2 tube questions: ID'ing Siemens EL34s, and mismatched biases?

[StingRay85]

This is common knowledge. RFT is actually not a company but was a collection of companies in East Germany. Some had codes printed on the bottom of the base, some didnt't. I have about 100 of those RFT, about 40 of them new in box. From all the different types of EL34 I have, what strikes me the most is that the pins are such high quality that you never see damage or corrosion on them. The design was afterwards copied by Electro-Harmonix, where it is still in use. Just like Philips, Siemens had acid etched codes on each indivual tube. Their high quality tubes (E83CC, E88CC, E84L) used different codes. Siemens stopped quite early making preamp tubes, and sourced them from Ei. Siemens never made EL34 or GZ34. Ei made a EL34 with a pointy top, but it was not a big success

 

[LeverAction Gypsy]

Got them in today, no etched codes that I can find on the glass. One has 91 and one has 98 in raised letters on the bottom of the base.

What tubes are you referring to? Siemens? RFT? Teslas? The Teslas wont have etch codes. Many EL34 types wont but Mullard & Amperex will have 'xf' codes with 1 being earliest and xf4 being more recent. The best way to actually ID tubes is know the plate design and the identifying markers. Tesla EL34s for instance...double halo getters that are on top of each other. Ameperex EL34s will be double D getters for example. Post a pic so we can see what you got

 

[LeverAction Gypsy]

You make a lot of excellent points here. Really, what's written on a tube means nothing. This is why you need to learn to be able to identify the internals of various tubes, especially those you like. Back in the golden era of tubes, so many companies made tubes for other companies, then put that company's label/logo on the tube for them. It was a normal practice. The simple way to explain it is that 'it was just business.'

Even then, not all factories put their etchings on the tube. Sometimes, you'll find a tube made by GE for RCA, or even Amperex, and it won't have the GE etchings or dots. Most of the time it will. But not always. But the internals, never change. Of course, through the years, companies like GE had a few different plate structures they used, so if you like GE's, or particular plate structure, learn them. This way you'll know 'your' tube when you see, no matter what the label says on it.

The only power tubes I use (and actually own) are 6550s and 5881s. Both types I have a good stockpile of vintage Tung Sol tubes. The 5881s are all marked Tung Sol most likely because they were mostly military use 6L6GBW (5881 alt designation)...BUT of the 30 or so vintage Tug Sol 6550s most are not labeled Tung Sol - but all have the 'Tung Sol Stop Sign box' at the top of the tube with 6550 in the box and USA3 under the box. Also date code on tube starts with 322....so like you mention (sounds like you know your tubes haha) the painted label is least important. Second least important is the manufacturer code. I have had Tung Sol 6550s in the past that were labeled G.E with the 188 manufacturer code - which is G.E - but they had the clear EIA / identifier codes.

 

[LeverAction Gypsy]

This is common knowledge. RFT is actually not a company but was a collection of companies in East Germany. Some had codes printed on the bottom of the base, some didnt't. I have about 100 of those RFT, about 40 of them new in box. From all the different types of EL34 I have, what strikes me the most is that the pins are such high quality that you never see damage or corrosion on them. The design was afterwards copied by Electro-Harmonix, where it is still in use. Just like Philips, Siemens had acid etched codes on each indivual tube. Their high quality tubes (E83CC, E88CC, E84L) used different codes. Siemens stopped quite early making preamp tubes, and sourced them from Ei. Siemens never made EL34 or GZ34. Ei made a EL34 with a pointy top, but it was not a big success

Siemens preamp tubes were actually made in huge numbers. If you go on ebay and punch in Siemens ECCxx you'll see many auctions, most are $20-30 tubes with shipping unless they are 'special'. Look for the Siemens mark of = with a / through it. They had a bright and clean tone some people feel they made the best 12AT7/ECC81. Personally I like the Telefunken ECC801 (vacuum tube mics) but its subjective. I'm not 100% clear but I think E.I started from Telefunken selling out - since they had the Telefunken tooling until the Bosnia war bombed it away. If they made E.I tubes on non Telefunken tooling I never saw that code on any tubes but 'smooth plates'. Telefunken sold out I think 1975 or maybe earlier, but they were still making <> tubes in the later 60s. E.I was done by 1995 so whatever stock is left over - thats it. Easiest way to see an E.I is they did a bunch of smoothplate tubes like Telefunken but with shiny silver/chrome plates. They also did standard gray plates. Look for a <> on the bottom of the pins for Telefunken - E.I has the etch code. E.I etch code is a half circle with a dot in it.

