The ST-35 which is an UL amp with about 370V on the plates and screens will be definitely be hard on tubes not designed for higher than the normal spec of 300V. I think one good mod would be to put 100 ohm resistor right at the screens (pin 9) of each EL84/6BQ5.
Even with a tough tube like the JJ's or even tougher 7189 compatible EV Russian NOS I would recommend even adding Dave Gillespie's EFB mod as documented in diytube or std fixed bias with a separate PS transformer if you don't want SS (it will cost more $ though). The dynakit adjustable bias kit is still cathode bias with some adjustment, but it won't give you all the advantages of the preceding.
You can run the tubes at 27mA for longer life and better sonics as documented by Dave.
You might be able to do a deal on shipping the EH's back if you phone right away. Shipping will be low $ for those tubes anyway.
Even with a tough tube like the JJ's or even tougher 7189 compatible EV Russian NOS I would recommend even adding Dave Gillespie's EFB mod as documented in diytube or std fixed bias with a separate PS transformer if you don't want SS (it will cost more $ though). The dynakit adjustable bias kit is still cathode bias with some adjustment, but it won't give you all the advantages of the preceding.
You can run the tubes at 27mA for longer life and better sonics as documented by Dave.
You might be able to do a deal on shipping the EH's back if you phone right away. Shipping will be low $ for those tubes anyway.
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If you go to the Tubelab simple PP EL84 amp thread under tubelab it was found that the EH EL84's didn't stand up. That amp runs the EL84's a bit above spec too. The reason designers or manufactures do this is sonics and power. The GL's come from the same manufacturer and so are much the same in that they can't be run over spec.
Jim McShane cautions running them over spec on his tubes site too.!
Jim McShane cautions running them over spec on his tubes site too.!
I'm running Sovtek EL84M now. I will employ the EFB in a few weeks. rhing kindly spec'd out a parts list on another forum. I'm getting my build notes together for this (I'm fairly anal regarding stuff like this... my wife just says I'm prepared)
I don't know if it's me or the amp. Sometimes it sounds lovely (I can't use all the typical audiophile terms like soundstage, etc.) Sometimes it sounds a little flat, dull. It is very revealing (oh, there's a term) of the source material. CD's of older 60' and 70's music show the limitation of the original recording. CD's recorded in 90's and newer do really shine in most instances. I do suffer from tinnitus that comes and goes. May be a factor.
Speakers are Infinity RSb's so they should not contribute to the "flat" sound. Crossovers were recently recapped. The tweeter and mid pots were completely disassembled, cleaned and bathed in deoxit. I think it's the source material.
I often use Weather Report "Palladium" as a reference song. It's from the 70's but very well recorded. Bass is missing, which I understand is common for this amp. The opening notes should knock you over when played reasonably loud. I don't get that effect.
I anticipate the EFB will alleviate that to a degree.
I don't know if it's me or the amp. Sometimes it sounds lovely (I can't use all the typical audiophile terms like soundstage, etc.) Sometimes it sounds a little flat, dull. It is very revealing (oh, there's a term) of the source material. CD's of older 60' and 70's music show the limitation of the original recording. CD's recorded in 90's and newer do really shine in most instances. I do suffer from tinnitus that comes and goes. May be a factor.
Speakers are Infinity RSb's so they should not contribute to the "flat" sound. Crossovers were recently recapped. The tweeter and mid pots were completely disassembled, cleaned and bathed in deoxit. I think it's the source material.
I often use Weather Report "Palladium" as a reference song. It's from the 70's but very well recorded. Bass is missing, which I understand is common for this amp. The opening notes should knock you over when played reasonably loud. I don't get that effect.
I anticipate the EFB will alleviate that to a degree.
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