And yet another tube question 12au7

erniejade

I recently received a big box of tubes that I will be posting in a little bit on another thread.

I am still looking for the "right" combo of tubes for my sacd player. Cayin scd50T that takes 2 6922 and 1 12au7. I use the tube output mainly for SACD while redbook is getting fed to a w4s dac2.

So far, I have tried the EH that came with the unit from RAM. They had a lot of high end but, got raspy sounding fast and light on the bass.

Next I tried Sylvania JAN 6JD8 1972 made with an early 60's mullard. Big bass improvement. Mids came in more natural sounding but, still a hair raspy in the top end.

Next I tried some mullard Gt. Britain matched pair 6jd8 from Vintage tube service with the same mullard 12au7, Big time improvement. Much more bass, smoother mids, not raspy in the highs but, I still feel something is missing.

Next up Seimens gold pin E88cc that Kevin from Upscale suggested with the same mullard 12au7. They brought a bit more mids out that i liked and it is a wonderful tube.Still a nice and smooth top end. Not sure if I like the Gt. Britain ones or this set better. They both are great performers.

This round I am going to try out some Amperex Holland 6DJ8 that have the cartoon on them (BB) but, I am going to change out the 12au7. In my possession, I have what looks like a westinghouse, carbon 12au7 that I am thinking of trying next. The writing is hard to read but i can make the word westinghouse on it, plates are a weird carbon blackish color ,at the top of the tube reads made in the USA and a few dots above where it reads 12AU7. I took a look on the web and several people were saying this is supposed to be a jem of a tube.

I also have and ITT 12au7. Not sure on the date or anything else outside of a 302 on the body of it.

Also what I think is a mullard but not sure of anything on it since names were rubbed off outside of 12au7 and right under it says I9E and whatever was written on it was green lettering, plates are long black.

Next up Synivania that says USA. Right under the 12au7a reads H6V and on the right of that has 96, 84,and whats under the 84 i cannot read but looks like a 21? or 2 something grey plates.

Out of the 12au7's i listed, what do you think would match up well with the Amperex Holland? Or even any of the 6DJ8 that I have listed.

erniejade

I forgot to add the current mullard i was using is labeled daystrom made by mullard Gt. Britain ecc82 with the numbers 347 & 1022. I got this one from vintage tube service. I thought he said it was an early 60's one.?

erniejade

I forgot to add the current mullard i was using is labeled daystrom made by mullard Gt. Britain ecc82 with the numbers 347 & 1022. I got this one from vintage tube service. I thought he said it was an early 60's one.?

I also have a I think late 60's GE that trav0810 sent me. He is also where I got the Amperex from. On a side note, Great person to deal with and chat with.

doctor r

If you like the Mullard 12au7, but thought there was a little missing, look for a 50s or 60s Amperex 12au7. They help move you out from that warm wool coat to a more open and extended sound with the fundamentals still as sound as the Mullards. The actual Bugle boys can be a little too forward, but there are a lot of other Amperex options (orange globe are the least desirable in my experience). If you decide to look at the Mullard again I have a single long plate from Andy at Vintage Tube Service that needs a nice home. It was acquired for use in a phono pre that found a new home shortly after I got the tube.
Rick

heiney9

Does the Westinghouse have a long arm D shaped getter and the number 337? If so, and based on you description that is a real Westinghouse tube. Westinghouse only manufactured their own tubes for a very short time early on. I have these are they are among my favorite American made tubes for my rigs. After about the mid fifties all Westinghouse tubes were outsourced and made mostly by RCA and GE.

The ITT tube is rebranded tube and I don't recognize the "302" as an EIA code. The Philips made tubes have an acid etched code toward the bottom that consists of 2 lines of code. Does the ITT have a code like that? If not, it's either American or Japanese. Is the 302 vertical or horizontal?

Philips (Mullard) never made a black plate tube and Philips long plates (always gray) are rare and early tubes. The "I9E" tube you refer to is an American black plate tube most likely made by Sylvania.

