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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Apr 29, 2013 1:43 pm
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Location: Natural Bridge, Virginia
BMW2002Ti wrote:
Bill,

Nice detective work! These kinda issues seem more prevalent in amps 30 watts & above. For many parasitic type oscillations in big amps (80-100 watts), I've used ferret beads for the PI and output stages. It's an old Ham Radio trick. I've seen some Ampeg SVT and V4 with wires wrapped in beads.

http://www.diyaudio.com/forums/tubes-va ... neral.html

Anyhow, good lucj with your amp. I've never owned or repaired a Trainwreck. Have played on a few. Great amps!


Thanks. :D

Interesting. I'll read the link and any other info I find.

Wish I could say I've played a real Trainwreck although I have driven a few real train wrecks. :lol: :lol: :lol: :lol:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Apr 29, 2013 2:01 pm
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BMW2002Ti wrote:
Bill,

Nice detective work! These kinda issues seem more prevalent in amps 30 watts & above. For many parasitic type oscillations in big amps (80-100 watts), I've used ferret beads for the PI and output stages. It's an old Ham Radio trick. I've seen some Ampeg SVT and V4 with wires wrapped in beads.

http://www.diyaudio.com/forums/tubes-va ... neral.html

Anyhow, good lucj with your amp. I've never owned or repaired a Trainwreck. Have played on a few. Great amps!


Yeah, we used to have parasitic supressors in most of the heavy transmitters. The old resister with the hair thin wire coiled around it. :shock:

Art


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Apr 29, 2013 2:09 pm
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Art1 wrote:
BMW2002Ti wrote:
Bill,

Nice detective work! These kinda issues seem more prevalent in amps 30 watts & above. For many parasitic type oscillations in big amps (80-100 watts), I've used ferret beads for the PI and output stages. It's an old Ham Radio trick. I've seen some Ampeg SVT and V4 with wires wrapped in beads.

http://www.diyaudio.com/forums/tubes-va ... neral.html

Anyhow, good lucj with your amp. I've never owned or repaired a Trainwreck. Have played on a few. Great amps!


Yeah, we used to have parasitic supressors in most of the heavy transmitters. The old resister with the hair thin wire coiled around it. :shock:

Art


Well, my hair is pretty thin, but I'm not sure of it's resistance. :lol: :lol: :lol:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Apr 29, 2013 4:43 pm
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bluesky636 wrote:
63supro wrote:
Nice Bill, real nice, Congrats! Now you really gave me the itch. I decided I'm going to build the Build Your Own Clone Royal Tweed. It's supposed to have the circuits from the 5F1 Champ, 5F2a Princeton, 5F10 Harvard and the 5E3 Deluxe all in one amp. This thing has a cut switch for the negative feedback loop and a switch to take out the tone stack foe the 5F1. I know I already have a 5e3, but the circuit in the BYOC unit is 11 watts where the circuit in my current 5e3 is a little more juiced to the 15-18 watt range. I just want the head to save a little space because I already have a few speaker cabs. We'll see. I have to get past the expense of my second eye surgery for Glaucoma. Nothing to mess with since I make my living as a professional photographer. My insurance covers most of it but I still have my deductibles. :cry:


Thanks. :D

No, no, no. You've already built your quota of easy amps. You need to build a hard one now. Since I did a Trainwreck Express, you need to do something like a Dumble Overdrive Special clone. :lol: :lol: :lol: :lol:

Hope everything goes well with your eye.

I went to my doc today. He wants me to be able to support 100% of my weight in two weeks while wearing the soft cast/boot and just using the walker for stability. I can start driving this weekend (obviously will have to switch between a loose fitting shoe to drive and the boot to walk) and return to my physical office on May 6 instead of working from home. Should be interesting.

My doc screwed up one of the diagnoses codes to insurance, so there is a $1500 claim insurance refuses to cover. I have to call my doc's billing person tomorrow and tell them to fix it.


Good luck with your foot. Putting all your weight on it will be a little nuts at first, but you'll be fine. Last major foot surgery I had was in 76. They rebuilt my foot because of a congenital birth defect that went arthritic. The insurance companies are rough.

Anyway, I like simple stuff. Simple controls, and low wattage amps. You inspire me to move forward. This next one will probably be my last and used for some recording dates I have this summer with some of my cohorts.

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Mon Apr 29, 2013 8:08 pm
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63supro wrote:
Anyway, I like simple stuff. Simple controls, and low wattage amps. You inspire me to move forward. This next one will probably be my last and used for some recording dates I have this summer with some of my cohorts.


