WM-5 EL-37

[ronton3]

I have just recently finished recapping a 2nd WM-5 and now have a pair. I am using 5881's right now, I have KT-66's waiting in the wings, but I also have my favorite EL-37's sitting idly by and wonder if they could be a drop in, I am using 12BH7's in the driver position without changes and things sound good. I have read a bunch of threads and haven't seen the EL-37 mentioned but a paper on the Williamson Amp in general contained this quote: Option 3: EL37 Pentode
Another - but unmentioned by Williamson - choice was the Philips/Mullard EL37. But this valve was also a competitor's product and very likely an import.
I did a search of the forum but found no mention of using them with the WM-5. Does anyone know if this will work, is it a good idea to use the 12BH7's in the preamp stage also. Thanks for any opinions.

 

[century tek]

EL-37's are another variant of the 6L6 family and will drop in and work but the heater current draw is more with EL-37's than with 5881's.

EL-37 draws 1.4A of heater current.
5881 draws 0.9A of heater current.

It might heat up your power transformer more and I have also heard that these amps are hard on power transformers so I wouldn't recommend it for more than 1/2 hour or less for testing purposes.

 

[ronton3]

Thanks for the input, your info gave me the knowledge to check the KT66 heater current draw(original tube for the WM-5) it is 1.3 which is very close to the EL-37, I also discovered that the 7027 is .9 like the 5881 so I have several choices., the 8417 is 1.6, maybe getting a bit high.

 

[pjrengineer]

Curious if anyone else tried el37 in w5m but it is not like I need to hunt down more tubes. The kt66 and 6L6 sound great as is

 

[tuberadios69]

Thanks for the input, your info gave me the knowledge to check the KT66 heater current draw(original tube for the WM-5) it is 1.3 which is very close to the EL-37, I also discovered that the 7027 is .9 like the 5881 so I have several choices., the 8417 is 1.6, maybe getting a bit high.

Better make sure the W5M can accept the 7027A. I'm pretty sure it can not. If the tube socket is not wired to accept 7027's, it will see a dead short. It would likely take out your power transformer. Another example, while the McIntosh MC-240 amp's output tube sockets are wired to accept 7027A's or 6L6GC's, the MC-30 mono blocks are not. I know this from personal experience.

 

[GordonW]

Well- I have done quite a bit of research, and have some experience in Knight KB-85 amps using EL37s- and IME, the EL37 is much closer to an EL34, than a 6L6.

I would be reticent to put them into a W5. Especially given how easy it is, sometimes, to damage the output transformers in W5s...

Regards,
Gordon.

 

[zackthedog]

Well- I have done quite a bit of research, and have some experience in Knight KB-85 amps using EL37s- and IME, the EL37 is much closer to an EL34, than a 6L6.

I would be reticent to put them into a W5. Especially given how easy it is, sometimes, to damage the output transformers in W5s...

Regards,
Gordon.

I'm working on some Fisher 100-X amps for a fellow AKer right now, and you can use either EL37's or 6L6GC's in those amps. Those amps are cathode bias so there's no change to be made. I don't think they'd be a problem in a W5, honestly. I was about to check the one pair of EL37's that came with the amps, they test strong, but I want to see how well they bias and balance. I'll try them in one of my Williamson amps and see if they're much different from the KT66's I'm using now.