In regards to Philips manufactured tubes, the ONLY way to identify their manufacturing origin is by the acid etched code. Just because it says "Made in Gt. Britian" doesn't make it Mullard. Mullard have a dozen different factories all over making tubes and while the basics are the same a Mitcham made tube sounds different than a Blackburn made tube which sounds different than a Whyteleafe made tube all with marking "Made in Gt. Britian", not to mention the different construction variations over time. Or "Made in Holland" doesn't always mean made in Heerlen Holland. Cross labeling and buying other manufacturers stock to fill orders was very common back then.

H9

heiney9

erniejade wrote: »

I forgot to add the current mullard i was using is labeled daystrom made by mullard Gt. Britain ecc82 with the numbers 347 & 1022. I got this one from vintage tube service. I thought he said it was an early 60's one.?

I also have a I think late 60's GE that trav0810 sent me. He is also where I got the Amperex from. On a side note, Great person to deal with and chat with.

Not familiar with 347 & 1022 sometime these were internal stock codes manufacturers put on the tubes before inserting them into the gear. If it's a Philips tube it should have acid etched codes toward the bottom. 2 lines of code, the top being the tube type indentifier and change code. Meaning if the tube had minor changes internally a new code would be used. For example the first (short plate) 12AU7/ECC82 code used is Gf0. Those 3 digits tell me a lot. 1) Gf means its an ECC82 2) Gf indicates short plate 3) 0 indicates this the first iteration of this tube. As example Gf5 means the same thing except this the 5th time they have made minor changes to the tube. It also indicates a later (older) tube.

The 2nd line indicates place of manufacture and the date. Prior to about 1960 (this varies a bit) the 2nd line of code has 3 digits. The first being the factory the tube was made at B=Blackburn (Great Britain) M= Mitcham (Great Britain) the delta triangle meaning made in Heerlen Holland. The next number is the year and the next number is the month. After about 1960 it went to 4 digit code also indicating the week.

So: Gf1 over B2C2 = ECC82, short plate, 1st revision, made at the Blackburn plant England, 1962, with the rest indicating month and week. The most important are the top line and the first two digits of the 2nd line.

Hope this helps

H9

P.s. Up to about 1955 they also put a variation of the codes in white lettering on the base between the PINs.

erniejade

The mullard from vintage tube. I was told it was a 60's "better sounding" mullard.

and the ITT. formatting is messed up in this post sorry.

erniejade

Here is the westinghouse. I will say the combo of the westinghouse & the Amperex BB is nice! Way better then I thought! I like the westighouse au7 with the BB better then the Mullard BB combo in the cayin.

Its hard to read much on it since a lot of the writing has worn off.

heiney9

What are the codes on the Daystrom? Etched down towards the bottom. Looks like small halo getter which makes it after 1961. Colored tip usually indicates low noise, special selection for something like medical grade equipment.

The ITT tube is hard to tell but it appears American made, but it could be Japanese.

I find the Westinghouse to be an excellent 12AU7 and fairly rare for if it's legit as this seems to be. A bit of a sleeper as the real thing is hard to come by.

H9

erniejade

on the bottom of the tube between the pins has Y and the number 7 in the 1st mullard pic, i have a shot of the writing on the bottom right but, its hard to read it.

I agree on the westinghouse being a sleeper. I almost passed it over in the box of stuff I picked up. When i took a look at it, the color of the plate and the dots were gray on the other one. The other one kind of looked like a ge coloring. looked different then the other westinghouse that was in the box so I looked it up. I am glad i did!

heiney9

Is the Y 7 imprinted in the glass? The very early Philips tubes and some Siemens (before about 1956) had chalky white letter codes painted on the bottom between the pins. Almost all tubes have some sort of letter/number imprinted in the glass between the pins. It's not important unless it's a diamond shape, then we know it's a Telefunken.

Your Westinghouse sounds like the real deal. Yellow print, 337 is the EIA code for Westinghouse tubes, 3 gray dots (a bit different looking than GE), charcoal to charcoal silverish long plates (muddy looking), long arm "D" type getter means it's a true Westinghouse. Not a rebranded tube.

Look on the outside of the tube envelope towards the bottom for something like this on the Philips made tubes like the Daystrom you have. Many later Daystrom tubes were made in Japan on Philips equipment. Japanese tubes don't have the etched codes like "true" Philips tubes.