Preamp Tubes? - Who, What, When, Where, Why, and How?

[RiverRatt]

Marty, check this tube out.

RCA 7025 Cleartop - USA

These share some similarities with the Sonotone - except they have flat sided spacers like the AU7A. While you're on the tubemonger database, do a search for "cleartop". There are some interesting Brimars that come up.

 

[MartyStrat54]

Marty, check this tube out.

RCA 7025 Cleartop - USA

These share some similarities with the Sonotone - except they have flat sided spacers like the AU7A. While you're on the tubemonger database, do a search for "cleartop". There are some interesting Brimars that come up.

[The following is just some assorted ramblings I had while trying to answer this post.]

Well, I will say that I haven't been thinking as clear as I have in recent days. I made sort of a stoner remark about these tubes. In other words, cleartops in general. I mean they have side getters. However, I just don't run into that many and the ones I do are not 12AX7's. How rare do you think the Brimar's are? Well, I doubt if I will ever hold one. The RCA side getter 7025 reaffirms my belief that your Sonotone's were made by RCA. As I said, they were probably spec tubes and so the spacers could have been of Sonotone's design. In fact, Sonotone could have supplied the parts to RCA and the tubes were put together on one of RCA's tube lines.

You always have to realize that all of the big electronics companies knew that the way of the tube would be over well before the consumer knew it. RCA had solid state amps in their labs back in the early fifties. It was like when I was young. Did I buy an 8-track player or a cassette deck for my car? Well all of the R and D was in cassettes, which ended with metal oxide tape (that would rust if it got wet). 8-tracks became a thing of the past, but then the CD killed both the cassette and vinyl. I knew about the CD and I warned my friends that in the very near future, their vinyl and cassette tapes would become garbage. Most consumers never saw it coming. It was the same way with tubes. One minute Marantz dealers were praising their tube power amps and a week later all of the tube amps were in the back of the store and the new solid state stuff was center stage.

The point is, RCA may have needed some orders to keep their tube line going. Sonotone may have already decided to scale back, but had orders for their tubes. Everybody did work for everybody. I mean GE and Sylvania were in bed for so long, it's sometimes hard to tell who made the tube. Sylvania was making tubes for RCA by 1970 and the Japanese were making a certain percentage and RCA was doing buy outs from other companies. Most of the tubes had the RCA octagon. Other companies were actually branding them as RCA's. That's why I try to stick with 1966 and below for RCA tubes. 1959 was a super year for RCA 12AX7's.

I only have a small amount of cleartops and I believe them to all be 12AU7's. I'm sorry that I had a brain fart about them.

 

[RiverRatt]

I'm not trying to obsess over these tubes, I've just been doing a few image searches and those were a couple of the more interesting ones I've found. FWIW there's a clear top GE on eBay right now that was made in Canada that looks similar to the RCAs. The Brimars were unexpected, as was a Marconi 7025A cleartop that I ran across somewhere. I guess I'm just interested in the oddities like this that don't fit into any of the stereotypes for a particular manufacturer. I'm having some medical issues that have kept me close to the computer and on some pretty heavy narcotics lately, too. That tends to make search results a lot more interesting.

 

[MartyStrat54]

Oh I am more than interested in any of this. It is the unique and odd tubes that I find intriguing. I just wish there was a book called, "The Complete History of Tubes." With chapters on what happened after 1966 and who really was still making tubes after 1966. A couple of chapters on what role Mullard and RFT played in supplying tubes labeled as "Made in USA." Did Tungsram make tubes for American companies? All the tube companies that ever was in business in the USA and when did they close their doors. You know, stuff like that. That's what I wish I knew...all of that.

 

[MartyStrat54]

If you are just glancing over the posts here in this thread, please feel free to ask any question you may have. There are several guys who can answer your questions.

 

[MartyStrat54]

Show me your tubes! Got any pic's of your favorite tubes? It does not matter if it is current production or NOS. Show us what you got, what position you use it in and why it is your favorite V1 or V2 tube?

