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Fet version of Marshall Superlead Plexi

Started by KMG, January 21, 2011, 05:04:47 PM

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KMG






Preamp section:



Volume controls & tonestack has standard values like in original tube prototype MARSHALL 1959SLP.

For PA is used "Fet power amplifier with transformer output" 40W version.

J M Fahey

Hi KMG, congratulations on your impressive work.

Gabriel

Indeed , you really are a "Fet man". Fantastic amp! I whish i could do something like this one day...

will316

I can't tell by looking, but is this a master volume amp or straight forward plexi? If it isn't master volume, can it be easily modded to be? Also wondering if it has an effects loop? It's quite an impressive set up nontheless. I hope to have the skill to build one someday. That's a really neat looking rig, and if it sounds like a "real" plexi, you've built a masterpiece! Guys like you and Mr. Fahey are truly artists when it comes to this stuff. I am in awe of your talents. Major manufacturers would be wise to swoop in and hire you guys. Astonishing, to say the least!
I picked the wrong week to stop sniffing glue...

KMG

QuoteI can't tell by looking, but is this a master volume amp or straight forward plexi? If it isn't master volume, can it be easily modded to be? Also wondering if it has an effects loop?
Yes it`s mod of standard Plexi, added master volume after tone stack & passive (because preamp has low output impedance due to source follower at output) loop.



polo16mi

Wow man!!!  Awesome work!!!

It´s look very professional.  :tu:

Perhaps can you post some sample sound of it?

joecool85

Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

KMG

I'm not a good guitarist to record samples. Wait untill my friend will come to visit me.

joecool85

Quote from: KMG on January 28, 2011, 07:01:48 AM
I'm not a good guitarist to record samples. Wait untill my friend will come to visit me.

Fair enough.  Although I've put up clips of my less than stellar playing (and gotten razzed for it).
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

polo16mi

Quote from: KMG on January 28, 2011, 07:01:48 AM
I'm not a good guitarist to record samples. Wait untill my friend will come to visit me.

I´m no so far away of your playing skill, but i think that anybody that stand up front a Marshall can´t resist to play (and want to ear too) is a A5 chord at full power  8)

will316

I'd like to hear a Am to G progression hammered out a la VH's Aint Talkin Bout Love (the greatest song ever!) Seriously, that's a lick I try any amp/guitar/pedal etc. with. If I can crank the gain but still get that twang of the Am going, I'm thrilled. Some triads and barre chords helps too. High gain scooped stuff is fairly easy to achieve as long as you stick to power chords-bigger more complex chords that retain clarity at high gain is or should be an amp builder's goal along with "flavor" or signature tone for lack of better words. Last but not least, I dig straight forward aesthetics that have a unique, trademark look. Mr. Fahey's amps have a very nice look that is very singular but under the hood the modular, retrofittable aspect to his designs are something no major players have thought of. The right promotion of that aspect alone would sell mountains of his product. Whirlpool saw that wisdom 20+ years ago when they designed their direct drive washing machines and it earned them some 80% or so of the market. That coupled with brute strength along with ease of servicability truly put them at the top of the game. If it aint broke, why fix it?
I picked the wrong week to stop sniffing glue...

phatt


Just quitely, ar-hum.
That efx loop is about the fastest way to stuff up an other wise good system.
Never insert EFX loops at that point in the circuit as it will give Trouble down the track :trouble

I'd hate to see such good work go to waste. 8|
Phil.

KMG

Quote from: phatt on January 29, 2011, 02:25:19 AM

Just quitely, ar-hum.
That efx loop is about the fastest way to stuff up an other wise good system.
Never insert EFX loops at that point in the circuit as it will give Trouble down the track :trouble

I'd hate to see such good work go to waste. 8|
Phil.
I do not understand what is wrong with the effects loop?
Buffered output of a guitar-level (see the preamp section) is passed through a passive loop in the PA, which also has a  guitar-level sensitivity.

phatt

Hi KMG,
         Sorry if I misread your schematics but they are quite hard to follow.
From what I see your EFX loop is wired as per my rough drawing.

If this is not right then please correct me.

If it is right then you are walking into trouble as the signal can suffer massive loss and the tone controls under some conditions will hardly be working.
Phil.

KMG

The tone stack output (J5.3) signal is first fed to the buffer stage (Q11) & after scaling down goes to the preamp output (J6). This preamp output is connected to loop.
I never use signal from tone stack to drive high capacitance loads.