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I finally had a chance to crank the amp, and it is certainly a glorious beast! Pretty thrilling to be next to the cab at drummer volume. I started working towards sound clips for y'all over the past few days, and I'm starting to get annoyed. It has reminded me how much I dislike my playing...

It's alive!! It was pretty late by the time I finished wiring everything and finding / fixing a few goofs, so I haven't had much time to fully test and wasn't able to crank it up. One thing I wasn't expecting, my IIB lead drive pot switch is pull to open rather than pull to close like the...

Thanks for the compliment! Interesting. When you say schematics, are you referring to the one JRB32 put together? I would expect #1 to have negligible impact on the high gain mode and mostly increase the rhythm mode gain in upper frequencies. You'd especially have increased rhythm mode...

When you say +/++, is it switchable with a mid pull pot? I’d love to do an amp with a switchable ++, but haven’t seen a schematic or good pictures. JRB32 sent me some pictures of a ++ amp that also had an R2 mod, so I wasn’t able to tell what was ++ and what was R2

I can put something together. Any sounds in particular you’d be interested in?

Congrats on the amp! Pull bright on Volume 1 half way on makes no sense to me either, the pull switch either brings a capacitor into the circuit or not. The effect of the bright switch is less noticeable the higher the Volume 1 setting, and has no effect when Volume 1 is on 10. Maybe that’s...

A lot of people used double wattage carbon comps for stability purposes, the resistance value is more constant under temperature rise. Screen current increases dramatically in a Class A/B power amp when loaded, looking at DC dissipation won’t give the full story. Most small wattage metal oxides...

Made some progress. Looks like I have a ways to go, but it should come together pretty quickly if everything goes OK as I think I have the big stuff addressed already. Hopefully before the weekend is gone I’ll be able to fire it up!

Thank you! It’s the preamp board I’m going to use to convert the IIB to a C+

Found a couple hours to start working on this, progress thus far:

Got the new preamp board in today, she fits the IIB like a glove!

She’s a beauty!

I’m working on a recreation of an HRG as an offshoot from a project to convert my IIB to a C+. Biggest unknown in my eyes is the output transformer, I have several to compare. We shall see how it goes!

Sounds good! A number of folks have reached out about these, once I verify everything is working correctly I’ll be willing to sell them!

Welp, I took the plunge. Designed a new board for a fab house and hit submit on a prototype order. I probably should've spent more time checking it over, but feeling lazy, we'll see how it goes. Good thing I don't mind purple!

I always wondered what they specifically meant by this, I’ve only heard Randall reference this in context of the output transformers. Maybe the varnish they used is no longer available? I’m not sure the 60 and 60/100 output transformers of this era are a big departure from commonly available...

I did some lower volume A/B testing tonight against a Mark III HRG blue stripe, Mark IVA and a JP-2C. All Boogie amps were setup for 60W by using two power tubes and the four ohm tap with an 8 ohm load. The closest sounding amp is the JP-2C. I prefer the one I built, it sounds a bit more open...

The trouble they’d run into is which version? 60? 60/100? Simul? Coli? Which power transformer? What chassis width? Reverb? EQ? Problem is people seem to be particular about many of these items when chasing the “holy grail” IIC+, and all of these variants make a reissue impractical. Boogie used...

Unfortunately, that’s not quite how the circuit works. Boogie used a VTL5C4 here, and for the EQ reference, because of its lower on resistance compared to a VTL5C1. They limited the current for the LDRs thru R91 so that it protected the LDRs and switched relatively quickly. There is a trade off...

If I’m thinking correctly, you want a faster ON to OFF transition / decay time. You might be pumping too much current thru the LEDs, changing the memory behavior. If you’re looking at the sloclone schematic, measure the voltage across R77 (470 ohm) when the amp is in the lead mode with the...