EL509/519 -> 6LF6 Adapter

[Claus]

Hi

Has anybody here used EL509/519 instead of 6LF6 in Futterman OTL amplifiers. I have a Homemade NYAL/Futterman OTL3E and only 12 6LF6 left, and no chance to get more of them.
What I have in mind, is making a Magnoval to Duodecar adapter, so that i can use EL509/519 instead of 6LF6.
I think George Kaye does something like that to old Futtermans.

Claus

[fdegrove]

Hi Claus,

First of all keep in mind that is quite likely going to take more than an adaptor to make this work.

Secondly: if you're going to use magnoval tubes such as the EL509,wouldn't then be better to change the duodekar sockets and replace them with magnoval types?

Cheers,

[Claus]

Hi Fdegrove

I´m aware of that it takes more then just plugging the tubes into the adapters. But I pretty much like the adapter ideer at a start, cause then I don´t have to make a new PCB board (Approx. 40 *20cm). But if it works, I might etch two new boards, and buy a truck load of EL509.

What scares me a little bit, is that the 6LF6 has 40W plate dissipation and the EL509 has only 35W, maybe 2 truck loads then, or I could use 8 tubes instead of 6. But that means a new PCB.

Claus

[fdegrove]

Hi,

What scares me a little bit, is that the 6LF6 has 40W plate dissipation and the EL509 has only 35W, maybe 2 truck loads then, or I could use 8 tubes instead of 6. But that means a new PCB.

I think what George does is change the plate voltages and adjust the bias si the maximum rarings are not surpassed.

Would you have a link to the circuit diagram of the OTL 3 so we can have a look at it?

I know the one I've seen so far run the EL509 at 170VDC and Vg at -40V.

The anode caps of both tubes seem to be the same type so that would safe you some money.

Also I can check here in Belgium as well if they can find any more 6LF6's.
Don't get your hopes up though,it was already problematic 10 years ago.

Cheers,

[Claus]

Hi

I don´t think that Kay change the plate voltage, but maybe the bias. But the 35w is probely first a problem, when the amplifier pulls low impedance speakers, and the bias current won´t change must there.

I have only a photocopy of the schematic. I´ll will try to make a scan of it.

Thanks for our offer, to try to find them in Belgian, but this race is over. You will only find overpriced tubes in small numbers, nothing like 12(14) from the same batch. And the 6LF6 was never that popular on this side of the pond, we used PL509/519.


Claus

[P.Lacombe]

Claus,

You can use Svetlana EL509/6KG6 tube at 40 W plate dissipation, with adequate (moderate) ventilation. It is a very rugged device, I never had any problem.

Regards, Pierre Lacombe.

[Claus]

Hi Pierre

OK thats good, the specs for Svetlana has 35watt as max, but they might be a little conservative.
I think I will give it a try.

Claus

[fdegrove]

Hi,

In OTL designs the tubes are rarely driven to their maximum dissipation in the first place since most designs are run in class AB2.

However,it seems wise when changing from 6LF6s' to EL 509s to take at least some precaution.

A tube that's often still around at TV repair stores and is very sturdy is the EL/PL 519.

My two Eurocents,

[SY]

This is all too bad. The 6LF6 was a GREAT tube, very versatile, very rugged. I'm down to my last four, and will no doubt have to start trying those 509/519 types before long.

[fdegrove]

SY,

Unfortunate as it may seem,the writing has been on the wall for at least a decade.

What is left?


The obiquitous triode regulator tubes such as the 6080/6AS7
(estimated stock is close to 1.000.000)

The EL509 is still produced in both Russia and Serbia.

Other USSR tubes:

6C33C AKA 6S33S

6C19P AKA 6S19P

For DIY projects I'ld stay clear from anything else since sooner or later the asking price for that odd ball tube is going to be so high as to render diy not an economical option.

Best,