Metropoulos Forum

RS ultra linear tap What is it and can is it or can it be used ? I have done some googling on this but im not finding much.Did marshall use this tap?

As far as i know you hooked the screen grids up to the UL taps on the OT. This helped reduce distortion. It was a kind of HiFi type thing i think. 70's Fenders utilised this a bit as did very early Hiwatts among others.

What k ohm tap goes with what tubes?? all i seem to find is u can use this that and the other but what fits what?? This is the hold up for now..If i use 6l6 tubes will i need the 5.6k grid resistors?
Thanks
Darrell

Are you thinking of running your JTM 45 in UL mode? Other than what i've writen i have no idea. Thats one for Larry i think.

@ Darrel

Write exactly what you intend to do, but in an English, what also I may understand, then maybe I can give you the right advice.

Your English always was a problem for me to understand at all

Larry

On the RS out put transformer It has different Ohms tap for the power tubes.
What tap goes with what tube?
Is the tap for 6l6gc the 6K6 tap and the one for EL34's an 8K tap the transformer is a Marshtrans RS clone.
Is there one tap on the transformer that I can use to run both 6l6gc's or El34? Thanks guy's for bearing with me.
Darrell
Oh I was just woundering what the UL tap was Im not going to use it..

Ah-ha! My German head now understood all you've said

The RS OT isn't made for using EL34's

From its primary impedances you can use:

the 6.6K taps for 6L6 or KT66

the 8.0K taps for KT66 or EL84

the 9.0K taps for EL84 or 6V6

the screen grids you may connect to the UL taps instead to a constant voltage source like usual, if you're after a more HiFi like sound.

The UL taps are kinda stabilizing local feedback for the output tubes and are enhancing the stage's bandwidth to the lows as well as to the highs at the expense of a slightly reduction in output power.

Larry

If I was to use the UL tap how do i do it?
Larry!
Thank you very much :>)
Darrell

darrell wrote:If I was to use the UL tap how do i do it?

Disconnect the screen's voltage supply and also the patch cable between both tube sockets. Then connect each of the concerning UL taps to the corresponding tube's screen grid, but to pin 6 on the tube socket and put in 470 ohms/2W screen resistors from pin 6 to pin 4, if they still aren't there.

Larry

somebody in a PM wrote:I spoke with brian of marshtran and he said I can use el34 with the RS transformer but he didnt say what primary taps to use would you know?

Shure! The lowest possible primary impedance on the RS OT is 6.6K, but 2 EL34's require usually 3.4K primary impedance, so this is a mismatch of 1:2

When you go into an OT with 1:2 mismatch, then you have to go out with the reversed mismatch of 2:1

Means, with EL34's on the 6.6K you have to set the secondary to 16 ohms for a 8 ohms cabinet or to 8 ohms for a 4 ohms cabinet.

Yes, a OT is like a transmission

Larry

The 470 ohm resistor is still there and i have 5.6 k on the screen grids Pin 5 if you will .. Do i need to change any of these ( Im not going to Use the UL tap)Resistors or leave them.?

darrell wrote:... and i have 5.6 k on the screen grids Pin 5 if you will .. Do i need to change any of these

Pin 5 is the control grid!

But you can leave all as it is.

Larry

Thanks Larry
If i run 6l6gc's I need to match the speaker impedance / 16 ohm out put to 16 ohm cab? and if i run el34 i need to run the same 16 ohm out put to a 8 ohm cab.
Just double checking
Thanks again
Darrell

Yep - with the 6.6k primary.

Larry

Thanks man I would be lost with out you..
This needs to be re worked and made a sticky.
Piece to all
Darrell