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mars_hall

NAD kind of

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About a month ago I had been studying up on a new toy that would be a change of direction for me.  Most of the amps out of Jet City are Soldano or THD clones and I have had really good luck with the JCA100HDM and JCA50H I have.  For the price and actually for any price, these two amps kick it all over the barn yard.  So I figured I'd try one of the clones they had offered for a few years, that wasn't in the Soldano line. 

This one is an Amelia and it is a clone of the very respectable Cornford MK II, designed by Martin Kidd, the designer/mind behind Victory amps.  The voicing of the Amelia is a different animal altogether from the SLO stuff and/or Marshall and having listened to the clips in Youtube , I decided to take a shot. 

These amps are not that common these days so I had patiently waited maybe 3-4 months for this one to come along.  When I went over to Lafayette to pick it up, the owner had attempted a significant mod to the amp trying to convert it to something that was right for him.  He had poor tech skills and worked as a shipping supervisor in a pork processing plant and probably had seen a soldering iron before, but never held one before. 

The mod he applied via the kit from Epic-Tone was a rats nest of sky wires, stacked resistors and caps art with twisted and bent leads.  The attempt at conversion would move the amp into the range of something close to a Splawn Nitro OD.  The guy was into southern rock, but figured this would get him a bit closer to that sound everyone wants.  He confessed it didn't, so he was selling it and moving on to a DSL40.  The guy said he just couldn't get the amp to sound right. 

The sound of the amp was nothing like the original Amelia or Cornford and the controls and added switches no longer functioned close to the intended modification,  let alone the original amp.  You could turn treble all the way up and the entire amp would fade to nothing.  No sound at all.

I was lucky enough to coax a true schematic for the Amelia from a source close to Jet City.  The whole amp and designer was kept a secret by Jet City, but in the end the designer became known, though the details of the design implementation still kept secret.

A lot of the time when people do schematics, they leave out details or throw the parts at the paper in the quickest manner to get it done.  They have it in their heads and that is all that matters.  The logic of the flow and interconnects often goes missing.  So I took the schematic given to me and did a redraw to put it into a logical order, input to output at the speaker, one that I could follow and make sense of the voicing used. 

I removed every bit of the rat's nest modification that had been attempted and ordered the 35 or so components that had been removed during the life of the Splawn misadventure.  The artwork of the original PCB remained silk-screened with outlines and designators, where the OEM parts once sat. 

So I diligently restored the circuitry back to the original set and second guessed myself and whether I had done everything exactly, before turning it on and watching the unanticipated sparks fly.  This was my first turn with a high voltage amp and I was unsure if more had been done to the amp outside the mod.  The mod had not been followed exactly but was fairly close. 

Well, there were no sparks and when I plugged in, expecting the divinity of the cosmic most high to appear right before my eyes, it was a total no show of awesomeness.  I thought to myself, well there goes a chunk of change and wasted time.   I felt somewhat confident in the reversal of the rat's nest, but the warm and fuzzy of productive spent effort was totally missing.  How could anyone actually like this amp?  Thrashers?  Tweakers?

Then I thought to myself, this previous guy had no idea what he was doing during the mods and probably just threw the tubes back at it getting them back in and up and running.  I started checking the tubes and he had a Mesa STR 12AT7 in the V1 position, which is exceptionally limp for the initial preamp tube.  It cuts the gain way down and it OK for a blackface circuit, but never a Splawn beastie.   I had a GT 7025 laying around from an Egnator swap and I pulled the AT7 and dropped in the right animal. 

Firing up the amp, it changed its entire tonal palette.  It was much closer to what I had expected.  Looking at the other tubes he had thrown in, I found a Mullard in the V3 spot and immediately put it in the V1 spot pulling the 7025 and replacing V3 with an old GE AX7 tube I had lying around.  Someone had loved this amp at some point in time.  The amp sprung to life and I now have what I was hoping for in the first place.  Actually it is sounding a bit better than I could have hoped for.

 

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I don't know what is better, the amp repair or the wright up. Well done!

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Success is a meal best served warm, with high gain.  Congrats!

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Fantastic.  I've been a fan of Jet City Amps for a long time, I've owned four of them and sold the last of them a month or so ago because I really didn't need a fire breather of an amp like that.  (It was the JCA20HV)  Rather unique take on their 20 watt head, darker and less gain than usual.  

Nice job on the restoration.  Well worth the read.

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59 minutes ago, DetroitBlues said:

...  I really didn't need a fire breather of an amp like that. 

