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Dropped a SIF Ba

A few days ago i decided to move my system around. I very carefully removed all the valves from my pre and then dropped one of the Ba's

My plea is therefore; Does anyone on DIY have a SIF Ba or any other Ba with the large tipped envelope ?

I will pay handsomely for either one or a pair, or i can trade from a collection of "stuff" :)

If the trade is for a large or heavy item i will meet you halfway on postage.

Hallo Martin,

Thanks very much for the reply, i have a picture of the good valve. It may not be a SIF as there are no markings on it. But i bought a pair advertised as made by SIF.


  • ba valve 001.jpg
    ba valve 001.jpg
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Thanks for the info, this one is an older valve (no pun intended).

I haven't had any problems so far with hum, they are a bit microphonic though. Though nowhere near as bad as my previous amp that ran 27's and 12's

As you have 8 of them would it be rude to ask for a pair of them. Then i'll have my well used one as a spare.

Diy martin said:
Hello Peter,

That is a PTT2S-sif from France , the coating is removed from the glass, because i can see some silver colour spray on the bass.


I'd just like to point out that silver paint on the base does not necessarily mean it is a SIF tube. I have a tipped envelope Ba with paint intact over the glass branded "Siemens Ba". Also with the Siemens logo and numbered on the other side.

I do think it is a SIF tube but for another reason - in your closeup of the base the paint is sort of thick and rough. The SIF tubes I have seen have paint like that while the Siemens tubes have a smoother, thinner coat. ;)

I have a few of these tubes - mostly Valvo box plates - and am going to try for a little Ba + 71A amp.

exurbia what do you have this tube driving?
:) thanks to everyone that has replied to the thread :D

Kevin, i don't have the curves handy for the Aa, but i can give you some details.
heater 4V 0.5 A
Ual max 400V
Ua max 250V
typical use 220V on anode
-2 V on grid
anode current 3mA

piffpaff, the Ba's are microphonic but i have mine mounted on dampers. Acoustic feedback through the valve glass is no problem. I have mine running with an active anode load made up with the large envelope 12hg7, they look great together. rectifiers are two Az 1's the whole amp is dual mono.

panos, the Ba is a great sounding valve. the 27 is nice especially the punched and mesh plate versions. I have also tried the 12A and the type 40 as preamp valves. They were both excellent.
Same information as I already have. I guess it would be nice to know what to expect in terms of mu, rp, and transconductance for the Aa, but I guess it is not out there. Judging from construction I am assuming the mu is quite low, but I haven't actually bread boarded anything yet to evaluate these..


I have tried 27 in a mu stage so far and the measured figures are astonishing as far as distortion is concerned. Moreover I triead RE084 and RE134. Sounwise the 27 is good but the resolved detail is mediocre, moreover, on the mustage there is some problem with microphonics.
The Re types are outrageous in terms of noise and microphonics and did not managed to tame these under any circumstances.
All of these tubes were greately outperformed by my main preamp that uses D3a in Se mode with good ouptut transformers
My current line stage is 26 dht transformer coupled using UTC HA-133 opts. It's acquitted itself against various other line stages, and the only area I have a complaint with is it is not the last word in bass extension.

It's quiet and not terribly microphonic, but it took a lot of work to get it that way.

The D3A is a great tube, I use one triode connected in the front end of my phono stage, 5842 on the output side.