Took a chance on these EL34... Anyone else try them?

[Nigel]

Mismatched means asymmetrical clipping which means more even order harmonics. Bass won't be as hard, and it will feel looser.

Matched tubes is marketing. HiFi? SURE! Playing funk/metal need max headroom and clarity? Match away! Rock/Blues? Mismatch is the way, all day.

 

[War_in_D]

Follow up. Checked another quad today, and I think it's safe to say that my GM numbers may be questionable at best. I just don't think that my tester is repeatable enough to put what I would feel like is an accurate number on it. I think the tester is good for checking the tube from a pass/fail standpoint, checking for leaks and shorts and maybe giving you a "round about" number on GM for that particular tube. Beyond that, I don't feel like it's going to be of much use. Especially for any kind of accurate matching.

I think the issue comes from the way you test for pass/fail and then test for GM on this Hickok 800. To test for pass/fail you would use the supplied settings on the roller for a given tube and set everything to that to start. Once everything is warmed up, you do a line check to make sure your meter is reading "zero" and then hit the GM button and that gives you the pass/fail on the tube. I usually set a timer for about 2 minutes to make sure that the tube is warmed up, then check for shorts/leaks and then check for pass/fail using the bias and english settings.

But, when you want to measure transconductance (GM), you have to rotate the english wheel to one of three red dots that correspond with the Micromhos scale on the meter. These three Micromhos scales run from 0-1500, 0-6000 and finally from 0-15000. You choose the dot based on what the specs on the roller tell you the tube should be for it to test as "new". On the EL34/6CA7 it's a GM of 6000 for "new". So, I'm using the 15000 red dot on the knob and then checking the 0-15000 scale on these ELs because the 0-6000 scale might not be enough to cover it if the tube is particularly strong and exceeds the GM for a new tube. What I'm finding is that when I rotate the english knob from 90 (when checking for pass/fail) to the 15000 red dot to check GM, I'm just about sure I'm not hitting the same exact spot on that knob every time I switch tubes which is then causing the Mircrohoms to swing from tube to tube. Since the range of that scale is from 0-15000, there is a wider margin of error if you dn't get that knob in exactly the same place each time, if that makes sense. I rotated that knob while I had the GM button pressed and it swings pretty wildly with just very little movement, so I could see how just a slight variance between where that knob is set could produce unreliable results from a matching standpoint.

I think I'm just going to check these tubes for pass/fail and shorts/leaks, and as long as they are good there and bias up in the amp and don't drift.. I'm not going to worry about it too much. LOL

 

[LP Freak]

Follow up. Checked another quad today, and I think it's safe to say that my GM numbers may be questionable at best. I just don't think that my tester is repeatable enough to put what I would feel like is an accurate number on it. I think the tester is good for checking the tube from a pass/fail standpoint, checking for leaks and shorts and maybe giving you a "round about" number on GM for that particular tube. Beyond that, I don't feel like it's going to be of much use. Especially for any kind of accurate matching.

I think the issue comes from the way you test for pass/fail and then test for GM on this Hickok 800. To test for pass/fail you would use the supplied settings on the roller for a given tube and set everything to that to start. Once everything is warmed up, you do a line check to make sure your meter is reading "zero" and then hit the GM button and that gives you the pass/fail on the tube. I usually set a timer for about 2 minutes to make sure that the tube is warmed up, then check for shorts/leaks and then check for pass/fail using the bias and english settings.

But, when you want to measure transconductance (GM), you have to rotate the english wheel to one of three red dots that correspond with the Micromhos scale on the meter. These three Micromhos scales run from 0-1500, 0-6000 and finally from 0-15000. You choose the dot based on what the specs on the roller tell you the tube should be for it to test as "new". On the EL34/6CA7 it's a GM of 6000 for "new". So, I'm using the 15000 red dot on the knob and then checking the 0-15000 scale on these ELs because the 0-6000 scale might not be enough to cover it if the tube is particularly strong and exceeds the GM for a new tube. What I'm finding is that when I rotate the english knob from 90 (when checking for pass/fail) to the 15000 red dot to check GM, I'm just about sure I'm not hitting the same exact spot on that knob every time I switch tubes which is then causing the Mircrohoms to swing from tube to tube. Since the range of that scale is from 0-15000, there is a wider margin of error if you dn't get that knob in exactly the same place each time, if that makes sense. I rotated that knob while I had the GM button pressed and it swings pretty wildly with just very little movement, so I could see how just a slight variance between where that knob is set could produce unreliable results from a matching standpoint.

I think I'm just going to check these tubes for pass/fail and shorts/leaks, and as long as they are good there and bias up in the amp and don't drift.. I'm not going to worry about it too much. LOL


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Put them in your amp, bias it up and see how close they are to each other

 

[SpiderWars]

I think @psychodave has been thru all this and uses the Maximatcher. Maybe he'll chime in on that Hickok 800 tester you have.

