The Amp Garage

Seems a high screen voltage for 6550. That figure for effective load makes sense for the high screen voltage. They recommend 4.5 or 5K for similar plate voltages but screens at 300. I visited a site the other day that claims KT90 is not a true beam tube. I think the information is BullS but here is ...

Do you run the screens at 300V or up with the plates?

Thanks, I'll go for 4 slotted sides. I realise the rotating baffle system isn't the full rotating speaker deal but expect that for the $5.00 price tag it will deliver acceptable performance in small venues at lowish volume, they wouldn't put them in the organs if they were totally useless, we will s...

I've just scored a leslie unit in good order from an '70's Hammond, paid a fiver (about US$2.50 at current dismal exchange rate). Rotating styro baffle, 2 speed, 8" speaker, assume approx 20W. I want to build an enclosure but would like to know if its better to have it open all around the axis of ro...

I see no point.
A single gain stage of 12ax7 etc can provide more than ample voltage gain to overdrive a following stage.

EL90 can pretend to be a 6V6, but in 7pin socket

I don't have the 5902's yet, but they will be in there. So could I go with a small transformer (in terms of current rating)? How do you determine the current draw, anyway? I think that would come in right handy. Though I will be running the plates at a higher voltage (about 100V, I am thinking). Yo...

Well, that cct will draw micro amps.
How have you decided to run the 5902's?

oops, an edit turned into a quote

Yes, you are looking for effective plate to plate load or Rpp. For pentode and beam tubes this is chosen with regard to distortion, plate dissipation and power requirements. I suggest you read information on loadlines here http://greygum.net/sbench/sbench101/ Valvewizard.co.uk also provides a quick ...

I imagine things change will change unexpectedly and non-linearly if you overwind to the extent where magnetic saturation of core occurs.

If you visit http://www.valvewizard.co.uk/ you can find a couple of extremely simple mods to standby switching and heaters that you may think worth including.

You may not require R27. As an exercise why not plug values into Duncan's power supply calculator. Providing you know PS transformer specs the results are surprisingly good. (Note: in the calculator the source resistance of transformer for a full wave rectifier is half total resistance across the tr...

This topic already active in garage talk
http://ampgarage.com/forum/viewtopic.php?t=7686

Actually I should have left the words "plate and" out of the sentence "Said another way, and ignoring overall supply sag, plate and screen supplies that are independant of ..." so I didn't really put it so clearly after all. :? :) Guitar amps are probably the biggest end use of current production re...