Tube thoughts from Ken..

[rooster]

I found this in my notes, thought I would post it for the few. This is reprinted from Gregg Levy's site (Hi-Test) and I find it very interesting. This was written by Gregg, and this is Gregg talking when he says 'I have owned thirteen TW amps..' :





"Trainwreck Tubes

The power of the internet to propagate myths is well known. So it's not surprising that there is incorrect information floating around the web regarding the tubes that Ken Fischer preferred in his Trainwreck amps. What is surprising is how wrong the prevailing myths are and the near complete absence of discussion of the tubes that Ken really did like. The record needs to be set straight:

-Ken Fischer did not prefer the current production Tungsram, EI, BEL, Siemens/RFT and Sovtech tubes that he originally put in his amps and he did not design his amps to sound the best with these tubes.

I can make these assertions, because I have owned thirteen original Trainwreck amps and spent a lot of time with Ken. Ken and I heard tubes and amps the same way. He asked me to help him voice a number of the original Express, Liverpool and Rocket amps and I sold him quite a few NOS tubes as well.

Ken's choice of tubes for his amplifiers was shaped by the same problem facing amp builders today: most customers were unwilling to pay more for an amp equipped with NOS tubes. Accordingly, Ken selected the best sounding tubes that were readily available in quantity at wholesale prices.

-During the mid-1980's to the early 1990's, Ken purchased National labeled BEL, Tungsram and EI 12AX7 tubes for his amps. Looking back at his preamp tube selections, Ken would quickly share his disappointment with the Tungsram 12AX7's: "after six months, they sound like a wet blanket over the amp."

-Similarly, Siemens EL34's made by RFT in East Germany were installed in Express amps and Reflector/Sovtech EL84's were used in Liverpool and Rocket amps, because they were deemed the best sounding current production power tubes.

In the tube section of the original Trainwreck owner's manual, Ken wrote "we suggest that you experiment with various types and brands to find the sound and reliability you are looking for." I can think of no more compelling indication that Ken believed there were better tube choices for his amplifiers.

So what tubes did Ken really like in his amps?

Ken placed a much stronger emphasis on NOS power tubes than many amp
enthusiasts/guitar players do today and he strongly believed they should be closely matched. Based on the meaningful difference in the feel and sound of the early (Stancor) transformer amps versus the new (Pacific) transformer amps as well as variances in individual amp response, Ken liked a variety of NOS power tubes:

-In Express amps, Ken preferred wing plate Telefunken EL34's, Mullard EL34's from the XF2 production era and early metal base Philips EL34's. For years, some players struggled with a glitch in the Express' class A-B circuit. In response, Ken came up with a speaker specific resistor fix that partially addressed the issue. Later, an astute Express owner hipped Ken to the ability of the metal base Philips EL34's to negate the glitch.

-In the Liverpool amps, Ken liked Telefunken and Valvo EL84's.

-In the Rocket amps, Ken had several favorites: Telefunken 7189's, grade specific 1960's Valvo EL84's and Siemens & Halske E84L's. He also liked a counter-intuitive combination of Telefunken 7189's and early Hamburg production Valvo EL84 pairs in his personal Rocket.

Ken's preamp tube preferences were also strongly shaped by the different transformers in his amps:

-In the darker old transformer amps, Ken preferred a 1961-1968 Amperex 12AX7 in V1 and the same late 1970-1972 Amperex 12AX7's in V2 and V3.

-In the brighter new transformer amps, Ken favored an early to mid-1960's Amperex 12AX7 in V1 and the same midrange enhancing 14mm Mullard 12AX7's in V2 and V3.

-Ken also liked Mazda chrome plate 12AX7's in V1.

For the Rocket's tube rectifier, Ken preferred a Mullard GZ34 from the 1962-1967 production period.

Ken may have told you differently, but after many years of advising guitar players, he learned that it was often better to confirm people's ill gotten pre-conceptions rather than laboring to expose them as myths. Unfortunately, I just underscored my need to better heed his sage advice. Thanks Kenny!"


