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Thanks! But, I don't have a "TUBE-EATER" to "enjoy" ! Now- an epic tale of 19 years and counting from Amperex 7308's !

Posted by Bambi B (A) on August 17, 2010 at 21:33:11

In Reply to: Enjoy your TUBE EATER!!! (nt) posted by wheezer on August 16, 2010 at 15:20:22:

wheezer,

In 25 years of owning 13 pieces of tube gear- not all in use at once of course, I've only ever had one operational tube failure- the arcing of a General Electric 6550A power output tube in a 1985 Audio Research D-115 MKII power amplifier in 1989. And, this event was sufficiently traumatic, I made a painting of the event (see below).

Because it was my first tube power amplifier, and did not recognise the signs of failure in the output tubes -the tubes had begun to crackle a bit only in the first 15 or so seconds when switched on. So, I paid the price- Bob Hovland retubed it and replaced the sacrificial resistor ARC typically uses to protect more valuable stuff. Some ARC owners complain about the sacrificial resistor, wondering if William Z. Johnson had never heard of fuses,..

Theatre for the Death of a General Electric 6550A

But, perhaps the resistor is a device to make owners careful about the tubes. Certainly, the bill resulting from the D115 retubing has made me more careful! Since that time- 21 years- I've never had another power tube failure.

I did ruin- push some 6DJ8's over the edge with the SP10. Just to judge the sonics without a large investment, in 1991, thinking of trying NOS in the SP10 to replace the 4- year old originals, bought some 1961 Amperex white labeled ECC88 6DJ8's off Ebay for $8 each- these were high-testing- 90%, pulled from a tube oscilloscope. However, in the high gain ARC SP10 phono positions, they went noisy in about 10 hours.

That $32 experiment I though was a valuable lesson in the 6DJ8 world- the 130V, 1.8W rated 6DJ8 is not rugged enough for the SP10- it has to be tough 6922's and the Sovtek 6H23 or better yet, because they're low noise, the 7308. I also learned that those early 60's white label Amperex ECC88's are just fantastic- before they became noisy, those 6DJ8's made the best sound ever from the SP10. If the gear can use that rating, they are the most open, transparent, refined 6DJ8 family tube I know. There was an SP10 owner here a few years ago, Thom, who had a big pile of NOS Amperex Bugle Boy ECC88 and he used to just feed them to the SP10. He however, got 100's of hours from those as compared to my 10.

In 1991, I replaced the 1987 tubes with a combination of Gold Aero MC phono selected Amperex 7308's for the phono stage and everything else was ARC Sovteks.

Impending Doom or cruel hoax of the gods? In December, 2009, a faint noise that began to become noticeable when I was near the speaker, developed in V-9 which is a line stage gain tube. That Sovtek 6H23pi-EB was one of the 1991 ARC tubes, so it had been there 19 years.

So, at the end of the year I replaced 10 of the 12 control chassis tubes with Amperex and Valvo E188CC / 7308's, however, V-1 and V-2, the two first position phono gain tubes are still the 18 year-old Gold Aeros- testing 95% of new (EICO 666).

In my view, the single D115 was pilot error which has not recurred in 21 years and does not designate the D115 an unreliable piece of gear. Likewise, the SP10, in having provided a high standard of sound quality from one set of tubes for 18 years hardly constitutes any distance relative to a "tube eater".

Also, many of the other pieces of tube gear have most or all of their original tubes from the mid 1960's: 1958 Scott 330D tuner- all but 2 orig., 1965 Fisher 800 receiver- all original, 1964 McIntosh MX110 all but 2 tubes original, McIntosh MC240- all but the 4 output tubes and 2 others, 1961 EICO HF-14 integrated- all original Mullard's, and the Audio Research SP8 preamp I bought in 1985 still has all it's original tubes which has late Siemens ECC83's and ECC81, Philips ECG 6922's, and GE 12BH7.

So, among my equipment, I have tubes as old as 52 years, many tubes in their mid-40's , and 25 years old in The Audio Research SP8 a make that the audio newbies somehow believe can just can not be provided with tubes that last! The most recently retubed piece, the SP10, was replacing tubes 19 years old- and 2 of those are still in excellent condition.

Sorry to disappoint those with Schadenfreude ambitions, but I don't own a "tube-eater"-no upper nor lower case example!

Fortunately, not tube-eaters as it appears Audible Illusions Modulus are. The proof of this is the indisputable fact that the AI Modulus is so stressful on their tubes, some buyers- the article mentioned it's mostly those living in mobile homes, have had to resort actually to reducing the current to the tubes so they'll survive!

-It's a pity too, as my memory of the (unmodified) Modulus sound is very positive and according to AI Factory Bulletin No. 5, there a lot of good NOS 6922'a that will work just fine and might refine an already very good sound for an entry level, budget preamp. The early-mid 60's -Siemens 6922 is among my favourites. I'm a bit surprised you didn't now of the factory NOS recommendations- it was on their site for years. You might've thereby avoided some of the work and expense on your Modulus. Of course, as you say, the tubes are not by any means the whole story in sonic refinement and we should certainly consider the middle ground of gear with room for improvement to passive, active components, transformers chassis, power supply, and controls- like the AI.

Your experience is a valuable lesson to us all. I certainly feel even more fortunate that the Audio Research SP10 never had to have it's balls cut off like some poor AI's owners seem to have been compelled to do!

Sorry for another long post and, thanks again for your patience with my so-called "humour" -and good wishes.

Cheers,

Bambi B

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