The Amp Garage

im worn out please accept my sloppy clips ive been writing terrifying jokes for 40 hours https://www.dropbox.com/s/b7krctki168811z/sibly.MOV?dl=0 https://www.dropbox.com/s/x6kb17b4crv28hv/wcm.MOV?dl=0 Love it! Which version, in this thread, are these clips made from? Is it the schematic that Bepone...

pdf64 wrote: ↑Fri Mar 31, 2023 3:31 pm

xtian wrote: ↑Fri Mar 31, 2023 3:16 pm … the 6550s are biased at about 25% dissipation, 630v on plates and only 300v on screens, provided by the UL OT...

I can’t get my head around that, it seems more like split rail pentode than UL?

I'm puzzled as well. How would a UL primary drop the screen voltage?

If you want to try something a little different, try a combination of Fixed/Cathode. Size the cathode resistor for 15-20 % of what you would typically use for a common cathode resistor and generate the rest of the bias with the fixed bias circuit. Do not bypass the common cathode resistor - it will ...

here is the schematic, missing first gain 1MA V1 gain stage, 180k/2k7, second half 130k/1k8 V2 CF: 150k/1k8, cathode follower 82k cathode (intended compression, not like "normal" 100k/100k) sema.jpg Is the hand drawn schematic pretty much what you ended up with? I have a donor amp I may try this on.

Cool chassis design. Did you fabricate it yourself?

Bruce Clement, BC Audio, makes a lot of octal Marshall style amps. He typically does DC heaters on the 6SL7's to keep the noise down.

Reeltarded wrote: ↑Sun Oct 30, 2022 4:31 am Granted, it feels more like knowledge than a girl licking a wind sock and whispering the contents of her purse.

That created a slightly disturbing visual that I can't un-see

So on the standard JTM45 w/KT66 -> 8k Prim, would it be a good mod to remove the 470K screen grids and replace with 1K or 1.5K to better protect the screens? Might add a little squish to the PA?

When the load line crosses the Vg1=0 line far below the knee (as it does when the primary impedance is too high), it takes less Vg1 voltage swing to reach the point where the screen current shoots up, and it's much more likely that the screens will be over-stressed. This would only be of concern wh...

EL34 plate loading is around 3400 ohms, while it's around 8000 for KT66s. Optimally you'd obtain a new output transformer that's wound for KT66s but using the next higher impedance tap on the speaker jacks is a perfectly good workaround. KT66 are not much different from 6L6, and would really like a...

A local pub that's about a mile from my house has live music every Saturday night - typically cover bands that mostly appeal to Gen X'ers. Many of the guitarists are favoring smaller/lighter rigs ranging from small combos, floor modelers, pedal board amps, etc and most produce a pretty decent sound ...

500VA

Yep, the schematic above is for a RT66.
Antidote is based on JTM45.
From the Dr himself:
https://www.youtube.com/watch?v=PsymtzV7Jhg

I had a discussion with tech support at Tube Depot, specifically about the new production Tung-Sol 5881's. I wanted to put them in an amp with a 500vdc B+, he cautioned against it - stating that they would likely have a greatly reduced lifespan.

Why not build a higher powered amp with power scaling? Then you have one amp that covers at home/studio and gig volumes.

5W is still pretty loud

Be careful with the plate voltages on 5881's, I think they're only rated for 400v.