the original preamp tubes were Sylvanias and sounded decent, and the replacments (Chinese) sounded like microphonic-dirt, the story got interesting around the power tubes. The original Sylvania 6l6's were still pretty strong and were running at about 50 ma each. The new Chinese tubes ran at 25 ma each. I tossed in a trimpot, a couple of 1 ohm 2-watt cathode resistors and set the bias. I wrote this on his service ticket, and totalled the bill. When he picked up his amp, he got all twisted and told me "I brought you Mesa selected tubes, that doen't need to be biased, and besides theres no bias pot in this amp, Mesa said so". After much argument, we called Mesa, and Randall (who, at the time, still would talk to you on the phone), insisted that I refund the customer's money, and "not charge him for modifications his amp didn't need". He continued to insist that "something was wrong" and "are you sure you know what your doing.." and such. Thanks to Mesa hype, the concept of Biasing is no longer valid. I soon got disgusted with the whole repair business and took ten years off.

7/9/2000 5:53 PM

andyfuchs

This whole thread reminds me of a bizzarre experience I had while I was managing a service shop that was "Mesa Authorized". A customer brought me a MK-1 for a retube (I asked him when was the last time he brought eggs to a diner and asked him to cook them, but he missed the joke), and he brought in a full set of Mesa "selected" replacement tubes (cause Mesa says there's nothing better for their amps). Well besides the original preamp tubes were Sylvanias and sounded decent, and the replacments (Chinese) sounded like microphonic-dirt, the story got interesting around the power tubes. The original Sylvania 6l6's were still pretty strong and were running at about 50 ma each. The new Chinese tubes ran at 25 ma each. I tossed in a trimpot, a couple of 1 ohm 2-watt cathode resistors and set the bias. I wrote this on his service ticket, and totalled the bill. When he picked up his amp, he got all twisted and told me "I brought you Mesa selected tubes, that doen't need to be biased, and besides theres no bias pot in this amp, Mesa said so". After much argument, we called Mesa, and Randall (who, at the time, still would talk to you on the phone), insisted that I refund the customer's money, and "not charge him for modifications his amp didn't need". He continued to insist that "something was wrong" and "are you sure you know what your doing.." and such. Thanks to Mesa hype, the concept of Biasing is no longer valid. I soon got disgusted with the whole repair business and took ten years off.

7/9/2000 7:00 PM
Cole	Mesa's been doing that for years since their supply of Sylvania 6L6s ran out (the STR387s, I think.) I remember reading a Guitar Player article years ago where someone (Aspen Pittman?) was pissing and moaning that Peavey used all the good 6L6s in their new 5150, and how they should have been saved for MKIs and Fenders... someone else remarked how without Sylvanias, their original MKI "wasn't an amp anymore" (which would make sense going from 50ma to 25ma bias).

7/9/2000 7:00 PM

Cole

Mesa's been doing that for years since their supply of Sylvania 6L6s ran out (the STR387s, I think.) I remember reading a Guitar Player article years ago where someone (Aspen Pittman?) was pissing and moaning that Peavey used all the good 6L6s in their new 5150, and how they should have been saved for MKIs and Fenders... someone else remarked how without Sylvanias, their original MKI "wasn't an amp anymore" (which would make sense going from 50ma to 25ma bias).

7/11/2000 3:16 AM
Paul C	I was an authorized shop and got screwed by boogie also. Seems that when MARS came to town they jumped ship. The owner of my store got into it with Mesa and to make a long story short they ain't talkin' no more. BUT for spite they dropped the service shop WITHOUT TELLING ME!! Sent in about $150 in invoices only to be rejected #%&!*!!! Now about them tubes - Had to stock 'em for warranty work, but I'd ignore the ratings and take a whole pile of 'em and match them myself. Funny thing is the amps didn't seem to sound any better - OUCH!! Paul C

7/11/2000 3:16 AM

Paul C

I was an authorized shop and got screwed by boogie also. Seems that when MARS came to town they jumped ship. The owner of my store got into it with Mesa and to make a long story short they ain't talkin' no more. BUT for spite they dropped the service shop WITHOUT TELLING ME!! Sent in about $150 in invoices only to be rejected #%&!*!!!
Now about them tubes - Had to stock 'em for warranty work, but I'd ignore the ratings and take a whole pile of 'em and match them myself. Funny thing is the amps didn't seem to sound any better - OUCH!! Paul C

7/10/2000 4:54 AM
Steve Ahola	Randall: I had bought a quad of Mesa EL84's a few years back and I believe that they were sold as a matched set (with factory tape around them). But maybe not... that was quite awhile ago. As far as I could tell they were the same as the Sovteks I bought marketed by Ruby Tubes. Each matched to within +/- 3mA. I bought some GT EL84's (made by Tesla?) and have yet to find an amp that they sound decent in. The first quad I bought had a #4 rating and I exchanged them for some with a #7 rating. Maybe it is a matter of taste but I like the Sovteks a lot better. John Stokes mentioned the music store selling Mesa and GT tubes without any discounts. I'm not sure how Randall Smith gets away with it but the Mesa dealers all agree not to discount his products; if they do, they can lose their franchise... As for GT, I got a good deal on them once at GC ($12 for the $18 NOS 12AX7's) evidentally that saleman was not told that they aren't supposed to discount the GT's (other than maybe knocking a buck off each tube if you buy several). From time to time GC does advertise specials on certain GT sets, but other than that the prices seem to be set in stone... --Thanks! Steve Ahola P.S. When you buy a set of tubes that aren't matched properly bring them all back for exchange or refund... Check whatever ratings might be on the box, the tube, or on a sticker and pick out the ones that seem to be the closest. BTW I believe that all of the Mesa amps that use EL84's are cathode biased so they can get away without having adjustable bias. However for the fixed bias 6L6 and EL34 amps, the bias measurements reported here have been ridiculous— like 12 or 15mA for some of the modes... I think that they set it so low so that none of the tubes you might put in would run hot enough to damage the amp or the tubes. Much better to add the bias adjustment pot and set the bias yourself for the particular tubes you use. I think that Ruby tests their tubes as well as Mesa does. P.P.S. Someone here mentioned measuring the screen current... perhaps you can tell us how to measure that— measure the voltage drop across the screen grid resistor and divide that by the resistance? What are good settings to aim for with the various tubes (EL84, EL34, 6L6, 6V6)? Thanks!

