That's it. Of course being in Australia I had to use the PT with the 240V primary but still, I managed to build an amp where the stock(ish) value of 270ohm biased the amp just shy of 100%, which is where you want it to be in a cathode biased amp. And that's with the B+ being in the recommended voltages, not 30-40V higher. It does make a difference.
I have used Mojo transformers in the past and they work just fine when biased properly. But the MM trannies do sound better - clearer, sweeter, etc. Mojo are (I believe) made by Heyboer, who can make an excellent transformer. But Mojo's spec must be to a price because they don't quite sound as good as the MMs to me. The GDS I like in the Marshall 18W are also Heyboer but made to GDS spec, and sound fantastic.
Being in the home of the kangaroos, you are only a short hop (pun intended) away from one of the best minds in the transformer world- New Zeland’s own Simcha Delft!
So if I go the Tweed route, on my previous build I subbed out the kit's carbon comp resistors with carbon films from Amplified parts... same this time? "Moar Mojo" with the comps????
Some will disagree, but let’s just say, I’ve done blind a/b tests with some of the best ears, where carbon comp, carbon film, and metal film were used (of course matched by actual value not printed value… and no one could tell which was which. Personally, I truly believe what folks hear between the older amps and new are a combination of 2 things: transformers are built a LOT different and it affects tone, AND, the “magic” they hear from the carbon comps is due to them being drifted so far out of spec, they are comparing apples to oranges.
That said, carbon comps look “right”, but are prone to drifting out of spec after some time, developing micro cracks and absorbing atmospheric moisture, causing the Rice Krispies syndrome old Fenders have (snap, crackle pop and hiss).
Carbon films are cheap, and don’t suffer the fate of the carbon comps as frequently… and you can sound cool saying you use carbon resistors.
Metal Films really don’t have any of the problems of carbon types. I’ve heard folks say they sound sterile, but any testing I’ve done, no one heard it (and no one ever called a Soldano SLO sterile). But they are the most expensive and look out of place.
The joke I’ve been running with is: I’d love to extract all the moisture that vintage carbon comps absorb, bottle it and sell it as “vintage mojo”
End of the day, you’ll hear opinions from everyone, so take it as you will and do what you want. (And for fun, read Randall Aiken’s white papers… lots of good info and debunking of a lot of myths scientifically)