Well, just make sure you post all the gory details right here. This will probably be my last amp for a long while, but I do have some other mods in mind for my BDRI. :wink:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Wed May 01, 2013 9:15 pm
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Tried a little tube swapping to see what the effect on amp hiss and overall gain would be. Stuck a NOS JAN GE 5751 in V1. The hiss did drop a bit, but not as much as the gain did. To get the drive back up to where it was with a 12AX7 in V1 required a volume increase that brought the hiss up to about where it was. Oh, well. The hiss isn't really bad at normal playing levels (typical of a Trainwreck) but the acoustics in my room are such that the hiss sounds louder at my playing position than it does right in front of the speaker cab. Also, the Boss 63 Fender Reverb pedal generates a lot if hiss that gets amplified.

I ordered some aluminum shielding foil from Stew Mac (21"x13") to line the floor of the amp cab instead of the aluminum tape I used. The Stew Mac foil is thicker than the tape and will line the bottom in one piece instead of the three overlapping pieces of tape I currently have in the cab.

I found some non-corrosive silicone RTV on Amazon that I will use to hold the power supply caps together (there is some looseness in their mounting) as well as tack down the critical wires to prevent noise, and a few other items. This circuit is known to be very sensitve to wire positioning and component location, so anything that can be done to keep things in place is good.

Finally, I'm contemplating replacing the 30 volt drop zener diode with the 40 volt drop one, but I'm not sure it will make much more of a difference. The 30 volt zener brought my plate voltage down by 25 volts at my bias point (475 VDC to 450 VDC) so I don't think an additional 5 to 10 volt drop will be that significant.

I'm hoping that my guitar instructor will be able to come over Friday afternoon to give the amp a good work out. I may record a demo of him playing the amp instead of forcing ya'll to listen to my pitiful playing. :lol: :lol: :lol:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 03, 2013 5:32 pm
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Boy, this things makes funny noises if you look at it wrong. :lol: :lol: :lol: :lol:

I decided after playing the amp for a while to remove the gain switch. I found that sometimes if the switch is flipped with the volume turned up, it would star the amp oscillating. :shock: Also, when the V1 cathode bypass cap was disconnected and the volume turned up, the amp would hum. So I pulled the switch, soldered the cap to ground and plugged the hole. When I installed the amp back in the cab and flipped on the power, I was greeted with a horrible crackling noise and howl. I immediately shut the amp off and started looking for the problem.

After about 30 minutes I found that the shorting input jack was no longer shorting. :( There was a visible gap between the shorting prong and the tip prong. Another 20 minutes was spent bending things to get them to make contact. Finally I got it and I intalled the amp back in the cab, flipped on power and was greeted with a slight hiss. Success.

After all the wiring mods and dressing changes, the amp is now very quiet. Up to about 1:00, the amp hiss is no louder than any of my other amps. Beyond that, the hiss get pretty loud. There is no significant hum, and best of all, I can dime all the controls and not have the amp break into a howling, squealing mess.

I think it is truly and finally complete. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 03, 2013 5:48 pm
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And now for what everyone has been waiting for: What does this beast sound like?

I decided this time that instead of subjecting everyone to my plinking and plucking, I would ask Vinny Roth, my guitar instructor to try the amp out and make a little demo of it. For an hour, he put the amp through it paces. It didn't smoke, catch fire, or explode. Vinny loved it. Here is a little 6 minute demo using my MIM Standard Strat with Fender SCN pickups. Vinny gave the guitar and amp a workout with various switch settings, volume levels (the tone controls were set as shown in the picture and the amp volume was set to 11:00 with everthing controlled from the guitar). Don't look for a lot of visual action as all I have is a digital recorder and still camera. I hope you enjoy Vinny's playing and the sound of the amp.

Without further ado, it gives me great pleasure to present the Bluesky Amps Wrecking Ball Debbie.


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 03, 2013 5:53 pm
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So, what do ya think? :mrgreen:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 03, 2013 5:54 pm
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Bill, very cool! It's amazing what things in an amp can cause feedback. I've had amps with microphonic jacks, too. Resistors, caps, soldered leads, even sockets. Good find.

" Non-corrosive silicone RTV on Amazon " FWIW, I've been using a glue gun with standard glue sticks. Seems to be a bit more prescise in applying, versus RTV.

http://www.amazon.com/Stanley-GR20K-Tri ... s=glue+gun

Edit: Boy does that amp sound good! These dual 6L6GCs are the way to go. Good OD potential with the tube's characterisitic D chiming in. Very nice!


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 03, 2013 8:54 pm
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BMW2002Ti wrote:
Edit: Boy does that amp sound good! These dual 6L6GCs are the way to go. Good OD potential with the tube's characterisitic D chiming in. Very nice!


Thanks. By the way, the power tubes are JJ E34Ls, not 6L6GCs. The 12AX7s are all JJs also. 8)

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 03, 2013 9:07 pm
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Very 6L6GC like tone. Those E34L are great tubes. It's been awhile since I've put those into an amp.

Very nice range of tone.


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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Fri May 03, 2013 9:16 pm
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BMW2002Ti wrote:
Very 6L6GC like tone. Those E34L are great tubes. It's been awhile since I've put those into an amp.

Very nice range of tone.


