On The Bench - Mercury Magnetics Jet City JCA20H 20 watt Upgrade
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- เผยแพร่เมื่อ 8 ส.ค. 2018
- In which we dive headlong (and headstrong) into a control group comparison between two Jet City JCA20H amplifiers - one stock and one modified with Mercury Magnetics Transformers. Let's go!!
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I've done factory mods for Jet City for 4 years and I actually prefer the Demeter Bulldog M6 output transformer Jet City offered. It was made by Demeter Windings in the UK and got rid of a lot of the stock fizz & tightened up the bass while giving about 10% more perceived volume. These amps actually hit max output at around 7 on the Master Volume & the Demeter holds up nicely all the way to full without mushing out like the stock tranny. Mercs are way overpriced and the Demeter does the job for around 90 bucks.
Great video!
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Larger transformer is wider bandwith and considerably less distortion in the lower region. That's the "smear". The bass is getting smothered.
One of the simplest amps to mod, the Epi Valve Junior has just the same quality. Swapping stock with a Hammond 125ESE in that one brings out cleaner defined lower tones.
Cool demo......Thanks for making this comparison. Interesting results. I pretty much hear the same differences that you mention. Stock = smokier/flatter eq response...…..Mercury = Clarity/more frequencies coming through/more character.
The Mercuries are definitely more focused and more compressed. Thanks I was on the fence about changing the transformer in my Amelia, order tonight, Thanks again.. Please do more videos.
nice I'm getting this same config for mine thanks for showing how it would sound after the changes
It's my sincere pleasure. Thanks for tuning in.
Definitely can hear the difference. Mercury sounds tighter. Also adds a little more woodyness to the guitar.
I actually like the fuzzier sound of the original. Both sound good, just different. The one with the Mercury sounds a bit more dynamic, and with more headroom.
Thanks a lot! Very, very nice video!
I assume that top-soldering thing is really handy for doing mods. You don't have to take the board out.
Loved this video man! Definite difference! Would really like to see videos where you then do other mods like maybe a be/Jose and depth mods. Resonance mod?
I equipped my Marshall JVM 205H, 50 watt amp head with Mercury input, output and choke. Night and day difference. Like going from mono to hi-fi stereo. Better tone control sensitivity and a slight increase in volume. Beautiful!
I had a build where I had not only the PT and OT in the same orientation, but it was quietest when the OT was directly in front of the PT. You just never know, I guess.
Thanks for posting the comparison. Now I understand why guitarists like Mercury transformers. The Mercury amp sounds a little smoother, they way an amp should sound. The other one sounds a little noisy and not quite as clear.
It's a different sound, but I much prefer the Mercurys. I put an oversized Mercury Vibroverb OT into my 2000's Custom Vibrolux. It was listed on the Fromel website as a (kind of) drop in fit. After some repositioning of the Reverb trans. I finally got it to fit - the amp went from ~37bs to 46 !! That thing is a beast! It does sound good though. I was looking for more clean headroom - I don't think that happened (hard to tell since I put in a NFB loop at the same time - part of the Fromel delux mods kit). It's weird when you carry it since the weight is so heavily concentrated right under the handle. It was ~$245 delivered, so ~3x the $$ of a stock replacement. To me it's worth it
You were correct with 90 degrees.
SRT Amplification - Yeah, I realized that almost immediately. I made the mistake of shooting that part early in he morning before I was fully caffeinated. 😎
I think having the xfrmrs rotated 90 degrees is helpful (reduces noise) when the transformers are in close proximity to one another. Those two are probably far enough away, that it makes little difference.
SRT Amplification - agreed. I just found it strange. Why WOULDN'T you mount them in opposition? Beats me.
@@GranvilleGuitars Especially when Mike Soldano was one of the owners, and designer.
I could definitely hear the difference the modded amp has more "authority" with the chords. However, this could be a negative to some people who can't play as well especially a beginner all your mistakes will be very apparent (nothing to hide behind) I had a jtm 45 handwired clone for a couple of years and when you played the wrong chord or the wrong note believe me everyone heard it loud and clear! The stock amp was made for the beginning guitarist who wants a tube amp and I think it achieved that goal. Very interesting to hear the two transformers side by side.
Mercuries are definitely tighter...... Nice vid, thanks.
Peter Cornell - Thanks for watching. I agree. Just plain more FUN.
Hey great video man I have the custom 22 I’m looking to stall a ez81 tube rectifier. I do not want to do the SAG resistor.. other than powering the filaments I think it should be straight forward what do you think?
Next time you have the modded amp open swap out the pilot light. They are notorious for failing on the gen one Jet City amps.
How much did all this cost? I'm curious if this will make the jet city sound more like a soldano
If you love tone and playing guitar it's definitely worth a couple or three benjamins
One thing I've wondered is if putting similar compatible tubes of lower demand can make better use of the stock transformers? I am planning on putting Russian 6p43pe in place of the el84s in my 20h to see if the 6p43pe lower filament draw, lower typical operating voltage will relieve the pt a bit. The limiting values are the same for both tubes also.
I realize this is two years old, but if you have tried this, It would be interesting to hear your thoughts.
Can you explain to me what is exactly the function of the choke? Great video! Thx
danimolina08 - Thanks for the kind remarks. A choke is an inductor placed in the DC rail between filter capacitors in place of a voltage dropping resistor. Although it replaces a resistor the job it performs is very different. Instead of reducing the voltage, it smooths the residual AC ripple out of the DC voltage. A choke is a must for a firmer more authoritative feel to a power supply or in smaller amps when AC noise is of concern.
Granville Guitars thank you for your reply!
Is it fair to assume that the real advantage of the big iron reveals itself at highest levels of volume by retaining a full spectrum of dynamic response and better definition?
Jaime Nôro - I would say that that is indeed a fair assessment. More iron - better performance.
Thanks for the reply. I've been thinking about upgrading, at least, my Engl Blackmore's OT. Even though it sounds great at low and medium volumes, it totally thins out at loud gig levels, and I suspect the real tiny output transformer is the cause. I've never seen such a small OT for a 100 watt tube amp. What do you think?
Jaime Nôro - you could certainly try that and it would likely be an improvement. But in my opinion that amplifier has other design problems that will cause that effect.
Really? Could you elaborate a bit? What problems do you mean? Could they be improved?
Jaime Nôro - Those amps just have tons of gain stages and elaborate switching. When you design something that way, you invite those kinds of issues. If you don't like it the way it is then it's fair easier and more advisable to get a different amp. In a very general sense I dislike and do not do extensive modifications to any amp. I sincerely feel that if your present amp isn't meeting your needs, then another amp is called for. I only did this transformer swap as an interesting experiment.
Gotta question, did you do the original layout for the Matamp USA company? Thanks..
I did not.
Off topic question but how possible would it be to install tube sockets and use some solid wire to extend the leads to the board? I just don't care for board mounted tube sockets.
It's not difficult at all to convert it, but in reality it's a non issue.
Mercury are great transformers, I have one on my Twister DD …
I brought my first generation ( stock no mods) JCA 20 to the United Kingdom with me from California. Anyone here know if the stock transformer has a winding for the UK?
Great demo man! What model were the transformers? Did you put in 20 watts or higher?
Cedric Spencer - Thanks! Just the normal 20 watter.
The chassis in those amps looks like it was fitted back to front? The knobs should not be on the same side as the metal grid, this is on the back of the amp?
I moved the back panels to the front and vice versa. I liked the look. Doesn't effect the amp in away other than cosmetics.