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EL509/519 -> 6LF6 Adapter

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Claus

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Joined 2001
#1
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
 
#2
FUTTERMAN

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,😉
 
#3
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
 
#4
FUTTERMAN

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.
Click to expand...

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,😉
 
#5
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
 
#8
OTL

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, 😉
 
#10
TOO BAD...

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,😉
 
#11
Well, the nice thing about DIY is that oddball tubes can be right at home. The DIYer can enjoy whatever life he gets from them, then rebuild with something else. I've got some mint NOS EL38s sitting in the garage. The amp they're going in has Eico iron (UL taps, 6600 ohm p-p). It'll be fun listening for a couple of years, then I'll have to redo the bases and convert back to a mundane old EL34. That's a typical tradeoff.

When my last 6LF6s are starting to puff a bit going uphill, I suppose I'll get off my lazy butt and make another sweep tube work on this chassis. Looking at the characteristics of the EL509, it looks like a fine candidate for screen drive, albeit with a dB or so less power than I can get with 6LF6s.
 
#12
EL509

Hello,

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.
Click to expand...

Probably the Svets are O.K. for that.
However don't do that with the Yugo EL509,those are textbook Philips EL509s' and rated for 35W max.

Also for info:

The EL 509 is available with octal base,so no anode cap.

And did you know that the KT90 is basically a rewired EL509?

Those having replacement problems may try to locate some NOS EL 519 which have even better ratings than the 509.
Be ware that some vendors consider both as being equivalent.
Which is only true in one way: going from EL509 to 519 is O.K. not always the other way around.

Another fabulous sweeptube was the 6KD6 which is probably long gone as well.

Cheers,😉
 
#14
Hi,

Heres a link to a OTL tube amp I have its a Prodigy Audio Labs amplifier.
Click to expand...

From reading your website it seems you think the amp is based around a Futterman design.

If memory serves me the OTL1 used the 6LF6 output tubes.

So, assuming this is the case it seems yours is like an OTL1 minus the dedicated regulated PSU.

Have you considered drawing the circuit diagram of your amp?

6LF6s are getting really hard to come by, maybe time to convert the amp to 6KG6s...If the output uses PCBs this may turn out to be a major PITA though...

Cheers,😉
 
#17
Partial schematic

for the Prodigy OTL is located here:

http://www.pi.infn.it/~federico/Immagini/prodigy.zip

It's a postscript file, so you'll have to deal with it. I've converted a couple of futterman types to 6KG6 a few years back. They'll work in place of 'LF6, just have to watch the heater current and deal with new plate caps, plus you'll lose about 20% of output power @clip... BUT at least you can get'em.
 
#19
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