Afterglow Questions

[pboser]

In this case, it developed an internal short circuit which cause it to blow fuses immediately. It is not repairable.

That's my recollection of mine as well.  I think I got a pair of new and improved (but pre- PGP8) transformers from Bottlehead. 
Paul, while I've got you :-)  What suggestions do you have for upgrading my Afterglows?  I know I will replace the PS caps, am thinking of a switch for the cathode resistor (for 2A3 and 45/46 capability).  Any other suggestions?
Thanks,
Pete

P.S.  Every time I drove from NJ to Washington DC when my daughter was in college there, I'd pass the sign for Joppa, MD on I-95.  Even though we've never met, it made me think of you. (and tube audio - not sure that's healthy)

[Doc B.]

That's my recollection of mine as well.  I think I got a pair of new and improved (but pre- PGP8) transformers from

Yeah, those were the transformers we had made locally, by DeYoung. They were really well made, but took six months to get and we finally had to move on to another winder. Over the years we've had a lot of winders - some long term like MagneQuest and a couple companies we were done with after one shitty batch (won't name them but well known). The current winder gets stuff to us in a just a few weeks, and that plus the quality and ease of working with them has kept them as our primary (pun intended) winder for many many years.

[Paul Joppa]

...
Paul, while I've got you :-)  What suggestions do you have for upgrading my Afterglows?  I know I will replace the PS caps, am thinking of a switch for the cathode resistor (for 2A3 and 45/46 capability).  Any other suggestions?
Thanks,
Pete...

The other Paul (Birkeland) has done several restorations - he would have the best advice, especially for what parts are getting old and should be replaced.

What iron do you have now? IIRC, Afterglow had both deYoung and PGP8 power transformers at different times, and their voltages are enough different that some adjustment in operating points would likely be worthwhile. Also, you'll want to adjust the driver plate voltage for optimum results.

Here are some thoughts on sonic upgrades, as opposed to restoration and fixing known issues:

The original Afterglow had a TFA-204 series feed output transformer, which is very sweet sounding but limited in the deep bass. Parallel feed can get you better bass and better power supply noise isolation, but you'd need both new plate chokes and output transformers - not cheap. The original Paraglow output iron from Magnequest may be hard to find (though I think I have a pair of EXO-36 8 ohm outputs lying around) but there are some other options around.

The shunt-reg driver used in Paramount and Kaiju is a sonic upgrade, and also offers adjustable driver voltage. It's not entirely straightfoward to apply it to a 'glow though.

[Paul Birkeland]

PJ's suggestions are all items that I've built into some of our vintage amps.  I tend to replace every single capacitor in a Bottlehead amp that old and replace the cathode bias resistor for the output stage with something much, much larger.  For a directly coupled 2A3 circuit, the 2nd revision of the Paramount 2A3 driver stage design that PJ came up with is still ridiculously good and something we have not been able to improve upon in the last ~10 or so years, and I would recommend adding that during the reconstruction.  It will allow you to dial in the current of the 2A3 very tightly, which will provide the perfect balance of power output from the amp and happy output iron.

I have also rebuilt these vintage amps onto 8x10 chassis plates, as well as other larger chassis designs with significantly more space to allow for better cooling and a less constricted layout.

[pboser]

Thank you for the replies, Doc, Paul and Paul,

Yes, I have the DeYoung power transformers, and TFA-204 outputs, which I now recall I used briefly as a S.E.X. upgrade before the Afterglow build.  Thanks for the suggestions - is it improper of me to ask if I can see the Paramount/Kaiju driver design?  And PJ, are you looking to sell those EXO-36s? (I have a pair of EXO-45 Cobalts on the shelf and am considering just doing the Afterglow as a straight rebuild -  a tuneup for the next project, which can be more free-form.)

Another question - how deep is the deep bass where the TFA-204 is deficient?  Are we talking about 20-40 Hz, or higher than that?  It might be academic on many speakers, but it's good to have the right tool for the job.

Thanks for letting me ramble, and for your comments, and any more comments/suggestions you might still be willing to offer.  Sound Practices may have been my initial tube DIY inspiration, but the S.E.X. amp was my start, and this community one of the great resources and inspirations, so I am grateful to Dan, Eileen, PJ, PB, and the rest of the Bottlehead world.

Pete

[Paul Birkeland]

Yes, I have the DeYoung power transformers, and TFA-204 outputs, which I now recall I used briefly as a S.E.X. upgrade before the Afterglow build. 

Cool, that's certainly a worthwhile iron combination for a rebuild.

Thanks for the suggestions - is it improper of me to ask if I can see the Paramount/Kaiju driver design? 

It's entirely likely that you could purchase the old soft-start manual, I'd e-mail Doc B. and ask.  The manual will come with the schematic and setup instructions.  If you ordered two Stereomour II shunt regulator upgrade kits, you'd get the boards you need, the heatsinks you need, and most of the components.  I can assist with part numbers for what you're missing.  I would also imagine that Doc B. would just give you the soft-start manual for free with that order. 

Another question - how deep is the deep bass where the TFA-204 is deficient?  Are we talking about 20-40 Hz, or higher than that?  It might be academic on many speakers, but it's good to have the right tool for the job.

The old spec is 40Hz.  I have a pair of 300B amps with the TFA-204 that I should measure to get a better data set on what that transformer will and won't do.