The Amp Garage

It was mentioned above to look at Full Wave Capacitor input, which is different than Full Wave Bridge Capacitor input, so I was pointing out that was wrong. You'll notice under the former, the hammond sheet mentions .71x total secondary. Yes on heater current; had that figure doubled in my head for ...

I'm using a stand-up mounted version of Mojotone's JTM45 PT in one of my builds which runs 3x 12AX7 and 2xKT88 requiring a total of 4.5A of heater current whereas the transformer is rated for 5A. Assuming you're still keeping it at 3x 12AX7, total heater draw with 4x 6V6 would be 2.9A. Despite bein...

Start here: https://www.hammfg.com/electronics/transformers/rectifier You are describing a capacitor input full wave rectifier. The center tap connected to the junction of the stacked resistors help keep the voltage evenly distributed across the series capacitors. Factors which impact the actual B+...

That Hammond document is a great resource. Assuming you keep the same arrangement as the originals with full-bridge rectification and the CT connecting to the junction between the series reservoir capacitors, you would treat it like a full-wave bridge rectification of a non-center tapped PT. So for...

That Hammond document is a great resource. Assuming you keep the same arrangement as the originals with full-bridge rectification and the CT connecting to the junction between the series reservoir capacitors, you would treat it like a full-wave bridge rectification of a non-center tapped PT. So for...

Given I want my rectified B+ at X volts, what is the calculation for xformer secondary voltage where the center tap isn't grounded, but goes in the middle of the first two series filter caps like on a 100w Marshall?

Not sure how happy Dave F would be about me spelling it out. Email him, he'll reply. If you are familiar with the option switches on his ther amps, not hard to deduce.

Late to the discussion here, but I’m building a Little Sister and, after hours of staring at gut shots, have solved this mystery. The DPDT Bright/Tight switch, when ON, adds a 0.0022uF coupling cap in series after the 0.022uF coupling cap after the second gain stage. It also adds a 0.68uF electroly...

Usually see the CF and previous stage in same tube, but for purposes of a mod I'm thinking of, would be easier if in different tubes. Any good reason NOT to do that?

The 220n cap on the Jose mod blocks dc from the CF so there is no DC on the master, which would make the master scratchy, and also put it in parallel with the 100k Rk (for purposes of DC). You have to also realize that the 220n cap is also in series with your tone caps, which DOES slightly change th...

Anyone done that? If so, opinion?

I much prefer low plate classic cleans, but I can see the argument for high plate on the OD stages.

What about a 1uf cap to block the dc from the cathode follower and a relay to switch the output between the stacks? Any foreseeable issues there? The 1uf should be more than large enough to be transparent. I see what you're saying about using 2 dpdt to switch the output of each cap, but that assume...

I'm not trying to tell you what to do - I may be misunderstanding, but, I'd use a 0.1µF cap to feed the A side COM of a DPDT relay... A side NO and NC would go to the two individual TSs. Jump NO of the A pole of the relay to the NC of the B pole, then jump from NC to NO. Connect the B side COM to G...

What about a 1uf cap to block the dc from the cathode follower and a relay to switch the output between the stacks? Any foreseeable issues there? The 1uf should be more than large enough to be transparent. I see what you're saying about using 2 dpdt to switch the output of each cap, but that assumes...

Running both stacks in a channel switching config. attached to one cathode follower, outputs switched after stack and master. Anyone done this? My questions would be: 1) resistors to isolate each stack? 2) better to do this, or put a 1uf dc blocking cap after the cathode and just switch stacks with ...