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Received some of those German "postroehren", SQ gold pin pentodes. D3a is mentioned before like possible good driver. C3g is a very interesting tube, too, inside and outside shields, loctal socket, low noise, linear. Nice triode - connected curves; with OP, say, Uak=182V/Ugk=-3V/Ia=12mA we`d have µ=40 and rp~2k6. Looking good for the (300B) driver, RIAA stage input tube, etc. Must try it soon and report. But, 6 of 15 D3a was defective right from the box, white getter = air inside the tube through barely visible crack between the pins... The best thing is, those quality tubes can be (still) found relatively cheap. Some informations and pictures from the Web: http://www.jacmusic.com/nos/C3g-C3m-info.html http://www.tubecollection.de/ura/postroehren.htm http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Behoerden/Post/C3g.htm And detailed "Telefunken" data: http://frank.pocnet.net/sheets/128/c/C3g.pdf
Sweet! Bad about the cracked ones but it sounds like a good find in spite of that.
Fortunately, I bought those tubes from reliable German company, and they promised to exchange the defective ones. If someone needs the source for these tubes, I`ll E-mail the details.
glad to see someone use a pentode as a driver. I've found them to be simple to implement and very involving sound-wise. Kevins Garage
Hey, welcome to the forum and feel free to present some of your projects, make a suggestions, etc. Yes, we "believe" in pentodes here, too - you mentioned EF86 and "Neumann" on your interesting DIY pages. Friend of mine is in (expensive) constant search for EF86 and EF806S - not just for the mikes, but even "Matchless" guitar amp... German engineering at that time was something...and those pentodes, especially "postroerhren" and "SQ", gold-pins types. For example, I found the comparison of the prices of some tube types in Germany (TFK, Valvo, Lorenz, Siemens), about 1955.; in the well regarded "Das grose Roehren-Handbuch" by Ludwig Ratheiser": -ECC81 - 14DM -ECC82, ECC83 - 13 DM -EL34 - 18 DM -EL156 - 21 DM -GZ34 - 12 DM -E180F - 30 DM -C3g - 42 DM
I've mostly played around with the EF86, making two triode-connected EF86 preamps. Very detailed sound, yet not overly harsh or bright. I'm building a new one (once the metal work gets in) for someone else using onboard regulation, chokes, etc... I've also become interested in the EF40, EF12 and want to start using them. I also had some good sound out of a SE 300B amp using an SV83/EL84 - that was a budget version of a Loesch design. Kevin's Garage
Unfortunatelly, I have just 2-3 EF86, of different makers, of course, and didn`t try DIY with them, they are now (almost) scarce and expensive. But yesterday I get another 15 pcs of C3g and 4 pcs D3a (another 4 was broken ). Nice looking projects, I`m glad when I "found" someone who actually built something Probably you know this, but besides many old tube books on-line, there is a big pentode test on Pete Millett`s DIY pages. I like those cheap and "odd" tubes... http://www.pmillett.com/
there are some new EH EF86s coming out - still priced at $15ea - but I'll be checking them out to see how they match up sonically. They almost look like Mullard or Telefunken solid-plate copies. anyways - I'm looking forward to getting some c3g and d3a tubes