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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 31, 2013 12:30 pm
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The amp looks fantastic Bill. Congrats again on what I think is a job really well done!


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 31, 2013 3:09 pm
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Toronado wrote:
The amp looks fantastic Bill. Congrats again on what I think is a job really well done!


Thanks.

If you haven't heard the demo done by my guitar instructor Vinny Roth, here it is.


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 31, 2013 9:51 pm
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Check out the Amplates Facebook page: https://www.facebook.com/AMPLATES :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Jun 07, 2013 4:55 pm
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I installed a set of JJ gold pin 12AX7s tonight. Not for the gold pins, I know they don't make much difference. However, these are advertised as having a smoother, less harsh tone to them than even the regular JJs which I like and use in my other amps. You know what? They do sound nice. Definitely a nicer top end when the amp is really overdriven.

I bought three matched and balanced tubes from Eurotubes so I could swap them around without trying to remember which tube was the PI. I can't say that they are quieter than the regular tubes (to my ears, maybe a little), nor can I compare them to a good NOS 12AX7, but at $75 for all three (plus $8 shipping), I think they were worth it. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Jun 07, 2013 8:44 pm
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That's the thing that escapes most people, it's not just gold plating on the pins, it's a select tube and the gold plating on the pins are what denotes it as a special tube. Now, quit effing around and play that thing! :lol:

Seriously, great job on the whole thing, thread and amp. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Jun 07, 2013 9:12 pm
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shimmilou wrote:
That's the thing that escapes most people, it's not just gold plating on the pins, it's a select tube and the gold plating on the pins are what denotes it as a special tube. Now, quit effing around and play that thing! :lol:

Seriously, great job on the whole thing, thread and amp. :D


Thanks. :D

I have a couple more tweaks left to do. :lol: :lol: :lol:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 08, 2013 7:02 pm
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I now declare the amp to be finished. :D

Until I think of something else to do to it. :lol: :lol: :lol: :lol:

Here is the final schematic:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 08, 2013 9:08 pm
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Bravo. Good show and thanks.

Seriously. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 08, 2013 9:41 pm
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modwiz wrote:
Bravo. Good show and thanks.

Seriously. :D


It was my pleasure. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 08, 2013 11:00 pm
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Thanks for the education along the way...Enjoy the fruits of your labor!

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Jun 09, 2013 6:29 am
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Bill...It is time for you to take your bow! We even liked the "Encore"...thanks for the not only entertainment, but the education as well.

T2

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Jun 09, 2013 8:12 am
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Thanks guys. I enjoy build threads regardless of who does them. Wish we had more. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Jun 14, 2013 9:08 pm
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Of course, I had to make one more, ok, two more slight changes in voicing of the amp. :lol: :lol: :lol:

I increased the PI plate-to-plate snubber cap from 100 pF to 250 pF. This smooths the overdriven sound more and gets rid of a slight fizz I had with the bridge pickups of my Strat and Tele. I also decreased the 100K s l o p e resistor from 100K to 82K to thicken the lower midrange slightly. I haven't had the chance to crank it yet cuz its midnight here in Virginia and I have the windows open (nice cool night after yesterdays t-storms), but with the guitar volume rolled back a little it sounds good. Well, I did crank it for about 10 seconds and it still sounded good. :lol: :lol: :lol:

So the schematic now looks like this:

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and the tone stack looks like this:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Jun 28, 2013 9:34 pm
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Made a few changes to the amp that I should have done some time ago, but kept trying to band-aide things.

The first change was to get the B+ down to the range of a real Trainwreck (about 400 VDC).

If you recall, for whatever reason, when Weber shipped the amp they substituted Heybour transformers for the power and output trannys instead of the stock Webers that I asked for. Although they are really nice trannys, the voltage output of the power tranny is way too high and it doesn't offer the option of a lower output. The primary side is limited to a 120 VAC input. The AC output of the power tranny once installed was about 754 VAC, This translated to a plate voltage of about 475 VDC at a cathode current of 35 mA for the power tubes.

I next tried a zener diode in the center tap of the secondary windings which brought the plate voltages down to about 452 VDC with a cathode current of about 37 mA. Better, but still too high a B+.

Finally, I broke down and ordered the Weber power tranny. This tranny offers a voltage input of either 120 or 125 VAC and outputs of either 660 VAC or 720 VAC. I choose to use the 125 VAC input and the 660 VAC output. Bingo! My plate voltage dropped all the way down to 410 VDC at a cathode current of about 43 mA. Right where I wanted it. I also noticed that the bias point of the amp was reached quicker and was more stable than with the Heybour and zener configuration. Double bingo.

Finally, I made a last effort to tame some high end harshness when the amp is really overdriven (especially with humbuckers). First, I replaced the two silver mica 0.001 mF (total of 0.002 mF) that I used as coupling caps between the second and third gain stages (I had lost the caps from the kit and that was what I had on hand) with a 0.0022 mF Mallory 150 cap. I also replaced the 500 pF silver mica cap on the treble control with a 500 pF polystyrene cap (recommended by one of the members of the Trainwreck forum in the Amp Garage).

Initial testing shows the amp to be a little bit smoother in the highs with a solid overdrive (using my Strat). Its around midnight, so a full test and bias recheck will have to wait until later this weekend. Oh, and most important of all, the amp is still stable with no squeals when all of the controls are dimed (got to admit, that is a scary thing to do as the amp noise makes it sound like the amp is going to explode :lol: ). I'll report back after I make my final tests and tweaks.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri Jun 28, 2013 9:47 pm
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bluesky636 wrote:
....after I make my final tests and tweaks.


Final? OK, who are you and what have you done with bluesky636? :lol:

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