300b tubes

[patm]

I have about 130 hrs on my Paramounts now and I am ready to roll some tubes. I have a nice pair of 12AT7 Telefunkins in now and some Amprex 12au7's in the FP III and I was wondering what 300b's some of you have tried. I see that Emission Labs voids the warranty if there tubes are used in BH gear. I have read some negative feedback on there quality control and also some bad things about there customer support. Sophia"s are reasonably priced and I have read some positive reviews. EAT's are very expensive but seem to have only positive feedback.

[Paul Joppa]

The Paramount 2A3 version is direct coupled, which places an unusually high voltage on the 2A3 grid during the starting transient. A few tubes have problems with this - the Full Music/Sophia mesh (IIRC) will sometimes arc internally, and the EMLs will strip their cathodes very quickly. Right now I recommend against these tubes in the Paramount.

I have not heard of any problems with the 300B version of Paramount, which is not direct coupled. And most other 2A3s work fine in the Paramount.

With regard to EML, while Jac can be a little hot-tempered and impatient, he's also willing to go the extra mile to resolve customer problems. He took back the tubes from our customer who discovered this problem and studied them extensively in his lab. He determined what the problem was and even managed to restore a large part of their emission before returning them to the customer. His tubes still have a great reputation for sonic excellence.

It's my opinion (speculation) that the new-technology foil filament/cathode in the EMLs and similar tubes just does not work like the older designs. I don't know whether it's a different emissive material or a different thermal mass, but in any case they don't like the transient high grid voltage as the cathode heats up. Nothing really wrong with that, it's just new and unexpected. Our amps works with old tubes, and (I believe) their tube works in old amps. It's the combination of a new tube design and a new amp design that produced an unexpected problem.

We will eventually replace the C4S boards with our new design, which is in the Eros now. This new board has a slow-start option for the driver which should solve the problem; the prototype is currently undergoing listening and burn-in testing.

[andy2667]

Hi Paul,

The Soft Start feature is an excellent idea. I have recently replaced the Sovtek 12AT7 with old mullard 12AT7. Whenever I witch on the amp, I note that the 12AT7 glow bright for a second before return to normal. Just curious if this heart the tube life. I am considerting to add a thermistor with adequate current capacity to the primary of the power transformer (or easier to the power input socket) for limiting start up current but wonder if this has detrimental effect to the sound.

Looking forward to the soft start board for an upgrade. When would this be available?

Thanks

Andy

[Doc B.]

A bright glow at start up is typical for Mullard tubes and nothing to worry about

[andy2667]

Hi Doc,

Thank you for your advice. This greatly alleviate my concern. I have not had good experience in tube rolling and thus not know the character of the Mullard.

When I fist tried the Mullard, I just curious if the tube was exactly the 12AT7 equivalent or the online seller sold me fake tube.

Your advice not only alleviate my concern on the T7 tube but also re-assured that the one I got is probably not a fake/immitate Mullard.

By the way, the up comming soft start feature on the C4s is still tempting. Looking forward to the release of this new board.

[patm]

Thanks to all. I will await the C4S mod. In the mean time I think I will try a Sophia carbon. I will post my impressions.

[Thoburn]

Hi Dan/Doc B,

IIRC, In one of our conversations you said that the Sophia (didn't specify which) or the TJ 300B premium mesh plate were good choices. Do I remember that right?

Toby

[Air]

I run the TJ Meshplates in my 300B Parabee's and am very pleased with them. To my ears and in my gear they have been superb.

Regards, Chuck

[2wo]

I use a set of TJ meshplates in my own 300B amps. They sound great and have been reliable...John 

[Canefire]

JJ Tesla 300B are sounding really great in my Paramaounts.

[Rick58]

Hey!  New forum! cool!  I only own Paramounts, so the categories are most welcome.

As far as 300Bs, I got some Sophia Princess mesh plates (w/ the recommended by Sophia ceramic base, most expensive version of course!), sound great. I don't remember what was 'better' sonically over the stock EHs ... sorry. I know they fit better than the stock (oversize pins) EHs. I think it's been >6 months, no problems at all. Nice soft glow from the tubes in the dark, nice 'upgrade' from the stock tubes.

I do know one can tune the sound with the 12AT7. I have some Siemens & Halske NOS ones in there now, these give a more detailed crisp presentation than some others I have tried. Well, I think I only tried one other brand (RFTs) other than the stock 'generic' ones. This brought back the sound I was looking for after a preamp change (non-BH, sorry). They are different vintages, one 'flashes' briefly, the other does not (even when swapped between amps). I understand this is not a concern, and I have not experienced any issues having them in there for the better part of a year.

I would definitely be interested in an upgrade 'soft-start' C4S board if it is retrofittable ...? Hopefully that is the case.

Thanks for the new forum!  and best regards to all,  - Rick.

[Paully]

If you want to slum it, on the lower end of the price scale I have been very, very happy with my Shuguang 300B.