if one could?

[howardnair]

thoburn-Ye of Inquiring minds--i am very pleased with the sophia's-the sound in general is much more filled out-the bass especially-nothing is missing in the midrange and highs----{not that the shuaguang 2a3-c is a bad choice]---i hear more of the nuance of the music and the soundstage is very good-this with jazz- miles davis, kind of blue --glenn gould, bach --joni mitchell ,hejira-all lps--fm radio classical/rock--and my reel to reel, dave brubeck-i will put some rock on this evening-all in all good right out of the box-
a hhh yes  HAPPY THANKGIVING EVERYONE--HOWIE

 

[Thoburn]

Hi Doc,
What do you make of the EML ban on paper and oil coupling capacitors? (I have Jupiters for instance, which are beeswax and paper (oil??) )
On the EML site I think I ban on 'Large' coupling capacitors as well.

I don't know that what I think is relevant to what EML's policies are about capacitors.

What I am really asking is, "Would my Jupiter caps be a problem for the EML tubes"? They are not exactly PIO, but then I am not well versed in capacitor factors.

BTW, We live in Gig Harbor and are snowed in as well. May not be able to make it to my sister's house for turkey. Really sorry I sold my 4x4 pickup.

 

[Doc B]

Safe bet is don't use them. One the one hand I have a pair of custom Jupiters they made for me about 7 years ago that have held up beautifully and sound great in a big custom preamp with plenty of air flow and a very conservative voltage relative to the cap rating. On the other hand we have seen several Jupiters fail used in a S.E.X. amp chassis where it gets very warm. The Stereomour should run a bit more cool under the hood because of its vents (and the Paramount is pretty hot underneath - no Jupiters!), but I wouldn't take the chance. If you do decide to use them, keep them away from the hot bits.

No sign of the rain that is supposed to melt off the snow today. Looks like we may miss our big family Thanksgiving too.

 

[pboser]

The EML tube cannot handle the startup cycle of the present, no soft start ParaMOUNT 2A3 amp (or the now retired Afterglow/Paraglow), which is direct coupled between stages.

Doc,
I'm using my verable Afterglows modified to use 45s.  Is there a soft-start mod I could do to preserve the output tubes?  Some ideas I've had are to put a damper diode in the PS (but where would I put the tube??), or one of those delays I've seen somewhere to slow down the B+?  Of should I leave well enough alone?
Thanks,
Pete

 

[Doc B]

Are they arcing at startup?

 

[pboser]

No, they're just elderly, and I was considering steps to increase their life.................

 

[Doc B]

I think with this, what, Mk IV version of the SRC4S board? we may get a manual written for its general use in other circuits, and of course this one allows for the implementation of a form of slow start that addresses the direct coupling of driver and output tube.

The versatility of the SRC4S makes writing a manual for it a real challenge. What we can do is give folks the basics of how the thing works and how to generally calculate the component values on the board. But the sticky part becomes whether or not the builder has knowledge enough to derive what voltages and currents they may need for a given circuit, and what changes they might need to make to the power supply.

Certainly to some extent we can help folks here, particularly with something like our legacy kits where the operating voltages and currents are known. What we haven't worked out yet is how to support the use of the board in modified or non-Bottlehead designs.

Give us a little more time to get this kit out as a Paramount upgrade first, and then we will look into writing some instructions for more general applications.

 

[pboser]

OK, I'll keep an eye peeled for more general applications.  Thanks!
Pete

 

[Paul Joppa]

...
I'm using my verable Afterglows modified to use 45s.  Is there a soft-start mod I could do to preserve the output tubes?  ...

How old, exactly, are these amps?

The early Afterglows derived the driver plate current from the output tube cathode, and could not drive the grid positive under any circumstances. This appears to be the main danger to the new EML tubes. Not having tried it, I'm not going to guarantee it will work safely, but if it doesn't I'd be quite surprised.

This design makes it impossible to shunt-regulate the driver power, which is part of the reason the later designs (including the 2A3 Paramount) do it differently, but if you're cool with keeping the old design it does have that virtue.

As for extending the life, the power supply capacitors were electrolytics operating close to their maximum voltage specification, so replacing them might be a good idea if they're more than a decade old.  The actual voltage depends on which power transformer you have (there were several) and of course on your line voltage. If you post the tube pin voltages, we can assess that situation along with the operating points which may have drifted - the bane of direct coupled amps.

 

[pboser]

Thanks for the reply, Paul.  I can't pinpoint when I built them - I had a pair of the original SEX amps, then got the TFA-204s to upgrade them, then got the Afterglow kits to use the '204s.  I wasn't aware of variations on the Afterglows, but I'm certainly open to modifying them. The only mod I've done since I built them is to change the cathode resistor to use the 45 output tubes.  I won't get to check voltages today, but I'll take a look soon.  Is there a schematic of the later/latest version available?
Thanks again,
Pete

 

[InfernoSTi]

Not quite as smooth, but less than half the price, and with very good bass/mid bass is the JJ 2a3-40s.

For those looking for a new stock 2A3 tube, I'll second this comment: I am very much enjoying my JJ 2A3-40s....

John

 

[Clive]

Going back to EMLs......I read somewhere that the pins on the 45s (and probably the 2A3s) were fatter than is typical resulting in needing to bend back the connections in teflon tube sockets.  Can anyone verify if this is true or false?

 

[jrebman]

Hi John,

Glad to hear you like the JJs.  I have a couple hundred hours on mine now and the top end opened quite a bit more than it had been, so now I'm back to these as being preferred  over my shuguang 2a3z Treasures.  I think the Treasures will work really nicely with the Cornwalls though.

-- Jim

 

[Thoburn]

Safe bet is don't use them. One the one hand I have a pair of custom Jupiters they made for me about 7 years ago that have held up beautifully and sound great in a big custom preamp with plenty of air flow and a very conservative voltage relative to the cap rating. On the other hand we have seen several Jupiters fail used in a S.E.X. amp chassis where it gets very warm. The Stereomour should run a bit more cool under the hood because of its vents (and the Paramount is pretty hot underneath - no Jupiters!), but I wouldn't take the chance. If you do decide to use them, keep them away from the hot bits.

No sign of the rain that is supposed to melt off the snow today. Looks like we may miss our big family Thanksgiving too.

Just FYI,

I have the Jupiter high temperature caps running in my Stereomour for 5 years now. They sound great to me and look just like the day I installed them. Do note that they are the high temperature variant.

 

[mcandmar]

I have the Jupiter high temperature caps running in my Stereomour for 5 years now. They sound great to me and look just like the day I installed them. Do note that they are the high temperature variant.

That is good to know as i have a set of HT caps to put into my S.E.X. amp.  They are rated for 70c max which is the same as the Mundorf Supremes, but they will have to endure a constant 30-40c which had me a bit worried.