Can't really speak for the amp you had, but I have found that any amp I have placed on a lower wattage setting, the bottom end seems to disappears and I am left with something less than the full range of frequency.  Generally, the low end and full tonal roundness go missing.  People will throw words like "a loss of overhead" at you, which may or may not be an accurate accounting of the tonal loss and could very well be overly simplistic.

I usually buy higher wattage amps, not for the "in your face" scream, I hate being directly in front of a cabinet, but for the extra low end response and touch sensitive bloom.  You may recall at PSP and other of our "get-togethers", I can barely be heard, most of the time, and this is from a tendency to play at a lower level and dig into the pick attack for edge.  People will stereotype you by saying "Shit, he's got that 100/200 watt beast there, What's up with that?". but not realize the beast is intentionally not being goosed to full attention.  You get a different sound flapping speaker paper at the high end than the one you have worked with in closer quarters.  The dynamic range of change in the whole system is huge and wanted and also often unwanted additions come to play, with minute variations in the controls.  Harmonics and fundamentals kick in and kick out, buried in the dynamic mix of the variables.

The Amelia gain control doesn't really add more distortion, as you have probably come to expect most amps to do, but instead gives the signal something more akin to an increased sustain.  The hair is applied via the overdrive control at a later stage in the amp and this is far more subtle in a warmth spread that is heard, as opposed to an increased cutting edge.  The amp, to begin with, has a modern voicing, but the width of the edge is more refined to a set of fewer frequencies, which makes the ring contrast and ride the warm underbody, as opposed to dominating the tone.  Subtleties are there that come out the dynamics.

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Posted (edited)
3 hours ago, mars_hall said:

Can't really speak for the amp you had, but I have found that any amp I have placed on a lower wattage setting, the bottom end seems to disappears and I am left with something less than the full range of frequency.  Generally, the low end and full tonal roundness go missing.  People will throw words like "a loss of overhead" at you, which may or may not be an accurate accounting of the tonal loss and could very well be overly simplistic.

 

You might enjoy that amp head if you come across one.  It has a "depth switch" which all it really does is exactly what you want.  Massive amounts of low end that doesn't change the tone, just makes it deeper... if that makes sense.  Sort of like you "feel" it more than you hear it.

Edited by DetroitBlues

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Posted (edited)

I have found my Mesa KingSnake doesn't sound as good when on the 10 or 25 watt setting. No matter where the volume is set (yes you can turn it down when it's set for 100 watts) it sounds better with all 4 power tubes engaged.

Edited by pressure

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6 hours ago, DetroitBlues said:

You might enjoy that amp head if you come across one.  It has a "depth switch" which all it really does is exactly what you want.  Massive amounts of low end that doesn't change the tone, just makes it deeper... if that makes sense.  Sort of like you "feel" it more than you hear it.

I actually have the Custom 22 in my Reverb feed list.  This is same one as the 20, but Martin Kidd did his own tweak on it and I like what was done.  Martin is not the end all, but good at his trade. 

That said, a friend of mine took this design one further for one guy and you can hear the results on Youtube. 

Kevin Silva (Uncle Alberts in Indy) swapped out the EL84s with EL34s, installed a choke, and upgraded the transformers to handle the new setup as seen in the attached clip.  It isn't perfect, in as much as the voicing and overall gain was compromised, but I like a lot of the basis of what I hear.  Not all the farting, but a lot of the throat.  If the coupling and cathode caps were smaller, the gain would reduce, he could revert back to a 12ax7 in the second stage, and the fart-bucket bass emphasis would come back in line with where it should be.  The Custom 22 is essentially a sub-SLO clone, not the Cornford.

 

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+1 for bigger amps, bigger glass and biggef iron

  • Upvote 1

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2 hours ago, gpuma said:

+1 for bigger amps, bigger glass and biggef iron

Hurrumph!  +1

  • Upvote 1

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On 6/17/2020 at 4:43 PM, pressure said:

I have found my Mesa KingSnake doesn't sound as good when on the 10 or 25 watt setting. No matter where the volume is set (yes you can turn it down when it's set for 100 watts) it sounds better with all 4 power tubes engaged.

My Victoria Regal II can be run with only one tube in the power section (parallel single ended with an adaptive transformer) or two, and can run a variety of tubes, 6V6s all the way up to KT88s. And when I use two big bottle tubes (6L6, KT77, etc) it always sounds better, although a bit too loud for my purposes.

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On 6/21/2020 at 6:41 AM, 212Mavguy said:

Great post, great thoughts, great result!  

+1

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