Mini Wreck?

[stevlech]

I was thinking of doing something really similar- like a Champ outpur amp w/ Trainwreck preamp. Can't wait to hear your results!

[funkmeblue]

I used the output of the angela super single ended project

[sliberty]

Do you have any clips? And a schem?

[doctord02]

Hey Steve, I took an AX84.com P1 Extreme and rebuilt it with a trainwreck preamp stage and it sounded pretty darn good... The P1 Extreme is a single ended cathode biased amp, in this case running a single EL34.

I did find that I needed a little bit of a increase in gain to make up for the lack of a phase inverter, so I built a simple generic gain stage with the unused triode that the wreck usually ignores. This is located after the 10k clipping stage and right before the EL34.

I built it for a friend as a recording amp and he uses it all the time. The only other difference is it also has a master volume control with helps make it even more versitile...

[sliberty]

Doc,

Sounds a lot like what I am up to. Do you have a schematic for that build?

Thanks,
Steve

[gearhead]

I'd be quite interested too. I've got a 3/4 built extreme sitting around.

[Bigwan]

I'd be very interested in any schematics or layouts you guys have too. Would love to build a mini 'wreck as my first DIY project!

[sliberty]

Bigwan,

While this particular Mini Wreck thread did start with my question, I think I would advise against building a Mini Wreck as your first project. It is not a proven design (in fact its not even a completed design), and you might have problems that confuse you into thinking you made some mistake. You'd be better off starting your DIY career with something that has been built many times, and is known to work well. Also, if it is a project that others have built, you'll get more first hand help if you do have problems.

Having said that, the basic Mini Wreck concept is not very radical, and should work out OK, even if it might not sound like a Wreck in the end. Rumor has it the gain may be lower (without adding additional gain stages that are not part of the Wreck preamp). Depending upon just how "wimpy" it is, this might not be a bad thing for some people. The full blown Wreck can be a gain monster, and that can lead to DIY hell.

Good luck whatever you decide.

[Bigwan]

Your point is well made. I'll keep an eye on this thread anyway.

Cheers

Ian

[doctord02]

Doc,

Sounds a lot like what I am up to. Do you have a schematic for that build?

Thanks,
Steve

Steve, I just used the schematic that Nik did for the Extreme and replaced the pre with the Wreck schem. I can look for my notes on my gain stage resistor/cap values if you'd like, but it was pretty much a simple circuit that I largely just did by trial and error... I'll post the values when I get home this evening.

Dave

[sliberty]

Dave,

Thanks. Whatever info you have will be great.

I am actually thinking that rather than add an additional gain stage (assuming that gain is lacking, as others have suggested might be the case), maybe I would just add a cathode bypass cap to the 3rd stage (bypassing the 10K resistor). Who knows, it might be just enough...

I gutted my P1 chassis last night, and made my eyelet board. I also fitted the componenets to the board without soldering. Tonight I'll solder the board up, and wire up the heaters I guess I'll know soon enough.

Steve

[funkmeblue]

I ran the extra stage in parallel with the third stage into parallel 6v6s......plenty of gain for me and I used 6sl7 and there suppose to have 30% less gain.......this thing sounds really good

[funkmeblue]

I can e-mail a clip

[doctord02]

Hey Steve

So I used Nik's layout drawing as a guide, but there's and update schematic that may be better for the Extreme, here:

http://annex.ax84.com/media/ax84_m325.pdf

I just rewired the preamp using the Kelly '90 schematic:

https://tubeamparchive.com/viewtopic.php?t=1408

I just used the pots as spec'd for the Extreme, so it's not exactly the same tonestack as the wreck, but was close enough for rock 'n roll.

My gainstage that made use of the unused triode came after the 10k clipping stage consisted of a .022 cap from the anode of clip stage to a 470k resistor, feeding the input grid of the triode, and then another 470k resistor to ground. I believe the cathode resistor was a 1.5k.

Before that I had tried a cathode follower, but it didnt give me any gain so it didnt drive the power tube enough, so thats when I decided to use a simple gainstage. Ive got a really poor drawing attached...

[sliberty]

Doc,

Thanks - I see what you did. From your description, I guess you didn't bypass the cathode resistor on that extra stage, right?

When you back off of the guitar volume, how well does it clean up? Is it Wreck like?

How does the Wreck-based version of the amp sound compared to the Extreme?

Thanks,
Steve