I didn’t charge Gareth for my perambulations (didn’t think I knew that one, eh?) through his Cornell Romany Pro amp. If I charged folks for not fixing things I would be very well off. Anyway, it turned out that his problems with the amp were not faults, it just didn’t do what he wanted it to, so I didn’t actually fix anything, but spent a lot of time working out how it worked.
Make no mistake, this is a beautifully made amplifier; but I got the feeling in my water that there was some faulty thinking gone into the design of the amp.
Gareth turned up for his amp with a couple of packets of Macaroons! Chocolate and plain. Bliss!!!
So as a small “thank you” I offer this little piece of history of the origination of the macaroon thing.
A long time ago, when I was up to my neck in an industrial apprenticeship, I worked for some time with a hilarious cockney gentleman named Cyril Haffenden. If a problem reared its head, or if he just felt a bit stressed by it all (or any other reason, for that matter) he would pronounce in a loud cockney accent “THAT’S IT! BAGGER IT! A CAPPA CORFFEE AN’ A MACAROON!!!!
That’s where it came from, tempered by poetic license of my own.
Thank you, Gareth.
This amp knocked a year or two off my life expectancy, and foot or two off my hairline.
A schematic is the most valuable attribute to repairing an amp; with a working brain cell running a close second. I’m saying nothing about the latter, but the Romany Pro does not subscribe to the former. I found an owner’s manual (for the Romany) which told me where the knobs and switches were, but not much else. Back to the Secret Society again, then.
Nearly all valve amps have a working topography of:- preamp stage(s) (usually ECC83 based valves) into a phase splitter (if it’s a push-pull class AB amp) and into a push-pull output stage. The phase splitter arranges the signal to the output valves so that one half goes positive while the other goes negative. This results in the push-pull of the output stage.
This Romany Pro was different, and it took a while for me to figure out how it could work. Everything I tested, from the phase splitter on, was in phase. Without going into too much detail, that can’t work because the output transformer tries to sum two identical in-phase signals the resultant of which is zero. A zero watt amp is never going to catch on.
Then I noticed that the phase splitter, isn’t. It doesn’t (as the usual arrangement does) split the phase, it just puts identical signals to the output valves. The only way this can work is by reversing one of the secondary windings of the output transformer. I’ve no idea why people like Mullard spent years developing the phase splitter design. Unless it’s a lot better, of course.
I think a pallet-load of macaroons might be appropriate in this case, to go with my tea and oversized toupee.