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In Reply to: RE: " You need to consider voluntary euthanasia; you have no functional sensory apparatus." posted by Bambi B on August 16, 2010 at 13:49:24
Follow Ups:
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
Hi Bambi, I really am impressed with your tube knowledge. I recently acquired an ARC D70Mk2 which I rolled tubes into. I am using the SED winged 6550c's(which I like a lot) in the power section, JJ6922 and GE NOS 6Fq7's in the driver section. I am wandering if you have any thoughts on which 6FQ7's are the way to go in these amps? I like the GE's, but I'm sure that there are many alternatives. BTW, I also own a new quad set of GE 6550A's, ( I've owned them for over 20 years and never used them, kind of had a premonition that these tubes were going to be used someday); the only problem is I don't think they are a matched set! Any idea as to how critical it is that they be matched in order to use them in the amp? In my set-up, I also use a Jeff Rowland model 8 ss amp; which is also great. I am VERY pleased with the ARC though, compared it to the VT100Mk3 and a ARC Ref 110 and amazingly the D70 was better, at least IMHO!
I also own a CAT SL1 SIg with rolled in tubes... also supposedly a preamp that eats tubes( I never found that to be the case, BUT?) When I rolled in the tubes, the improvement was huge. You do have to be a little careful when you do this, as a friend did the same with his preamp and the result wasn't that great. After some experimentation, he did get it right though and now enjoys the results.
daveyf,
In my view, in buying the Audio Research D70, you've gotten one of the best audio bargains. Although I enjoy the extra power of it's close cousin- the D115, the D70 actually some things better- I can't think of a batter Chamber ensemble/Lieder amplifier- smooth, articulate, natural timbre, transparent- does everything well. I once thought of adding two D70 as L/R monoblocks to run the high and mid drivers of the Vandersteen 2C's and have the D115 work the woofers.
6FQ7's in the D70: In the last 10 years I bought quite a number of NOS tubes, but had neglected a couple of important types until nearer the end of the collecting, the 6FQ7's was among them. The D115 is my only use of this type (4 )
Rsearching the 6FQ7, it seems they were derived from the 6SN7. The 6SN7 was repinned, the bottle made more compact and to compensate fro those big, big plates proximity, an centre electrostatic shield was added between the plates- and it was called the "6CG7". Later, the shield was removed- cost reasons- and the 6FQ7 was born. You'll see tubes marked "6FQ7/6CG7" but the real 6CG7 has the centre shield.
In NOS, I often prefer to buy the earlier and/or military versions of tubes, and while I bought some CA 6FQ7/6CG7- “cleartop”, I concentrated on buying centre shield 6CG7's:
6FQ7/6CG7 (4) TOTAL: 9
5- RCA 6FQ7/6CG7- “cleartop” - NOS
4- RCA 6FQ7/6CG7- cleartop- TNOS
6CG7 (4) TOTAL: 51
13- RCA 6CG7- “cleartop”- center shield- US- NOS [5,8
5- RCA 6CG7- "chrometop" black plate, D gtr, cn shd- NOS [8, 14
1- GE 6CG7- center shield- NOS [5*
11- Omega by Hitachi- black plate- square gtr- cnt shd-NOS [3
2- Tung Sol- US- TNOS
7- Westinghouse 6CG7- blk pl, D gtr- NOS [1.5
8- Westinghouse 6CG7- blk pl, D gtr- Used? [1.5
4- RCA 6CG7- grey pl, halo gtr, cn shd- TNOS [6
The "[5,8" are the prices paid, so you can see this type was inexpensive 5 years ago!. The most unusual tubes are the Hitachi's. These are my only Japanese tubes and they are black plate with a square getter! I have no idea of their age.
-As time went on, I discovered there are special favourites among 6CG7s and the competitin was between the RCA 6CG7- “cleartop”- centrre shield- and the RCA 6CG7- top getter "chrometop" black plate, D getter, centr shd. There is also a TungSol camp, but the heavy favourites are the RCA's. I bought more of the "cleartop" version, but the sonic champ is supposed to be the black plate, D-getter "chrometop". I say "supposed to" as I can't say I've really evaluated this type. I only tried the cleartop in the D115 very briefly- too briefly really to comment. However, from that experience and reading a lot of opinions, I'm convinced one of the RCA's will do very well in the D115 and I believe that either should be quite nice in the D70.
The CAT SL1 at the time (1987) happened to be the only serious competitor to my beloved ARC SP10- the SL-1 is really outstanding. Bob Hovland thought the SP10 and the SL-1 were the two best preamps then as well. It is just brilliantly refined. I haven't actually heard of tube survivability issues with the SL-1 in the way the ARC SP10 and AI Modulus have become known. And, like your SL-1 experience, in 23 years of the SP10, I've never had a tube life problem except with briefly tried, experimental Amperex ECC88's.
You have very good taste in gear!
Cheers,
Bambi B
Bambi, Like I said before, I am VERY impressed with your tube knowledge! The 6FQ7's I am currently using are in fact the NOS GE 6CG7's with the center shield.( after a closer look).
I think that they sound very nice in the D70mk2.
I am still amazed at the D70; it really is a 'SMOKIN' deal at its current ridiculously low price.
I agree that your D115 is also a great amp; I listened to one extensively about 15 years ago and felt then it was a winner. IMHO, ARC went backwards somewhat after the D series, particularly with the hybrid models and all of the ss models. Many of my a'phile friends are beginning to snap up the D70's as fast as they become available. One of my friends sold his BAT VK 75SE and replaced it with a D70Mk2!( with the left over sums, he bought a ton of vinyl).
BTW, I also think your SP10 is a GREAT preamp, easily on a par with the best tube units on the market today and better IMHO than almost all of the ss stuff currently available. If you read the review in the s'phile mag recently of the CAT Renaissance, you will also see that it still holds it head VERY high.
Again, IMHO, we both have good taste in gear. Or maybe, our ears do...:0)
Cheers
DaveyF
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