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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 29, 2013 7:55 am
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shimmilou wrote:
bluesky636 wrote:
....after I make my final tests and tweaks.


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


:lol:

Its not just that I like to tinker (I do), but this has all been a big help in understanding amp design and why designers do what they do, what works, what doesn't, etc. Plus its fun. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 29, 2013 3:05 pm
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I know what you mean, same here. As far as amps are concerned, what others think of as a chore, I think of as fun. Just like Steve Martin sang; "I get paid for doing this". :wink:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 29, 2013 3:43 pm
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Well, here is the "final" schematic ( :lol: ). Notice the significantly lower power supply voltages compared to the previous schematic I posted. Also notice the change in the tonestack configuration. I went with the traditional 5F6A Bassman/JTM45 Bluesbreaker (with a 56K s l o p e resistor) type stack. I prefer the interaction that this tonestack exhibits compared to the previous schematic's Trainwreck Express tonestack. Plus, the midrange is thicker sounding. The final bias setting for the E34L power tubes is:

CATHODE CURRENT 44 mA
PLATE CURRENT 42 mA
PLATE VOLTAGE 405 VDC
% MAX PLATE DISS 68%

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Edit: I left out the fuse on the PT secondary center tap.

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Last edited by bluesky636 on Wed Jul 03, 2013 4:43 pm, edited 1 time in total.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 29, 2013 5:05 pm
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I was going to ask about the tone stack before. What is your impression of connecting the tone pots together, end-to-end without the wiper jumpered to one end of the pots on the treble and middle, the way that you have them now, as opposed to the way they were in the last version with the pot wipers on the treble and middle jumpered to one end of the pots, with the pots not connected end-to-end?

I like the pot wipers jumpered to one end of each pot, so as to allow no signal out when the tone pots are all at minimum. It seems that I have more control over the tone this way, especially the mids.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 29, 2013 8:40 pm
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I'm guessing that you have played Blackface/Silverface amps before and prefer that type of tone stack. I never have. All I own and have played are my 5F6A clone and BDRI, both with the vintage Tweed Bassman/early Marshall tone stack. I prefer a more middy sound. I did not like the way I previously had the tone stack in the Wrecking Ball wired. It did not provide the control that I preferred from my 5F6A. For the record, most of the Trainwreck Express schematics I have seen are wired either Blackface/Silverface or 5F6A style. This schematic was rather unusual and was representative of one particular Express. I wired it that way when I was fighting squealing problems when diming the controls as it seemed to help. It wasn't the entire solution and as it turned out, did not have to stay wired that way.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 29, 2013 9:51 pm
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OK, cool. That confirms what I thought and yes, I like less mid-range.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sat Jun 29, 2013 10:29 pm
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shimmilou wrote:
OK, cool. That confirms what I thought and yes, I like less mid-range.


To each his own. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Jul 01, 2013 4:57 pm
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bluesky636 wrote:
nedorama turned me on to Amplates (http://amplates.com/) so I designed a new front panel and had Joe build it for me. It turned out great. :mrgreen:

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Much more professional looking.

When I get a chance, I'm going to take the amp to Action Music (http://www.actionguitar.com/) in Falls Church, VA and ask them to try out the amp and get their impressions.


Glad I could help! Looks stunning!

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Jul 01, 2013 5:14 pm
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Thank you again! It took a couple of tries to get the "Wrecking Ball" font to my liking (he couldn't match the brass name plate), but I am very pleased with the results. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Wed Jul 03, 2013 1:20 am
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Finally got a chance to crank up my amp. I have to say that changing power transformers to drop the B+ from about 475 VDC at the bias set point to 405 VDC at the final set point has really made a difference. Plus changing the 0.0022 coupling cap from a silver mica to a Mallory 150, the silver mica 500 pF treble cap to 510 pF polystyrene and the 100K s l o p e resistor to 56K have really made the overdrive highs much smoother and the overall sound thicker and more midrangy like I like. Very happy now.

I'm also intrigued by geetarpicker's (a member of the Amp Garage's Trainwreck formum and owner of two real Express amps) use of two fairly high capacitance cables to help tame the beast. My bright switch only uses a SPST switch to select a 100 pF bright cap or none. I never liked the 500 pF cap. I'm thinking of putting back in a DPDT switch to select a 100 pF bright cap, no cap, and about a 1500 pF cap across the guitar input jack to tame bright pickups. I use two 10' Planet Wave American Stage cables (with a buffered Radial Bones Twin City A/B/Y switch to select between two amps in between). The cables are rated at only 28 pF/foot and this would make sort of a bright/flat/roll off switch. what do you think?

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Last edited by bluesky636 on Sun Jul 28, 2013 4:37 pm, edited 1 time in total.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Jul 28, 2013 4:36 pm
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I decided to try the 1000pF cap in parallel with the 100K plate resistor on V2B as recommended in the Trainwreck forum on Amp Garage. That was the magic fix! The overdrive highs are much thicker and smoother with no loss of highs when the guitar volume is turned down for a clean sound. Overall high frequency noise is noticeably reduced. Even better, I can actually use the Bright switch with a humbucker equipped guitar without the high frequency noise increasing. I was also able to drop the PI plate to plate cap from 250pF back to 100pF. The amp is stable with all controls dimed.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Jul 28, 2013 5:01 pm
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Very tasty...Great looks, Great tone. Hey how'd the ankle heal up?

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Jul 28, 2013 5:55 pm
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Arnold Layne wrote:
Very tasty...Great looks, Great tone. Hey how'd the ankle heal up?


Thanks.

I still have problems with my foot swelling if I don't wear a compression stocking and am on my foot too much. People don't realize how long it takes for foot surgery of any complexity to heal. Its kind of a catch-22. You need to keep it elevated and stay off of it as much as possible, but you have to walk on it to get around.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun Jul 28, 2013 6:59 pm
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Here are the frequency response plots for the plate resistor bypass capacitor. The first one is with a 100pF cap (that was the smallest the calculator provides. No "0" pF.). Note that the high frequency -3dB point is above 10kHz.

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Here is the frequency response with the 1000pF cap. The high frequency -3dB point is now about 3kHz.

Image

Here is an explanation of the calculator which can be found at

http://ampbooks.com/home/amplifier-calc ... capacitor/

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Jul 29, 2013 5:43 am
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bluesky636 wrote:
Arnold Layne wrote:
Very tasty...Great looks, Great tone. Hey how'd the ankle heal up?


Thanks.

I still have problems with my foot swelling if I don't wear a compression stocking and am on my foot too much. People don't realize how long it takes for foot surgery of any complexity to heal. Its kind of a catch-22. You need to keep it elevated and stay off of it as much as possible, but you have to walk on it to get around.


I understand Bill. I had reconstruction on my left foot. They fused three joints into one bone. I have no side to side movement of that foot, but have no pain issues with it. It took me nine months just to walk properly and close to two years of rehab till it was 100%. It tales a long time and can be seriously painful through the healing process. The swelling eventually goes away.

Just keep at it.

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