Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: zendragon63 on April 19, 2015, 12:12:21 am
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I am an admitted fan of 'wreck' topology; even after over 40 years of playing various genres of music, the touch sensitivity if it has fundamentally changed the way I approached the electric guitar in the last few years. For the better (though I think some would argue that). :icon_biggrin: However, some food for thought: if you bypass the 3rd clipping stage with a simple DPDT and one capacitor, these amps become much more versatile by softening that aggressive edge. (There is what is called the fast gradual but I think this is a little different since you are bypassing the 3rd stage entirely)
Attached is what you could view as the antithesis of the hot swtich. I am not a fan of pedals but you could always do a relay. I found that I only use the real high gain for stuff like ZZTop or if you really want to get the sustain thing going. If you look at the gain structure, and the wide open 2nd stage (meaning not much attenuation out of the 2nd stage) there is still more than enough still to severely overdrive the power tubes to the point that I had to put a voltage divider going into the EL84. You still have a wide pallet of volume and tones to control from the guitar either with or without that 3rd stage. Putting a 12AY7 as V1a/V1b sweetens it up even more IMHO. YMMV.
Point is that while trainwreck topology is simple and sounds great, you don't have to really give any of it up to get a lot more. Regards
dennis
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Nice Dennis,
Questions for you:
Do you get any popping using the switch like that? Also you are VVR'ing the entire amp is appears. Do you prefer this to only controlling the power tubes and/or pi? Have you ever tried a ppimv and VVR together? If so, results/opinion?
Thanks for sharing that.
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Dennis,
You always come up with GREAT ideas!
Thank you for sharing.
with respect, Tubenit
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It seems that this particular design grafted the Express front end onto the Rocket's PA, thus it would be extremely easy to overdrive the EL84's, so bypassing one gain stage is a good workaround. Do you have some soundclips with and without the extra gain stage?
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It seems that this particular design grafted the Express front end onto the Rocket's PA, thus it would be extremely easy to overdrive the EL84's, so bypassing one gain stage is a good workaround. Do you have some soundclips with and without the extra gain stage?
Yes it's true that el84s are easier to blast their grids but you can remedy that with the pi adjustment on the tail resistors w/out a voltage divider and/or pot preceding it. I think Dennis made some changes here over the standard 'wreck values, same for some other areas like the front-end of the preamp and even the presence circuit values. The front end is actually a Fendery front into a pseudo 18w PA section but may be thinking Liverpool instead? But to me what makes a 'wreck a 'wreck is the extra clipping gain stage.
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But to me what makes a 'wreck a 'wreck is the extra clipping gain stage.
Only if you are referring to the Express... The Rocket has a CF driven stage thus having less than unity gain, i.e., it does not have an "extra gain stage". The gain stage bypass that the OP used is a good soltuion, but it is not the same as having either the Express nor the Rocket, IIWIS...
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I've done a few like this, the most (in)famous being a 2 6V6 combo that goes to all the jams. "Turn it down Mike!" No, no popping when switching as long as you ground the caps with a resistor when they're out of circuit.
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I guess I should have specified 'wreck' as either the Liverpool or the Express. It is that simple lower gain clipping stage that sets it apart from the rest of the herd. And Jazbo is right--the Rocket it is not; more of a customized Vox AC30. I think you can reference any previous existing circuit(s) or pieces of out of familiarity. Really nothing new under the sun here though. Again the point is that the 'wreck' is a great sounding high gain flame thrower, low parts count, and most that build a 'wreck' like 'em a lot (including me) but IMHO you can get significantly more versatility with little effort. The band I play in now is mostly classic rock stuff and blues based tunes--it just gives me more and I decided to throw it out there as food for thought.
Jojo, the switch doesn't pop much at all for some reason. You can always put a 4.7 meg across the contacts if it gets annoying. I use the VVR thing on just the PA/ PI for lower gain amplifiers whose sound are not so dependent on the voltage sag from PA screen. To my ears, this circuit style just sounds better scaled down across the board unless. Even if you have a master volume before the PI, you wont get that saggy drop that help the compression and bloom. And it's not everyone's cup of tea.
I don't have any sound clips at this time but I will try get something together. Regards
dennis
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I forgot about the Rocket too. I don't have a schem in my library & neither does Doug after looking. However in my mind it's always about the Express then the Liverpool.
About that clipper gain stage, I remember a few years ago Merlin talking about amps out there like the Soldano SLO having a cascading chain of them? At least two if not three all in a row?
Zen, I'm like you in that in my older years playing the same stuff as you that while playing out I need more basic circuits yielding great solid tone that I shape vs overly distorted one trick ponies. Nothing against amp overdriving coolness in my home or even at practice & rehearsals but it's just not good for perfoance stuff. I also really love a loud, pure, and clean tone to display the guitars, pickups, speakers, & what technique I continue to work on.
Relying on distortion all the time is also a crutch as well as a disguise for poor playing and technique.
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The switchable gain stage and VVR make this circuit very flexible. Without them the Trainwreck is the original one trick pony.