The Difference Tubes Make Is Huge! - Nos 12ax7 Reviews Contained

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Brought my 1964 Marshall JTM45 replica I posted about in the following thread to one of my friend's house. http://www.marshallforum.com/thread...ica-best-one-youve-ever-seen-pic-heavy.93202/

The amp started with a couple of Shuguangs in the power section with a current production Tungsol in V2 and a TheTubeStore 7025 in V3.

My friend has in his possession a few boxes of NOS and ANOS preamp tubes which we experimented quite a bit with. The power amp tubes were easy. He had 2 pairs of GEC KT66s ; one with the grey glass (50s) and another with clear glass which the date codes indicated they were from 1963. Unfortunately, the latter pair tested way too far from each other ; 11mA, to be exact. So I passed on those and got the grey glass ones which seem to be more sought after and tested with 3 to 4mA so much more acceptable. Biased at 36mA. Honestly, after hearing those, the Shuguangs won't ever be in my amp! GEC or bust! I've read dozens of time about the figurative wet blanket being lifted from the amp and although it's cliché to say this, nothing could be a better analogy than that. Fortunately, my friend gave me a good price on those.

It was quite surprising to hear just how much of a difference the preamp tubes were making in V1 alone. Really, really surprising! Unfortunately, we didn't have the luxury of time, so we had to stop after a short while. Otherwise, we could've continued for hours and hours. Here's a quick summary of my findings.

Short plate Blackburn Mullard (short plate) : pulled from my SuperLead. It sounded harmonically congested, polite, and quite smooth. Laidback presentation.
Tokyo Shibaura (Toshiba) : My friend's go-to 12AX7 for testing amps. Wow! Incredibly creamy midrange, dripping with vintage vibe, like you're listening to old records... in a good way!
RCA grey long-plate : WOW!!! The amp sounded full, larger-than-life, had an addicting 3D sound that fills the room beautifully. Harmonically complex midrange. Always heard of those for Fender amps but in this JTM45, it was a match made in heaven.
Tungsram : My friend hyped this one but even he was quite underwhelmed with how it performed. Hairy, and forward-sounding in an abrasive way, this one didn't last long.
RFT : smokey in a good way, but was rather bass-shy. Of course, one can crank the bass, especially on a bass circuit like a JTM45 but I did not purely for benchmarking purposes. Good option for taming a bass-heavy amp and giving it a nudge in a vintage direction.
Amperex : clean, very good-sounding tube, single-line runs sounded very good. If I hadn't heard the RCA, I might've gone for this one but it lacks the richness and complexity of the RCA, IMHO.
Unnamed Japanese tube : I forget which brand this one was. Very forward presentation, it was a run-of-the-mill tube, nothing special. Adequate, but there's so much better out there.

We even tested some in V2 and noticed a subtle difference in presentation. Surprisingly, my current production Tungsol which I had pulled from my SL ended up among the favorites, but ultimately, I went with another ANOS tube. Can't even remember which one right now as I'm running on very little sleep. I can update the thread once I get back home. Don't think it's a mystery which tube I got for V1. The RCA, baby! Honestly, that thing sounded so good, huge, and rich, I'm thinking of trying it in my SL for kicks. I'll experiment once I have some free time.

Oh, and I'll also be purchasing a Toshiba tube on my own since my friend wasn't too keen on selling that particular one. They're relatively cheap as the prices seem to hover around the $40 mark. Not bad. I'll buy one if only to change things up, once in a while. It's a surprisingly great tube.
 
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GIBSON67

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I have been buying CBS longplates, which can be RCA grey plates that have been relabeled. Fantastic V1 tubes, especially if they are fairly strong testing!
 

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I have been buying CBS longplates, which can be RCA grey plates that have been relabeled. Fantastic V1 tubes, especially if they are fairly strong testing!
Do you have pics of those just so I can check them out? :)
 

GIBSON67

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I've seen two different kinds, one seem to me to be RCA grey longplates, and the others are GE grey longplates with etchings. I'll see if I can get some pics.
 

dslman

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Ive got a few GE longplates from 63-64 ,they have the vintage vibe going on, and full sounding.
Never tried a RCA.
 

RickyLee

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Great info.

I have been considering building a JTM45, as I have the parts to get going on two more projects. As for transformers, I will probably just go with one of the early 80's Drake output transformers from my stash. The power transformer I might end up buying another Classic Tone, the model that I used in my Plexi build that I went nutso on and ended up turning into a hot rod hybrid LOL . That power transformer has the 5V tap and dual secondary HT options which is great.

But I have been craving a JTM45 for awhile, and then even more after I was using my old Fender Deluxe Reverb for many gigs last year. Oddly enough, I was running that little Deluxe more like a Marshall and playing Trower material LOL. But the tone from a pushed tube rectified amp has really grown on me. And yeah, the Clapton Bluesbreaker tone I have always held in the highest regard as well.

Gonna gave to dig out some of my old 12AX7 glass here real soon as well . . . .
 

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