Thanks again. :D

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun May 05, 2013 5:26 pm
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SOME LESSONS LEARNED BUILDING A HIGH GAIN AMP

I learned a lot building this amp, mostly that a high gain amp is a real PITA to get working properly. :lol: :lol: :lol: :lol:

The Weber JAVA kit is actually a fairly simple amp. Much simpler, I think, then the Weber 5F6A clone that I built last year:

viewtopic.php?f=13&t=65668

The 5F6A clone only has two gain stages, one of which uses a low mu 12AY7 for the input. The voltage amplifier uses a single 12AX7 with the second triode wired as a unity gain cathode follower. The Wrecking Ball, on the other hand, has three gain stages, all 12AX7s, configured for pretty high gain. The 5F6A also has a fairly large amount of negative feedback between the output tranny secondary and phase inverter (loop gain is about 54% of the open loop gain) compared to much less negative feedback in the Wrecking Ball (loop gain is about 65% of the open loop gain). All of this gain in the Wrecking Ball results in an amp that teeters on the edge of instability. :shock:

As a result of all this gain, great care needs to be taken in the layout and wire dress of the amp. Yes, I know that statement is true of any amp, but it is even more important in a high gain amp. In fact, I can see where this is one situation where a high quality PCB based amp might be more effective and possibly sound better than a hand wired eyelet or turret board based amp. The PCB based amp has the advantage of being able to use powerful computer simulators to determine the best layout of components and routing of signal and power lines (along with good grounding) resulting in a stable, low noise amplifier with tremendous "clean to mean" capability. Unfortunately, the average home amp builder doesn't have access to such methods.

Given that the JAVA is a kit with a pretty fixed parts layout (though I did move a number of components around in building it), grounding schemes and wire dress are still pretty open to changes. The late Ken Fischer, the designer and builder of the Trainwreck amps, was pretty much a genius when it came to component layout and wire dress. Either that, or he experimented a lot and got lucky. :lol: I'm definitely no genius, so I had to experiment a lot and was rewarded in the end with a stable, hum free, low hiss (unless the volume is dimed) amp. The final test with this amp is to dime all the controls. If the amp does not become a squealing, howling mess, you did a good job. I got lucky and succeeded, passing the test (Although I don't demonstrate it often because someone in the next room could sneeze and start the amp oscillating from changes in air pressure. :lol: :lol: :lol: )

So what is the takeaway from all this?

1. Take your time. That is probably the most important thing. Follow the schematic, wiring diagram, or instructions carefully. If you deviate from them, make sure you understand the possible impact, positive and negative, of the change you made.
2. Use the least amount of wire possible. Keep your wire runs as short as possible, and avoid running signal wires or signal and power wires parallel to each other. If wires have to cross, make sure that they cross at as close to 90 degrees as possible to avoid coupling.
3. If you can't achieve short runs that are not close to other wires, route the wire around and as far away as you can from the other wires. I found that when taking a roundabout approach, tucking the wires against the metal chassis helped to absorb any stray noise. On the other hand, some wires had to be "flown over" the offending noise source.
4. Keep AC sources, particularly heaters, as far away for signal lines as possible.
5. If all other measures fail, use shielded cable. Ground the shield at the signal source end and leave it open at the signal end.
6. Ken Fischer was able to build a lot of his amps with no or minimal grid input resistors on the tubes, due to his skill in layout and wire dress. I wasn't so successful. If used, mount them directly on the tube socket (many amps mount them closer to the input jack than to the tube).
7. Use good, low noise/low microphonic tubes, especially in V1. In my case, my JJ 12AX7s are quite quiet. I am looking at some low noise NOS tubes from KCA NOS Tubes (https://www.kcanostubes.com/).
8. Finally, if you are building a clone, either from scratch or an existing kit, do some research. Learn as much about the design and build techniques of the amp you are cloning as you can. It is definitely a big help. Also, look for any on-line forums that specialize in that amp (Trainwreck and Dumble have a big following on http://ampgarage.com/forum/). They can really pull your butt out of the fire if necessary. :lol:

I'm sure there is more I could say, but I think those are the most important points. If you have any questions about this build, feel free to ask.

Oh. My non-corrosive RTV that I planned to use to tack wires down arrived yesterday. I'm almost afraid to open the amp up to apply it for fear I may look at it wrong and it may scream at me the next time I plug in. :lol: :lol: :lol: :lol:

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Post subject: Re: New Amp Build - Trainwreck Express Clone
Posted: Sun May 05, 2013 6:24 pm
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Bluesky,

Very good points to follow.

I had one question. Have you heard about capacitance & resistance "leakage" using black tagboards? I ask this because I have read where ppl had trouble hunting down oddball hum & other noises. Finally, going to phenolic turret boards to minimize this leak. The claim is the color pigment in the boards has black carbon.

I recall that Ken used mil spec turret boards on his original Trainwreck amps.

Thanks! Great learning experience for us all.

:D :mrgreen: :D


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