Emission Labs Tubes

[patm]

This may be old news but I just noticed it. Emission Labs is now Guaranteeing there tubes with the Paramount using the soft start mod. There is a nice note thanking Paul Joppa for his Support. I have been using a pair of 300b mesh plates in my Paramounts for two years and I love them. This is good news.

[Jim R.]

Hi Pat,

Unfortunately, if you do have a problem in your case they won't  honor the warranty.  Why?  because you're using a PIO coupling cap -- in their list of no-nos, theysay that one must use a film foil or metalized film type -- no PIOs.

Also, the EML problem with the paramounts was only with the direct coupled 2a3 version.

Hope that helps clarify things a bit.

-- Jim

[Gerry E.]

I have been using the standard EML 300B with my V1.1 (soft-start) Paramounts for a couple of months now.  I was aware of this policy but after reading Pat's post I wanted to read it again.  I had some trouble finding it, but finally did.  Here's a link for anyone wanting to read it (scroll down about 1/3 of the page for the Paramount section):

http://www.jacmusic.com/html/diversen/amplifier-problems.htm

Pat, was this the page you were referring to?  Thanks.

Gerry   

[Jim R.]

Ok, I found the page where EML states all their warranty conditions -- so here it is, straight from the horse's mouth:

http://www.emissionlabs.com/html/guarantee/conditions.htm

See note 8 in regard to the PIO caution.

This said, I'm aware of many folks using EML tubes in various amps with Mundorf SIOs as coupling caps and have nevver had a problem -- perhaps due to the unusually high working voltage of 1200v, but whatever, in the real world this does not seem to be an issue with these caps.  No, this doesn't mean I'm endorsing them, just as I'm not condemning them -- but just reporting what EML states.

I personally will probably not use any of my ampohm PIO caps in any amp where I plan to use EML tubes, but those are half the rated working voltage of the Mundorfs.  Note, the Mundorf silver/gold/oil and silver/gold are metallized film types and are not a problem.

Hope this helps,

Jim

[Doc B.]

I have been using the standard EML 300B with my V1.1 (soft-start) Paramounts for a couple of months now.  I was aware of this policy but after reading Pat's post I wanted to read it again.  I had some trouble finding it, but finally did.  Here's a link for anyone wanting to read it (scroll down about 1/3 of the page for the Paramount section):

http://www.jacmusic.com/html/diversen/amplifier-problems.htm

Pat, was this the page you were referring to?  Thanks.

Gerry   

Allow me to clarify something for those who may come across this thread in the future:

Jac probably doesn't know that the Paramount is a direct coupled amplifier only when wired in the 2A3 configuration. The 2A3 configuration was the situation in which EML 2A3 tubes were arcing over at start up due to the 2A3 tube drawing excess current before the driver tube heats up. For this situation PJ created the soft start circuit. In the 300B configuration the amp is RC coupled - with a metallized film cap, not a PIO - and these potential issues simply do not exist when using any brand of 300Bs in the stock Paramount. Naturally while we are happy to have bottleheads share their ideas about modifications to their stock Bottlehead products, we can't take any responsibility for problems generated by a mod that alters the kit from its stock configuration.

[jdm]

Does this apply to using a Mundorf SIO as the parafeed cap or is it just for the coupling cap?  I am using a teflon film (0.1 uF, 600 V, Aura T) for the coupling cap and a Mundorf SIO (5.6 uF, 1000 V) for the parafeed cap in original Paramounts and have not experienced any problems with the EML 300B's.

Jim

[Grainger49]

Parafeed is like a coupling cap.  It couples the tube plate to the output transformer.

[Paul Joppa]

Does this apply to using a Mundorf SIO as the parafeed cap or is it just for the coupling cap?  I am using a teflon film (0.1 uF, 600 V, Aura T) for the coupling cap and a Mundorf SIO (5.6 uF, 1000 V) for the parafeed cap in original Paramounts and have not experienced any problems with the EML 300B's.

Jim

The EML issue is with grid voltage that does not stay close to ground, so it's only the grid coupling capacitor. Leakage in the parafeed cap will produce a little DC current in the output transformer, but usually not anywhere near enough to affect its operation. The reason for that is the DC resistance of the output transformer is a thousand times less than that of the grid resistor.