SOT: Firefly amp stuff and questions

[brett]

Hi.
I've just finished building a Firefly valve amp, designed by Doug Hammond.  It's an excellent project, even for someone who hasn't built a valve amp before (like me).
My question is about impedance and the output transformer.  In the most recent schematic at Doug's site,  (http://home.cfl.rr.com/dbhammond/Firefly_sch_R3.gif) the primary z is shown as 22.5 kohms (8 ohm secondary).  However, the transformer connections (2 and 5) shown at Paul Marossy's site (http://www.firebottle.com/ampage/homebrew.cgi?cat=ga&sb=&so=hl&page=1076726808cSGgrKj) correspond to a primary z of 8.2 kohms.
I've used Paul's wiring layout, but wish to know whether and how the lower primary impedance will affect the output tube and amp.  I suppose there'll be extra output current (?) Extra power? Different tone?  Shorter tube life?  As you can tell from these questions, I know little about tubes.

thanks for any help

[Alex C]

This thread should help.

[brett]

Thanks Alex.  That thread had everything I was looking for.  
I have obviously missed some of the old firefly threads.
As always - search, search and search again.
The Firefly is so excellent - I'll post some pics on my site soon.

[Paul Marossy]

brett-

So, was there anything misleading on my Firefly page? I think I have all the bugs worked out on that one now...

EDIT: Oh darn, I see that my chassis layout has that OT secondary mistake on it. I'll need to fix that.  :oops:

[brett]

Paul.
your site was FANTASTICALLY helpful.  Finding it (and your layout in particular) was what made me go ahead with building a firefly.

BTW, my "cascode" tube glows a lot more than the 2 x normal stage tube.  Is this normal?  The tubes are different brands (one is a large plate and one a regular plate 12AX7), so that might partly explain things.

Again, many thanks for the excellent information at your site.

[Paul Marossy]

Paul.
your site was FANTASTICALLY helpful. Finding it (and your layout in particular) was what made me go ahead with building a firefly.

brett-

That's cool, I like it when I can help people like you out and hopefully be somewhat of an inspiration.  

Anyhow, I'm going to fix that layout in the next day or two. As far as the cascode tube goes, I wouldn't worry about that too much - as long as your heater voltage is within 5-10% of what is specified, you're fine.  I have noticed that some tubes seem to be brighter glowing than others.

[Paul Marossy]

Just for the record, I've updated that chassis layout to show 2 and 4 on the OT secondary, and the connection to ground at the volume control.  

It can be found here: http://www.diyguitarist.com/PDF_Files/FireflyChassis.pdf