Smokebreak wrote:Leo, do you remember the 6.3V transformer you used?
Pretty sure it was the Hammond 10 amp model. IIRC it had metal bells didn't look quite like the one in Mouser's photo. I ran a 240V muffin fan off the 120 line so it's not a wind tunnel but does keep the amp way cooler than no fan at all and fan noise is negligible. Fan blowing up into the chassis, mounted to bottom cover where there's plenty of room inside. There's an octet of vent holes around each output tube base for "assisted" airflow in the direction it would naturally take, and a large exit vent overhead covered with punched aluminum deco grill. Without the fan, the aluminum grill gets so hot it expands & bends. That's what convinced me it needed a fan.
The PT is fine(not even using the fil taps), but my fil transformer is really hot
No sure with out going back to re-read it all, but if you have a separate, too hot, filament transformer why not split the duty with the windings you are not using on the PT? Also, not DC right? You'd need twice the current.
Fan! That hasn't been on my radar up to this point, so thanks for bringing it up! Owner has the amp now but I'll see it again soon, for tweaks, so I'll monitor the heat situation.
rp, that's good idea, I had thought about splitting up the outputs with different windings, but I just figured I had plenty in that 10A winding.
The owner and I agree the amp is amazing for guitar. Obviously Marshally but darker, angrier, crunchier, with the same amount of gain as say a plexi. Very articulate too. Just huge sounding with some volume.
For bass, the reports I'm getting is that we're 85% of the way there. There's still too much mids for him. Even with the mod that puts a large cap across the LC network to swamp it when the mid pot is at "0", there's still a little mid bump. I even used a 50K pot instead of 25K, but still too many mids.
So, I'm looking for suggestions. I could just mod the james stack a bit, or even construct a bridged T type mid cut, but I can tell he's gonna want more of a mid dip than can be accomplished by cranking the bass and treble on a James....or maybe just shift the dip...I'm not sure yet.. Any other ideas? Just stick in a SVT stack? Hopefully I'll get to tweak it soon.
You do not have the required permissions to view the files attached to this post.
I'll be revisiting this amp this week and I'm looking for ideas. It's a Sunn Model T 2nd Gen. Schematic attached.
1. I'll be looking to kill some mids, perhaps variably. I'm thinking I'll start with a mig muff style/bridged T notch filter. Apparently it need to lose some dbs around 800hz. Where would be the best place to put this? after the 1st stage? any other ideas?
2. If I wanted to disconnect the stock mid circuit, or take it out, so to speak, what's the best way to do that, with respect to the way the cathode of the 3rd stage is involved with the neg voltage network? Just disconnect the mid pot from ground?
You do not have the required permissions to view the files attached to this post.
I ended up scribbling up a circuit after some reading and came up with a mid cut that has both variable amount of cut, and variable frequency selection. The 100K pots are dual gang, and the switch is a 2P4T. Both ranges are rather extreme but you get the idea. You can simulate this w/ the TSC and the Big Muff setting.
The variable resistors move the mid dip up or down the spectrum(200-1150hZ here), maintaining the q. Increasing the bypass cap at the same proportion as decreasing the cap to ground changes the amount of cut(-18 to -40 here)
I got the idea here : http://www.diystompboxes.com/smfforum/i ... ic=25788.0
This should be great for tweaking, Now if only I could find a dual ganged trimpot!
You do not have the required permissions to view the files attached to this post.
That's what convinced me it needed a fan.