7/10/2000 4:54 AM

Steve Ahola

Randall:

    I had bought a quad of Mesa EL84's a few years back and I believe that they were sold as a matched set (with factory tape around them). But maybe not... that was quite awhile ago.

    As far as I could tell they were the same as the Sovteks I bought marketed by Ruby Tubes. Each matched to within +/- 3mA.

    I bought some GT EL84's (made by Tesla?) and have yet to find an amp that they sound decent in. The first quad I bought had a #4 rating and I exchanged them for some with a #7 rating. Maybe it is a matter of taste but I like the Sovteks a lot better.

    John Stokes mentioned the music store selling Mesa and GT tubes without any discounts. I'm not sure how Randall Smith gets away with it but the Mesa dealers all agree not to discount his products; if they do, they can lose their franchise... As for GT, I got a good deal on them once at GC ($12 for the $18 NOS 12AX7's) evidentally that saleman was not told that they aren't supposed to discount the GT's (other than maybe knocking a buck off each tube if you buy several). From time to time GC does advertise specials on certain GT sets, but other than that the prices seem to be set in stone...

--Thanks!

Steve Ahola

P.S. When you buy a set of tubes that aren't matched properly bring them all back for exchange or refund... Check whatever ratings might be on the box, the tube, or on a sticker and pick out the ones that seem to be the closest.

    BTW I believe that all of the Mesa amps that use EL84's are cathode biased so they can get away without having adjustable bias. However for the fixed bias 6L6 and EL34 amps, the bias measurements reported here have been ridiculous— like 12 or 15mA for some of the modes... I think that they set it so low so that none of the tubes you might put in would run hot enough to damage the amp or the tubes. Much better to add the bias adjustment pot and set the bias yourself for the particular tubes you use.

    I think that Ruby tests their tubes as well as Mesa does.

P.P.S. Someone here mentioned measuring the screen current... perhaps you can tell us how to measure that— measure the voltage drop across the screen grid resistor and divide that by the resistance? What are good settings to aim for with the various tubes (EL84, EL34, 6L6, 6V6)? Thanks!

7/10/2000 5:55 AM
Randall Aiken	Steve wrote: "BTW I believe that all of the Mesa amps that use EL84's are cathode biased so they can get away without having adjustable bias." That's just my point, Steve. Most people automatically assume because an amplifier is cathode biased it doesn't need to be adjusted, and all tubes will somehow magically adjust themselves to be at the correct bias level. It ain't so! Those two Mesa tubes biased up at 27mA and 48mA in both fixed and cathode biased modes of operation. They would have been just as happy burning up in a Mesa amp as any other amp. FWIW, the guy at the music store said Mesa doesn't sell matched pairs of their EL84 tubes, only the single boxes. "Someone here mentioned measuring the screen current... perhaps you can tell us how to measure that — measure the voltage drop across the screen grid resistor and divide that by the resistance? What are good settings to aim for with the various tubes (EL84, EL34, 6L6, 6V6)? Thanks!" As for screen current, you are correct. Just measure the voltage drop across the screen resistor and divide by the resistance value (you might want to measure the resistor first to make sure it hasn't drifted in value from what is marked on the body). There are no settings to "aim for" in screen current. It is what it is, at that particular screen voltage. Typical values for EL84 are 3-5mA, and for larger tubes, such as EL34/6L6/5881/etc. it can be around 5-10mA. If you look at a tube data sheet, you will see a value for "zero signal grid number 2 current". This is the typical screen current at idle. Randall Aiken

7/10/2000 5:55 AM

Randall Aiken

Steve wrote:

"BTW I believe that all of the Mesa amps that use EL84's are cathode biased so they can get away without having adjustable bias."

That's just my point, Steve. Most people automatically assume because an amplifier is cathode biased it doesn't need to be adjusted, and all tubes will somehow magically adjust themselves to be at the correct bias level. It ain't so! Those two Mesa tubes biased up at 27mA and 48mA in both fixed and cathode biased modes of operation. They would have been just as happy burning up in a Mesa amp as any other amp. FWIW, the guy at the music store said Mesa doesn't sell matched pairs of their EL84 tubes, only the single boxes.

"Someone here mentioned measuring the screen current... perhaps you can tell us how to measure that — measure the voltage drop across the screen grid resistor and divide that by the resistance? What are good settings to aim for with the various tubes (EL84, EL34, 6L6, 6V6)? Thanks!"

As for screen current, you are correct. Just measure the voltage drop across the screen resistor and divide by the resistance value (you might want to measure the resistor first to make sure it hasn't drifted in value from what is marked on the body).
There are no settings to "aim for" in screen current. It is what it is, at that particular screen voltage. Typical values for EL84 are 3-5mA, and for larger tubes, such as EL34/6L6/5881/etc. it can be around 5-10mA. If you look at a tube data sheet, you will see a value for "zero signal grid number 2 current". This is the typical screen current at idle.

Randall Aiken

Page 2 of 7