Electro Harmonix "Big Bottle" 6CA7's

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Electro Harmonix "Big Bottle" 6CA7's

Postby (iiipopes) » Tue Aug 04, 2020 1:36 pm

Has anybody swapped out their skinny bottle EL34's for the Electro Harmonic "Big Bottle" 6CA7's?

Years ago, I had a 1975 (first year issue) Marshall Master Volume, known as the 2203. The band I was in also played some "clean" songs as well as those with overdrive. After having the amp re-biased from the OEM 6550's to EL34's, that was a help, but occasionally even that was a little to much grit. So with the help of my tech, we researched and found the Electro-Harmonix "Big Bottle" 6CA7's. Now in the meantime, I also had a set of original Sylvania 6CA7's, which do have different plates and a couple more internal differences to the EL34's, Mullard style, but pin-out and bias the same.

WOW!!! I got all the same overdrive when the song called for it, but when I backed it off, it had a sweetness and shimmer that just does not happen with EL34's, but a more robust tone than 6L6GT's. Alas, that amp finally died, and I thought that was that.

Fast forward twenty years. Marshall has a fairly new amp called the Origin 50. The controls were reminiscent to my old amp and its 50-watt companion, the 2304. I bought one. Yes, it had the same midrange push my old amp had all those years ago before changing power tubes; otherwise, the tone stack was IDENTICAL in tone, even to the "Tilt" knob, which is essentially a variable bright control, which I had modded my 2203 to have the same control over the input jack all those years ago.

Yeah, I had to: I found a matched pair of new Electro Harmonix "Big Bottle" 6CA7 tubes and ordered them. Serendipity. When I opened them, and took out the pair of EL34's, both pairs were labelled with identical biasing ratings, so I didn't have to call my friend to re-bias my amp!

Tone: I HAVE MY TONE BACK!!! They have that same sweetness I had all those years ago, overdrive when called for, and the same tonal characteristics from the tone stack. AHHHH!!! Oh, yeah - you should hear my Rick 12 jangle through it!!!

Bottom line: if you want more sweetness out of your amp than EL34's, try the Electro Harmonix "Big Bottle" 6CA7's: same plates as 6550's, more robust than 6L6GC's, bias the same as EL34's, and, at least to my ears, more headroom for a bigger tone.
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Electro Harmonix "Big Bottle" 6CA7's

Postby (8mileshigher) » Tue Aug 04, 2020 4:26 pm

Great post, Scott !
Great story when an old guitar or amp is found or in this case, the tone is re-created.
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Re: Electro Harmonix "Big Bottle" 6CA7's

Postby (iiipopes) » Tue Aug 04, 2020 5:44 pm

Thanks. I mis-typed. The 50-watt version of my amp was the 2204. And both of these were simply called the "Marshall Master Volume," and were made from 1975 through 1980, before the JCM800 series came out.
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Re: Electro Harmonix "Big Bottle" 6CA7's

Postby (scott_s) » Wed Aug 05, 2020 12:03 pm

Feels good when tonal things come together! Do you find yourself preferring beam power tubes over pentodes in other amps, too?
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Re: Electro Harmonix "Big Bottle" 6CA7's

Postby (iiipopes) » Wed Aug 05, 2020 12:58 pm

scott_s wrote:Feels good when tonal things come together! Do you find yourself preferring beam power tubes over pentodes in other amps, too?

Frankly, the only other tube guitar amplifier I ever used on a regular basis was a 1978 Silver Face Vibrolux, purchased when new, which I left stock, and later sold after a career reversal in the early '90's to make a house payment. Now that I've been back on my feet for a lot of years now, I may go hunt one of those down as well. And of course, I left my Ampeg SVT stock and finally sold it for a profit, also in the early 90's, when the cost a complete re-tube was about the same that I could sell the amp for; I sold it for a solid-state Carvin PB300, which was my main amp for many years, and now resides with an SWR Triad with an updated real crossover in my rehearsal hall.

Speaking of Fender & Marshall, I also recently got a Fender Tre Verb, and the optical setting on the trem and the '65 setting on the verb are almost identical to the "real" Fender amps I have played through. Great pedal if the traditional tones are what you are after.
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