Want to build a Twreck with 2xEL84

[harryk]

Hi All! I am new in this forum but very pleased of the information I can get from advanced and experienced Twreck fans here. I have build tens of tube amps based on Marshall, Fender and Vox topologies but now I am really seeking the holy grail with a low wattage Twreck project. I have heard some very great sounding samples of Twreck sound in some net page but I cannot remember what model was played in that clip and with what power tubes. If I undestand right, the biggest part of Twreck sound is based on a high gain preamp and not the power amp distortion. I am also looking Twreck magic touch responsivness and dynamics based on guitar volume pot adjustments while playing. My simple question is: What Twreck to do to get it`s magic sound without 2xEL34s and with lower power. Regards Harry

[skyboltone]

Build a Liverpool, remove two tubes, change the OT to 8500 ohm primary, adjust PI cathode resistor to suit?

Dan H

[gearhead]

It's actually the reverse of what you mention. The Trainwrecks (express at least, and assume liverpool) are designed to distort first at the power tubes, then the PI, and lastly at the preamp stage, as you increase the volume.

[harryk]

Thank you of fast replys. Your answers show to me that I am not familiar with different Twreck models. In the end it is the same if it is preamp or poweramp distortion. I only want to know what model is best to start with and which Twreck suits best to my requirements. I checked Liverpool schem and now want to know how critical are different rail voltages to the tone of this amp model. I have a PT with 2x300V/110 mA. Is this ok for this project? Regards Harry

[gearhead]

Also, if you want a two EL-84 Trainwreck, you can do one based on the first Liverpool; it has a half-power switch.

Dana's quest from a year+ ago:

https://tubeamparchive.com/viewtopic.ph ... rpool+dana

Don't know how the half power switched mode sounds in comparison to the full 4 EL-84s engaged. Maybe Dana will chime in here. If you're going for a purely 2 EL-84 config, scaling to that might be better.

[gearhead]

In the end it is the same if it is preamp or poweramp distortion.

Actually, the brilliance in Ken Fischers design is how much you can control the level of and what stage (PT/PI/PAT) of distortion by your input (vol knob, etc,). Prime example of this is our very own geetarpicker's clip:


http://www.youtube.com/watch?v=Y2_12Ler9B8

[harryk]

This was just the very same clip I was referring. Amazing dynamics and sounds. What Twreck model Ken is playing in this clip? Reagards Harry

[gearhead]

Glen is playing a Trainwreck Express.

Express = 2xEL-34 (or 6V6)
Liverpool = 4 EL-84

Fundamentally the same tonestack for both.

Rocket = Ken Fischer's take on a Vox AC30.

[UR12]

Also, if you want a two EL-84 Trainwreck, you can do one based on the first Liverpool; it has a half-power switch.

Dana's quest from a year+ ago:

https://tubeamparchive.com/viewtopic.ph ... rpool+dana

Don't know how the half power switched mode sounds in comparison to the full 4 EL-84s engaged. Maybe Dana will chime in here. If you're going for a purely 2 EL-84 config, scaling to that might be better.

The short answer is that there is very little difference. Mostly just a drop in volume and that isn't really all that much. At 15 watts it is still loud. It is interesting to note that when you go to 15 watt mode you are now operating 2 tubes into the same primary impedance. In other words the amp is running 4 tubes into a 5.2k primary and when you switch to two tubes you are still using the 5.2k tranny. If you went with the old theory of pulling two tubes in a marshall and doubling the secondary. 4 becomes 8, 16 becomes 32 etc then you should be able to rematch the primary with the correct imp. If you are designing an amp to be 15 - 18 watts then you need to find a OT primary imp that sounds and responds like the original. I would start out looking for something in the 10K range and go from there. Of course that would depend on what tubes you were running and your b+ voltages. Just my 2 cents

[harryk]

Maybe I start a Liverpool project with 2xEL84 combination. Playing with my band and a pretty noisy drummer, I now play a guitar amp with 2x6V6 tubes and never have to turn my amp fully on. I`ll come back when I have something to show with this project. Thank`s to everybody. Harry

[harryk]

I started my Twreck "Mini Liverpool" project yesterday. Mini means 2xEL84 tubes. I am going to use either Hammond 124E or Hammond 1608 OT which I already had and EZ81 in rectification instead of silicon. Otherwise I am going to follow Liverpool original schem. Which of those OTs suits better to this project? 125E cuts pretty heavily low frequencies compared to 1608 as far as I know. I`ll report when amp is ready. Regards Harry