Noob question. My toroid secondaries measure 21.5V each. Is it safe to proceed and connect/test my Iron Pre board? Only the PSU section stuffed so far. I had the toroid made locally. Spec was for 2 x 18V secondaries, but they actually measure 21.5V 🤔
take care of having 35Vdc caps after bridge
put next step size heatsinks on BD transistors
or just put pair of regular small ones, back to back, with some thermal goop in between
sec. voltage being slightly higher than specified is pretty normal in this case
voltage is most certainly for full load condition, and small xformers are having worse stabilization factor than big ones
put next step size heatsinks on BD transistors
or just put pair of regular small ones, back to back, with some thermal goop in between
sec. voltage being slightly higher than specified is pretty normal in this case
voltage is most certainly for full load condition, and small xformers are having worse stabilization factor than big ones
Naaaah. Pa (to the left) is approx just as much chicken as MZM (to the right)
I should know, I feed them both.
I can report, after a long layoff, I finally have the balanced Iron Pre finished and playing music. I had a scare when I first hooked it up in the system (balanced out to Aleph J)…lots of hum and a major channel imbalance. Turns out if you give me more than two wires to work with I get a little confused, cause I had the XLR output wiring all mucked up. After that fiasco I was able to sit down and listen to music for a couple of hours. I haven’t had that much fun enjoying music in a long time. Wonderful sounding preamp. It seems to me that the bass wasn’t as deep and controlled the last time time I listen to the stereo…but it’s been awhile. I didn’t notice any high frequency tilt as others have reported. When I have a chance I’ll do a shootout with other preamps on hand. Thanks ZM and all those that made this possible. I realize it’s a huge group effort to get a kit to the end user and support them during the build. Thanks again!
Yes. Eggs allready. And four roosters to butcher once big enough.
Is that measured under load? It's common for transformers to measure higher than the nominal voltage on the bench, with no load.
Why do you run 2 volume controls for the balanced version? Is a 4 gang not cost effective? Could you just double up the wires to a 2 gang?
Because there are two holes in the chassis to fill. I didn’t design it, but I like the ability to control balance.
No!
My Iron Pre also hums a little at max volume. I've suspected that the long run of wires from near the Cinemag to the volume pots at the front of the case act as little antennas. They carry signal and at max volume are at lowest impedance.
I've had a couple of sources, usually powered by wall warts, that would hum if ground was lifted (discontinuous) between that source and the amp. I had a ground lift switch in a passive pre with a step up line transformer, and I could switch the hum on and off that way.
what's difference when using SE input vs. Bal input?
are those cables, routed to vol pots, coaxial?
if not, you either need proper coaxes (4+1 or 5+1) or twisted triples