trinityamps.com

The Tramp can run a variety of tubes including an EL34. Though an EL34 will run stock on the amp with the bias switch in the 6L6 setting it is not optimal for the tube. For optimal EL34 performance you want about half the primary impedance on the OT compared to a 6L6. All this means is you want to use the 2.5K tap instead of the 5K tap. 5K is brown-yellow and 2.5K is brown-white btw...

All that aside here is how you wire your rotary switch to use any tube!
The rotary switch is normally 3 positions. I show here how to set it up for six positions, so make sure you set the switch for 6 positions first.

The positions are as follows
1. 4R @ 5K (furthest CCW)
2. 8R @ 5K
3. 16R @ 5K
4. 4R @ 2.5K
5. 8R @ 2.5K
6. 16R @ 2.5K (furthest CW)


So say you have an 8R cab and want to run a 6L6. Set your bias switch for 6L6 and the impedance selector at position 2.
Now you want to run your 8R cab with a EL34. Set the bias switch for a 6L6 but set the impedance selector at position 5 now.
Now if you want to go stock and run a 6V6 with your 8R cab. Set the bias switch for 6V6 and the impedance selector at position 2.

Very simple! You can even try running tubes at different impedances just to see what it sounds like too. You'll get some variation in tones.


Here's how you wire your rotary switch.
(note set the switch for six positions first!!!)














I have a little hand drawn schem of the switching, it's a bit messy but if anyone would like to see it I can redraw and post.

_________________
http://pdfelectronics.com

Good details. I have a schematic I will post.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Simple effective and about to become part of my Tramp head and eventually will find its way into the Combo.

Thanks

_________________
Fantasy Noise is what my shop of dreams is called and was the only way to beat my addiction, like many here I suffer from G.A.S.


Tele's make the best noise

will the tramp that i ordered come with this switch? if i'm getting the combo with the jensen speaker, what will i have to do to change the tubes from 6v6 to 6l6 to el34?

Yes the switch that comes with your kit will be like the one pictured. Make sure it is set for 6 positions if your doing this mod. The manual will say how to change the number of positions.

Set for 5K when using 6V6 or 6L6 then set the bias switch in the appropriate setting.
Set for 2.5K when using EL34 and set the bias switch to the 6L6 setting.

Make sense??

_________________
http://pdfelectronics.com

Yeah. Thanks. I'm having Stephen build mine. Do you know if he sets it for the 6 positions?

If you ask him for it with the 6 positions to accommodate the EL34 I am sure he can set that for you.

_________________
http://pdfelectronics.com

Hi,

I'm running an EL34 in my Tramp and I switched to the 2.5k tap as suggested. I've literally JUST made the change 10 mins ago so I haven't played through it that long yet, but I'm curious what you mean when you say "optimal".

Will there a difference in tone? Longer tube life? or?

I guess you could say this was my first mod since amp-camp...or possibly first mod ever!

Cheers!
James

Each type of tube has impedances and voltages that it's designed to work best at. EL34s provide their best power level and tone with a lower load impedance. They can sound harsh or "brittle" at a higher load impedance.

_________________
Great tones come in small glass jars!

how do I wire dpdt toggle for 2.5k and 5k taps?

Wire a SPST toggle with the middle (common lug) going to the plate and the outside terminals having the OT primaries (5K and 2K5).

_________________
http://pdfelectronics.com

You mean SPDT right?

Ya sorry!!

_________________
http://pdfelectronics.com

There appears to be an error in the Tramp switch schematic. The schematic shows both EL34 & 6L6 using the 2.5K switch setting. Shouldn't the 6L6 (and 6V6) use the 5K switch settings (Positions 1, 2, & 3) and the EL34 use the 2.5K switch settings (Positions 4, 5, & 6)?

Experience has it correct in the text explanation for the 3 different tubes but the schematic seems to contradict the text for the 6L6. Am I reading things right or does the switch schematic need to be changed?

Thanks - Tom

Is that rotary switch in trouble with those Plate voltages?

Yes, thanks. A typo. Correcteded schematic posted.


Electrical Specifications:
• Working voltage: 250VAC or
250VDC max.
• Dielectric strength: 1,000VAC @ 25°C
• Current capacity: 5A continuous
• Contact rating: 150mA/250VAC/DC DC

Power is 38W at this and we run at 400 VDC so anything up to about 100 ma should be good. If in doubt, use a heavier DPDT toggle switch.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I am doing my build now. I understand the 6 position rotary switch and how it is wired, but I have one question about the toggle switch that normally selects the 6v6 or 6L6. In your photo (above) you only show the (yellow) wire going from bridging the top of the toggle 6v6/6L6 switch over to pin 8 on the tube; you do not show the other two wires going to this 6V6/6L6 toggle from the 750 5w and 560 5w resisters. Before I do something wrong, I have to ask:

Are these other two wires going from the 750 and 560 resisters to the toggle wired just the same as in the normal Tramp schematic?

Thanks

Yes they are wired the same

When I took that photo the amp was not done and those two wires were not in place yet.

_________________
http://pdfelectronics.com

I just wired the impedance rotary switch as described in this thread. This was very easy to do. I am making a label for the combo that gives settings for different tubes, but want to make sure I get it right.

Would a KT88 take the same impedance setting (4, 5 or 6) as the EL34 ? Same bias setting (set to 6L6)?

I believe KT88 actually want to see 5K primary impedance. So you'd tread them like a 6V6/6L6 on the rotary switch (use positions 1,2 or 3) and then set the bias switch to 6L6.

_________________
http://pdfelectronics.com