If you read this then you also read the section that deals with the 'glitch' found in the Express. Interesting, eh? It's a power tube thing apparently and it may be addressing the fact that V5 takes such a hit when pushed? Honestly, I'm not clear on this but Gregg seems to be. Maybe ask him. I do know that the Liverpool does not suffer from this according to Gregg - and - since both preamps are similar/identical, then clearly it is something in the Class AB performance of El34s in the Express. Also FWIW, I have purchased some tubes from Gregg over the years and he definitely knows his tubes and TW amps.

[geetarpicker]

Never heard of this "glitch" and I bought my first Express directly from Ken back in the day. We had many technical discussions on circuit design and his amps in general.

That said I do remember his preference for Xf2 Mullards, though he was pretty open to say try a bunch of preamp tubes until you find things that you like.

Pretty sure Gregg also stated that Ken would bias Express amps quite cold, which I never heard from Ken in many discussions we had on the subject. Still, Ken was also quite open to the concept of setting bias by ear, as long as you didn't red plate the tubes on the hot end of things.

[Littlewyan]

Glen do you recall what Pre Amp valves your Express came with? Did Ken give you the option of buying NOS valves?

[Richie]

What is the Glitch thing?

[Mark]

This has been brought up before, here are other comments and thanks for Glen to give us his experiences.

http://ampgarage.com/forum/viewtopic.ph ... rs&start=0

[geetarpicker]

Glen do you recall what Pre Amp valves your Express came with? Did Ken give you the option of buying NOS valves?

EI preamp tubes, & Siemen EL34s. I don't remember if Ken mentioned any other tube options at that point but we talked about it later on...

[Reeltarded]

Ken would have truly loved the EH6ca7s in the Express. I have no doubt. They compare as near equals to the real Mullards if not better just because of the price excitement. 6:1 ratio.. I'll take em.

[Blackburn]

I also remember Gregg telling me the bias point he'd found and later confirmed with Ken, after biasing by ear for best tone, was 20mA. Should put the dissipation wattage at 8w, no? I'm assuming the plates being around 400v and that's what I get. Sounds too low, but hey, I never build no Express... Yet.

Miles, how do you feel about those compared to those Winged Cs? Cost ratio, I know, but tone? I'm gonna convert a Bassman/JTM build into a JMP and will be looking for a good pair of them. Thought I'd have to dip into the wallet for NOS, but if you really think they're that good, I'll give them a shot.

[Mark]

That does seem pretty cold biasing.

Perhaps others here can share what they bias their amp to.

I don't have much experience in biasing by ear. I did experiment with my Champ clone (this amp has a Mercury Magnetics output transformer to extend bass response) where I had two 1K resistors on a switch, when the switch was in it was 500 ohm and when it was out it was 1K ohm.

I found I didn't hear any difference between the two bias points when the amp was played clean. I found when the amp was dimed (using a Les Paul) the hotter bias was brighter and edgier while the cooler bias had less high end (by comparison) and had more bass response.

I should point out this was a one time exercise and I have tried to replicate it again. Which is to say, I don't consider it conclusive information.

[matt h]

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[Reeltarded]

I have never had a Winged C in any amp for more than 5 minutes. That is how I feel about those. They just aren't even what people claim.. not even.

EH power tubes are making me happy. Next I need 88s so let us pray.

I wouldn't doubt the function of an Express with sub -30 bias for getting the grits up and going super clean though.

[Blackburn]

Matt, nope. I recall that was for a regular Express and I'm quite sure my memory is correct. And remember, Ken said bias doesn't need to be changed when switching from 6CA7s to 6V6s. Weird.

Miles, thanks for the tip. Them Wings are expensive! I'll give the EHs a shot. I'm also curious about 88s. Eventually...

[geetarpicker]

I remembering hearing somewhere that Greg's favorite guitar music is punk rock.

[matt h]

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[Reeltarded]

I love lower B+. It's so rockin'. You can do almost anything in there. Wheeeeee!