One thing I've noticed is that not all tubes stay where they test new for long. Just going from idle operation I've had some quads stay stable forever and others drift fairly early in their life (maybe only a tube or two of four).

 

[War_in_D]

Put them in your amp, bias it up and see how close they are to each other

It's going to be a while before I use them honestly. But, I have another theory on testing them that I'm doing on the last quad. I'm going to run through the quad strictly for pass/fail and not touch any of the knobs during that test, and then readjust the knobs for GM and run the quad back through again without touching anything. I'm curious to see if I can a more reliable GM number that way.

 

[LP Freak]

It's going to be a while before I use them honestly. But, I have another theory on testing them that I'm doing on the last quad. I'm going to run through the quad strictly for pass/fail and not touch any of the knobs during that test, and then readjust the knobs for GM and run the quad back through again without touching anything. I'm curious to see if I can a more reliable GM number that way.

You will, I have a Hickok 600A and do it that way.

 

[War_in_D]

You will, I have a Hickok 900 and do it that way.

Yeah, that last quad came out quite a bit closer and I'm going through the other 8 right now while the settings are the same. So far, much closer across the board. I was just going about it the wrong way before. I've only had this tester for about 4 months, and haven't used it very much so I'm kind of learning my way around it.

 

[War_in_D]

Done rechecking all 12 tubes for GM, and not touching the english knob. Results are MUCH better with regard to how closely they match. The GM read consistently low for a new tube (GM 6000 = new), but I chalk that up to the tester probably being out of calibration. I let the tubes warm up a bit longer this time too, a minumum of four minutes vs. two minutes and held the GM button down a bit longer as I noticed some of the tubes would drift a tad and then settle down. Results below:

Quad 1: GM 4750/5000/5250/5250
Quad 2: GM 5000/4750/5000/4750
Quad 3: GM 5000/5000/5000/4750

My apologies for the wonky stuff I was spewing earlier, definitely a result of my inexperience using a tube tester. I've tested a few quads and duets of power tubes with it since I got it but I'm going to have to go back and retest them using this testing methodology.

 

[Fret-Shredder]

Done rechecking all 12 tubes for GM, and not touching the english knob. Results are MUCH better with regard to how closely they match. The GM read consistently low for a new tube (GM 6000 = new), but I chalk that up to the tester probably being out of calibration. I let the tubes warm up a bit longer this time too, a minumum of four minutes vs. two minutes and held the GM button down a bit longer as I noticed some of the tubes would drift a tad and then settle down. Results below:

Quad 1: GM 4750/5000/5250/5250
Quad 2: GM 5000/4750/5000/4750
Quad 3: GM 5000/5000/5000/4750

My apologies for the wonky stuff I was spewing earlier, definitely a result of my inexperience using a tube tester. I've tested a few quads and duets of power tubes with it since I got it but I'm going to have to go back and retest them using this testing methodology.

Good news. Thanks again for the effort.

 

[matttornado]

For what it's worth, I feel that slightly unmatched pairs/quads sound better than matched. That's been a pattern for me for a few years. Experimented with this and it seems to be a thing, with my amps anyway. Like a quad of 34s that bias from 32-39 ma.

I agree. I have a 12mA difference with the quad in my superlead. I pair the highest with the lowest. Sounds great.

 

[Kapo_Polenton]

I have 4 of these that came with my Bugera 1960, honestly, I swapped in some other tubes and then went back to these. To me they are essentially like most others, rebranded chinese and for Marshalls or that Marshall sound, I think you will be happy (enough) with them. I have learned not to split hairs too much on tubes unless they either have too fat a low end or no top end. ( Kind of felt that about the reissue mullards, the top end got meh pretty quick) These tubes sound good and crunchy to my ears. Not spikey, well balanced and no saggy ass syndrome.

 

[jabps]

Good news. Thanks again for the effort.

Yep and further these Bugera's are the chinese EL34B's. The same tube Ruby and TAD relabels as BSTR's which I love in my amps. My favorite EL34's are the original Winged C's and the EL34BSTR's. Have a small hint of 6L6 to them IMO. What I run in my Marshalls. I took a chance on buying some as well. Thought it was for one quad set and I got three quads lol. Frankly for me, this was the only tube I was worrying about and its been in short supply way before the current issue. One quad of these from the Tubestore, the "preferred" series is over 200 dollars.

The black base chinese EL34's are the A's, those are more along the lines of the traditional Siemens/Mullard type EL34's.

I personally prefer both chinese versions of EL34's other than the original Winged C's and knock on wood have not had any failures. In fact I prefer the chinese 6L6's as well. They always sounded the best in my Peavey 5150's, JSX, XXXs, power amps ala Boogie etc... And now my EVH 50W. I always felt I had a good base to evaluate the chinese 6L6's as my original 5150 Block came with Sylvania's.