 

[LeverAction Gypsy]

Telefunken labeled Siemens - Telefunkens NEVER had etch codes on the side...its hard to see the =/= but its on the side....anything etched on the side says - I'm not a real telefunken

ECC81 SIEMEN TUBE n668 | eBay

Used tested strong

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[LeverAction Gypsy]

heres a pretty good close up of the Siemens EIA etch code -

 

[LeverAction Gypsy]

Here from the EIA etch code you can see the 'triangle' mark of Amperex, Heering Holland. Seller says they are Phillips like Mullard...well Phillips but Holland. So so tubes will help a dark sounding amp like a G.E long plate does.

2x Tube Valvo ECC83 Ecc 83 12Ax7 Audio Tubes short ribbed plate same code i63 | eBay

All Valvo Audio Tubes are slightly used with the VAlvo Logo on the tube. AF twin triode. no boxes for these tubes.

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[LeverAction Gypsy]

A little hard to see but here are Telefunken looking smoothplate ECC83s with an etch code on the side - the upsidedown half circle with a dot in it - mark of E.I Yugoslavia

 

[LeverAction Gypsy]

The really good Mullard tubes wont have a 'B' codes etched on the side look for a lower case 'm'...or look in the pins for the 'm' code...2 seams at the top

Valvo Mullard ECC83 Audio Tube, Bottom Code DM-mCP, D Foil Getter, Long plates | eBay

Find many great new & used options and get the best deals for Valvo Mullard ECC83 Audio Tube, Bottom Code DM-mCP, D Foil Getter, Long plates at the best online prices at eBay! Free shipping for many products!

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1 vintage 1957 Mullard square getter long plate 12AX7 ecc83 tube -tested- mC1 | eBay

12AX7 ECC83. 1957 mC1 Square D . (Code: MC1 B7D). (Blackburn Factory made in 1957). TUBE's TEST RESULT's TESTED NOS! Tubes TESTED AND sounded good in my BOGEM AMP! No microphonics!

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[LeverAction Gypsy]

Heres an example of how you can get taken and way over pay - the red tips means they were pre screened - usually for medical equipment. That said they were usually screened for medical equipment to work and not fail - but not screened for tone with guitar amps. I had red tipped Telefunkens and while they sounded great like all telefunken nothing really different. - so these 'Phillips' all 15mm gray plate Heerling Holland 1960s are really nothing special. If you see lots of a certain type of NOS tube available on ebay for $30-40 all day....save your money for Telefunkens or RFT big halo getters if you want a quicker break up. Only thing with RFTs is they are slightly noisy if you compare to Telefunken. You could easily buy a quad of <> Telefunken for likely $100 less than these over priced Amperex/Phillips and you would have what most would agree - all other preamp tubes are measured against - Telefunken smooth plate ECC83

12ax7 ecc83 tube Philips tubes preamp quad valve b339 cv492 e83cc b759 selected | eBay

Other class quality (otherwise equal): 7025 ; CV4004 ; E83CC ; M8137. Similar Tubes Normally replaceable-slightly different: 0AX7 ; 12AX7A ; CV492 ; E2164. ECC83 = 12AX7 = B339 = 95-127-01 = 6L13 = CM1 = ECC83S.

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[LeverAction Gypsy]

last one...these can be SUPER HARD to find...not the reissue but the real thing - Genelex B759 tube = ECC83. I had one apx 15 yrs ago and sold it for $700 then. The way you find these things cheap is thrift store stereo consoles, tube gear ect. It was in a Harmon Kardon amp I bought for the Tung Sol 6550s in it. The B759 had a tube shield over it so I had no idea until it was home. I had no paperwork for the tube and it did have a slight crack at the base but did not affect the tube tone or function. Sound? I still felt the Telefunkens sounded better...I still shouldve kept it

Genalex Gold Lion B759 / 12AX7 / ECC83 Vintage Preamp Tube Tested England NOS | eBay

<p>New old stock vintage Genalex Gold Lion B759/12AX7 pre amp tube. Open box, other random box </p>

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