Are these the same tubes as the EL84-S that Groove Tubes carries? Slovakian origin?
The EL84S is the JJ EL84
The EL84Y is the Ei EL84
The EL84R is the Sovtek EL84
In all the above, they are run and distortion matched rather than statically matched. This means they are tested over the entire operating range.
As a bit of side info ....
Many folks do not match, in any way, EL84 tubes. Mesa EL84 tubes as an example are not rated or matched. Mesa does do some great matching though on their 6L6 and EL34 tubes.
Most EL84 amps are cathode biased. Some folks think the Fender Blues Jr is a cathode biased amp as it has EL84 output tubes. This is not the case. It is a class A/B Grid Biased amp. El84 tubes were chosen for that amp as they were less pricy for Fender than 6V6 tubes.
The EL84R is what is found in most high production EL84 amps. These are a robust tube but replacing them with most anything else will really open up an amp as these make an amp (to my ears) sound as if a blanket was placed over the amp. But ... they are a reliable tube.
The EL84Y is a good sounding tube but the least reliable of any of the EL84 types. On an amp with a split bias such as a Mazerati or RxEX, a cool trick is to use a duet of these on one side and a duet of the EL84S on the other side. The duets in these amps are side pairs, not inner and outer duet pairs as in most grid biased amps that use four output tubes.
The EL84S is rated as a 12 watt tube, standard EL84 specs but in test they easily can dissipate 14 watts and hold up better than one would expect. I think these are the best current production EL84 tubes out there and rival many NOS types.
The Electro Harmonix EL84 is also out there and is a pretty nice tube. It is not as strong as the JJ but does have some cool sonic attributes. It does hold up nicely and is more reliable than the Ei. This tube has welded plates rather than crimped plates and at time you will find their match go south in some factory runs pretty fast. I think this is due to impurities in the plate welds where the heat treating of the plates was done before the plates were welded together rather than after the fact so as they heat up there are gasses released inside the tube from the impurities of the weld that were not removed in heat treating after plate welding.
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roscoenyc: Almost every piece of gear I have except for my tuner has at least one knob. Those are for adjusting. PSA for the "too much bass" crowd.
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The Bad Poodle: cause we all know Too much bass increases "tube rattle"....
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