 

[RiverRatt]

I don't have any pics. How do you post them?

I tried yours & Joe's method for preamp tube swapping last night. If it's not hurting the tubes, it's sure a lot quicker and easier to compare. V1 was a hard-fought contest. It ended up being between the 20-20 GE you sent me and my 1966 Mullard. These two tubes sounded a LOT alike. The Mullard won out - it had just a little more "hair" and it had a little more punch than the GE. NOW I have sitting in front of me a new contender. Smooth plates. Diamond bottom. Bring it on.

 

[MartyStrat54]

That's what I'm talking about. A fistfight between a Mullard and a Telefunken. Serious fun.

 

[racko7566]

I'm really glad you guys mentioned rolling tubes in standby, it makes a world of difference in comparing sounds without forgetting the last sound. Thanks guys.

 

[wegman]

So I have this straight. You can put the amp on standby and safely swap out the pre-amp tubes with the amp on?

 

[racko7566]

Out of all the preamp tubes in the world, which one do you think makes the most dramatic changes in sound, be it good or bad?

 

[racko7566]

So I have this straight. You can put the amp on standby and safely swap out the pre-amp tubes with the amp on?

Yea, the guys said just dont bang them around when the filaments are hot.

 

[wegman]

Yea, the guys said just dont bang them around when the filaments are hot.

Wow that's cool. I never would have even considered doing that.

Thanks man

 

[racko7566]

Go back to page 56 of this thread and you can read about it. Its about 3 quater of the way down and written by Solarburn. OOhhh and dont look straight at him youll be blinded.

 

[MartyStrat54]

Out of all the preamp tubes in the world, which one do you think makes the most dramatic changes in sound, be it good or bad?

That's a tough one, because you have American and European tubes and also what makes the best V1 and V2.

I would say my favorite American tube would be my 30-30 RCA 7025. That's one smokin' tube. It can be used in V1, but look out...it's an ICBM. A real monster in V2. My favorite American V1 would be either a 1959 RCA medium Gray Plate, or a 1960-64 Raytheon Black Plate. I also like medium gain 7025's in V1. There's just so many good ones.

My favorite European tube would be a Philips or Amperex (same tube) ECC83/12AX7. To me, this edges out the Telefunken smooth plate in the V1 position. I've also used a medium gain Amperex 7025 in V1 with a high gain Amperex 12AX7 in V2 and this is a deadly combo of Dutch tube technology.

A lot has to do with the brand of amp and the "brand" of power tubes that are being used. I think a Telefunken sounds really good in the first gain stage of a Fender amp. I think Tele's seem to blend better with a 6L6GC versus the EL34 (IMO) The Tele is definitely one of the top three sounding tubes. The smooth plate being the most sought after. I have run a Tele in V1 with a high gain Amperex in V2 and I doubt if anyone one would not like that particular sound. The thing about a Tele is that they all sound different. Depending on the year, the materials used and the machinery, the Tele's all have different sounds. Then you have to remember that RFT made Telefunkens (no diamond on the bottom). I just found this out myself. However, the RFT/Tele's are very,very nice sounding tubes. They have a unique plate assembly and they do not look anything like a Tele.

This is one of those subjects where there can be several winners. Each of us has a different tonal sound we are striving for.

 

[racko7566]

Thanks for the great info Marty. I'm like a sponge for info lately, regenerating long lost brain cells I guess. Anybody else? * NEXT, cough, cough *

 

[MartyStrat54]

I wish I had a cough like that!

 

[MartyStrat54]

Is that a guitar you are holding Racko, or a bong shaped like a guitar?

:cool2::cool2::cool2::cool2:

 

[wegman]

I hope this works.

Anyone have word on these?

 

[MartyStrat54]

If you have bought those...they're nice. Did you get them, or is that an auction picture?